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Critical Reviews

Day 310: Review – Interfacing with alpha motor neurons in spinal cord injury patients

Figure 1 from the paper showing EMG recordings and the transformation using deconvolution to motor neuron spike trains
Figure 1 from the paper showing EMG recordings and the transformation using deconvolution to motor neuron spike trains

Spatiotemporal spinal maps of ipsilateral a-MNs. (A) Experimental set-up for ankle plantar flexion. (B) HD-EMG is decomposed into a-MN spike trains using a convolutive blind-source separation technique. (C) The spinal output to generate the neural drive to muscles is estimated from the a-MN spike trains.

The world is on fire, we’re protesting for a future, but today I have my review paper due so instead of writing about my frustrations I’m going to share my review. Today we’re looking at the effects of trans-spinal direct current stimulation (tsDCS) on alpha motor neurons and how we can determine that effect using electromyography. It’s actually a very cool paper, the work is well done, and it’s open source so you can read it if you’re interested.

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Day 296: Review – Spinal Rhythm Generation by Step-Induced Feedback and Transcutaneous Posterior Root Stimulation in Complete Spinal Cord–Injured Individuals

Black and white diagram showing the front and back of a human with the the placement of electrodes over the lower abdominal area and separate electrodes over T11-T12 of the spinal cord a third image to the right shows the side of the spinal column with spinal cord to depict the location of the back electrodes with relation to the spinal cord
Black and white diagram showing the front and back of a human with the the placement of electrodes over the lower abdominal area and  separate electrodes over T11-T12 of the spinal cord a third image to the right shows the side of the spinal column with spinal cord to depict the location of the back electrodes with relation to the spinal cord

Transcutaneous posterior root stimulation: Paravertebral and abdominal skin electrode placement (this is just a portion of figure 1 of this paper.

Normally I’m somewhat excited to post these, but with everything going on you’ll have to pardon my lack of joy. However, it’s been two weeks so I need to review another paper so I’m sharing it here as well as sending my PI a copy. The study is a few years old, but it’s open access so you can read it if you’re interested. Transcutaneous spinal cord stimulation (TSS) is one part of my research in case you couldn’t tell from all the spinal cord and TSS studies and posts. I find it interesting and it gives me hope that we can help a whole lot of people living with spinal cord injury. Anyway give it a read and get out there and protest for a better world.

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Day 282: Review – Transcutaneous spinal cord stimulation of the cervical cord modulates lumbar networks

Experimental Setup and tSCS electrode placement (A) H-reflexes were evoked via stimulation of the tibial nerve and recorded in the soleus muscle during a consistent background contraction of ≈5% peak muscle activity. The left leg was held static in an extended position, and stimulation to evoke the H-reflex was delivered with the left arm at 0°. (B) tSCS was delivered via two 2.5 cm round cathodic electrodes placed midline at C3-4 and C6-7 (cervical) or T11 and L1 (lumbar) spinous processes. Two 5 × 10 cm rectangular anodic electrodes were placed bilaterally over the iliac crests.
Experimental Setup and tSCS electrode placement (A) H-reflexes were evoked via stimulation of the tibial nerve and recorded in the soleus muscle during a consistent background contraction of ≈5% peak muscle activity. The left leg was held static in an extended position, and stimulation to evoke the H-reflex was delivered with the left arm at 0°. (B) tSCS was delivered via two 2.5 cm round cathodic electrodes placed midline at C3-4 and C6-7 (cervical) or T11 and L1 (lumbar) spinous processes. Two 5 × 10 cm rectangular anodic electrodes were placed bilaterally over the iliac crests.

Experimental Setup and tSCS electrode placement (A) H-reflexes were evoked via stimulation of the tibial nerve and recorded in the soleus muscle during a consistent background contraction of ≈5% peak muscle activity. The left leg was held static in an extended position, and stimulation to evoke the H-reflex was delivered with the left arm at 0°. (B) tSCS was delivered via two 2.5 cm round cathodic electrodes placed midline at C3-4 and C6-7 (cervical) or T11 and L1 (lumbar) spinous processes. Two 5 × 10 cm rectangular anodic electrodes were placed bilaterally over the iliac crests.

It’s that time again! My biweekly critical review paper is due for my PI. He gets a copy and so do all of you. This is a particularly interesting study that falls in line with a lot of research that I am doing, so it’s interesting to see how other groups are progressing. Overall I think this is a great study and while it is behind a paywall, I think I summed it up very well. The drawing they did (above) is awesome, especially for a scientific journal where we normally use simple line figures. Anyway, let’s get to it.

