Effects on MEG coherence with working memory load

We examined magnetoencephalography (MEG) coherence in the 5 bands (alpha1, alpha2, beta1 and beta2) while the subjects were performing working memory tasks. MEG signals were recorded from 5 healthy males using the whole-head SQUID system. The tasks required comparing each of the current stimulus to the one that appeared on either verbal or spatial attributes 1-3 trials previously. The results showed that coherence in the beta2 (19 - 30 Hz) band between regions of left hemisphere dominance significantly increased with increasing memory load during verbal working memory tasks. On the other hand, no significant changes of coherence with increasing memory load during spatial working memory tasks were obtained between any pair of sensor sites in the beta2 band. These results suggest that the spatial and verbal working memory tasks differently modulate the component of the neural circuit, and greater connections between the cortex regions of the left hemisphere increase with verbal working memory load.