Evidence for Attentional Sampling in the MEG Gamma Band Response A Landau, H Schreyer, S van Pelt, P Fries |
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ESI for Neuroscience in Cooperation with MPS, Germany
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| Overt exploration behaviors, such as whisking, sniffing, and saccadic eye movements are often characterized by a theta/alpha rhythm. In addition, the electrophysiologically recorded theta or alpha phase predicts global detection performance. These observations raise the intriguing possibility that covert selective attention samples from multiple stimuli rhythmically. Previously we found that following a reset event to one location, detection performance fluctuated rhythmically. Additionally, different locations were associated with opposing phases of the rhythmic sampling. This suggests that selective attention entails exploration rhythms similar to other exploration behaviors. Spatial attention has been mechanistically linked to gamma band activity in visual brain regions. Gamma synchronization is a proposed mechanism supporting inter-areal communication of attended stimuli. Here, we used MEG to identify bilateral sources of gamma induced by two corresponding contralateral stimuli. We found that gamma band-limited power fluctuated at a theta/alpha rhythm, and the phase of this fluctuation predicted behavioral outcome. Importantly, different behavioral outcomes were preceded by opposing phases of the theta/alpha fluctuations. These findings provide further support for the idea that attention to multiple locations is supported by sequential sampling and suggest a functional role for cross frequency coupling between sustained gamma band response and lower frequencies in the theta/alpha range. |
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