Name: a pilot study on the repetitive transcranial magnetic stimulation of a&#946; and tau levels in rhesus monkey cerebrospinal fluid
Uploaded: 2021-09-03T15:00:00
Description: Watch this Scientific Journal Video about A Pilot Study on the Repetitive Transcranial Magnetic Stimulation of AÎ² and Tau Levels in Rhesus Monkey Cerebrospinal Fluid at JoVE.com

The authors would like to thank Sichuan Green-House Biotech Co., Ltd for providing the monkey chair and other relative devices. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

All the experiments were performed under the Guidance for the Care and Use of Laboratory Animals, formulated by the Ministry of Science and Technology of the People&#39;s Republic of China, as well as the principles of the Basel Declaration. Approval was given by the Animal Care Committee of the Sichuan University West China Hospital (Chengdu, China). Figure 1 shows the single-blind, self-controlled study design used here.
1. rTMS devices
<ol>
	<li>Use an 8-shap...

<ol>
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A&#946;1-42, a well-established biomarker of AD, is a CSF core biomarker related to A&#946; metabolism and amyloid plaque formation in the brain and has been widely used in clinical trials and the clinic26. Recent studies have shown that the CSF A&#946;42/A&#946;40 ratio is a better diagnostic biomarker of AD than A&#946;42 alone because it is a better indicator of the AD-type pathology27,28. Tau...

Amyloid-&#946; (A&#946;) and tau are important CSF biomarkers. A&#946; consists of 42 amino acids (A&#946;1-42), which is the product of transmembrane amyloid precursor protein (APP) hydrolyzed by &#946;- and &#947;-secretases1. A&#946;1-42 may aggregate into extracellular amyloid plaques in the brain because of its solubility characteristics1,2. Tau is a microtubule-associated protein that is mainly present in axons and is involved in anterograde axonal transport3. Abnormal tau hyperphosphorylation is mainly induced by the imbalance between kinases and phosphatases, resulting in the detachment of tau from microtubules and the formation of neurofibrillary tangles (NFT)1. The concentration of tau increases in the CSF because tau and phosphorylated tau proteins (pTau) are released into the extracellular space during the neurodegenerative process. Previous studies have shown that CSF biomarkers are relevant to the three main pathological changes of the Alzheimer&#39;s disease (AD) brain: extracellular amyloid plaques, intracellular NFT formation, and neuron loss4. Abnormal concentrations of A&#946; and tau present in the early stage of AD, thus allowing early AD diagnosis5,6.
In 2016, Tsai et al. found that non-invasive light-flickering (40 Hz) reduced the levels of A&#946;1-40 and A&#946;1-42 in the visual cortex of pre-depositing mice7. Recently, they further reported that auditory tone stimulation (40 Hz) improved recognition and spatial memory, reduced amyloid protein levels in the hippocampus and auditory cortex (AC) of 5XFAD mice, and decreased pTau concentrations in the P301S tauopathy model8. These results indicate that non-invasive techniques could impact A&#946; and tau metabolism.
As a non-invasive tool, transcranial magnetic stimulation (TMS) could electrically stimulate neural tissue, including the spinal cord, peripheral nerves, and cerebral cortex9. Moreover, it can modify the excitability of the cerebral cortex at the stimulated site and in the functional connections. Therefore, TMS has been used in the treatment of neurodegenerative disorders and prognostic and diagnostic tests. The most common form of clinical intervention in TMS, rTMS, can induce cortex activation, modify the excitability of the cortex, and regulate cognitive/motor function.
It was reported that 20 Hz rTMS had an in vitro neuroprotective effect against oxidative stressors, including glutamate and A&#946; and improved the overall viability of monoclonal hippocampal HT22 cells in mice10. After 1 Hz rTMS stimulation, the &#946;-site APP-cleaving enzyme 1, APP, and its C-terminal fragments in the hippocampus were considerably reduced. Notably, the impairment of long-term potentiation, spatial learning, and memory in hippocampal CA1 was reversed11,12. Bai et al. investigated the effect of rTMS on the A&#946;-induced gamma oscillation dysfunction during a working memory test. They concluded that rTMS could reverse A&#946;-induced dysfunction, resulting in potential benefits for working memory13. However, there are few reports on the effects of rTMS on tau metabolism and the dynamic changes in A&#946; and tau in CSF before and after rTMS. This protocol describes the procedure for investigating the effects of rTMS at different frequencies (low frequency, 1 Hz; high frequencies,20 Hz, and 40 Hz) on A&#946; and tau levels in rhesus monkey CSF.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anesthesia Puncture Kit for Single Use</td>
			<td>Weigao, Shandong, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CCY-I magnetic field stimulator</td>
			<td>YIRUIDE MEDICAL, Wuhan, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>GraphPad Prism version 7.0</td>
			<td>GraphPad Software, Inc., San Diego, CA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Human Amyloid Beta and Tau Magnetic Bead Panel</td>
			<td>EMD Millipore Corporation, Billerica, MA 01821 USA</td>
			<td></td>
			<td>liquid chip detection</td>
		</tr>
		<tr>
			<td>MILLIPLEX Analyst 5.1</td>
			<td>EMD Millipore Corporation, Billerica, MA 01821 USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Monkey Chair HH-E-1</td>
			<td>Brainsight, Cambridge, MA 02140 USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zoletil 50</td>
			<td>Virbac, France</td>
			<td></td>
			<td>zolazepam&#8211;tiletamine</td>
		</tr>
	</tbody>
</table>

