第17回日本神経科学会(名古屋)1993.12.7-9

サル下側頭葉皮質TE野ニューロンに対する刺激図形のコントラスト極性反転および輪郭線化の影響

伊藤南、藤田一郎、田村弘、田中啓治 
理研 フロンティア 思考電流、新技術事業団さきがけ21、理研 情報科学

TE野は物体視の中枢とされ、細胞は中程度に複雑な図形特徴に選択的に反応する。物体像の脳内表現形成を調べるために、最適図形特徴のコントラスト依存性を調べた。極性反転は45例中31例で反応が65%以上減弱し、輪郭線表示は19例中13例で反応が半減した。12例中9例で極性反転により選択性が変化した。大多数のTE野細胞ではコントラストの極性は図形特徴の重要な構成要素である。


EFFECTS OF CHANGES IN STIMULUS CONTRAST POLARITY ON CELL RESPONSES IN THE MACAQUE INFEROTEMPORAL CORTEX.

Ito, M., Fujita, I., Tamura, H. and Tanaka, K.
Neurosci. Res.Suppl. 18: s186

  Area TE of the macaque inferotemporal cortex is thought to be crucial for object vision and most cells in TE respond selectively to particular complex features of objects.  To understand how these selective responses represent the images of objects, we examined their sensitivity for changes in contrast polarity of the optimal stimuli.
  Recordings were made in anesthetized, immobilized monkeys(Macaca fuscata).  After isolation of single cell activity, we first determined the optimal stimulus.  Several tens of 3D objects were presented to search for effective stimuli.  Video-images of effective stimuli were simplified step by step to determine the necessary and sufficient features for the maximal responses.  Then, the contrast polarity of the image was reversed or the feature was expressed only with outlines, and changes of responses were examined.  The contrast reversal decreased the responses by more than 65% in a majority of cells (31/45,69%), and the outlilne-expression of the critical feature did not activate a majority (13/19, 68%).  The contrast sensitive cells are distributed throughout a most anterior-posterior range of TE (from A20 to A3.9).  Several modifications of the critical feature were made to examine if the selectivity remains after the contrast reversal.  In 75% of cells (9/12), the selectivity seen under appropriate contrast polarity was partly changed under the reversed contrast or outline-expression.  We conclude that the contrast polarity is an important factor for image representation by most cells in area TE.


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