Spatial-temporal stimulus interactions in primate SI hand cortex neurons

描述(申请人提供)：我们将在猴子体感手部皮质长期植入微电极阵列，以研究神经元的反应，重点是施加两种在空间和时间上不同的刺激的影响。结果将揭示与人类触觉加工相关的语境效应，并可能与物体辨别的基础有关。这项研究的长期目标是确定躯体感觉系统如何以及在哪里调节物体感知和相关能力，以便更好地表征躯体感觉处理的各个方面，这些方面是导致幻肢综合征或中风或其他对躯体感觉系统的神经损伤的神经现象的基础。指导这项提议的想法是，物体歧视需要整合来自手部的信息，而这种整合很可能涉及初级躯体感觉皮质(3b区)。我们假设，当两个刺激在空间和时间上更接近时，3b区神经元的反应将受到调制，但即使刺激之间有相当大的距离，也会发生调制。我们基于这一假说：1)几条证据表明，在时间上施加的近刺激(在相邻的手指或胡须上)调制了神经元对感受野中刺激的反应，2)可以在3b区发现的半球间相互作用，以及3)初步研究表明，这种环绕调制的来源并不局限于空间上邻近的刺激。在目标1中，我们将机械地刺激成对的手指位置，以评估神经反应的调制可能如何与两个刺激的空间和时间接近有关。在目标2中，我们将局部注射利多卡因来阻断来自一只手的输入，并表征另一只手对刺激的反应，以推断对侧大脑半球正常水平的自发活动对塑造3b神经元活动的影响。因此，我们将研究对手部或手部各部位的刺激反应之间的相互作用，以研究在远距离刺激的背景下，躯体感觉皮质中的神经元如何对感受野中的刺激做出反应。相关性：躯体感觉系统中神经元的正常功能不仅与理解正常的触觉有关，而且与理解中风或躯体感觉皮质损伤的恢复有关(即，了解病变改变处理的程度，以及在治疗或不治疗的情况下，正常功能在多大程度上恢复到该区域)。未来的实验(背柱病变)计划进一步测试这一点，但拟议的研究是解释此类未来研究所必需的基础工作的一部分。

DESCRIPTION (provided by applicant): We will chronically implant microelectrode arrays in monkey somatosensory hand cortex to study neuron responses, with the focus on effects of applying two stimuli that vary in spatial and temporal proximity. Results will reveal contextual effects that are relevant to human tactile processing and may relate to the basis of object discrimination. The long-term objective of the study is to determine how and where the somatosensory system mediates object perception and related abilities in order to better characterize the aspects of somatosensory processing that underlie neurological phenomena like phantom limb syndrome or recovery from stroke or other neurological damage to the somatosensory system. The idea guiding the proposal is that object discrimination requires integration of information from across the hand, and this integration is likely to involve primary somatosensory cortex (area 3b). We hypothesize that responses of area 3b neurons will be modulated when two stimuli are nearer in spatial and temporal proximity, but that modulations will occur even when stimuli are separated by substantial distances. We base this hypothesis on 1) several lines of evidence that near stimuli (on adjacent digits or whiskers) applied closely in time modulate the neuron response to the stimulus in the receptive field, 2) interhemispheric interactions that can be unmasked in area 3b, and 3) preliminary studies indicating that such sources of surround modulation are not limited to spatially proximate stimuli. In Aim 1, we will mechanically stimulate paired finger locations to assess how modulation of neural responses may be related to spatial and temporal proximity of the two stimuli. In Aim 2, we will administer local lidocaine injections to block input from one hand and characterize responses to stimulation on the opposite hand, in order to deduce effects of normal levels of spontaneous activity from the opposite hemisphere on shaping 3b neuron activity. Thus, we will examine interactions between responses to stimuli delivered to sites across the hand or hands to investigate how neurons in somatosensory cortex respond to a stimulus in the receptive field, in the context of a distant stimulus. Relevance: The normal functions of neurons in the somatosensory system are relevant not only for understanding the normal sense of touch, but also to understanding recoveries from stroke or damage to the somatosensory cortex (i.e., understanding the extent to which processing is altered by lesions and to what extent normal function returns to the area with or without therapy). Future experiments (dorsal column lesions) are planned to test this further, but the proposed study is part of the foundational work necessary to interpret such future studies.