
Massive electrode array will do first large-scale recording of brain activity - rpm4321
http://www.kurzweilai.net/massive-electrode-array-system-will-do-first-large-scale-network-recording-of-brain-activity
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georgewfraser
This isn't the first array of this type; it isn't even the tenth. There are
two major commercially available systems. Neuronexus is based on printed
circuits and is used mostly in rodents. The Utah array is micromachined and
more robustly packaged, and is used mostly in monkeys and some humans.

[http://neuronexus.com/products/neural-
probes](http://neuronexus.com/products/neural-probes)
[http://www.blackrockmicro.com](http://www.blackrockmicro.com)

~~~
blauwbilgorgel
This will be the first of this scale. On both those sites the most channels I
could find was 64. This program is planning 10.000 channels for unprecedented
resolution and scale.

Since 16 channels is enough to predict if a subject is looking at a face or
not, it is exciting to research what this large-scale system is going to be
capable of. Next to neuroscience, it could help with healthcare (research into
dementia, epilepsy and schizophrenia).

~~~
marvin
The article wasn't clear on this, what is a "channel" in this sense? What is
actually measured, from a physical perspective?

~~~
simonster
A "channel" usually means an individual contact on the device from which you
can record a signal. A single channel may record "spikes" (action potentials)
from dozens of neurons, but of those typically only 0-3 are distinguishable,
depending on how close the electrode is to the neurons and how close the spike
shapes are to each other. With ordinary metal electrodes, one can usually
isolate action potentials from an average of 1-1.5 neurons per electrode.

However, not all channels are created equal. High channel count arrays
typically have high contact densities. If the contacts are very close to each
other (<100 microns or so), adjacent channels may record signals from the same
neurons. I'm not entirely sure how this will affect the actual number of
neurons one can isolate, but I'm eager to see. The contacts will record
signals from fewer neurons than if the density were lower, but the increased
density may make it possible to isolate signals that would otherwise be lost
to noise, and will certainly make the process of determining which action
potentials came from which neurons simpler.

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adamzerner
I used to work in a lab that did some single-neuron recording and some array-
recording. We recorded from monkeys. The monkeys had to have a chamber surgery
in order for electrodes to be inserted into the brain.

This article mentions that they'll be recording from many areas
simultaneously. I would think this would mean multiple chamber surgeries in
different areas.

I know that these surgeries do damage to the monkeys. Could a monkey sustain
so many chamber surgeries? What about other animals?

~~~
simonster
Usually multi-shank arrays like the one depicted in the press release are
chronic, so no chamber is necessary. Instead, they are implanted directly into
the brain during surgery and wired to a port on the animal's head. There's
still some risk, since one still has to remove the skull above the target site
and also cut and resew the dura mater, but the skin can be sewed back together
after implantation and the bone will eventually regenerate. Unlike in an acute
preparation with a chamber, there is no exposed dura that needs to be cleaned
regularly to prevent infection, and the electrodes are inserted just once
instead of repeatedly.

If the recording contacts are sufficiently dense, the total area of skull that
needs to be removed to implant 1000 channels worth of arrays may actually be
less than in a conventional two-chamber (maybe even single chamber) acute
primate preparation. But we'll see.

~~~
kghose
The OP's point about damage still holds. After implanting the chronic arrays
you have to wait about 3 weeks before recording (the area is silent). It is
assumed that the responses are normal after that - and it seems so. But we
have a lot of results from arrays that have no counterpart from single
electrode recordings so we really don't know.

You are basically jamming a pincushion into the cortex. Trauma is inevitable.
The denser the array the more the damage (the more mass you are jamming into
cortex). You most likely have a perturbed cortex that has recovered from
damage.

Is this the same as original intact cortex?

~~~
simonster
Yes, the typical caveats of putting things in the brain still apply. But I'm
expecting that the increased density in these arrays will come mostly from
putting multiple contacts on each shank rather than putting the shanks closer
together, which may not produce any more damage than an ordinary Blackrock
array.

