MRC Institute of Hearing Research, Nottingham, United Kingdom.
J Neurophysiol. 2013 Aug;110(4):973-83. doi: 10.1152/jn.00547.2012. Epub 2013 May 29.
This study investigates the temporal properties of adaptation in the late auditory-evoked potentials in humans. The results are used to make inferences about the mechanisms of adaptation in human auditory cortex. The first experiment measured adaptation by single adapters as a combined function of the adapter duration and the stimulus onset asynchrony (SOA) and interstimulus interval (ISI) between the adapter and the adapted sound ("probe"). The results showed recovery from adaptation with increasing ISI, as would be expected, but buildup of adaptation with increasing adapter duration and thus SOA. This suggests that adaptation in auditory cortex is caused by the ongoing, rather than the onset, response to the adapter. Quantitative modeling indicated that the rate of buildup of adaptation is almost an order of magnitude faster than the recovery rate of adaptation. The recovery rate suggests that cortical adaptation is caused by synaptic depression and slow afterhyperpolarization. The P2 was more strongly affected by adaptation than the N1, suggesting that the two deflections originate from different cortical generators. In the second experiment, the single adapters were replaced by trains of two or four identical adapters. The results indicated that adaptation decays faster after repeated presentation of the adapter. This increase in the recovery rate of adaptation might contribute to the elicitation of the auditory mismatch negativity response. It may be caused by top-down feedback or by local processes such as the buildup of residual Ca(2+) within presynaptic neurons.
本研究探讨了人类晚期听觉诱发电位适应的时间特性。研究结果被用于推断人类听觉皮层适应的机制。第一个实验通过单个适应器来测量适应，适应器的持续时间和刺激起始异步（SOA）以及适应器和适应声音（“探针”）之间的刺激间间隔（ISI）是作为一个组合函数进行测量的。结果表明，随着 ISI 的增加，适应会恢复，这是可以预期的，但随着适应器持续时间的增加，即 SOA 的增加，适应会增强。这表明听觉皮层中的适应是由持续的而不是起始的适应器反应引起的。定量建模表明，适应的建立速度几乎比适应的恢复速度快一个数量级。恢复速度表明，皮质适应是由突触抑制和缓慢的后超极化引起的。与 N1 相比，P2 受适应的影响更大，这表明这两个偏转来自不同的皮质发生器。在第二个实验中，用两个或四个相同的适应器的序列代替单个适应器。结果表明，在重复呈现适应器后，适应的衰减速度更快。这种适应恢复率的增加可能有助于诱发听觉失配负波反应。这可能是由自上而下的反馈或局部过程引起的，例如在突触前神经元内残留 Ca(2+)的积累。
