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SUMMARY:Organization of neuronal population activity in auditory cortex. -
  Kenneth D Harris\, Imperial College London
DTSTART:20110621T103000Z
DTEND:20110621T113000Z
UID:TALK31838@talks.cam.ac.uk
CONTACT:Dr. Cristina Savin
DESCRIPTION:Recordings of single neurons have yielded great insights into 
 how sensory information is represented in the neocortex. However\, any one
  neuron functions as part of a population whose combined activity underlie
 s cortical information processing. This talk will describe some results ob
 tained by recording from populations and individual morphologically identi
 fied neurons\, in rat auditory cortex. Auditory cortical populations produ
 ced structured activity patterns both in response to acoustic stimuli\, an
 d spontaneously without sensory input. Population spike time patterns were
  broadly conserved across multiple sensory stimuli and spontaneous events\
 , exhibiting a generally conserved sequential organization lasting for app
 roximately 100ms. Both spontaneous and evoked events exhibited sparse\, sp
 atially localized activity in layer 2/3 pyramidal cells\, and densely dist
 ributed activity in larger layer 5 pyramidal cells and putative interneuro
 ns. Laminar propagation differed however\, with spontaneous activity sprea
 ding upward from deep layers and slowly across columns\, but sensory respo
 nses initiating in presumptive thalamorecipient layers\, spreading rapidly
  across columns. In both unanesthetized and urethanized rats\, global acti
 vity fluctuated between “desynchronized” state characterized by low am
 plitude\, high-frequency local field potentials and a “synchronized” s
 tate of larger\, lower-frequency waves. Computational studies suggested th
 at responses could be modelled by a simple dynamical system model fitted t
 o the spontaneous activity immediately preceding stimulus presentation\, r
 eflecting a nonlinear self-exciting system in synchronized states and an a
 pproximately linear system in desynchronized states.
LOCATION:Cambridge University Engineering Department\, CBL Rm #438 (http:/
 /blg.eng.cam.ac.uk/t/bin/view/Public/Directions)
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