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Day 268: Review – Magnetospinography visualizes electrophysiological activity in the cervical spinal cord

Reconstructed currents of MSG from the cervical spondylotic myelopathy subject. There are two different sets of plots, the furthest left shows the electrophysiological recording taken from the epidural space and the other set shows the reconstructed currents using MSG. They agree fairly well.
Reconstructed currents of MSG from the cervical spondylotic myelopathy subject. There are two different sets of plots, the furthest left shows the electrophysiological recording taken from the epidural space and the other set shows the reconstructed currents using MSG. They agree fairly well.

This is the results of the cervical spondylotic myelopathy subject. The left graphs are the ascending spinal cord evoked potentials (this was electrophysiological recordings taken from the epidural space) by stimulation of the lower thoracic cord showing conduction block at the C4/5 disc level. The right graphs are the reconstructed currents at the midline of the cervical spinal canal (red) and 2 cm lateral (blue). The leading component (the first waveform in red) attenuated and disappeared through C4–6, and the trailing component (the second waveform in red) disappeared at C5/6. The perpendicular inflow components greatly attenuated at C4/5 (the second waveform in blue).

Another two weeks, another critical review. This time I was more critical than review, unlike the last one where I was blown away at the possibilities. Why was I more critical with this one? Well in my opinion, the authors took a baby step when they should’ve taken a leap. All that aside, it is an interesting study and one I hope has several follow up experiments. This one is open access as well, so have a read for yourself if you’re interested.

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Day 254: Review – A Brain to Spine Interface for Transferring Artificial Sensory Information

Fig.1 of paper showing drawing of implanted electrodes and the two experimental setups for the rat.
Fig.1 of paper showing drawing of implanted electrodes and the two experimental setups for the rat.

Experimental setup for artificial sensory discrimination using DCS and brain-to-spine interface. (a) Rats were implanted with recording electrodes in motor cortex (M1), somatosensory cortex (S1) and striatum (STR) and dorsal column stimulating electrodes in the thoracic epidural space.  (b) Behavioral setup for artificial sensory discrimination using DCS (c) Setup for the brain-to-spine interface consisted of two modified aperture width tactile discrimination boxes.

If you ever were to read one of my review papers, this one’s for you. It’s so awesome and falls in line fairly closely to the things I want to accomplish, albeit going a different route to get there. I’m super excited to share this with all of you and I hope I did the study justice in my summation and while I admit, I had far too much enthusiasm with this one, it shouldn’t take away from just how amazing this is, see for yourself! The study is open access too, so if you want to know more details, you can go take a look!

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Day 239: Review – Burst-modulated waveforms optimize electrical stimuli for charge efficiency and fiber selectivity

Example processed nerve responses during stimulation trials.
Example processed nerve responses during stimulation trials.

Example processed nerve responses during stimulation trials. The individual CNAP responses for each stimulus (thin traces) were averaged (thick trace, n=20 stimuli). All traces are shown from time 0 to 6ms. The top trace corresponds to an amplitude of 0, the bottom 1mA, and the traces in between are arranged in increments of 0.2mA. Peak latencies and heights (o’s) and widths at half peak height (x’s) were extracted from the averaged signal. The peaks labeled for the 0mA trial are due to noise and baseline activity. These peaks are not actual response peaks from the nerve and are ignored.

Another two weeks, another critical review and as always since my PI gets a copy, so do you. Technically this should’ve come yesterday, but I really wanted to follow up with the Roosevelt mess going on. In any case today we are looking at something not quite spinal cord stimulation, but has applications in the spinal cord stimulation field. Let’s take a look!

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Day 224: Review – Cortical and Subcortical Effects of Transcutaneous Spinal Cord Stimulation

Figure 1 of the paper showing the experimental set-up and the type of pulse used for stimulation
Figure 1 of the paper showing the experimental set-up and the type of pulse used for stimulation

Experimental set-up. (A) Participants were comfortably seated in a customized chair during transcutaneous electrical spinal stimulation (TESS) or sham-TESS for 20 min. TESS was delivered using a surface electrode on the back of the neck between C5–C6 spinous processes segments (cathode) and a surface electrode in each anterior crest of the hip bone (anode) using a custom made 5 channel stimulator (BioStim5, Cozyma). Electrophysiological and behavioral outcomes were tested before (Pre) and immediately after, 15, 30, 45, 60 and 75 min after the end of the stimulation or sham stimulation period. (B) Schematic representation of the type of current used during TESS. We used 5 biphasic pulses at 5kHz with each biphasic pulse lasting for 200us. The middle scheme shows the blocks of 5 biphasic pulses passed at a 30Hz frequency. Lower part of the schematic shows the number of pulses delivered in one second.

