Friedman Robert M, Chen Li Min, Roe Anna W
Department of Psychology, Vanderbilt University, Nashville, TN 37240-7817, USA.
J Neurophysiol. 2008 Dec;100(6):3185-96. doi: 10.1152/jn.90278.2008. Epub 2008 Oct 15.
Stimulation of the skin evokes topographically organized activation in somatosensory cortex. This representation is context dependent, however, since a different cortical topography is observed in area 3b when stimulated with complex tactile stimuli that evoke the von Békésy funneling illusion. Here we report on the population responses, as observed with intrinsic optical imaging, of area 1 and area 3b in the anesthetized squirrel monkey to pressure indentation of distal finger pads. Individual finger pad stimulation revealed that area 1 exhibited a smaller magnification factor than 3b, as evidenced by a smaller area of activation elicited by distal finger pad stimulation. Effects of paired finger pad stimulation produced largely similar effects in area 1 and area 3b. Paired finger pad stimulation produced reductions in the area of digit activation in area 1, suggesting the presence of lateral inhibition and funneling of information in area 1. Suppressive effects were stronger for paired stimulations at adjacent than at nonadjacent sites. Single-unit recordings revealed a mixture of either a summation or a suppression of the response to paired finger stimulation, compared with single finger pad stimulation of the primary digit. However, the average population response showed that paired finger pad stimulation resulted in response suppression. Based on this study and previous studies, we suggest the presence of at least three distinct ranges of lateral inhibition in areas 3b and 1.
对皮肤的刺激会在体感皮层中引发按拓扑结构组织的激活。然而，这种表征依赖于上下文，因为当用诱发冯·贝凯西漏斗错觉的复杂触觉刺激进行刺激时，在3b区会观察到不同的皮层拓扑结构。在此，我们报告了在麻醉的松鼠猴中，通过内在光学成像观察到的1区和3b区对远端指腹压力压痕的群体反应。对单个指腹的刺激显示，1区的放大系数小于3b区，远端指腹刺激引发的激活面积较小就证明了这一点。配对指腹刺激在1区和3b区产生的效果大致相似。配对指腹刺激使1区中手指激活面积减小，这表明1区存在侧向抑制和信息汇聚。相邻部位的配对刺激比非相邻部位的配对刺激抑制作用更强。与对主要手指的单个指腹刺激相比，单单位记录显示对配对手指刺激的反应既有总和也有抑制。然而，平均群体反应表明，配对指腹刺激导致反应抑制。基于本研究和先前的研究，我们认为在3b区和1区至少存在三种不同范围的侧向抑制。
