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Sergey Stavisky
of our new preprint: we found speech-related neural activity obtained using multielectrode recordings in the dorsal (!) motor cortex of people with paralysis. 1/
Speaking is a sensorimotor behavior whose neural basis difficult to study at the resolution of single neurons due to the scarcity of human intracortical measurements and the lack of animal models. We...
bioRxiv bioRxiv @biorxivpreprint
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
It’d be great to observe what motor cortical populations do during speaking with single-neuron resolution, but how? There’s no direct animal model, and intracortical recording requires surgery. 2/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @BrainGateTeam
Our in was that we already have multielectrode arrays chronically placed in people with tetraplegia as part of the clinical trial to restore movement and communication. 3/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
The “problem” (opportunity!) was that these arrays are in the dorsal ‘hand knob’ area involved in arm and hand movements — not speech. But as far as we know, no one had actually looked for speech-related activity there. 4/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
We asked two of our participants, who are able to speak, to do a simple prompted speaking task. 5/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
The very cool, and surprising, result was that lo and behold, there was strong firing rate modulation on many electrodes when producing different speech sounds. Here’s an example neuron's spike rasters and trial-averaged firing rates: 6/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
Most neurons also responded to simple (non-speaking) movements of the lips, jaw, and tongue, so we think this activity reflects motor control of the articulators, rather than higher-level processes like language. 7/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
Could these signals be useful for building speech BCIs to help people who cannot speak? We think so! We could decode amongst a set of syllables pretty well, despite having only 200 electrodes in a sub-optimal part of the brain. 8/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
This makes me optimistic about intracortical approaches for speech BCIs, but there’s still a long road from this limited proof of feasibility to a real-time system synthesizing continuous speech. Recent work from the ECoG folks is paving the way in this domain. 9/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
What about the neural population dynamics during speaking? There are a lot of interesting questions one could ask. As newcomers to speech from the arm control field, we chose to start by bringing what we know. 10/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
We tested for whether two major motor cortical population dynamics features previously described by our group during arm movements were also present during speaking. 11/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @MattAntimatt
Neural dynamics motif #1: Population activity is dominated by a large condition-invariant signal (CIS) when initiating speaking. Here we applied the methods of Kaufman et al 2016 (): 12/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
Neural dynamics motif #2: Strong rotatory dynamics are present during speech production. Here we applied the methods of Churchland, Cunningham et al 2012:
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
Why this is the case is a fascinating open question. It may be that if these are effective computational strategies for generating the right muscle commands for arm and hand movements, then they’re also well-suited for generating speech-producing muscle commands. 14/
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Sergey Stavisky 30. pro 2018.
Odgovor korisniku/ci @sergeydoestweet
Another open question is whether finding this activity in "arm" motor cortex is due to remapping because of the participants' tetraplegia. We don't think this is the case, but a definite answer is elusive because we'd need intracortical recording in able-bodied people. 15/15
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