a pilot study on the repetitive transcranial magnetic stimulation of a&#946; and tau levels in rhesus monkey cerebrospinal fluid

Previous studies have demonstrated that a non-invasive light-flickering regime and auditory tone stimulation could affect A&#946; and tau metabolism in the brain. As a non-invasive technique, repetitive transcranial magnetic stimulation (rTMS) has been applied for the treatment of neurodegenerative disorders. This study explored the effects of rTMS on A&#946; and tau levels in rhesus monkey cerebrospinal fluid (CSF). This is a single-blind, self-controlled study. Three different frequencies (low frequency, 1 Hz; high frequencies, 20 Hz and 40 Hz) of rTMS were used to stimulate the bilateral-dorsolateral prefrontal cortex (DLPFC) of the rhesus monkey. A catheterization method was used to collect CSF. All samples were subjected to liquid chip detection to analyze CSF biomarkers (A&#946;42, A&#946;42/A&#946;40, tTau, pTau). CSF biomarker levels changed with time after stimulation by rTMS. After stimulation, the A&#946;42 level in CSF showed an upward trend at all frequencies (1 Hz, 20 Hz, and 40 Hz), with more significant differences for the high-frequencies (p &lt; 0.05) than for the low frequency. 
After high-frequency rTMS, the total Tau (tTau) level of CSF immediately increased at the post-rTMS timepoint (p &lt; 0.05) and gradually decreased by 24 h. Moreover, the results showed that the level of phosphorylated Tau (pTau) increased immediately after 40 Hz rTMS (p &lt; 0.05). The ratio of A&#946;42/A&#946;40 showed an upward trend at 1 Hz and 20 Hz (p &lt; 0.05). There was no significant difference in the tau levels with low-frequency (1 Hz) stimulation. Thus, high-frequencies (20 Hz and 40 Hz) of rTMS may have positive effects on A&#946; and tau levels in rhesus monkey CSF, while low-frequency (1 Hz) rTMS can only affect A&#946; levels.

The results showed that rTMS could affect the A&#946; and tau levels in rhesus monkey CSF. CSF biomarker levels changed with time after rTMS stimulation at different frequencies (1 Hz, 20 Hz, and 40 Hz).
A&#946;42 and A&#946;42/A&#946;40 
As shown in Figure 4A, after 1 Hz rTMS stimulation, the A&#946;42 levels gradu...

Watch this Scientific Journal Video about A Pilot Study on the Repetitive Transcranial Magnetic Stimulation of AÎ² and Tau Levels in Rhesus Monkey Cerebrospinal Fluid at JoVE.com

A Pilot Study on the Repetitive Transcranial Magnetic Stimulation of A&#946; and Tau Levels in Rhesus Monkey Cerebrospinal Fluid

Here, we describe the procedure for a pilot study to explore the effect of repetitive transcranial magnetic stimulation with different frequencies (1 Hz/20 Hz/40 Hz) on A&#946; and tau metabolism in rhesus monkey cerebrospinal fluid.

Previous studies have demonstrated that a non-invasive light-flickering regime and auditory tone stimulation could affect A&#946; and tau metabolism in ...

