Amplitude and frequency characteristics of attentional modulation of gamma-band synchronization within and between monkey areas V1 and V4 I Grothe1, S D Neitzel2, S Mandon2, A K Kreiter2 |
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1Fries lab, Ernst Strüngmann Institute (ESI), Germany |
| Gamma-band synchronization (GBS) has been proposed to serve as a mechanism of selective attention. We have previously reported enhancement of local, intra-areal GBS in V4, when attention was inside the V4 receptive field (RF). Recently, we also reported inter-areal GBS between V4 and V1. A local V4 population selectively synchronized with only one of its multiple V1 input populations, namely that one representing the attended stimulus. Here, we characterize the interactions between intra- and inter-areal GBS in more detail; in particular frequency, timing and amplitude modulations of intra- and inter-areal GBS with attention. The monkeys had to attend one of two simultaneously presented, non-overlapping shapes, placed within the same V4 RF. Attention could be directed in- or outside the V1 RF, but was always within the V4 RF. For both monkeys, we found a clear increase in V1 gamma-band power with attention inside the V1 RF. The peak frequency of the inter-areal GBS was similar to that of the local V1 GBS, whereas the local V4 peak frequency was higher. Our findings might indicate that the local V1 GBS is fully engaged in the selective inter-areal routing process whereas other processes and interactions contribute to the V4 GBS. |
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