Grant: CIHR Fellowship

Sensory overload (oversensitivity to lights, sounds, touch, etc.) is common in autism. Normally, the brain prevents this by suppressing activity to predicted sensory inputs. This allows only unexpected inputs (which are more informative) to be sent forward for full processing. We will test a theory that predictions are carried by alpha/beta (~10-30 Hz) rhythms in the deep (feedback) layers of cortex. They suppress the gamma (>30 Hz) rhythms in upper cortical layers that feedforward sensory inputs. Both increased gamma and reduced alpha/beta have been seen in autism. Our model posits that the reduction of alpha/beta "releases" gamma, causing overly heightened excitation to sensory inputs and thus sensory overload. Evidence for this theory is thus far based on observed correlations. There have been no causal manipulations of brain circuitry that can directly test it. Our aim is to provide direct tests. We have new technology to record neural activity across all cortical layers while we selectively deactivate upper vs deep cortical layers. We will also suppress gamma vs alpha/beta rhythms in different layers by manipulation of different classes of neurotransmitter receptors (NMDA vs AMPA). This will directly test a hypothesis of how the cortex regulates sensory processing and a mechanism of sensory overload. This can lead to a new understanding of the fundamental mechanisms of cortical processing and lead research towards improved symptom management and therapies for ASD.