<div dir="ltr">Hi Richard,<div><br></div><div>I'm sorry to say I haven't ready your linked paper, though I will soon. Jeff Rodny, Chris Kello, and I have a paper in a special issue of <i>Language, Cognition, and Neuroscience</i> on the topic of evidence for and against grandmother cells. The issue was organized by Jeff Bowers, and he wrote a very helpful summary of the contributions here: <a href="http://www.tandfonline.com/doi/full/10.1080/23273798.2016.1267782">http://www.tandfonline.com/doi/full/10.1080/23273798.2016.1267782</a>.</div><div><br></div><div>In our paper, we discuss evidence and provide a computational model as a proof of concept to argue that single unit responses (whether localist or distributed) may be transient across various timescales without affecting "behavior". I wonder how well this maps onto your concept of a virtual pattern? The basic insight we offer is that, to the extent neurons and neural systems are plastic, relationships between external features and single unit activity may be metastable. Brief snapshots of these relationships can exhibit a high measured stability, particularly for a subset of neurons selected <i>because </i>of their stable responses during the recording window. Thus, 30% of neurons may be highly selective for 30 minutes, 10% may be highly selective for 2 hours, etc.</div><div><br></div><div>That being said, we present this side of the argument as a counterpoint to the ongoing debate over distributed and localist representations, in which both sides explain only the static properties of the representations. Neither my coauthors nor I feel that all representations in the brain are likely to be so transient, and even if this were true it would present a serious challenge to what is even meant by representation (not a challenge that we are eager to tackle).</div><div><br></div><div>Your thoughts and feedback are welcome on the paper:</div><div><a href="http://www.tandfonline.com/doi/abs/10.1080/23273798.2016.1242760">http://www.tandfonline.com/doi/abs/10.1080/23273798.2016.1242760</a><br></div><div><a href="http://cogmech.ucmerced.edu/pubs/RodnyETAL2016-LCN.pdf">PDF link</a><br></div><div><br></div><div>Best,</div><div>Tim Shea</div><div>University of California, Merced</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Aug 26, 2017 at 8:54 PM, Richard Loosemore <span dir="ltr"><<a href="mailto:rloosemore@susaro.com" target="_blank">rloosemore@susaro.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br>
Back in 2010 I wrote a paper with T.A. Harley in which we argued
that "concepts" (like [grandmother]) are likely to be <b>virtual</b>
patterns of activity on neural circuits and NOT hard coded into the
circuits themselves.<br>
<br>
So, for example, a virtual pattern of activity might come and go
between active and dormant states, or it could move around the brain
(perhaps from one column to another).<br>
<br>
In support of this conclusion, we pointed out that common
interpretations of brain imaging data were simply not consistent
with the usual assumption, which is that neurons directly
represented concepts. We pointed, in particular, to the infamous
Jennifer Aniston Cell paper, where the virtual concept hypothesis
was the only viable one.<br>
<br>
And yet, the "virtual" idea is almost completely absent from the
literature. Why? If concepts are virtual, this would make a
nonsense of many interpretations of neuroscience results, because
firing patterns would only have a weak relationship to meaningful
entities like concepts. (Think about it: if concepts can wander
around the cortex, what is the point in saying that a particular
place in cortex corresponds to a semantically tangible thing?).<br>
<br>
Anyway, I note that a recent paper from
Laura N. Driscoll, Noah L. Pettit, Matthias Minderer, Selmaan N.
Chettih, and Christopher D. Harvey (Dynamic Reorganization of
Neuronal Activity Patterns in Parietal Cortex):
<br>
<br>
<a class="m_3760612682936224190moz-txt-link-freetext" href="http://www.cell.com/cell/pdf/S0092-8674(17)30828-0.pdf" target="_blank">http://www.cell.com/cell/pdf/<wbr>S0092-8674(17)30828-0.pdf</a><br>
<br>
(Overview here:
<a class="m_3760612682936224190moz-txt-link-freetext" href="http://news.harvard.edu/gazette/story/2017/08/brain-flexibility-changes-the-way-we-remember-and-learn/" target="_blank">http://news.harvard.edu/<wbr>gazette/story/2017/08/brain-<wbr>flexibility-changes-the-way-<wbr>we-remember-and-learn/</a>)<br>
<br>
... brings yet another confirmation of the "virtual" concept
hypothesis. The most parsimonious interpretation of their results
is that the activity patterns are changing precisely because the
"concepts" (when active) are not identifable with fixed hardware,
but are actually virtual.<br>
<br>
It seems to me this is one of the most important issues in all of
neuroscience, since it changes the flavour of every result out
there.<br>
<br>
What do you think?<br>
<br>
---<br>
<br>
Richard Loosemore<br>
<br>
<br>
<br>
Reference<br>
<br>
Loosemore, R.P.W. & Harley, T.A. (2010). Brains and Minds: On
the Usefulness of Localization Data to Cognitive Psychology. In M.
Bunzl & S.J. Hanson (Eds.), Foundational Issues in Human Brain
Mapping.Cambridge, MA: MIT Press<br>
<br>
<a class="m_3760612682936224190moz-txt-link-freetext" href="https://www.academia.edu/563588/Brains_and_Minds_On_the_Usefulness_of_Localization_Data_to_Cognitive_Psychology" target="_blank">https://www.academia.edu/<wbr>563588/Brains_and_Minds_On_<wbr>the_Usefulness_of_<wbr>Localization_Data_to_<wbr>Cognitive_Psychology</a><br>
<br>
</div>
</blockquote></div><br></div>