Adult Intensive Training Improves Auditory Azimuth Selectivity Of Rat A1 Neurons Degraded By Early Noise Exposure

This experiment used behavioral method and conventional electrophysiological techniques to study the improved impact of intensive training to the influence of azimuth selectivity of A1 neurons degraded by early white pulsed noise exposure during early postnatal critical period.1. The influence of early white pulsed exposure on azimuth selectivity of rat A1 neurons during early postnatal critical periodNoise rats (NR, n=15) were fed in special environment with white pulsed noise during the early postnatal period until ten weeks. The control rats (CON, n=15) were fed in standard conditions after birth were used as age-matched controls. And ANR rats (ANR, n=9) were fed in standard conditions until 35 day after birth, and then housed in special environment with white pulsed noise until ten weeks. The CON rats were fed in standard conditions after birth were used as age-matched controls.We found that the NR rats'proportion of the azimuth-selective neurons declined significantly compared with the CON group, for the AR (Azimuth range, AR) of DS curve (Directional selectivity curve) are different between NR group and CON group by+10dB and+30dB. The AR of NR group was significantly larger than CON group (p<0.001). Especially in the 5°～34°of BAz (Best azimuth), there were more significant difference between the two groups (p<0.05). In addition, the average AR gradually decreased with CF increasing for three CF categories. And there are differences between two groups for all three CF categories (p<0.05), especially in the 3.1-9.5 and 9.5-30kHz frequency (p<0.001). And we found that the ANR rats' proportion of the azimuth-selective neurons didn't declined significantly compared with the CON group, for the AR (Azimuth range, AR) of DS curve (Directional selectivity curve) are no significantly different between ANR group and CON group by+10dB and+30dB. The AR of ANR group was similar as CON group (p>0.05). There were no significant differences between the two groups in all BAz regions (p> 0.05). In addition, the average AR gradually decreased with CF increasing for three CF categories, but no significant differences between two groups in all three CF categories (p>0.05).2. Adult intensive training improves azimuth selectivity of rat Al neurons degraded by early white pulsed noise exposureAll rats were divided into three groups, EXP, PNR, and CON. EXP rats (n=11), housed in noise environment like NR group until 35 day after born, then trained to select a target auditory stimulus of specific orientation (P36-P70); and PNR rats (n= 8), housed in noise environment like NR group until 35 day after born, then passively moved to experimental equipment with no relations between auditory stimulus and reward (P36-P70); CON rats (n=15), housed in standard conditions until 35 day after birth, and then trained to select a target auditory stimulus of specific orientation (P36-P70).The training results showed that there were no significant differences among the three groups (p>0.05) in the beginning of the training on correct scores, latency and azimuth deviation. And there were significant differences (p<0.05) between EXP group and CON group in the middle of the training on correct scores, latency and azimuth deviation. Then no significant differences were found between EXP group and CON group in the end on correct scores, latency and azimuth deviation.The electrophysiological results confirmed that the EXP rats'proportion of the azimuth-selective neurons were the similar as the control group, for there were similar results between EXP group and CON group (p>0.05) on AR. And in all regions of BAz, there were no significant differences between the two groups (p>0.05). In addition, the average AR gradually decreased with CF increasing for all three CF categories, but no significant differences in all three frequency of CF categories (p> 0.05).The results between PNR group and CON group were identical as the NR group and CON group.