Sensory gating

Sensory gating describes neurological processes of filtering out redundant or unnecessary stimuli in the brain from all possible environmental stimuli. Also referred to as gating or filtering, sensory gating prevents an overload of irrelevant information in the higher cortical centers of the brain. The pulvinar nuclei of the thalamus play a major role in attention, and filter out unnecessary information. Although sensory gating is largely automatic, it also occurs within the context of attentional processes. Though the term sensory gating has been used interchangeably with sensorimotor gating, the two are distinct constructs.

The cocktail party effect illustrates how the brain inhibits input from environmental stimuli, while still processing sensory input from the attended stimulus. The cocktail party effect demonstrates sensory gating in hearing, but the other senses also go through the same process protecting primary cortical areas from being overwhelmed.

Information from sensory receptors make their way to the brain through neurons and synapse at the thalamus. The pulvinar nuclei in the thalamus function as the gatekeeper, deciding which information should be inhibited, and which should be sent to further cortical areas. Sensory gating is mediated by a network in the brain which involves the auditory cortex (AC), prefrontal cortex and hippocampus. Other areas of the brain associated with sensory gating include the amygdala, striatum, medial prefrontal cortex, and midbrain dopamine cell region (GABAergic neurons only). Research of sensory gating primarily occurs in cortical areas where the stimulus is consciously identified because it is a less invasive means of studying sensory gating. Studies on rats show the brain stem, thalamus, and primary auditory cortex play a role in sensory gating for auditory stimuli.

The paired-click paradigm is a common non-invasive technique used to measure sensory gating, a type of event-related potential. For normal sensory gating, if a person hears a pair of clicks within 500 ms of one another, the person will gate out the second click because it is perceived as being redundant. Evidence of the gating can be seen in the P50 wave, occurring in the brain 50 ms after the click. Low values of the P50 wave indicate that sensory gating has occurred. High values of the P50 wave indicate a lack of sensory gating. Individuals with schizophrenia only reduce the amplitude of S2 by 10-20%, whereas individuals without schizophrenia reduce the amplitude of S2 by 80-90%.

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