Coding space-time stimulus dynamics in auditory brain maps

Abstract

Sensory maps are often distorted representations of the environment, where ethologically-important ranges are magnified. The implication of a biased representation extends beyond increased acuity for having more neurons dedicated to a certain range. Because neurons are functionally interconnected, non-uniform representations influence the processing of high-order features that rely on comparison across areas of the map. Among these features are time-dependent changes of the auditory scene generated by moving objects. How sensory representation affects high order processing can be approached in the map of auditory space of the owl's midbrain, where locations in the front are over-represented. In this map, neurons are selective not only to location but also to location over time. The tuning to space over time leads to direction selectivity, which is also topographically organized. Across the population, neurons tuned to peripheral space are more selective to sounds moving into the front. The distribution of direction selectivity can be explained by spatial and temporal integration on the non-uniform map of space. Thus, the representation of space can induce biased computation of a second-order stimulus feature. This phenomenon is likely observed in other sensory maps and may be relevant for behavior.

Stimulus‐specific adaptation to visual but not auditory motion direction in the barn owl's optic tectum

“…Sensitivity to auditory motion direction has been reported in the owl's external nucleus of the inferior colliculus (ICx) (Wagner & Takahashi, 1992;Wang et al, 2012Wang et al, , 2014, the main source of auditory input to OT. Recently, (Wang & Pena, 2013) demonstrated that directional selectivity in the ICx can be explained by adaptation to excitation in asymmetrical spatial receptive fields.…”