Sensorimotor Network Contributions to Rhythm, Syntax, and Domain-general Cognitive Processing

Rhythm and syntax have many behavioral, theoretical, and neural similarities that suggest that some of the underpinning neural resources may be shared. However, no work has sufficiently examined neural overlap within the same group of participants, nor has anyone examined contributions of beta oscillations—which are theorized to underpin predictive coding—to rhythm and syntax behavior using transcranial alternating current stimulation. This dissertation outlines three experiments that used functional magnetic resonance imaging and transcranial alternating current stimulation to identify potentially overlapping neural circuits recruited by both rhythm and syntax that are distinct from domain-general multiple demand processes. In the first experiment, the pre-supplementary motor area was identified as a candidate region that overlaps across rhythm and syntax but is distinct from multiple demand cognition. The second and third experiment examined how beta band pre-supplementary motor area activity contributes to syntax and rhythm behavior respectively. Participants who received targeted beta band transcranial alternating current stimulation to the pre-supplementary motor area responded more accurately to syntactically complex sentences compared to a group who received sham stimulation. Furthermore, participants who received the same stimulation responded more quickly during a rhythm discrimination task compared to peers who received sham stimulation. These three experiments suggest that beta oscillations in the pre-supplementary motor area are possibly involved in both rhythm and syntax perception. I propose that these phenomena indicate that predictive coding of temporal events is the shared mechanism between rhythm and syntax, and I highlight additional experiments that can be performed to critically examine this theory.