KU Leuven, Campus Gasthuisberg, O&N 2, Herestraat 49, bus 1021, 3000 Leuven, Belgium.
J Cogn Neurosci. 2013 May;25(5):777-89. doi: 10.1162/jocn_a_00355. Epub 2013 Mar 7.
Stimulus repetition produces a decrease of the response in many cortical areas and different modalities. This adaptation is highly prominent in macaque inferior temporal (IT) neurons. Here we ask how these repetition-induced changes in IT responses affect the accuracy by which IT neurons encode objects. This question bears on the functional consequences of adaptation, which are still unclear. We recorded the responses of single IT neurons to sequences of familiar shapes, each shown for 300 msec with an ISI of the same duration. The difference in shape between the two successively presented stimuli,that is, adapter and test, varied parametrically. The discriminability of the test stimuli was reduced for repeated compared with nonrepeated stimuli. In some conditions for which adapter and test shapes differed, the cross-adaptation resulted in an enhanced discriminability. These single cell results were confirmed in a second experiment in which we recorded multiunit spiking activity using a laminar microelectrode in macaque IT. Two familiar stimuli were presented successively for 500 msec each and separated with an ISI of the same duration. Trials consisted either of a repetition of the same stimulus or of their alternation. Small neuronal populations showed decreased classification accuracy for repeated compared with nonrepeated test stimuli, but classification was enhanced for the test compared with adapter stimuli when the test stimulus differed from recently seen stimuli. These findings suggest that short-term, stimulus-specific adaptation in IT supports efficient coding of stimuli that differ from recently seen ones while impairing the coding of repeated stimuli.
刺激重复会导致许多皮质区域和不同模态的反应减少。这种适应在猕猴下颞（IT）神经元中非常明显。在这里，我们想知道 IT 反应中的这些重复诱导变化如何影响 IT 神经元对物体的编码准确性。这个问题涉及到适应的功能后果，目前还不清楚。我们记录了单个 IT 神经元对一系列熟悉形状的反应，每个形状显示 300 毫秒，ISI 持续时间相同。两个相继呈现的刺激之间的形状差异，即适配器和测试，以参数方式变化。与非重复刺激相比，重复刺激的测试刺激的可辨别性降低。在适配器和测试形状不同的某些条件下，交叉适应导致可辨别性增强。这些单细胞结果在第二个实验中得到了证实，我们在猕猴 IT 中使用层状微电极记录了多单位尖峰活动。两个熟悉的刺激依次呈现 500 毫秒，ISI 持续时间相同。试验由相同刺激的重复或交替组成。当测试刺激与最近看到的刺激不同时，小神经元群体对重复测试刺激的分类准确性降低，但与适配器刺激相比，测试刺激的分类准确性提高。这些发现表明，IT 中的短期、刺激特异性适应支持对不同于最近看到的刺激的高效编码，同时损害对重复刺激的编码。
