Triple model of auditory sensory processing: a novel gating stream directly links primary auditory areas to executive prefrontal cortex.

The generally accepted model of sensory processing of visual and auditory stimuli assumes two major parallel processing streams, ventral and dorsal, which comprise functionally and anatomically distinct but interacting processes in which the ventral stream supports stimulus identification, and the dorsal stream is involved in recognizing the stimulus spatial location and sensori-motor integration functions. However, recent studies suggest the existence of a third, very fast sensory processing pathway, a gating stream that directly links the primary auditory cortices to the executive prefrontal cortex within the first 50 milliseconds after presentation of a stimulus, bypassing hierarchical structure of the ventral and dorsal pathways. Gating stream propagates the sensory gating phenomenon, which serves as a basic protective mechanism preventing irrelevant, repeated information from recurrent sensory processing. The goal of the present paper is to introduce the novel 'three-stream' model of auditory processing, including the new fast sensory processing stream, i.e. gating stream, alongside the well-affirmed dorsal and ventral sensory processing pathways. The impairments in sensory processing along the gating stream have been found to be strongly involved in the pathophysiological sensory processing in Alzheimer's disease and could be the underlying issue in numerous neuropsychiatric disorders and diseases that are linked to the pathological sensory gating inhibition, such as schizophrenia, post-traumatic stress disorder, bipolar disorder or attention deficit hyperactivity disorder.