Figure 1.

A neuro-computational model of SC multisensory integration. External visual and auditory inputs to the multisensory layers of the SC are abstractly represented as derived from either the visual (AEV) or auditory (FAES) subdivisions of the anterior ectosylvian sulcus (AES) or non-AES sources (“Visual area”, “Auditory area”). Each input region contacts principal (excitatory) neurons in the SC through competitive or cooperative pathways: the projections from non-AES sources are arranged to be functionally competitive across the modalities. This is implemented via independent excitatory projections (A and V) as well as reciprocal inhibitory synapses. A, This computation dominates the default, or naïve state that exists without covariant cross-modal experience. B, Projections from AES are arranged to be functionally cooperative (AV), moreover these input regions can suppress the native competitive mechanism through dedicated inhibitory synapses. Excitatory and inhibitory AES projections are strengthened by covariant cross-modal experience and instantiate multisensory enhancement capabilities in the neurotypic adult.