This protocol uses serial cisterna magna CSF sampling method to explore the effects of rTMS on alpha-beta and tau levels in rhesus monkey. This technique uses a novel CSF sampling method allowing for repeated CSF sampling under fully awake conditions with low risks of adverse events. Demonstrating the procedure will be Ying-Qian Zhang, a research assistant from the Department of Physiology at Southwest Medical University, and Hui-Xin Tan, a graduate student from Sichuan University.After administering analgesia and confirming successful anesthetization, place the five-year-old male rhesus monkey on the operating table in the lateral decubitus position and disinfect the area around the lower back. Hunch its back and bring its knees toward the chest. Insert a spinal needle between the lumbar vertebrae L4 to L5 and push it in until there is a pop indicating entry into the lumbar cistern where the ligamentum flavum is housed.Continue to push the needle further until there is a second pop indicating entry into the dura mater, then withdraw the stylet from the spinal needle and collect drops of CSF. Next, perform catheter insertion under fluoroscopic guidance by inserting the epidural catheter through the puncture needle into the subarachnoid space until it is buoyant in the cisterna magna. Then for port implantation, make a five centimeter incision from the puncture site toward the head and isolate the skin from the subcutaneous tissue to place the sampling port.Connect the port to the end of the epidural catheter, implant the port under the skin and suture the incision. For CSF collection, use the cage bars to restrain the monkey and keep its back bent. Then wipe with an alcohol swab and insert the syringe into the center of the sampling port to extract CSF from the cisterna magna through the catheter.Discard the first 200 microliters of CSF, then collect one milliliter of CSF for analysis. Fix the monkey on the monkey chair before the experiment to avoid interruption during the rTMS intervention, then collect CSF for biomarker analysis when the monkey is awake to avoid the influence of anesthetic drugs. On the third day after the subarachnoid catheterization and two weeks before the start of the experiment, subject the monkey to adaptive training with the monkey chair twice a day for 30 minutes each time.Conduct the rTMS adaptive training or sham stimulation one week after the adaptive training with the monkey chair and one week before the start of the formal experiment to avoid hindering the progress of the experiment by vibrations and sounds during the stimulation process. For sham stimulation, use a sham coil that produces vibration and sound but does not generate a magnetic field. After stimulation, offer food to the monkey to help it adapt to the process.Localize the bilateral dorsolateral prefrontal cortex according to the international 10 to 20 system and conduct three different sessions of rTMS using three different frequencies without a washout period exceeding 24 hours. Perform the first, second, and third sessions twice a day for three consecutive days. To analyze the four CSF biomarkers, use a minimally invasive catheterization method to collect the CSF.Collect CSF at five time points with four samples at each time point at three-minute intervals. After collecting a total of 60 samples for three frequencies, number and store them in a minus 80 degree Celsius refrigerator for up to one month. After the experiment, subject all samples to liquid chip detection according to the manufacturer's instructions.After one hertz rTMS stimulation, Abeta42 levels gradually increased over 24 hours. Similarly with rTMS at 20 hertz, the Abeta42 levels increased with time and reached a peak at six hours after stimulation. In contrast, after 40 hertz stimulation, Abeta42 levels significantly increased immediately at the post-rTMS time point, then decreased slowly.The ratio of Abeta42 to Abeta40 showed an upward trend after stimulation with one and 20 hertz rTMS and significantly increased two hours after stimulation. However, there was no significant difference in the ratio at 40 hertz. The tTau levels in CSF immediately increased after 20 and 40 hertz rTMS stimulation and decreased gradually.However, there was no significant difference after one hertz stimulation. The pTau level immediately increased after 40 hertz stimulation and decreased to below baseline level after 24 hours. In contrast, for the one and 20 hertz stimulation, the pTau level showed a downward trend.Researchers requiring multiple samples of monkey CSF can consider this serial cisterna magna CSF sampling method.

a-pilot-study-on-repetitive-transcranial-magnetic-stimulation-tau

Research

JoVE Journal

Neuroscience

A Novel Approach for Documenting Phosphenes Induced by Transcranial Magnetic Stimulation

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical stimulation of the occipital cortex, but also by non-invasive Transcranial Magnetic Stimulation (TMS)1 of the same cortical regions. The intensity at which a phosphene is induced (phosphene threshold) is a well established measure of visual cortical excitability and is used to study cortico-cortical interactions, functional organization 2, susceptibility to pathology 3,4 and visual processing 5-7. Phosphenes are typically defined by three characteristics: they are observed in the visual hemifield contralateral to stimulation; they are induced when the subject s eyes are open or closed, and their spatial location changes with the direction of gaze 2. Various methods have been used to document phosphenes, but a standardized methodology is lacking. We demonstrate a reliable procedure to obtain phosphene threshold values and introduce a novel system for the documentation and analysis of phosphenes. We developed the Laser Tracking and Painting system (LTaP), a low cost, easily built and operated system that records the location and size of perceived phosphenes in real-time. The LTaP system provides a stable and customizable environment for quantification and analysis of phosphenes.

