要旨
In our previous VSDI studies carried out on anesthetized cats we reported that spontaneous ongoing cortical activity in areas 17 and 18 represented dynamic spatial patterns, and about 20 of these patterns resembled the functional architecture of orientation domains. These patterns covered a large cortical areas of up to the entire imaged areas of up to 6X6 mm (Grinvald et al., 1989; Arieli et al., 1995; Arieli et al., 1996; Tsodyks et al., 1999; Kenet et al., 2003; Ringach D.L., 2003). To find whether these results are relevant to the awake behaving primate we preformed VSDI of ongoing cortical activity in the visual cortices of awake monkeys simultaneously with measurements of single unit activity and the local-field potential. We found coherent activity also in the awake monkey. However, the dynamics was very different form that found in anesthetized cats and in a single epoch we could not recognize any pattern that look like the known functional architecture. Nevertheless we found that such patterns do appear: the pairwise correlation among pixels of known functional architecture as a function of the orientation difference between these pixels or their ocularity index had the same stereotypic shape for evoked activity and for spontaneous epoch. Similar results were obtained also in the anesthetized monkeys. However, in the anesthetized monkey spontaneous cortical activity that resembled the functional architecture were also found just like in the anesthetized cat. Scrutinizing the data for on-going activity we found that the two OD maps were spontaneously represented to a much larger extent than orientation representations. Cortical states with >0.5 correlation to OD domains appear 6 of the time and span 20 Of the imaged area (~2X2 mm). Cortical states with >0.5 correlation to VH, domains appear for 0.1 of the time and span ~10 of the imaged area, (~1X1 mm). Furthermore, cortical states which resemble OD maps tend to switch into their corresponding orthogonal states. We also found that the size of the area that spontaneously represent orientation maps or OD maps were varied from one time window to the next. We’ve also found a strong positive correlation (e.g. 0.89) between the coverage area activated during given state and its duration. Namely, states which cover large cortical area last longer then states which span small cortical area.
