Less Segregated Processing of Visual Information in V2 than in V1 of the Monkey Visual Cortex

Abstract

To test the possibility of cross-talk between parallel pathways dealing with different aspects of visual information such as orientation, direction of motion and colour in cortical area V2, we quantitatively analysed visual responses of 121 V2 cells recorded from anaesthetized and paralysed macaques and compared them with those of 147 V1 cells. A selectivity index of visual responses was calculated for each neuron, which was then classified as selective or not to a particular attribute of visual stimuli. Twenty-one percent of the V2 neurons had dual selectivity to both colour and direction of stimulus motion (C&D cells). In V1, only 5% of the cells were C&D cells. Thus, the proportion of C&D cells significantly increased from V1 to V2. We also carried out cross-correlation analysis of spike trains recorded simultaneously from pairs of V2 neurons or pairs of V1 neurons. In V2, correlated firings could be observed between cells with completely different optimal orientation, such as orthogonal, while it was never observed in V1. The cross-correlation analysis further indicted that functional interactions in V2 were more widespread than those in V1. These results suggest that neurons which have different functional properties become less segregated, and that functional interactions become more widespread in V2 than in V1.

Input to V2 Thin Stripes Arises from V1 Cytochrome Oxidase Patches

“…Hubel and Livingston (1987) concluded that it represents a specialized color system in the primate. At least 13 other reports have focused on the physiological characteristics of cells in different V2 stripe classes (DeYoe and Van Essen, 1985;Peterhans and von der Heydt, 1993;Levitt et al, 1994;Ts'o, 1995, 1999;Gegenfurtner et al, 1996;Tamura et al, 1996;Yoshioka and Dow, 1996;Kiper et al, 1997;Xiao et al, 1999Xiao et al, , 2003Ts'o et al, 2001;Moutoussis and Zeki, 2002;Shipp and Zeki, 2002). The verdict from these studies has been mixed, with some investigators confirming that colorselective cells are more prevalent in thin stripes, and others dissenting.…”

Representation of Angles Embedded within Contour Stimuli in Area V2 of Macaque Monkeys

“…One candidate representing another line component is subthreshold excitatory interactions mediated by the long-range horizontal connections within area V2. Horizontal connections in the primary visual cortex are known to connect multiple cortical columns sharing the same orientation preference (Ts'o et al, 1986;Ts'o and Gilbert, 1988;Gilbert and Wiesel, 1989), but some V2 neurons having an orthogonal orientation preference show cross-correlation peaks near 0 msec, suggesting that horizontal connections may contribute to the formation of angle selectivity (Tamura et al, 1996). Complex integration beyond the CRFs has been observed in area V2 (von der Heydt and Peterhans, 1989;Bakin et al, 2000;Zhou et al, 2000).…”

Görsel Si̇stemde Paralel İşlem

“…Aynı çalışmada V1 lezyonunda görme keskinliği-nin azaldığı, V2 lezyonunda ise daha kompleks görsel ayırım testlerinin etkilendiği, bir diğer çalışmada V2 alanında birden fazla modaliteye yanıt veren hücre sayısının, V1 alanından daha fazla olduğu bulunmuş-tur. Bu bulgular, V2 alanının V1 alanına göre daha kompleks görsel işlemlerle ilişkili olduğunu göster-mektedir (19,27).…”

“…V2 alanında sitokrom oksidazla gösterilen ve VI'in farklı işlevsel bölgelerinden projeksiyon alan, farklı fonksiyonlarla ilişkili olduğu ileri sürülen açık, koyu kalın ve koyu ince çizgi bölgelerinde bulunan hücrelerin yanıt özellikleri birbirlerine benzerlikler göstermektedir, açık, ince ve kalın çizgiler birbiri ile bağlantılıdır (11,27,30).…”

“…Bu basamakta hücreler gitgide daha kompleks ve spesifik uyarılara duyarlı hale gelmektedirler. Örneğin inferior temporal korteks hücreleri V4 alanı hücrelerine göre, V4 alanı V2 alanına göre, V2 alanı V1 alanına göre, V1 alanı lateral genikulat hüc-relerine göre daha kompleks uyarılara yanıt vermektedir (13,19,27,36).…”