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SUMMARY:Geometry of population coding in large and transcriptomically-iden
 tified cortical populations - Ken Harris\, University College London
DTSTART:20241011T160000Z
DTEND:20241011T170000Z
UID:TALK221707@talks.cam.ac.uk
CONTACT:Samuel Eckmann
DESCRIPTION:Two-photon calcium imaging has made it possible to record from
  tens or hundreds of thousands of neurons simultaneously\, offering an opp
 ortunity to understand the large-scale structure of the neural code. I wil
 l discuss some applications of this approach asking how visual and non-vis
 ual information are encoded in large populations of mouse visual cortex\, 
 and how the nature of this code differs between cell types as identified b
 y mouse lines or by post-hoc spatial transcriptomics. \n\nBoth visual and 
 non-visual information are encoded with a geometry where the variance of t
 he nth dimension scales as a power law n^(–alpha).  The exponent  is lar
 ger for spontaneous activity than for sensory responses\, and is larger fo
 r inhibitory than excitatory populations\, indicating a lower-dimensional\
 , more redundant code. Around 30% of the reliable spontaneous variance of 
 excitatory populations was predictable from behavior assessed by video\, a
 nd around twice as much in inhibitory populations. The spaces of behaviora
 lly- and visually-driven activity overlapped only in one dimension\, which
  accounted for 25% of visually-evoked variance in inhibitory populations b
 ut only 5% in excitatory populations.  Visual cortical responses to sound 
 stimuli occupied the behavioral dimensions\, and were coincident with star
 tle responses\, suggesting they primarily reflect sound-evoked changes in 
 alertness.\n\nPost-hoc transcriptomic analysis of imaged cells revealed th
 at inhibitory cells coupled to spontaneous dimensions in a manner correlat
 ed on their fine transcriptomic type\, but their sensory responses only co
 rrelated with coarse transcriptomic type.  Analyses to date indicate no co
 rrelation between the spontaneous or visually-evoked activity of excitator
 y cells and their transcriptomes.
LOCATION:CBL Seminar Room\, Engineering Department\, 4th floor Baker build
 ing
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