Alexander PROEKT (University of Pennsilvania) has given a talk.
http://proektlab.org/index.php
Short abstract:
Conscious perception is highly integrated-- the world appears to us as meaningful scenes composed of an arrangement of objects each one of which is a complex stimulus composed of multiple features. During normal wakefulness these perceptual experiences are correlated with the features of the outside world. Integrated experiences bearing little resemblance to sensory stimuli can also arise spontaneously during dreaming and in drug-induced hallucinatory states. In order to give rise to integrated perceptual experiences, neuronal activity within the vast cortical networks involved in perception must be coordinated. In this talk, I will present our work performed in mice in different states of consciousness (wakefulness, general anesthesia, and ketamine-induced dissociative state) which suggests that such coordination may be mediated by travelling cortical waves. I will show that visual evoked responses in awake mice can be well approximated as an interaction between two travelling waves reliably evoked by suprathreshold stimuli. The feedback (3-6Hz) wave modulates the amplitude of the faster (30-50 Hz) feedforward gamma wave and entrains firing of individual neurons in the visual (V1) and parietal (PPA) areas such that these neurons form a transient oscillatory assembly in the immediate aftermath of the stimulus. I will also present evidence that in the states when perceptual experiences are abolished (general anesthesia) intense visual stimuli fail to evoke the feedback wave and oscillatory assembly of neurons in V1 and PPA is not observed. Interestingly, during ketamine-induced dissociative state, spontaneous activity resembles a feedback travelling wave that entraines V1 and PPA neurons in the absence of the stimulus. Thus, our work suggests that the capacity to have integrated perceptual experiences is related to the formation of coordinated neuronal activity patterns orchestrated by feedback cortical travelling waves. During states associated with hallucinatory perception, these feedback travelling waves arise spontaneously and are unaffected by stimuli. Waking state is unique in that these waves of activity are reliably evoked by suprathreshold sensory stimuli.