MC and JR are supported by the German Research Foundation (DFG RE 2740/3-1).

Ethics statement: Human studies require written informed consent of participants before study entry. Obtain approval by the relevant ethics committee before recruitment of participants. Make sure studies are in accordance with the Declaration of Helsinki. The representative findings reported here (Figure 4) are based on a study performed in accordance with the Declaration of Helsinki amended by the 59th WMA General Assembly, Seoul, October 2008 and approved by the local Ethics Committee of the University of Freiburg. All subjects gave written informed consent before study entry6.
1. Safety Screening
<ol>
	<li>Screen the participant for potential contraindications for noninvasive brain stimulation3, e.g., by using questionnaires25.</li>
</ol>
2. Motor Cortex Localization
<ol>
	<li>Locate the participant&#39;s hand motor cortex by one of two distinct approaches, by locating the brain representation of the muscle of interest by transcranial magnetic stimulation (TMS)-induced MEP, or by locating the standard M1 position (C3/C4) based on the EEG 10/20 international system with a measuring tape26.</li>
	<li>For TMS-induced MEP recording ask the participant to remove any object that may be influenced by TMS magnetic field, including credit cards, mobile phones and metal objects in general.</li>
	<li>Ask the participant to sit comfortably.</li>
	<li>Verify connections between EMG amplifier and the computer used for signal configuration and acquisition when using a software interface.</li>
	<li>Turn on the EMG amplifier and connect EMG electrode cables.</li>
	<li>Clean participant&#39;s skin by softly rubbing with skin preparation paste in the regions of the hand where the electrodes will be placed. Remove excess with clean gauze pad.</li>
	<li>Attach EMG surface electrodes in a belly-tendon montage on the hand muscle of interest (e.g., M. abductor pollicis brevis of the right hand) and connect a ground electrode (e.g., on forearm). The purpose of the study determines which hand muscle to use. 
	Note: For reusable electrodes it is necessary to apply a small amount of conductive paste on the electrode surface before attaching it to the participant&#39;s skin.</li>
	<li>(optional step) Start the recording software for MEP acquisition if MEP data storage is desired.</li>
	<li>Check the EMG impedance values. Ensure that the impedance is &#60; 20 kOhm.</li>
	<li>Turn on the magnetic stimulator and charge the capacitor by pressing the corresponding &#34;charge&#34; button.</li>
	<li>Place a figure-of-eight TMS coil on the participant scalp on the interhemispheric fissure and move it to the motor cortex area (around positions C3/C4 of the EEG 10/20 international system). Hold the TMS coil at a 45o-50o angle referenced to the interhemispheric fissure27,28, with the handle oriented backwards, producing a cortical current flow from posterior to anterior29. 
	Note: Two distinct TMS coils are used for motor cortex localization: figure-of-eight or circular coils. If possible, use a figure-of-eight coil as it provides more focal brain stimulation30 and greater reliability of measurements of cortical excitability31.</li>
	<li>When the magnetic stimulator is charged (visible on the display), discharge the stimulator either by pressing the trigger button or by stepping on the foot switch or automatically by a software program. This will subsequently deliver a single TMS pulse through the connected TMS coil placed over the participant&#39;s scalp. Default TMS pulse settings (e.g., 100 &#181;s rise time of the induced current and 800 &#181;s decay time for monophasic stimuli; shorter decay times for biphasic stimuli) are specific to the device (firmware).</li>
	<li>Start with low stimulation intensity (e.g., set the intensity to 45% output using the stimulation intensity controller knob on the stimulator) and watch for MEPs visible on the EMG amplifier.
	<ol>
		<li>If no MEP is visible increase the stimulation intensity in 2-5% steps until an MEP is clearly present (e.g., 0.5-1 mV amplitude). Repeat stimulation by pressing the trigger button or activating the foot switch if pulse delivery is not automated. Inform the participant that stimulation will be slightly stronger and that limb movements, facial twitch and eye-blinks are expected. 
		Note: Establish a minimum interval of 5 sec&#160;between pulses to avoid low-frequency stimulation effects on brain excitability.</li>
	</ol>
	</li>
	<li>Move the coil radially in 1 cm steps around the initially stimulated site to find the spot with the largest MEP response following the application of single TMS pulses. From there, start again moving the coil to secure the &#34;hotspot&#34; (cortical area with maximal MEP amplitude). 
	Note: The use of a head cap (e.g., used for grid markings) for the localization procedure is not recommended since the cap needs to be removed for NEBS electrode placement and the hotspot position may be lost.</li>
	<li>Reduce the stimulation intensity in approximately 2%-steps using the stimulation intensity controller knob on the stimulator (MEP must still be present). This will avoid inaccuracy due to supramaximal stimulation. Reconfirm the hotspot by moving the coil radially in 1 cm steps around the hotspot and checking for MEP size. The hotspot should still correspond to the largest and most consistent MEP amplitude. 
	Note: Ask the participant to voluntarily contract the muscle of interest if the hotspot is difficult to find (e.g., no MEP present at high stimulation intensities). By doing so, the stimulation intensity needed to elicit MEP is decreased and it may be easier to identify relevant cortical stimulation sites. If this method is used, ask the participant to relax the muscle after finding a relevant stimulation site and adjust stimulation intensity so that reliable MEPs can be found when the muscle is at rest. Proceed to find the hotspot.</li>
	<li>Mark the hotspot position and coil orientation with non-permanent skin marker.</li>
	<li>For bilateral M1 stimulation, repeat steps 2.11 to 2.16 for the contralateral limb.</li>
</ol>
3. NEBS Electrode Preparation
<ol>
	<li>Connect cables to rubber electrodes, and place the electrodes inside the sponge bags. Make sure electrode size and sponge bag size do match. Materials are commercially available in standard sizes (e.g., 5x5 cm2, 5x7 cm2).</li>
	<li>Soak sponge bags on both sides with isotonic NaCl solution, but avoid excessive soaking to prevent salt bridges or dripping onto the volunteer.
	<ol>
		<li>This step is optional: To prevent leakage of NaCl solution when using bandages instead of rubber bands, place the electrodes and sponge bags inside non-conductive rubber sponge covers. 
