Figure 2.

Age comparisons of auditory brainstem response (ABR) and middle-latency response (MLR) thresholds, ABR latencies, temporal-ABR latency differences, and visual evoked potential (VEP) latency differences. A, Box and whisker plots of ABR thresholds across all tested pure-tone frequencies. Boxes denote the middle 50% of the data, and horizontal lines indicate the median of each distribution. Filled circles represent an individual monkey, with adult animals represented by black circles, and aged animals by gray circles. Aged monkeys had significantly higher ABR thresholds across frequencies compared with the adults. B, Box and whisker plots of ABR wave IV latencies across all tested pure-tone frequencies. Box and whisker plot as in A. Aged monkeys had significantly longer ABR wave IV latencies across frequencies compared with the adults. C, Box and whisker plot of the estimates of temporal acoustic information processing (temporal-ABR wave IV latency differences) across all tested pure-tone frequencies. Box and whisker plot as in A. Aged monkeys had significantly longer latency differences compared with adult animals across all tested pure-tone frequencies. D, Box and whisker plot of VEP P₇₅ latency differences between the 1 and 2 Hz stimulus presentation conditions. Box and whisker plot as in A. There was no age-related difference in VEP latency differences. E, Scatter plot of z score normalized measures of auditory processing (temporal ABR), auditory thresholds (threshold ABR), and auditory middle latency response thresholds plotted against normalized visual system processing (temporal VEP) scores. Dotted trend lines indicate nonsignificant relationships. Visual system function was not significantly associated with any measure of auditory function. *p < 0.05; **p < 0.01.