Development of the Somatic Sensory System

这个为期三年的项目将考察触觉辨别的发展。众所周知，触摸信息投射到大脑中被标记为S1的区域，即初级体感皮质。S1中的单个神经细胞对施加到身体特定局部区域的触摸做出反应，引起反应的区域被称为该细胞的“感受野”。对于给定细胞的感受场，最有效的触觉刺激可能具有特定的空间特征(例如对小点的偏好，或点之间的间隔距离)和时间特征(例如，快速振动或移动点，或保持触摸)。在最近对小猫的研究中，与成年猫相比，皮质细胞的反应似乎有限。然而，在猴子身上，婴儿表现出的触摸辨别力至少与成年人相当。这项研究将检测第一岁猕猴对图形触觉刺激的S1神经元和心理物理阈值的反应。反应类型将根据其编码应用于手部皮肤的几何网点图案的空间和时间特征的能力进行分类。刺激物将由自动辨别装置呈现。行为辨别(使用“相同或不同”的决定)和神经元的放电模式都将被定量测量。预计神经元在不同表面之间发出差异信号的能力将与在这些相同表面之间进行行为辨别的能力有关。

This three.year project will examine the development of tactile discrimination. It is known that information on touch projects to a region of the brain labelled S1, the primary somatosensory cortex. Single nerve cells in S1 respond to touch applied to particular local areas of the body, and the area eliciting a response is called the "receptive field" of that cell. The most effective tactile stimulus for the receptive field of a given cell may have particular spatial features (such as preference for small points, or separation distance between points) and temporal features (such as rapidly vibrating or moving points, or a maintained touch). In recent studies in kittens, the responses of cortical cells appeared to be limited compared to those in adults. Yet in monkeys, infants show touch discrimination that is at least equal to adults. This study will examine S1 neurons and psychophysical thresholds in response to patterned tactile stimulation, in macaque monkeys during the first year of age. Response types will be classified by their capacity to code spatial and temporal features of geometric dot patterns applied to the skin of the hand. The stimuli will be presented by an automated discrimination apparatus. Both behavioral discriminations (using a "same or different" decision) and neuronal firing patterns will be quantitatively measured. It is expected that the capacity of neurons to signal differences between different surfaces will relate to the capacity to make behavioral discriminations among these same surfaces.