		Note: Alternatively, cover the rubber electrode with conductive paste and place them directly on the participant&#39;s head, i.e., not using sponge bags or rubber sponge covers.</li>
	</ol>
	</li>
</ol>
4. NEBS Electrode Placement (Figure 1)
<ol>
	<li>Find the head marking(s) indicating the motor cortical hotspot and separate the hair around the area.</li>
	<li>To improve conductance clean the skin before electrode placement by gently rubbing the skin area around the head markings with a swab soaked with 40-50% alcohol or skin preparation paste. Do not scratch the skin! Remove excess with a swab and clean area again with isotonic NaCl solution. Dry the area afterwards. 
	Note: Make sure the head marking(s) remain visible; remark if needed.</li>
	<li>Place one electrode following the head marking for the M1 of interest (contralateral to the hand of interest). Bring the sponge as much as possible in direct contact with the skin. Place the electrode cable towards the participant&#39;s back to avoid disturbance during stimulation and/or task execution and to ease connection to the NEBS device. 
	Note: The hair below the electrode should get damp. In case of excessive hair moistening, use paper or hand towels to absorb the excess. 
	Note: For anodal tDCS, the electrode placed on the motor cortical hotspot of interest (increase of excitability is desired) corresponds to the anode, usually connected to the red cable. The cathode (usually connected to a black or blue cable) is placed on the opposite supraorbital area or M1 (see below). Conventionally, electrode placement is the same for tRNS, although in the classical protocol there is no polarity specificity due to the alternating current flow. Specific placement may be important if the stimulation settings include a stimulation offset.</li>
	<li>For unilateral M1 stimulation place the second electrode (for anodal tDCS: the cathode) over the contralateral supra-orbital area (corresponding to electrode Fp2 in the EEG 10/20 international system). Make sure the cable is oriented towards the back of the participant.</li>
	<li>For bilateral M1 stimulation skip step 4.4. Place the second electrode (for anodal tDCS: the cathode) on the opposite M1 following the head marking ipsilateral to the limb used in the study. Make sure the cable is oriented towards the back of the participant.</li>
	<li>Cover the head twice with an elastic bandage circularly in the medio-lateral direction to stabilize the M1 electrode, then use the remaining bandage to cover the head circularly in the anterior-posterior direction to stabilize both electrodes.</li>
	<li>Use an adhesive tape to fix the end of the bandage.</li>
	<li>Secure the cables with an adhesive tape on the participant&#39;s neck or shirt.</li>
	<li>Connect electrode cables to the NEBS device.</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/53367/53367fig2.jpg" /> 
Figure 2.&#160;Materials used for NEBS protocols. Conventional materials used in non-invasive electrical brain stimulation protocols include an NEBS device, electrode cables, conductive rubber electrodes, perforated sponge bags, rubber sponge cover (optional), isotonic NaCl solution and bandages. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53367/53367fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
5. Stimulation
<ol>
	<li>Switch on the NEBS device.</li>
	<li>Adjust NEBS device settings regarding stimulation type (tDCS or tRNS), intensity (e.g., 1 mA, 1.5 mA or 2 mA), duration (e.g., 10-40 min), ramping up and down (time between beginning of stimulation and maximum intensity, typically 8-15 sec), and additional factors related to stimulation type (e.g., frequency spectrum for tRNS). 
	Note: Conventionally, sham stimulation includes ramping up immediately followed by ramping down. Accordingly, the participant has the sensation of the stimulation but the duration of the stimulation is not sufficient to exert lasting effects on brain function. Some NEBS devices include a study mode which allows blinding of participant and investigator by entering a study specific subject code. The code determines stimulation settings automatically. Alternatively, a second experimenter may set the stimulation settings in each session and cover the display from the experimenter conducting the stimulation.</li>
	<li>Inform the participant about potential side effects associated with NEBS. Common adverse effects include skin itching/tingling or burning sensation underneath the electrodes, headache, and discomfort32. Burning sensation may be a sign of poor electrode contact with the skin.</li>
	<li>Start the stimulation. 
	Note: Common stimulation duration lasts approximately 10-20 min&#160;based on reports investigating changes on cortical excitability (see representative results section). Empirically, the maximum stimulation duration was set to 40 min3.</li>
	<li>Check for continuity of stimulation during ramping up and stimulation. If impedance is too high or electrodes are in bad contact with the skin, the stimulation may terminate automatically. 
	Note: In case the impedance is too high or the participant reports increasing discomfort during the stimulation try to decrease impedance by, e.g., better fixating the electrodes at the stimulation sites or adding conductive medium. NaCl solution may be added by using a syringe directly in the sponges after their placement on the head. 
	Note: For safety reasons some devices report the impedance throughout the stimulation. The NEBS device may shut off if impedance reaches a specific threshold (e.g., 55 kOhms).</li>
	<li>If NEBS is co-applied with execution of a motor task, start the testing/training after stimulation is ramped up and the participant is feeling comfortable with stimulation. In case the study does not include a motor task during stimulation, make sure the participant remains seated and awake during the stimulation period, and wait until stimulation is over.</li>
	<li>Check with the participant for side effects of the stimulation, e.g., by handing out a standardized questionnaire32 or directly asking the participant. In case of studies including multiple days of stimulation, take note of any possible side effects between days. 
	Note: For assessment of blinding efficacy, ask the participant after each stimulation session to guess which stimulation type (sham/condition) the participant underwent. If the experimenter is also blinded, the experimenter could also note his guess regarding the participant&#39;s stimulation type. Compare answers with the actual stimulation type to verify rate of correct guesses33.</li>
	<li>Disinfect electrodes and sponges with non-hazardous substances such as 40-50% alcohol. Thoroughly rinse in water afterwards. Let materials dry before storing.</li>
</ol>

The authors have nothing to disclose.

