Category Archives: #SfN14

#SfN14 Wednesday: Rehabilitation for Movement Disorders

I’m going to continue posting about things I saw at #SfN14 in the upcoming weeks, both here and on the Medium.com site for PLOS’s coverage of the conference.

One of the two interesting posters I saw today was unpublished work. But like my own work, it is unpublished because it is an in-progress engineering feat with tremendous potential. I was taken with their project, since they are attacking a similar problem as our lab with a different approach.

Developmental movement disorders are a lifelong issue for the patients diagnosed with them. They are not currently curable, but in many cases, treatments are available that can aid the lives of people with movement disorders.

In our lab, we are trying to develop treatments and assistive devices for children with dystonia, which has a relatively high incidence, as pediatric movement disorders go. Current treatments that are available tend to be focus on either relieving symptoms (e.g., botox injections) or affecting brain activity (e.g., levodopa treatment, deep-brain stimulation). At the moment, we are doing a lot of analysis on how well deep-brain stimulation works for children with dystonia, as well as examining vibratory biofeedback therapy. We’ve looked into non-invasive brain stimulation methods as a form of symptom relief with mixed results.

The poster I saw today, however, was both striking in its approach and appealing to my sensibilities. The lab group, based at UCSD, is developing a form of biofeedback therapy that really uses every non-invasive method we have our hands on to treat subject. (They are working with people who have Parkinson’s, but that is related to the same brain area as dystonia: the basal ganglia.) What they have accomplished is really less important than what they plan to accomplish. They are trying to combine EEG, EMG, and haptic feedback from small, commercially available PHANTOM haptic robots with a virtual reality display for rehabilitation tasks.

Biofeedback therapy is already used in rehabilitation contexts, such as psychotherapy. BIOPAC, who had an exhibition at the conference this year, worked with USC’s Institute of Creative Technology to develop Virtual Iraq, a multimodal virtual reality simulation of Iraq battle zones for the treatment of PTSD in our military veterans. In addition, there is an overwhelming amount of evidence that manipulating sensory feedback can facilitate motor learning. This approach also has the benefit of being a non-invasive technology, which is something I feel strongly should be attempted when possible. Invasive procedures always bear with them risk and emotional trauma, and it tends to be unclear whether it’s worth doing that to children.

I was really excited about the progress the research group has made on this project. While they are only currently examining how their setup can help patients with Parkinson’s, my feeling is that the technology has broader application in treating movement disorders.

My own exposure to dystonia research has been limited to pediatric cases, but there is one form of dystonia called focal hand dystonia (colloquially known as “writers’ cramp”). This form of dystonia forces the hand to take abnormal postures whenever you try to make voluntary movements of the hand. This disorder is known to happen in musicians and athletes, and can cripple careers. Normally, the only way to get rid of it is to stop playing and hope it goes way, but this technology has the potential to facilitate recovery. I’m anxiously looking forward to seeing how their work develops!

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#SfN14 Day Two: sensorimotor learning

During the morning session of #SfN14 today, I was able to survey some of the posters in the “sensorimotor learning” poster session. One poster that grabbed my attention was presented by Peter Butcher, who works for Jordan Taylor at Princeton University. Their work was exploring what kinds of sensory feedback are actually associated with sensorimotor adaptation.

“Sensorimotor adaptation” refers to how we accustom ourselves to changes in the environment. This is often probed using experiments that mess with sensory feedback or that apply unusual forces to subjects as they attempt to accomplish tasks. One of the most common paradigms for sensorimotor adaptation experiments is the “curl-field” paradigm. In these paradigms, subjects hold a robotic arm during reaching tasks, but the arm is programmed to apply a velocity-dependent force perpendicular to the direction of movement, and subjects have to compensate for this force to accomplish their tasks.

In the experiment Peter was talking about in his poster, subjects were required to move a cursor into a target. Two types of feedback were given: either end-of-movement visual feedback was given, or an integer value was given such that a score of 100 means you’re in the target. Only the case with visual feedback displayed adaptation; reward feedback does not cause the aftereffect you typically see when you return to full visual feedback. So the researchers asked: what is it about visual feedback that induces adaptation? They were able to determine that getting feedback about what direction the target is relative to your current position(without distance information) drives adaptation, while the converse (distance information without directional feedback) does not seem to cause adaptation. (Of course, having both kinds of feedback together gave the best adaptation results.)

What does this mean about how we learn? From a rehab perspective, understanding which aspects drive learning and adaptation can help shape the way we train and retrain movements.

The Translational Session of the TCMC Satellite – Part 1 #SfN14

I was unfortunately unable to attend the afternoon “computational” session of the TCMC satellite, but I found the morning session very stimulating! Instead of going into detail on any of the talks, I think I’m going to summarize the findings they discussed, and I’ll go into more detail on another occasion (or upon request). I don’t know which of the authors was the speaker in some of the talks, but you can find the event’s schedule here.

There were six 20-minute talks, but I will just talk about two I found interesting. The first talk was a study of whether motor memories are context-dependent. Previous research has shown that memory of fear conditioning in rats can demonstrate a context dependence. The researchers of this study tried to examine whether the state of the brain during motor learning can affect the development of motor memory. They used transcranial direct current stimulation (tDCS) to affect the state of the brain. tDCS basically means that two electrodes are applied to the head and a current is run between them, which flows through the skull and into the brain. They used a very typical task for studies in my field call a “curl-field task”. Subjects are asked to push a robotic manipulandum forward, but the robot applies a velocity-dependent force perpendicular to the direction of movement. These researchers used tDCS to associate an up- or down-regulation of somatosensory cortex with curl fields in opposite directions. Then, in error-clamp trials (where only tDCS is applied and movement of the robot manipulandum is constrained to be error-free by only allowing movement of the manipulandum toward the target), the subjects performed the tasks associated with the different types of tDCS applied as if the appropriate curl fields were active!

During questions, there was one researcher who prefers to use transcranial magnetic stimulation (TMS) who pointed out that when you use tDCS, you don’t really know what brain areas you are affecting because the current flows over relatively large areas of the brain. While this may be true, I was extremely interested in this study because in our lab, we have attempted to use tDCS to treat dystonia in a number of studies that have had mixed to negative results. If dystonia is related to a failure in motor learning, perhaps it is indeed possible to use tDCS to help patients retrain themselves?

Returning Absent Abilities: Developmental Dystonia Research and Device Development

The first times I visited my advisor’s pediatric neurology clinic at Children’s Hospital Los Angeles as a new graduate student, I found the experience both beautiful and heartwrenching. My advisor, Dr. Terry Sanger, specializes in pediatric movement disorders. At that point in my life, I’d had limited exposure to people who live with any sort of motor or cognitive disability. The kindness and caring of the doctors and the parents was deeply moving, but developmental movement disorders are a difficult challenge to live with.
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