Phosphenes are transient percepts of light that can be induced by applying Transcranial Magnetic Stimulation (TMS) to visually sensitive regions of cortex. We demonstrate a standard protocol for determining the phosphene threshold value and introduce a novel method for quantifying and analyzing perceived phosphenes.

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical ...

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

State-Dependency Effects on TMS:  A Look at Motive Phosphene Behavior

Transcranial magnetic stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.1,2 Within the field of TMS, the term state dependency refers to the initial, baseline condition of the particular neural region targeted for stimulation. As can be inferred, the effects of TMS can (and do) vary according to this primary susceptibility and responsiveness of the targeted cortical area.3,4,5

In this experiment, we will examine this concept of state dependency through the elicitation and subjective experience of motive phosphenes. Phosphenes are visually perceived flashes of small lights triggered by electromagnetic pulses to the visual cortex. These small lights can assume varied characteristics depending upon which type of visual cortex is being stimulated. In this particular study, we will be targeting motive phosphenes as elicited through the stimulation of V1/V2 and the V5/MT+ complex visual regions.6

In this article, we examine the effects of visually relevant state dependency on TMS induced motive phosphenic presentations.

Transcranial magnetic stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate ...

The Use of Magnetic Resonance Spectroscopy as a Tool for the Measurement of Bi-hemispheric Transcranial Electric Stimulation Effects on Primary Motor Cortex Metabolism

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of neurological and psychiatric disorders such as stroke and depression. Yet, the mechanisms underlying its ability to modulate brain excitability to improve clinical symptoms remains poorly understood 33. To help improve this understanding, proton magnetic resonance spectroscopy (1H-MRS) can be used as it allows the in vivo quantification of brain metabolites such as &#947;-aminobutyric acid (GABA) and glutamate in a region-specific manner 41. In fact, a recent study demonstrated that 1H-MRS is indeed a powerful means to better understand the effects of tDCS on neurotransmitter concentration 34. This article aims to describe the complete protocol for combining tDCS (NeuroConn MR compatible stimulator) with 1H-MRS at 3 T using a MEGA-PRESS sequence. We will describe the impact of a protocol that has shown great promise for the treatment of motor dysfunctions after stroke, which consists of bilateral stimulation of primary motor cortices 27,30,31. Methodological factors to consider and possible modifications to the protocol are also discussed.

This article aims to describe a basic protocol for combining transcranial direct current stimulation (tDCS) with proton magnetic resonance spectroscopy (1H-MRS) measurements to investigate the effects of bilateral stimulation on primary motor cortex metabolism.

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of ...

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals. Here we show a unique approach to investigate online physiological frequency-specific effects of tACS of the primary motor cortex (M1) by using single pulse Transcranial Magnetic Stimulation (TMS) to probe cortical excitability changes. In our setup, the TMS coil is placed over the tACS electrode while Motor Evoked Potentials (MEPs) are collected to test the effects of the ongoing M1-tACS. So far, this approach has mainly been used to study the visual and motor systems. However, the current tACS-TMS setup can pave the way for future investigations of cognitive functions. Therefore, we provide a step-by-step manual and video guidelines for the procedure.

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific ...