This protocol describes typical materials and procedural steps for modulation of hand motor function and skill learning using NEBS, specifically unilateral and bilateral M1 stimulation for anodal tDCS, and unilateral tRNS. Before choosing a particular NEBS protocol for a human motor system study, e.g., in the context of motor learning, methodological aspects (safety, tolerability, blinding) as well as conceptual aspects (montage or current type specific effects on a particular brain region) need to be taken into account. Advantages and limitations of the three strategies are presented in Table 1.
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td>NEBS type</td>
			<td>Advantage</td>
			<td>Limitation</td>
		</tr>
		<tr>
			<td>Common to anodal tDCS and tRNS</td>
			<td>Safe 
			Cheap 
			Easy to administer 
			Outlasting effect on cortical excitability (up to 90 min) 
			Improvement of motor function and motor skill learning in healthy subjects and patients with motor deficits 
			Functional focality is reached by combination of NEBS with a particular task</td>
			<td>Structural stimulation focality is limited and defined by electrode size and montage 
			Larger electrodes may stimulate cortical areas adjacent to the M1 of interest</td>
		</tr>
		<tr>
			<td>Unilateral M1 stimulation 
			(tDCS)</td>
			<td>Polarity specificity (direction of excitability change in M1 of interest can be chosen)</td>
			<td>Receiving electrode (cathode) is an active electrode and may exert a confounding effect on underlying brain area 
			Difficult participant blinding at higher stimulation intensities (current density &#62; 40 &#181;A/cm2, e.g., &#62; 1 mA / 25 cm2)</td>
		</tr>
		<tr>
			<td>Bilateral M1 stimulation 
			(tDCS)</td>
			<td>Polarity specificity (direction of excitability change in M1 of interest can be chosen) 
			Pronounced modulation of interhemispheric connection in addition to excitability increase of the M1 of interest (desired decreasing effect on the opposite M1)</td>
			<td>Difficult participant blinding at higher stimulation intensities (current density &#62; 40 &#181;A/cm2, e.g., &#62;1 mA / 25 cm2) 
			Higher risk of current shunting due to proximity of the electrodes</td>
		</tr>
		<tr>
			<td>Unilateral M1 stimulation 
			(tRNS)</td>
			<td>Least side effects 
			Improved participant blinding</td>
			<td>No polarity-specificity 
			Effects on excitability and motor behavior are more robust at high frequency spectrum (100-640 Hz)</td>
		</tr>
	</tbody>
</table>
NEBS, non-invasive electrical brain stimulation; M1, primary motor cortex; tDCS, transcranial direct current stimulation; tRNS, transcranial random noise stimulation
Table 1: Advantages and limitations of tDCS and tRNS.
From a methodological point of view subjects should always be screened thoroughly for contraindications for NEBS3,41 using questionnaires or standardized interviews (e.g., Keel et al., 200125). These do not differ between tDCS and tRNS. Absolute NEBS contraindications include: 1) skull deformation, e.g., due to fracture, as it may influence current flow and promote unexpected side effects; 2) Implanted medical device, e.g., cochlear implant and brain stimulator, as NEBS may negatively influence medical device functioning. For the use of TMS (e.g., for motor cortex localization (see protocol step 2)) ferromagnetic objects in the head/neck area, (e.g., shrapnel, surgical clips) also represent an absolute contraindication, as those objects may be dislocated by the magnetic field and pose a risk for the participant. Additional exclusion criteria are optional and depend on the study aims. Common additional contraindications include: 1) age above 85 years old; 2) pregnancy; 3) history of chronic skin disorders (mostly regarding the head); 4) adverse effects to previous brain stimulation protocols; 5) history of frequent or severe headache, e.g., migraine; 6) history of epileptic seizures; and 7) pacemaker. For participants with pacemaker a minimum safety distance of 10 cm should be kept between stimulation site and the pacemaker to prevent interference with its functioning.
Subjects should not be stimulated if any of the absolute contraindications apply. For safety reasons the NEBS device should have maximum output in mA range, should be battery-driven and should not be used while the charger is connected to electrical outlet. When applied per protocol, tDCS and tRNS are usually well tolerated32. Side effects of stimulation may include itching, tingling sensation, and headache outlasting the stimulation duration or triggering migraine attacks. However, from estimated 16.000 tDCS sessions (including multiple sequential sessions) no severe tDCS side effects were reported (Bikson M., personal communication, 2015; meta-analysis in preparation). Side effects can be minimized by careful stimulation electrode preparation and placement. This includes: 1. Skin inspection for lesions, 2. Applying