s Band Rhythms Influence Reaction Times

Despite their involvement in many cognitive functions, s oscillations are among the least understood brain rhythms. Reports on whether the functional role of s is primarily inhibitory or excitatory have been contradictory. Our framework attempts to reconcile these findings and proposes that several s rhythms co-exist at different frequencies. s Frequency shifts and their potential influence on behavior have thus far received little attention. In this human magnetoencephalography (MEG) experiment, we asked whether changes in s power or frequency in auditory cortex and motor cortex influence behavior (reaction times) during an auditory sweep discrimination task. We found that in motor cortex, increased s power slowed down responses, while in auditory cortex, increased s frequency slowed down responses. We further characterized s as transient burst events with distinct spectro-temporal profiles influencing reaction times. Finally, we found that increased motor-to-auditory s connectivity also slowed down responses. In sum, s power, frequency, bursting properties, cortical focus, and connectivity profile all influenced behavioral outcomes. Our results imply that the study of s oscillations requires caution as s dynamics are multifaceted phenomena, and that several dynamics must be taken into account to reconcile mixed findings in the literature.