Sample Preparation for Endopeptidomic Analysis in Human Cerebrospinal Fluid

This protocol describes a method developed to identify endogenous peptides in human cerebrospinal fluid (CSF). For this purpose, a previously developed method based on molecular weight cut-off (MWCO) filtration and mass spectrometric analysis was combined with an offline high-pH reverse phase HPLC pre-fractionation step.
Secretion into CSF is the main pathway for removal of molecules shed by cells of the central nervous system. Thus, many processes in the central nervous system are reflected in the CSF, rendering it a valuable diagnostic fluid. CSF has a complex composition, containing proteins that span a concentration range of 8 - 9 orders of magnitude. Besides proteins, previous studies have also demonstrated the presence of a large number of endogenous peptides. While less extensively studied than proteins, these may also hold potential interest as biomarkers.
Endogenous peptides were separated from the CSF protein content through MWCO filtration. By removing a majority of the protein content from the sample, it is possible to increase the sample volume studied and thereby also the total amount of the endogenous peptides. The complexity of the filtrated peptide mixture was addressed by including a reverse phase (RP) HPLC pre-fractionation step at alkaline pH prior to LC-MS analysis. The fractionation was combined with a simple concatenation scheme where 60 fractions were pooled into 12, analysis time consumption could thereby be reduced while still largely avoiding co-elution.
Automated peptide identification was performed by using three different peptide/protein identification software programs and subsequently combining the results. The different programs were complementary rather than comparable with less than 15% of the identifications overlapped between the three.

A method for mass spectrometric analysis of endogenous peptides in human cerebrospinal fluid (CSF) is presented. By employing molecular weight cut-off filtration, chromatographic pre-fractionation, mass spectrometric analysis and a subsequent combination of peptide identification strategies, it was possible to expand the known CSF peptidome nearly ten-fold compared to previous studies.

This protocol describes a method developed to identify endogenous peptides in human cerebrospinal fluid (CSF). For this purpose, a previously developed ...

Online Transcranial Magnetic Stimulation Protocol for Measuring Cortical Physiology Associated with Response Inhibition

We describe the development of a reproducible, child-friendly motor response inhibition task suitable for online Transcranial Magnetic Stimulation (TMS) characterization of primary motor cortex (M1) excitability and inhibition. Motor response inhibition prevents unwanted actions and is abnormal in several neuropsychiatric conditions. TMS is a non-invasive technology that can quantify M1 excitability and inhibition using single- and paired-pulse protocols and can be precisely timed to study cortical physiology with high temporal resolution. We modified the original Slater-Hammel (S-H) stop signal task to create a &#34;racecar&#34; version with TMS pulses time-locked to intra-trial events. This task is self-paced, with each trial initiating after a button push to move the racecar towards the 800 ms target. GO trials require a finger-lift to stop the racecar just before this target. Interspersed randomly are STOP trials (25%) during which the dynamically adjusted stop signal prompts subjects to prevent finger-lift. For GO trials, TMS pulses were delivered at 650 ms after trial onset; whereas, for STOP trials, the TMS pulses occurred 150 ms after the stop signal. The timings of the TMS pulses were decided based on electroencephalography (EEG) studies showing event-related changes in these time ranges during stop signal tasks. This task was studied in 3 blocks at two study sites (n=38) and we recorded behavioral performance and event-related motor-evoked potentials (MEP). Regression modelling was used to analyze MEP amplitudes using age as a covariate with multiple independent variables (sex, study site, block, TMS pulse condition [single- vs. paired-pulse], trial condition [GO, successful STOP, failed STOP]). The analysis showed that TMS pulse condition (p&#60;0.0001) and its interaction with trial condition (p=0.009) were significant. Future applications for this online S-H/TMS paradigm include the addition of simultaneous EEG acquisition to measure TMS-evoked EEG potentials. A potential limitation is that in children, the TMS pulse sound could&#160;affect behavioral task performance.

We describe an experimental procedure to quantify excitability and inhibition of primary motor cortex during a motor response inhibition task by using Transcranial Magnetic Stimulation throughout the course of a Stop Signal Task.

We describe the development of a reproducible, child-friendly motor response inhibition task suitable for online Transcranial Magnetic Stimulation (TMS) ...

Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic field pulses. The initiation of cortical activation or its modulation depends on the background activation of the neurons of the cortical region activated, the characteristics of the coil, its position and its orientation with respect to the head. TMS combined with simultaneous electrocephalography (EEG) and neuronavigation (nTMS-EEG) allows for the assessment of cortico-cortical excitability and connectivity in almost all cortical areas in a reproducible manner. This advance makes nTMS-EEG a powerful tool that can accurately assess brain dynamics and neurophysiology in test-retest paradigms that are required for clinical trials. Limitations of this method include artifacts that cover the initial brain reactivity to stimulation. Thus, the process of removing artifacts may also extract valuable information. Moreover, the optimal parameters for dorsolateral prefrontal (DLPFC) stimulation are not fully known and current protocols utilize variations from the motor cortex (M1) stimulation paradigms. However, evolving nTMS-EEG designs hope to address these issues. The protocol presented here introduces some standard practices for assessing neurophysiological functioning from stimulation to the DLPFC that can be applied in patients with treatment resistant psychiatric disorders that receive treatment such as transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), magnetic seizure therapy (MST) or electroconvulsive therapy (ECT).