the stimulation via a conductive medium like rubber electrodes covered with conductive paste or with saline soaked sponges, 3. Fading in and out the stimulation (a longer duration of ramping up and ramping down (e.g., 15 sec) is associated with less side effects), and 4. Impedance control. Participants usually habituate to skin sensations underneath the electrodes shortly after ramping up the stimulation. With tRNS in most cases skin sensations are less or not at all perceived compared to tDCS (consequently, similar rates of correct condition guess for sham and tRNS as compared to higher rates of correct condition guess with tDCS)6. This may be advantageous for studies where optimal blinding of participants is crucial. However, in the majority of studies participants were successfully blinded between real and sham tDCS, at least with low to medium stimulation intensities32,42. This is likely due to the implementation of a short ramping up and down for several seconds in the sham mode, which causes the tingling sensation42 but apparently does not alter cortical function2. Using an &#34;active&#34; sham mode that elicits the tingling sensation and automatically turns off stimulation after some seconds may be a superior method for blinding both participant and researcher as compared to simply placing the electrodes on the head of the participant and not starting the NEBS device.
For comparability of publications indicate the current density, electrode size (i.e., target area), electrode placement, conductive substrate between electrode and skin, duration for ramping up and down, stimulation duration and side effects. It should be noted that the declaration of stimulation intensity alone is not sufficient to estimate the current density delivered to the participant. For the calculation of current density divide the stimulation intensity (e.g., 1 mA, 1.5 mA, 2 mA) by the stimulated area. For instance, if stimulation intensity is 1mA and the electrode size is 16 cm2 the estimated current density is 0.0625 mA/cm2 (i.e., 1 mA/16 cm2 or 62.5 &#181;A/cm2).
From a conceptual point of view, several cortical areas of the motor system are accessible by NEBS, either directly if the area is close to the cortical surface or via remote network effects43,44. The primary motor cortex can be located either by TMS-induced MEPs or using the EEG 10/20 international system26. Using the latter technique in a healthy participant is faster and easier as compared to using TMS-induced MEPs, but TMS provides superior accuracy to localize the individual cortical motor representation of interest. While the necessity for or the functional benefit from using a TMS hotspot as compared to the 10/20 system is yet unproven, TMS-induced MEPs demonstrate functional integrity of M1 and the pyramidal tract. For patients with brain lesion (e.g., stroke) TMS-induced MEPs is therefore preferentially used to locate the motor cortical representation as it may be largely shifted due to lesion size and location, and secondary motor areas may generate the motor output.
NEBS electrode size or montage may impact cortical areas adjacent to the region of interest, resulting in limited focality of the stimulation itself45,46. Smaller electrode sizes (emitting electrode in case of tDCS) may limit the widespread and exert more focal effects onto M1, as suggested by modeling studies or software tools; similarly, less distance between electrodes may condense the electrical field46,47. However, the functional focality obtained by task specific activation of particular synapses11 or networks that are augmented by combining task/training with stimulation could be more crucial46: on one hand, functional imaging studies revealed different network changes after unilateral versus bilateral M1 tDCS, or tDCS versus tRNS, respectively14,15. On the other hand, the net effect of anodal tDCS and tRNS on motor behavior, e.g., learning, seems to be similar: Based on the few investigations with direct comparisons of stimulation type/montage, one could argue for positive effects on motor function as long as M1 contralateral to the tested hand is targeted by NEBS (in case of tDCS with anodal stimulation4-6).
Most robust behavioral effects are usually found when stimulation and task execution or training are carried out simultaneously13. Inconsistent results have been reported for NEBS and tasks applied consecutively1. Other electrode montages such as recently developed high-definition tDCS may increase stimulation focality48,49 but require future investigation regarding the behavioral consequences. Controlled studies evaluating tRNS effects on stroke motor rehabilitation and learning, as well as comparative studies of distinct NEBS strategies in patient populations are largely missing. Future studies with NEBS of the human motor system are necessary for a better understanding of promises and pitfalls of NEBS in clinical applications.