Well it’s been two weeks since the last critical review so it’s that time again. As usual, my PI gets a copy and so do all of you. Since I’ve done several of these now (this is number six) I have a category just for these reviews called critical reviews. This is a really new study which tries to help tease apart what we are actually stimulating when we apply transcutaneous spinal stimulation. I think it’s a super interesting paper and I hope you do as well.

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Day 210: Review – Cervical trans-spinal direct current stimulation: a modelling-experimental approach

Cervical trans-spinal direct current stimulation - Fig. 3
Cervical trans-spinal direct current stimulation - Fig. 3

Average magnitude of the E-field and average amplitude of its components in the spinal-WM in all montages along the z axis. Position of spinal segments is marked on the grey vertical bar, electrodes are represented by vertical bars and active connectors are marked with letter “A”. Volume plots of the E-field magnitude in cervico-thoracic spinal-WM, brainstem and cerebellum are represented at the right of the average distribution in each montage, with the corresponding colour scales

I lied! I did know what today was going to be on, it’s the fifth critical review paper. Since my PI gets a copy, so do you! To be honest, I need to create a category for these reviews (Update: I did make a category, Critical reviews), but for now, my first looking at elbow spinal stretch reflexes is here. My second where I review modulating spinal cord excitability with a static magnetic field here. The third where I review modulating the H-reflex while walking in spinal cord injury populations. Lastly, my fourth on Motoneuron excitability during voluntary muscle activity in a spinal cord injury population  can be found here. That said, let’s take a look at my latest review.

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Day 196: Review – Changes in Motoneuron Excitability during Voluntary Muscle Activity in Humans with Spinal Cord Injury

Figure 1
Figure 1

Figure 1. Experimental setup. A, Schematic representation of the hand showing the ulnar nerve and F-waves recorded from the first dorsal interosseous (FDI) muscle. B, On the left side, schematic representation of the head showing the electrodes placed at the cervicomedullary junction and on the right side a raw trace showing a cervicomedullary motor evoked potential (CMEP). C, A cartoon showing the concept of the visual feedback. Individuals were tested at rest (left single horizontal line) and during 5% (middle double horizontal lines) and 30% (right double horizontal lines) of maximal voluntary contraction (MVC).

A little detour from our spinal cord series for my fourth critical review paper. As usual, my PI get a copy and so do all of you! You can read my first looking at elbow spinal stretch reflexes here. My second where I review modulating spinal cord excitability with a static magnetic field here. Or the third where I review modulating the H-reflex while walking in spinal cord injury populations. Today is an interesting paper on motoneuron excitability while walking in spinal cord injury populations. It’s a really cool paper, so here’s my review.

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Day 182: Review – Modulation of soleus stretch reflexes during walking in people with chronic incomplete spinal cord injury

Fig2

Figure 2 of the paper showing examples of the soleus H-reflex (labeled H) during standing  and during different phases of walking in a participant without known neurological injuries (top) and in a participant with chronic incomplete SCI (bottom).

Today is my third attempt at a critical review paper. Since my PI gets a copy, so do all of you! You can read my first looking at elbow spinal stretch reflexes here. Or my second where I review modulating spinal cord excitability with a static magnetic field here. Today is an interesting paper on soleus stretch reflex and H-reflex. I really appreciate the methodology the researchers used and they did an excellent job of highlighting the limitations to the study, which is always important. Per the usual disclaimer, this is my third critical review, so you can take my opinion n the methodology and findings how you will. (more…)


Day 168: Review – Static magnetic field stimulation applied over the cervical spinal cord can decrease corticospinal excitability in finger muscle

Fig1

Figure 1 of the paper showing how the intervention was applied to the spinal cord

As mentioned in yesterday’s post, this is my second critical review paper. You can read my first looking at spinal reflexes here. Today we are looking at a novel way to modulate spinal cord excitability. Overall I find the paper very interesting. Although the authors performed a limited experiment and no follow up (as of now) has been done, it still looks very promising and would provide a new way to explore the circuitry of the spinal cord. This is my second attempt at a “critical review” so you can take my opinion on the methodology and findings how you will.

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Day 154: Review – Spinal stretch reflexes support efficient hand control

Fig1(A)

Fig 1 (a) from the paper, showing the multijoint perturbation away from target (red) with simultaneous flexion at the elbow and either flexion, extension, or no perturbation at the wrist joint.

Today is that critical review paper I promised. Everything following this introduction explains how the experiment was done, what they found, and why I think it is particularly interesting. To me the experiment was so well thought out I couldn’t think of anything I would change. Instead I focused on the methodology they used and why it highlights the importance of a well thought out experiment. This is really my first attempt at a “critical review” so take it how you will.

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