, 1989) Most studies testing the BBS hypothesis investigated dis

, 1989). Most studies testing the BBS hypothesis investigated distributed neuronal activations within a given area (Singer and Gray, 1995). Yet, a stimulus activates neurons distributed across several brain areas and the BBS hypothesis is meant to apply also to such interareal neuronal assemblies. As V4 neurons with two stimuli in their RF dynamically represent the attended stimulus, the BBS hypothesis predicts that they should dynamically synchronize to those V1 neurons that represent the Bioactive Compound high throughput screening same, i.e., the attended, stimulus. This prediction is confirmed

by our present results. Attention affected the gamma rhythm in area V1: while there was no significant attention effect on gamma power, there was a very reliable increase in gamma frequency. The absence of an attentional effect on gamma power in V1 disagrees with one previous ISRIB supplier study using small static bar stimuli (Chalk et al., 2010) and agrees with another previous

study that used very similar stimuli and task as our paradigm (Buffalo et al., 2011). The attentional increase in gamma peak frequency has not been reported before. It is intriguing, because attention to a stimulus is similar to an increase in stimulus contrast (Reynolds and Chelazzi, 2004), and higher contrast induces higher gamma-band frequencies in monkey area V1 (Figure S5A) (Ray and Maunsell, 2010). Higher contrast typically results in gamma power to increase (Henrie and Shapley, 2005; Chalk et al., 2010). Yet, for very high contrast levels, gamma power can saturate or even decrease, as is illustrated in Figure S5B, which explains why attention to our full-contrast stimuli did not lead to further gamma power enhancements. Figure 5 shows that the local gamma peaks had a certain width, overlapping for their

larger parts. While the gamma peak frequency at the relevant V1 site was 2–3 Hz higher than at the irrelevant V1 site, it Fossariinae was 4–6 Hz higher than in V4. If one considered these slightly different gamma peak frequencies without the coherence results, then the simplest interpretation would be the following: the rhythms at the attended V1 site, the unattended V1 site, and the V4 site reflect three independent sine wave oscillators with slightly, but distinctly different, frequencies; the width of the respective frequency bands is due to moment-to-moment deviations from perfect sine waves of the respective frequencies; those deviations are irrelevant noise. This interpretation entails that the three oscillators constantly precess relative to each other, because their peak frequencies differ. For example, in monkey P, the V1-attended gamma peak frequency was 65.3 Hz and the V4 gamma peak frequency was 59.5 Hz (Figure 5), i.e., the peak frequencies differed by roughly 6 Hz.

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