Non-invasive electrical brain stimulation (NEBS), the administration of electrical currents to the brain through the intact skull, can modify brain function and behavior1-3. To optimize the therapeutic potential of NEBS strategies understanding the underlying mechanisms leading to neurophysiological and behavioral effects is still needed. Standardization of application across different laboratories and full transparency of stimulation procedures provides the basis for comparability of data which supports reliable interpretation of results and evaluation of the proposed mechanisms of action. Transcranial direct current stimulation (tDCS) or transcranial alternating current stimulation (tACS) differ by parameters of the applied electrical current: tDCS consists of an unidirectional constant current flow between two electrodes (anode and cathode)2-6 while tACS uses an alternating current applied at a specific frequency7. Transcranial random noise stimulation (tRNS) is a special form of tACS that uses an alternating current applied at random frequencies (e.g., 100-640 Hz) resulting in quickly varying stimulation intensities and removing polarity-related effects4,6,7. Polarity is only of relevance if the stimulation setting includes a stimulation offset, e.g., noise spectrum randomly changing around a +1 mA baseline intensity (usually not used). For the purpose of this article, we will focus on work using tDCS and tRNS effects on the motor system, closely following a recent publication from our lab6.
The underlying mechanisms of action of tRNS are even less understood than of tDCS but likely different from the latter. Theoretically, in the conceptual framework of stochastic resonance tRNS introduces stimulation-induced noise to a neuronal system which may provide a signal processing benefit by altering the signal-to-noise ratio4,8,9. TRNS may predominantly amplify weaker signals and could thus optimize task-specific brain activity (endogenous noise9). Anodal tDCS increases cortical excitability indicated by alteration of the spontaneous neuronal firing rate10 or increased motor evoked potential (MEP) amplitudes2 with the effects outlasting the stimulation duration for minutes to hours. Long-lasting increases in synaptic efficacy known as long-term potentiation are thought to contribute to learning and memory. Indeed, anodal tDCS enhances synaptic efficacy of motor cortical synapses repeatedly activated by a weak synaptic input11. In accordance, improved motor function/skill acquisition is often revealed only if stimulation is co-applied with motor training11-13, also suggesting synaptic co-activation as a prerequisite of this activity-dependent process. Nevertheless, causality between increases in cortical excitability (increase in firing rate or MEP amplitude) on one hand and improved synaptic efficacy (LTP or behavioral function such as motor learning) on the other hand has not been demonstrated.
NEBS applied to the primary motor cortex (M1) has attracted increasing interest as safe and effective method to modulate human motor function1. Neurophysiological effects and behavioral outcome may depend on the stimulation strategy (e.g., tDCS polarity or tRNS), electrode size and montage4-6,14,15. Aside from subject-inherent anatomical and physiological factors the electrode montage significantly influences electric field distribution and may result in different patterns of current spreading within the cortex16-18. In addition to the intensity of the applied current the size of the electrodes determines the current density delivered3. Common electrode montages in human motor system studies include (Figure 1): 1) anodal tDCS as unilateral M1 stimulation with the anode positioned on the M1 of interest and the cathode positioned on the contralateral forehead; the basic idea of this approach is upregulation of excitability in the M1 of interest6,13,19-22; 2) anodal tDCS as bilateral M1 stimulation (also referred to as &#34;bihemispheric&#34; or &#34;dual&#34; stimulation) with the anode positioned on the M1 of interest and the cathode positioned on the contralateral M15,6,14,23,24; the basic idea of this approach is maximizing stimulation benefits by upregulation of excitability in the M1 of interest while downregulating excitability in the opposite M1 (i.e., modulation of interhemispheric inhibition between the two M1s); 3) For tRNS, only the above mentioned unilateral M1 stimulation montage has been investigated4,6; with this montage excitability enhancing effects of tRNS have been found for the frequency spectrum of 100-640 Hz4. The choice of brain stimulation strategy and electrode montage represents a critical step for an efficient and reliable use of NEBS in clinical or research settings. Here these three NEBS procedures are described in detail as used in human motor system studies and methodological and conceptual aspects are discussed. Materials for unilateral or bilateral tDCS and unilateral tRNS are the same (Figure 2).
<img alt="Figure 1" src="/files/ftp_upload/53367/53367fig1.jpg" /> 
Figure 1.&#160;Electrode montages and current direction for distinct NEBS strategies.&#160;(A) For unilateral anodal transcranial direct current stimulation (tDCS), the anode is centered over the primary motor cortex of interest and the cathode positioned over the contralateral supra-orbital area. (B) For bilateral motor cortex stimulation, anode and cathode are located each over one motor cortex. The position of the anode determines the motor cortex of interest for anodal tDCS. (C) For unilateral transcranial random noise stimulation (tRNS), one electrode is located over the motor cortex and the other electrode over the contralateral supra-orbital area. The current flow between electrodes is indicated by the black arrow. Anode (+, red), cathode (-, blue), Alternating current (+/-, green). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53367/53367fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="0" cellpadding="0" cellspacing="0" width="888">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">NEBS device (DC Stimulator plus)</td>
			<td style="width:271px;">Neuroconn</td>
			<td style="width:119px;"></td>
			<td style="width:197px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Electrode cables</td>
			<td style="width:271px;">Neuroconn</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Conductive-rubber electrodes</td>
			<td style="width:271px;">Neuroconn</td>
			<td style="width:119px;"></td>
			<td>5x5 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Perforated sponge bags</td>
			<td style="width:271px;">Neuroconn</td>
			<td style="width:119px;"></td>
			<td>5x5 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Non-conductive rubber sponge cover</td>
			<td style="width:271px;">Amrex-Zetron</td>
			<td style="width:119px;">FG-02-A103</td>
			<td>Rubber pad 3&#34;*3&#34;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">NaCl isotonic solution&#160;</td>
			<td style="width:271px;">B. Braun Melsungen AG&#160;</td>
			<td style="width:119px;">A1151</td>
			<td>Ecoflac, 0,9%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Cotton crepe bandage</td>
			<td style="width:271px;">Paul Hartmann AG</td>
			<td style="width:119px;">931004</td>
			<td>8x5m, textile elasticity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Adhesive tape (Leukofix)</td>
			<td style="width:271px;">BSN medical</td>
			<td style="width:119px;">02122-00</td>
			<td>2,5cm*5m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Skin preparation paste</td>
			<td style="width:271px;">Weaver</td>
			<td style="width:119px;">10-30</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Magnetic stimulator</td>
			<td style="width:271px;">Magstim</td>
			<td style="width:119px;">3010-00</td>
			<td>Magstim 200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">EMG conductive paste</td>
			<td style="width:271px;">GE Medical Systems</td>
			<td style="width:119px;">217083</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">EMG bipolar electrodes</td>
			<td>e.g., Natus Medical Inc. Viking 4&#160;</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">EMG amplifier</td>
			<td>e.g., Natus Medical Inc. Viking 4&#160;</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Cable for EMG signal transmission</td>
			<td>e.g., Natus Medical Inc. Viking 4</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:301px;">Data acquisition unit&#160;</td>
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non-invasive electrical brain stimulation montages for modulation of human motor function

