Data are from Brainard and Knudsen ( 29). L, left-ear leading R, right-ear leading.

The location of visual receptive fields, measured with prisms removed, is not altered in the tectum by prism experience. The dashed line indicates the normal regression of best ITD on visual receptive field azimuth. ( C) Eight weeks of prism experience causes the relationship between best ITD and visual receptive field azimuth to be shifted (purple symbols) systematically from normal (blue symbols). Best ITD is the midpoint of the range of ITDs that elicit more than 50% of the maximum response for that neuron. Downward arrows indicate the best ITD for each site. After the owl has experienced L23° prisms for 8 weeks, the ITD tuning of the neuron from a very similar site has shifted to 50 μs right-ear leading (purple symbols). Before prism experience (blue symbols), the neuron is tuned to 0 μs ITD. The visual receptive fields of both neurons are centered at 0° azimuth. ( B) The ITD tuning of tectal neurons before and after prism rearing. The contour lines indicate the correspondence of ITD values (for 6 kHz sounds) with locations in space. The globe represents space in front of the owl relative to the line of sight. ( A) The effect of L23°, horizontally displacing prisms on a visual receptive field location (encircled “V”). Experience with a prismatically displaced visual field causes adaptive adjustment of ITD tuning in the auditory space map. Traces of this early learning persist into adulthood, enabling adults to reacquire patterns of connectivity that were learned initially during the juvenile period.įigure 2 Functional traces of learning in the optic tectum of the barn owl. Various manipulations of auditory or visual experience, especially during early life, that change the relationship between auditory cues and locations in space lead to adaptive changes in auditory localization behavior and to corresponding changes in the functional and anatomical properties of this pathway. The midbrain localization pathway creates a multimodal map of space that represents the nervous system's associations of auditory cues with locations in visual space. The auditory localization pathway provides an opportunity to observe such adaptive changes and to study the cellular mechanisms that underlie them. One of the fascinating properties of the central nervous system is its ability to learn: the ability to alter its functional properties adaptively as a consequence of the interactions of an animal with the environment.

Auditory signal path