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SUMMARY:V&C Seminar // "Cortical activity is more stable when sensory stim
 uli are consciously perceived”
DTSTART:20150224T140000
DTSTAMP:20260509T131624Z
UID:7d59ad459fc0c1ec8dceb082843cccb3091853ea21b32c7143915600
CATEGORIES:Conferences - Seminars
DESCRIPTION:Aaron Schurger\,\nLaboratory of Cognitive Neuroscience\nBrain-
 Mind Institute\, Department of Life Sciences\, EPFL\nAbstract: According t
 o recent evidence\, stimulus-tuned neurons in the cerebral cortex exhibit 
 reduced variability in firing-rate across trials\, after the onset of a st
 imulus. However\, in order for a reduction in variability to be directly r
 elevant to perception and behavior\, it must be realized within trial – 
 the pattern of activity must be relatively stable. Stability is characteri
 stic of decision states in recurrent attractor networks\, and its possible
  relevance to conscious perception has been suggested by theorists. Howeve
 r\, it is difficult to measure on the within-trial time scales and broadly
  distributed spatial scales relevant to perception. We recorded simultaneo
 us magneto- and electro-encephalography (MEG and EEG) data while subjects 
 observed threshold-level visual stimuli. Pattern-similarity analyses appli
 ed to the data from MEG gradiometers uncovered a pronounced decrease in va
 riability across trials after stimulus onset\, consistent with previous si
 ngle-unit data. This was followed by a significant divergence in variabili
 ty depending upon subjective report (seen / unseen)\, with seen trials exh
 ibiting less variability. Applying the same analysis across time\, within 
 trial\, we found that the latter effect coincided in time with a differenc
 e in the stability of the pattern of activity. Stability alone could be us
 ed to classify data from individual trials as ‘seen’ or ‘unseen’. 
 The same metric applied to EEG data from patients with disorders-of-consci
 ousness exposed to auditory stimuli diverged parametrically according to c
 linically diagnosed level-of-consciousness. Differences in signal strength
  could not account for these results. Conscious perception may involve the
  transient stabilization of distributed cortical networks\, corresponding 
 to a global brain-scale decision.
LOCATION:SV2510
STATUS:CONFIRMED
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