Laboratorium voor Neuro-en Psychofysiologie, KU Leuven Medical School, Leuven, BE-3000, Belgium.
Laboratorium voor Neuro-en Psychofysiologie, KU Leuven Medical School, Leuven, BE-3000, Belgium
J Neurosci. 2014 Sep 17;34(38):12801-15. doi: 10.1523/JNEUROSCI.2154-14.2014.
Many studies measured neural responses in oddball paradigms, showing a different response to the same stimulus when presented with a low (deviant) compared with a high probability (standard) in a sequence. Such a differential response is manifested in event-related potential studies as the mismatch negativity (MMN) and has been observed in several sensory modalities, including vision. Other studies showed that stimulus repetition suppresses the neural response. It has been suggested that this adaptation effect underlies the smaller responses to the standard compared with the deviant stimulus in oddball sequences. However, the MMN may also reflect the violation of a prediction based on the sequence of standards, i.e., a surprise response. We examined the presence of a surprise response to deviants in visual oddball sequences in macaque (Macaca mulatta) inferior temporal (IT) cortex, a higher-order cortical area. In agreement with visual MMN studies, single-unit IT responses were greater for the deviant than for the standard stimuli. However, single IT neurons showed no greater response to the deviant stimulus in the oddball sequence than to the same stimulus presented with the same probability in a sequence that consisted of many stimuli. LFPs also showed no evidence of a surprise response. These data suggest that stimulus-specific adaptation, without a surprise-related boost of activity to the deviant, underlies the responses in visual oddball sequences even in higher visual cortex. Furthermore, we show that for IT neurons such adaptive mechanisms take into account a relatively short stimulus history, with weaker effects at longer time scales.
许多研究在离散刺激范式中测量神经反应，发现在序列中呈现低概率（偏差）和高概率（标准）刺激时，对相同刺激会有不同的反应。这种差异反应在事件相关电位研究中表现为失匹配负波（MMN），并在包括视觉在内的几种感觉模态中观察到。其他研究表明，刺激重复会抑制神经反应。有人认为，这种适应效应是奇数序列中标准刺激的反应小于偏差刺激的原因。然而，MMN 也可能反映了基于标准序列的预测违反，即惊讶反应。我们检查了猕猴（Macaca mulatta）下颞叶（IT）皮层中视觉离散刺激序列中对偏差的惊讶反应的存在，这是一个高级皮质区。与视觉 MMN 研究一致，单个 IT 反应对偏差刺激的反应大于对标准刺激的反应。然而，单个 IT 神经元在奇数序列中对偏差刺激的反应并不大于在由许多刺激组成的序列中以相同概率呈现的相同刺激的反应。LFP 也没有显示出惊讶反应的证据。这些数据表明，即使在更高的视觉皮层中，对刺激的特异性适应，而没有与惊讶相关的对偏差的活动增强，是视觉离散刺激序列反应的基础。此外，我们表明，对于 IT 神经元，这种适应机制考虑了相对较短的刺激历史，在较长的时间尺度上效果较弱。
