Capacity for plasticity in the adult owl auditory system expanded by juvenile experience.
In the process of creating a multimodal map of space, auditory-visual neurons in the optic tectum establish associations between particular values of auditory spatial cues and locations in the visual field. In the barn owl, tectal neurons reveal these associations in the match between their tuning for interaural time differences (ITDs) and the locations of their visual receptive fields (VRFs). In young owls ITD-VRF associations can be adjusted by experience over a wide range, but the range of adjustment normally becomes quite restricted in adults. This normal range of adjustment in adults was greatly expanded in owls that had previously learned abnormal ITD-VRF associations as juveniles. Thus, the act of learning abnormal associations early in life leaves an enduring trace in this pathway that enables unusual functional connections to be reestablished, as needed, in adulthood, even when the associations represented by these connections have not been used for an extended period of time.