The protocol presented here is for TMS-EEG studies utilizing intracortical excitability test-retest design paradigms. The intent of the protocol is to produce reliable and reproducible cortical excitability measures for assessing neurophysiological functioning related to therapeutic interventions in the treatment of neuropsychiatric diseases such as major depression.

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic ...

Bilateral Assessment of the Corticospinal Pathways of the Ankle Muscles Using Navigated Transcranial Magnetic Stimulation

Distal leg muscles receive neural input from motor cortical areas via the corticospinal tract, which is one of the main motor descending pathway in humans and can be assessed using transcranial magnetic stimulation (TMS). Given the role of distal leg muscles in upright postural and dynamic tasks, such as walking, a growing research interest in the assessment and modulation of the corticospinal tracts relative to the function of these muscles has emerged in the last decade. However, methodological parameters used in previous work have varied across studies making the interpretation of results from cross-sectional and longitudinal studies less robust. Therefore, use of a standardized TMS protocol specific to the assessment of leg muscles&#39; corticomotor response (CMR) will allow for direct comparison of results across studies and cohorts. The objective of this paper is to present a protocol that provides the flexibility to simultaneously assess the bilateral CMR of two main ankle antagonistic muscles, the tibialis anterior and soleus, using single pulse TMS with a neuronavigation system. The present protocol is applicable while the examined muscle is either fully relaxed or isometrically contracted at a defined percentage of maximum isometric voluntary contraction. Using each subject&#39;s structural MRI with the neuronavigation system ensures accurate and precise positioning of the coil over the leg cortical representations during assessment. Given the inconsistency in CMR derived measures, this protocol also describes a standardized calculation of these measures using automated algorithms. Though this protocol is not conducted during upright postural or dynamic tasks, it&#160;can be used to assess bilaterally any pair of leg muscles, either antagonistic or synergistic, in both neurologically intact and impaired subjects.

The present protocol describes the simultaneous, bilateral assessment of the corticomotor response of the tibialis anterior and soleus during rest and tonic voluntary activation using a single pulse transcranial magnetic stimulation and neuronavigation system.

Distal leg muscles receive neural input from motor cortical areas via the corticospinal tract, which is one of the main motor descending pathway in humans ...

In Vivo Imaging of Cerebrospinal Fluid Transport through the Intact Mouse Skull using Fluorescence Macroscopy

Cerebrospinal fluid (CSF) flow in rodents has largely been studied using ex vivo quantification of tracers. Techniques such as two-photon microscopy and magnetic resonance imaging (MRI) have enabled in vivo quantification of CSF flow but they are limited by reduced imaging volumes and low spatial resolution, respectively. Recent work has found that CSF enters the brain parenchyma through a network of perivascular spaces surrounding the pial and penetrating arteries of the rodent cortex. This perivascular entry of CSF is a primary driver of the glymphatic system, a pathway implicated in the clearance of toxic metabolic solutes (e.g., amyloid-&#946;). Here, we illustrate a new macroscopic imaging technique that allows real-time, mesoscopic imaging of fluorescent CSF tracers through the intact skull of live mice. This minimally-invasive method facilitates a multitude of experimental designs and enables single or repeated testing of CSF dynamics. Macroscopes have high spatial and temporal resolution and their large gantry and working distance allow for imaging while performing tasks on behavioral devices. This imaging approach has been validated using two-photon imaging and fluorescence measurements obtained from this technique strongly correlate with ex vivo fluorescence and quantification of radio-labeled tracers. In this protocol, we describe how transcranial macroscopic imaging can be used to evaluate glymphatic transport in live mice, offering an accessible alternative to more costly imaging modalities.

Transcranial optical imaging allows wide-field imaging of cerebrospinal fluid transport in the cortex of live mice through an intact skull.

Cerebrospinal fluid (CSF) flow in rodents has largely been studied using ex vivo quantification of tracers. Techniques such as two-photon microscopy and ...