Non-invasive electrical brain stimulation (NEBS) is used to modulate brain function and behavior, both for research and clinical purposes. In particular, NEBS can be applied transcranially either as direct current stimulation (tDCS) or alternating current stimulation (tACS). These stimulation types exert time-, dose- and in the case of tDCS polarity-specific effects on motor function and skill learning in healthy subjects. Lately, tDCS has been used to augment the therapy of motor disabilities in patients with stroke or movement disorders. This article provides a step-by-step protocol for targeting the primary motor cortex with tDCS and transcranial random noise stimulation (tRNS), a specific form of tACS using an electrical current applied randomly within a pre-defined frequency range. The setup of two different stimulation montages is explained. In both montages the emitting electrode (the anode for tDCS) is placed on the primary motor cortex of interest. For unilateral motor cortex stimulation the receiving electrode is placed on the contralateral forehead while for bilateral motor cortex stimulation the receiving electrode is placed on the opposite primary motor cortex. The advantages and disadvantages of each montage for the modulation of cortical excitability and motor function including learning are discussed, as well as safety, tolerability and blinding aspects.

To investigate the effects of NEBS on the human motor system it is important to consider appropriate outcome measures. One advantage of the motor system is the accessibility of the cortical representations by electrophysiological tools. Motor evoked potentials are frequently used as an indicator of motor cortical excitability. After application of 9 or more minutes of anodal tDCS at a current density of 29 &#181;A/cm2, motor cortical excitability is increased for at least 30 min&#160;in the majority of healthy volunteers19,21,22 (see also Figure 3). Cathodal tDCS mostly causes the opposite (excitability-decreasing) or no effect19,22. However, as discussed recently22, there is some variability in the response direction, with some subjects showing the opposite direction of effect for anodal and cathodal tDCS. This should be taken into account for sample size calculations in studies using NEBS. Interestingly, comparable changes in M1 excitability were found after unilateral and bilateral tDCS5,23, and simple motor function was similarly improved directly after each stimulation type5. Therefore it is currently under investigation whether additional down-regulation of excitability of the contralateral M1 using the bilateral M1 montage exerts specific benefits to motor behavior (see below). In contrast, resting state fMRI indicated clearly different cortical network changes: bilateral tDCS modulates functional connectivity in the primary and secondary motor and in prefrontal areas, while unilateral tDCS modulates functional connectivity in prefrontal, parietal and cerebellar areas34.
tRNS has just recently developed as a tool to modulate cortical excitability4. Due to the alternating current tRNS is applied without polarity specificity (as long as there is no offset of stimulation intensity). However, efficiency of tRNS seems to depend on the applied noise spectrum, with high frequencies (100-640 Hz) showing more robust effects than low frequencies (&#60;100 Hz)4. When directly compared to unilateral anodal tDCS, a similar but slightly longer lasting increase of M1 excitability (measured by MEP amplitude changes) was found after unilateral tRNS (Figure 3).
<img alt="Figure 3" src="/files/ftp_upload/53367/53367fig3.jpg" /> 
Figure 3.&#160;Time course of motor cortical excitability after different NEBS strategies. The MEP amplitude is shown as a function of time before and after 10 min&#160;of unilateral anodal transcranial direct stimulation (tDCS) or transcranial random noise stimulation (tRNS) applied to the primary motor cortex at a current density of 29 &#181;A/cm2 (1 mA / 35 cm2). Error bars indicate standard error. Note that tRNS exerts similar effects on motor cortical excitability compared to anodal tDCS. MEP amplitude returns to baseline levels after approximately 50 min&#160;for anodal tDCS and after 90 min&#160;for tRNS. From Terney et al. (2008)4 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53367/53367fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Despite the heterogeneity of study designs, a common concept starts to evolve from NEBS trials testing the effects of tDCS and tRNS on motor function: NEBS influences motor performance or skills when simultaneously applied with training/testing. Anodal tDCS and tRNS applied as unilateral M1 stimulation or anodal tDCS applied as bilateral M1 stimulation during training were all shown to improve implicit motor sequence learning4,35-38 on the serial reaction time task39. Similarly, unilateral anodal tDCS applied during motor training was shown to increase rate of learning in an explicit motor learning paradigm40. However, effects of cathodal stimulation on implicit and explicit motor learning seem to be different: while cathodal tDCS during training did not significantly affect sequence learning during implicit motor learning35, it was reported to negatively affect explicit motor learning40. The reasons for this discrepancy need further investigation.
In previous investigations focusing on more complex motor skill learning over multiple days anodal tDCS applied as unilateral M1 stimulation during training significantly enhanced visuomotor skill learning13,20. Skill was determined by changes in movement accuracy as a function of movement speed (i.e., the speed-accuracy-tradeoff). Strikingly, in a direct comparison of electrode montages and stimulation types, both unilateral and bilateral M1 anodal tDCS and unilateral tRNS all enhanced skill learning on a visuomotor word and letter tracing task6 (Figure 4A). With regard to the mechanisms, it is currently unknown whether tDCS and tRNS operate by the same mechanisms of action. However, the time course of skill gains within session clearly differed between tDCS and tRNS: Unilateral tDCS exerted major effects on skill gains immediately after stimulation started. In contrast, bilateral tDCS and tRNS slowly enhanced skill gains during sessions (Figure 4B). This divergence points to temporally specific interactions between the NEBS type and the motor learning process. This should be considered when choosing stimulation types for future investigations of the motor system in healthy subjects as well as patients with neurological disorders.
<img alt="Figure 4" src="/files/ftp_upload/53367/53367fig4.jpg" /> 
Figure 4.&#160;Enhancement of motor skill by training and augmentation by different NEBS strategies.&#160;(A) Changes in motor skill during three days of motor training per stimulation group. Skill increases significantly over time in the sham stimulation control group and is augmented further by each NEBS strategy. (B) Scatter plot of subcomponents of motor learning. All stimulation groups present significantly greater overall motor learning compared to the sham stimulation control group. Only unilateral anodal transcranial direct current stimulation (tDCS) reveals greater immediate effects on motor learning - i.e., initial changes in skill after onset of stimulation, compared to sham control and transcranial random noise stimulation (tRNS). DC:M1-SO = unilateral tDCS. DC:M1-M1 = bilateral tDCS. RN:M1-SO = unilateral tRNS. *p&#60;0.05, **p&#60;0.01. Error bars = standard error of the mean. From Prichard et al. (2014)6 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53367/53367fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function at JoVE.com

Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function

Non-invasive electrical brain stimulation can modulate cortical function and behavior, both for research and clinical purposes. This protocol describes different brain stimulation approaches for modulation of the human motor system.

Non-invasive electrical brain stimulation (NEBS) is used to modulate brain function and behavior, both for research and clinical purposes. In particular, ...

non-invasive-electrical-brain-stimulation-montages-for-modulation

Nanyang Technological University

Research

JoVE Journal

Behavior

13.0K Views.  Albert Ludwigs University Freiburg. Non-invasive electrical brain stimulation can modulate cortical function and behavior, both for research and clinical purposes. This protocol describes different brain stimulation approaches for modulation of the human motor system.

Video: Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function

Simultaneous Scalp Electroencephalography (EEG), Electromyography (EMG), and Whole-body Segmental Inertial Recording for Multi-modal Neural Decoding

Recent studies support the involvement of supraspinal networks in control of bipedal human walking. Part of this evidence encompasses studies, including our previous work, demonstrating that gait kinematics and limb coordination during treadmill walking can be inferred from the scalp electroencephalogram (EEG) with reasonably high decoding accuracies. These results provide impetus for development of non-invasive brain-machine-interface (BMI) systems for use in restoration and/or augmentation of gait- a primary goal of rehabilitation research. To date, studies examining EEG decoding of activity during gait have been limited to treadmill walking in a controlled environment. However, to be practically viable a BMI system must be applicable for use in everyday locomotor tasks such as over ground walking and turning. Here, we present a novel protocol for non-invasive collection of brain activity (EEG), muscle activity (electromyography (EMG)), and whole-body kinematic data (head, torso, and limb trajectories) during both treadmill and over ground walking tasks. By collecting these data in the uncontrolled environment insight can be gained regarding the feasibility of decoding unconstrained gait and surface EMG from scalp EEG.

