Willott J F, Parham K, Hunter K P
Department of Psychology, Northern Illinois University, DeKalb 60115.
Hear Res. 1988 Dec;37(1):1-14. doi: 10.1016/0378-5955(88)90073-1.
Extracellular recordings were obtained from inferior colliculus (IC) neurons on young (2-month) and very old (greater than 2-year) CBA/J mice in response to contralateral tone and noise stimuli. The old mice had a small loss of spiral ganglion cells throughout the cochlea and moderate hearing loss, manifested as an elevation of neuronal thresholds throughout the IC. There was an age-related increase (3% to 22%) in 'sluggish' neurons (auditory, but poorly driven by sound); however, most neurons responded robustly to sound. Nine response types were derived from post-stimulus time histograms (PSTHs); all types were found in both age groups with no difference in their relative incidence. Sustained responses remained vigorous in old neurons, as indicated by spike counts and temporal discharge patterns. The percentage of neurons that were spontaneously active increased with age in the ventral IC (the area most sensitive to high frequencies, including most of the central nucleus) and decreased in the dorsal IC (the area most sensitive to lower frequencies, including much of the dorsal cortex). Parameters of response areas (range, upper frequency cutoff, best frequency, and rate-best frequency) showed modest age differences, while rate-level functions showed little age-related change. While a significant correlate of old age was attrition of IC neurons from the population capable of responding robustly to sounds, the majority of individual neurons demonstrated a remarkable degree of normalcy in their responses.
在年轻（2个月大）和非常年老（超过2岁）的CBA/J小鼠的下丘（IC）神经元上进行了细胞外记录，以响应同侧音调及噪声刺激。年老小鼠的整个耳蜗螺旋神经节细胞有少量损失，伴有中度听力损失，表现为整个下丘神经元阈值升高。“迟缓”神经元（听觉神经元，但对声音驱动较差）随年龄增长有所增加（3%至22%）；然而，大多数神经元对声音反应强烈。从刺激后时间直方图（PSTH）中得出了九种反应类型；两个年龄组均发现了所有类型，其相对发生率无差异。如峰值计数和时间放电模式所示，老年神经元的持续反应仍然强烈。在腹侧下丘（对高频最敏感的区域，包括大部分中央核），自发活动的神经元百分比随年龄增加，而在背侧下丘（对低频最敏感的区域，包括大部分背侧皮质）则减少。反应区域的参数（范围、高频截止、最佳频率和频率-最佳率）显示出适度的年龄差异，而频率-强度函数显示出与年龄相关的变化很小。虽然与衰老显著相关的是能够对声音做出强烈反应的下丘神经元数量减少，但大多数单个神经元在反应中表现出显著程度的正常性。
