Fanselow E E, Nicolelis M A
Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Neurosci. 1999 Sep 1;19(17):7603-16. doi: 10.1523/JNEUROSCI.19-17-07603.1999.
We investigated the influence of four different behavioral states on tactile responses recorded simultaneously via arrays of microwires chronically implanted in the vibrissal representations of the rat ventral posterior medial nucleus (VPM) of the thalamus and the primary somatosensory cortex (SI). Brief (100 microsecond) electrical stimuli delivered via a cuff electrode to the infraorbital nerve yielded robust sensory responses in VPM and SI during states of quiet immobility. However, significant reductions in tactile response magnitude and latency were observed in VPM and SI during large-amplitude, exploratory movements of the whiskers (at approximately 4-6 Hz). During small-amplitude, 7-12 Hz whisker-twitching movements, a significant reduction in SI response magnitude and an increase in VPM and SI response latencies were observed as well. When pairs of stimuli with interstimulus intervals <100 msec were delivered during quiet immobility, the response to the second stimulus in the pair was reduced and occurred at a longer latency compared with the response to the first stimulus. In contrast, during large-amplitude whisker movements and general motor activity, paired stimuli yielded similar sensory responses at interstimulus intervals >25 msec. These response patterns were correlated with the amount and duration of postexcitatory firing suppression observed in VPM and SI during each of these behaviors. On the basis of these results, we propose that sensory responses are dynamically modulated during active tactile exploration to optimize detection of different types of stimuli. During quiet immobility, the somatosensory system seems to be optimally tuned to detect the presence of single stimuli. In contrast, during whisker movements and other exploratory behaviors, the system is primed to detect the occurrence of rapid sequences of tactile stimuli, which are likely to be generated by multiple whisker contacts with objects during exploratory activity.
我们研究了四种不同行为状态对通过长期植入大鼠丘脑腹后内侧核（VPM）和初级体感皮层（SI）的触须表征区域的微丝阵列同时记录的触觉反应的影响。在安静不动状态下，通过袖带电极向眶下神经施加短暂（100微秒）的电刺激，在VPM和SI中产生了强烈的感觉反应。然而，在触须进行大幅度探索性运动（约4 - 6赫兹）时，VPM和SI中的触觉反应幅度和潜伏期显著降低。在触须进行小幅度、7 - 12赫兹的抽动运动时，也观察到SI反应幅度显著降低，VPM和SI反应潜伏期增加。当在安静不动状态下施加刺激间隔<100毫秒的成对刺激时，与对第一个刺激的反应相比，对成对刺激中第二个刺激的反应减弱且潜伏期更长。相反，在大幅度触须运动和一般运动活动期间，当刺激间隔>25毫秒时，成对刺激产生相似的感觉反应。这些反应模式与在每种行为期间在VPM和SI中观察到的兴奋后放电抑制的量和持续时间相关。基于这些结果，我们提出在主动触觉探索过程中，感觉反应会被动态调节以优化对不同类型刺激的检测。在安静不动状态下，体感系统似乎被最佳调节以检测单个刺激的存在。相反，在触须运动和其他探索行为期间，该系统准备好检测触觉刺激快速序列的发生，这些序列可能是在探索活动期间多个触须与物体接触产生的。
