Parietal Beta Oscillations and Representational Momentum: A tACS Investigation

Representational momentum (RM) is a cognitive phenomenon characterized by forward displacement in memory for the final position of moving objects. Following an overview of visual perception, this thesis comprehensively examines RM, exploring foundational research, modulating factors (target, display, context, observer), and competing theoretical accounts of its origins and functions. The empirical study investigated whether parietal beta oscillations (17 Hz) contribute to RM mechanisms, given their role in motion processing and predictive perception. Ten healthy adults completed a rotation discrimination task across three sessions with transcranial alternating current stimulation (tACS): beta-tACS (17 Hz) over bilateral parietal cortex, theta-tACS (6 Hz), or sham. Participants judged whether a probe bar matched the final orientation of a rotating inducer at varying speeds (50, 70, 90°/s). Results showed no significant tACS modulation of RM magnitude. However, beta-tACS reduced overall accuracy and showed a numerical trend toward diminishing speed effects on RM. These findings suggest parietal beta oscillations may support general visuospatial processing during motion perception rather than specifically mediating motion extrapolation, highlighting the need for further investigation into oscillatory dynamics underlying predictive visual processing.