Influence of connection type on phase synchrony: analysis of a neural mass model.

Empirical studies have demonstrated synchronized frontal and parietal electrophysiological signals at 22-34 Hz during a conjunctive visual search task and at 36-56 Hz during a pop-out visual search task. Bidirectional (conjunctive) versus unidirectional (pop-out) information transfer between neuronal populations is hypothesized to underly this difference in synchronization frequency. This study modeled the influence of connection type (i.e., unidirectional vs. bidirectional) on phase synchrony between two neural populations using a neural mass model. Phase-locking values (PLVs) were used as the measure of synchrony between populations. Consistent with the connectivity hypothesis, the model revealed greater PLVs at 22-34 Hz when the two populations were connected bidirectionally than unidirectionally, but greater PLVs at 34-52 Hz when connected unidirectionally than bidirectionally. The model suggests that inter-population connectivity also changes with bottom-up versus top-down control of attention.