Abstract #440, Date Monday, Jan 28 2002 1:00PM - 12:00PM Session K8 Auditory Cortex: Plasticity and Maturation
Auditory Enrichment Enhances Evoked Potential Amplitude in Rat Auditory Cortex
Cherie R. Percaccio, Navzer D. Engineer, Nick C. Dempsey, Pritesh K. Pandya, Michael P. Kilgard
Prior research has demonstrated that environmental conditions influence cortical development. In this study, we characterize the effects of enrichment on evoked potentials in rat auditory cortex and document the time course of these changes. After weaning at one month of age, eight rats were chronically implanted with a ball electrode over AI and a ground screw over the cerebellum. Each rat was randomly assigned to either an enriched acoustic environment or standard housing conditions. The enriched environment housed 4-7 rats and consisted of a large cage with many sound sources, including motion detectors, bells, hanging chains, and a running wheel. A CD played 74 random tracks, including seven which were paired with a food reward to encourage attention to the sounds. The standard condition (n=4) consisted of single housing in a hanging wire cage. Middle latency auditory evoked responses (0-150ms) were recorded once a week from each animal for six weeks. Animals were tested with alternating noise bursts (68dB, 100ms) and tones (70dB, 9kHz, 25ms) delivered 125 times in random order (10s ISI). The amplitude of the evoked response to tones was greater (+60%) in animals raised in the enriched environment compared to the standard condition. Most of this enhancement was observed after only two weeks of exposure to the enriched environment, though the amplitude of the response continued to grow through week six. The evoked potential amplitude in response to the noise burst did not differ between the two groups. Our prior results from unit recordings in anesthetized animals indicate that enrichment lowers tone thresholds, decreases response latency, and increases frequency selectivity. It appears that the net result of these changes is to enhance the amplitude of the evoked response to tones, but not to the noise burst. These results support the hypothesis that environmental enrichment has an important influence on the development of cortical response selectivity.