Simultaneous Scalp Electroencephalography EEG, Electromyography EMG, and Whole-body Segmental Inertial Recording for Multi-modal Neural Decoding

Development of an effective brain-machine-interface (BMI) system for restoration and rehabilitation of bipedal locomotion requires accurate decoding of user's intent. Here we present a novel experimental protocol and data collection technique for simultaneous non-invasive acquisition of neural activity, muscle activity, and whole-body kinematics during various locomotion tasks and conditions.

Recent  studies support the involvement of supraspinal networks in control of bipedal  human walking. Part of this evidence  encompasses studies, ...

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during&#160;viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception.&#160; This article describes how to record motor evoked potentials (MEPs) from the lip muscles and how to disrupt the motor lip representation using repetitive TMS.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. ...

Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived &#8220;virtual lesion.&#8221; Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading.

Transcranial magnetic stimulation (TMS) is a technique for non-invasively disrupting neural information processing and measuring its effect on behavior. When TMS interferes with a task, it indicates that the stimulated brain region is necessary for normal task performance, allowing one to systematically relate brain regions to cognitive functions.

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily ...

Multifunctional Setup for Studying Human Motor Control Using Transcranial Magnetic Stimulation, Electromyography, Motion Capture, and Virtual Reality

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular function include transcranial magnetic stimulation, electromyography, and three-dimensional motion capture. The advent of readily available and cost-effective virtual reality solutions has expanded the capabilities of researchers in recreating &#8220;real-world&#8221; environments and movements in a laboratory setting. Naturalistic movement analysis will not only garner a greater understanding of motor control in healthy individuals, but also permit the design of experiments and rehabilitation strategies that target specific motor impairments (e.g. stroke). The combined use of these tools will lead to increasingly deeper understanding of neural mechanisms of motor control. A key requirement when combining these data acquisition systems is fine temporal correspondence between the various data streams. This protocol describes a multifunctional system&#8217;s overall connectivity, intersystem signaling, and the temporal synchronization of recorded data. Synchronization of the component systems is primarily accomplished through the use of a customizable circuit, readily made with off the shelf components and minimal electronics assembly skills.

Transcranial magnetic stimulation, electromyography, and 3D motion capture are commonly used non-invasive techniques for investigating neuromuscular function in humans. In this paper, we describe a protocol that synchronously samples data generated by all three of these tools along with the unique addition of virtual reality stimulus presentation and feedback.

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular ...

A Novel Experimental and Analytical Approach to the Multimodal Neural Decoding of Intent During Social Interaction in Freely-behaving Human Infants

Understanding typical and atypical development remains one of the fundamental questions in developmental human neuroscience. Traditionally, experimental paradigms and analysis tools have been limited to constrained laboratory tasks and contexts due to technical limitations imposed by the available set of measuring and analysis techniques and the age of the subjects. These limitations severely limit the study of developmental neural dynamics and associated neural networks engaged in cognition, perception and action in infants performing &#8220;in action and in context&#8221;. This protocol presents a novel approach to study infants and young children as they freely organize their own behavior, and its consequences in a complex, partly unpredictable and highly dynamic environment. The proposed methodology integrates synchronized high-density active scalp electroencephalography (EEG), inertial measurement units (IMUs), video recording and behavioral analysis to capture brain activity and movement non-invasively in freely-behaving infants. This setup allows for the study of neural network dynamics in the developing brain, in action and context, as these networks are recruited during goal-oriented, exploration and social interaction tasks.

This protocol presents a novel methodology for the neural decoding of intent from freely-behaving infants during unscripted social interaction with an actor. Neural activity is acquired using non-invasive high-density active scalp electroencephalography (EEG). Kinematic data is collected with inertial measurement units and supplemented with synchronized video recording.

Understanding typical and atypical development remains one of the fundamental questions in developmental human neuroscience. Traditionally, experimental ...

Conscious and Non-conscious Representations of Emotional Faces in Asperger's Syndrome

Several neuroimaging studies have suggested that the low spatial frequency content in an emotional face mainly activates the amygdala, pulvinar, and superior colliculus especially with fearful faces1-3. These regions constitute the limbic structure in non-conscious perception of emotions and modulate cortical activity either directly or indirectly2. In contrast, the conscious representation of emotions is more pronounced in the anterior cingulate, prefrontal cortex, and somatosensory cortex for directing voluntary attention to details in faces3,4. Asperger&#39;s syndrome (AS)5,6 represents an atypical mental disturbance that affects sensory, affective and communicative abilities, without interfering with normal linguistic skills and intellectual ability. Several studies have found that functional deficits in the neural circuitry important for facial emotion recognition can partly explain social communication failure in patients with AS7-9. In order to clarify the interplay between conscious and non-conscious representations of emotional faces in AS, an EEG experimental protocol is designed with two tasks involving emotionality evaluation of either photograph or line-drawing faces. A pilot study is introduced for selecting face stimuli that minimize the differences in reaction times and scores assigned to facial emotions between the pretested patients with AS and IQ/gender-matched healthy controls. Information from the pretested patients was used to develop the scoring system used for the emotionality evaluation. Research into facial emotions and visual stimuli with different spatial frequency contents has reached discrepant findings depending on the demographic characteristics of participants and task demands2. The experimental protocol is intended to clarify deficits in patients with AS in processing emotional faces when compared with healthy controls by controlling for factors unrelated to recognition of facial emotions, such as task difficulty, IQ and gender.

An EEG experimental protocol is designed to clarify the interplay between conscious and non-conscious representations of emotional faces in patients with Asperger&#39;s syndrome. The technique suggests that patients with Asperger&#39;s syndrome have deficits in non-conscious representation of emotional faces, but have comparable performance in conscious representation with healthy controls.

Several neuroimaging studies have suggested that the low spatial frequency content in an emotional face mainly activates the amygdala, pulvinar, and ...

