Spectrally enhanced acoustic environment disrupts frequency representation in cat auditory cortex

Sensory environments are known to shape nervous system organization. Here we show that passive long-term exposure to a spectrally enhanced acoustic environment ( EAE) causes reorganization of the tonotopic map in juvenile cat auditory cortex without inducing any hearing loss. The EAE consisted of tone pips of 32 different frequencies ( 5 - 20 kHz), presented in random order at an average rate of 96 Hz. The EAE caused a strong reduction of the representation of EAE frequencies and an over-representation of frequencies neighboring those of the EAE. This is in sharp contrast with earlier developmental studies showing an enlargement of the cortical representation of EAEs consisting of a narrow frequency band. We observed fewer than normal appropriately tuned short-latency responses to EAE frequencies, together with more common long-latency responses tuned to EAE-neighboring frequencies.