Sensory experience and the formation of a computational map of auditory space in the brain

The basic wiring of the brain is first established before birth by using a variety of molecular guidance cues. These connections are then refined by p atterns of neural activity, which are initially generated spontaneously and subsequently driven by sensory experience. In the superior colliculus, a m idbrain nucleus involved in the control of orienting behaviour, visual, aud itory, and tactile inputs converge to form superimposed maps of sensory spa ce. Maps of visual space and of the body surface arise from spatially order ed projections from the retina and skin, respectively. In contrast, the map of auditory space is computed within the brain by tuning the neurons to di fferent localization cues that result from the acoustical properties of the head and ears. Establishing and maintaining the registration of the maps i n the face of individual differences in the size and relative positions of different sense organs is an activity-dependent process in which the synapt ic circuits underlying the auditory representation are modified and calibra ted under the influence of both auditory and visual experience. BioEssays 1 999;21:900-911. (C) 1999 John Wiley & Sons, Inc.