Using a Split-belt Treadmill to Evaluate Generalization of Human Locomotor Adaptation

Understanding the mechanisms underlying locomotor learning helps researchers and clinicians optimize gait retraining as part of motor rehabilitation. However, studying human locomotor learning can be challenging. During infancy and childhood, the neuromuscular system is quite immature, and it is unlikely that locomotor learning during early stages of development is governed by the same mechanisms as in adulthood. By the time humans reach maturity, they are so proficient at walking that it is difficult to come up with a sufficiently novel task to study de novo locomotor learning. The split-belt treadmill, which has two belts that can drive each leg at a different speed, enables the study of both short- (i.e., immediate) and long-term (i.e., over minutes-days; a form of motor learning) gait modifications in response to a novel change in the walking environment. Individuals can easily be screened for previous exposure to the split-belt treadmill, thus ensuring that all experimental participants have no (or equivalent) prior experience. This paper describes a typical split-belt treadmill adaptation protocol that incorporates testing methods to quantify locomotor learning and generalization of this learning to other walking contexts. A discussion of important considerations for designing split-belt treadmill experiments follows, including factors like treadmill belt speeds, rest breaks, and distractors. Additionally, potential but understudied confounding variables (e.g., arm movements, prior experience) are considered in the discussion.

We describe a protocol for investigating human locomotor adaptation using the split-belt treadmill, which has two belts that can drive each leg at a different speed. We specifically focus on a paradigm designed to test the generalization of adapted locomotor patterns to different walking contexts (e.g., gait speeds, walking environments).

Understanding the mechanisms underlying locomotor learning helps researchers and clinicians optimize gait retraining as part of motor rehabilitation. ...

Paradigms of Lower Extremity Electrical Stimulation Training After Spinal Cord Injury

Skeletal muscle atrophy, increased adiposity and reduced physical activity are key changes observed after spinal cord injury (SCI) and are associated with numerous cardiometabolic health consequences. These changes are likely to increase the risk of developing chronic secondary conditions and impact the quality of life in persons with SCI. Surface neuromuscular electrical stimulation evoked resistance training (NMES-RT) was developed as a strategy to attenuate the process of skeletal muscle atrophy, decrease ectopic adiposity, improve insulin sensitivity and enhance mitochondrial capacity. However, NMES-RT is limited to only a single muscle group. Involving multiple muscle groups of the lower extremities may maximize the health benefits of training. Functional electrical stimulation-lower extremity cycling (FES-LEC) allows for the activation of 6 muscle groups, which is likely to evoke greater metabolic and cardiovascular adaptation. Appropriate knowledge of the stimulation parameters is key to maximizing the outcomes of electrical stimulation training in persons with SCI. Adopting strategies for long-term use of NMES-RT and FES-LEC during rehabilitation may maintain the integrity of the musculoskeletal system, a pre-requisite for clinical trials aiming to restore walking after injury. The current manuscript presents a combined protocol using NMES-RT prior to FES-LEC. We hypothesize that muscles conditioned for 12 weeks prior to cycling will be capable of generating greater power, cycle against higher resistance and result in greater adaptation in persons with SCI.

Spinal cord injury is a traumatic medical condition that may result in elevated risks of chronic secondary metabolic disorders. Here, we presented a protocol using surface neuromuscular electrical stimulation-resistance training in conjunction with functional electrical stimulation-lower extremities cycling as a strategy to ameliorate several of these medical problems.

Skeletal muscle atrophy, increased adiposity and reduced physical activity are key changes observed after spinal cord injury (SCI) and are associated with ...

A Simple Non-invasive Method for Temporary Knockdown of Upper Limb Proprioception

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are needed for clinical diagnosis of impairment, and to measure outcomes of proprioceptive training. The purpose of this simple, non-invasive method is to temporarily knockdown upper limb proprioception in healthy adults, to an extent that would be useful in the development and testing of upper limb proprioception measures. Knockdown models have two main advantages over studying humans with impaired proprioception: participant availability and the ability to control the extent of impairment across participants. Current published methods of temporary proprioception knockdown of the upper limb, such as ischemic nerve blocks and cryotherapy, are invasive, impractical, or uncomfortable for the participant. Here, vibration over the ulnar groove was used to reduce upper limb proprioception. High frequency vibration may reduce proprioceptive acuity by inhibiting pacinian corpuscle-induced input. The effect of vibration used in this protocol was confirmed using two quantitative measures. This method was simple to administer, comfortable for participants, and practical.

The goal of this protocol is to demonstrate a practical method to temporarily interfere with proprioception in the upper limb of healthy humans.

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are ...

An Automated T-maze Based Apparatus and Protocol for Analyzing Delay- and Effort-based Decision Making in  Free Moving Rodents

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper understanding of the neurobiological causes underlying the decision-making problems. A cost-benefit based T-maze task is used for measuring decision making in which rodents choose between a high reward arm (HRA) and a low reward arm (LRA). There are two paradigms of the T-maze decision-making task, one in which the cost is a time delay and the other in which it is physical effort. Both paradigms require a tedious and labor-intensive management of experimental animals, multiple doors, pellet reward, and arm choice recordings. In the current work, we invented an apparatus based on traditional T-maze with full automation for pellet delivery, door management and choice recordings. This automated setup can be used for the evaluation of both delay- and effort-based decision making in rodents. With the protocol described here, our lab investigated the decision-making phenotypes of multiple genetically modified mice. In the representative data, we showed that the mice with ablated medial habenular showed aversions of both delay and effort and tended to choose the immediate and effortless reward. This protocol helps to decrease the variability caused by experimenter intervention and to enhance experiment efficiency. In addition, chronic silicon probe or microelectrode recording, fiber-optic imaging and/or manipulation of neural activity can be easily applied during the decision-making task using the setup described here.

This article introduces an automated T-maze apparatus that we invented, and a protocol based on this apparatus for analyzing delay-based decision making and effort-based decision making in free moving rodents.

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper ...