Canonical properties of cortical circuits and dynamics for cognition and consciousness
To understand the neural basis of cognition, we must understand how top-down control of bottom-up sensory inputs is achieved. We have marshalled evidence for a canonical cortical control circuit that involves rhythmic interactions between different cortical layers. By performing multiple-area, multi-laminar recordings, we’ve found that local field potential (LFP) power in the gamma band (40-100 Hz) is strongest in superficial layers (layers 2/3), and LFP power in the alpha/beta band (8-30 Hz) is strongest in deep layers (layers 5/6). The gamma-band is strongly linked to bottom-up sensory processing and spiking carrying stimulus information, while the alpha/beta-band is linked to top-down processing. Deep layer alpha/beta projects to superficial layers and is negatively coupled to gamma. These oscillations give rise to separate channels for neuronal communication: feedforward for the gamma-band, and feedback for the alpha/beta band. Furthermore, thalamocortical interactions are especially important for generating alpha/beta rhythms. Different cognitive processes, such as attention, working memory, and prediction, all involve modulation of gamma and alpha/beta synchronization, both within and across areas of the frontal/parietal/visual network. These rhythms are also modulated by the overall state of arousal: during anesthesia-induced unconsciousness thalamocortical alpha/beta oscillatory synchronization is abolished. Based on these observations, we hypothesize that the interplay between deep-layer alpha/beta and superficial-layer gamma synchronization is a canonical mechanism to control cognition. Breakdown of this mechanism leads to loss of consciousness. My plan for future work is to causally test this hypothesis by manipulating alpha/beta and gamma synchronization. I am particularly excited to test whether these synchronization states control how we make predictions about future events.