运动结构背景对视觉系统神经元反应的调制作用

MODULATION OF MOVING TEXTURED BACKGROUND FOR THE RESPONSE OF NEURONS IN VISUAL SYSTEM

对蟾蜍的５６个视顶盖神经元的视觉反应进行了定量考察和分析，发现它们不仅对黑目标起反应，也对结构目标起反应．同相运动的结构背景使５３．５％的神经元的反应完全抑制，而异相运动则只有１０％的神经元完全被抑制，却有２１．６％的神经元反应增强．遮盖感受野（ＲＦ）中心区，则同相运动使某些细胞脱抑制，而异相运动使其抑制强度稍有增强．遮盖ＲＦ的外周区，几乎全部研究过的神经元对结构背景运动本身也起反应。本研究还发现，如果预先将一目标放在兴奋性感受野（ＥＲＦ）中央静止不动，并使结构背景在水平方向匀速移动较长时间后突然停止运动，则被研究过的６６个视盖神经元中有２９个发放一串脉冲，即神经元的运动后放电．各个神经细胞放电的脉冲多寡不一。若在ＥＲＦ中央不放置静止目标，仅是结构背景的水平运动不能诱发放电．此效应的出现，既与目标背景间反差符号（即目标为白色或黑色）无关，也与背景的运动方向无关。为诱发这一效应，不仅要求背景运动时间较长（至少在２０秒以上），而且目标的面积要有足够大。

Single unit bardingS form ophc teCtum of toads have revealed the moving textuals background to be very effcctive to modulate the neuronal activities in toad. 56 tectal neamns as,T7 and T4 etc.) were quantitatively analal. All of them asponded Well to the objat(homogeneous black or texted pattern caldboard) hodrintally moving thIDugh the excitatorytive field (ERF) of neuron, if the texted backgr Dund was held to be stationary. If thetextured batwund moved synchronouSly with the objat (i.e. in the in-pha Se movementcondition), 53.5% of there neurons in asponse to the moving objod were comPletely inhibital.Hoal, in the anti--phase condition, only 10% neurons were compledy inhibital and even21.6% acts w facilitated. the masking the rmhal arm of ac, some neamns were slightlydisinhibital in the in--phase condition, Whrm the strength of inhibition seems to be insllghtiy in the anti--phase tohdition. If the sunounding aam of the RF was masked, almostall neurons clearly asponded to the moving texted background alone and therefore it rather dtod to drmte the spilles elite by the moving object from those elldtal bythe moving backgnund in both in--phase and anh--phase conditions.The tectal neamns did not aspond to moving texted background alone. If an objed(e.g. 8 x & deg black square) held stationary in the acter of the ERF, while the textted backgIDund was moved for a period of the (e.g. 30s), some tectal neamns discharged a bait ofspilles within a few second after stopping the movis of the background. This response characterstic wu temporarily nabs 'neuronal motion aams--asponse'. 29 out of 66 neamns u0nder investigation showed this effed. The aam rate varied from a few spilles to rather long duration of discharges in diot neamns. Its appearance had independence either upon the signof the objed (i.e. black or white) / background contlast or upon the dation of background movement. In order to induce this effed it was mprit that not only the backgroundhad to be moved for rather long tabs (at least more than 20 s), but also the she of the objedhad to be large enough. It slnt likely that the optimum size of the objed was enoughto cover the Ear of the nearen.