Age predicts visual gamma oscillation frequency

Abstract

Event Abstract Back to Event Age predicts visual gamma oscillation frequency William Gaetz1*, Suresh Muthukumaraswamy2, Krish Singh2 and Timothy Roberts1 1 Children's Hospital of Philadelphia, Biomagnetic Imaging Laboratory, United States 2 Cardiff University, CUBRIC, School of Psychology, United Kingdom There is increasing interest in gamma oscillations (> 40 Hz) as an index of visual information processing. Recent reports have shown considerable inter-individual variability of induced gamma oscillation frequency and amplitude yet the underlying factors behind this variability are unclear. The purpose of the current study was to examine how gamma frequency and amplitude cortical measures relate to basic between subject factors such as age. Participants (N=41) ranged in age from 11 to 44 yrs (mean of 31 yrs). Stimuli consisted of vertical, stationary, maximum contrast, three cycles per degree, square-wave gratings presented on a mean luminance background. Stimuli were presented in the lower left visual field and subtended 4° both horizontally and vertically, with the upper right corner of the stimulus located 0.5° horizontally and vertically from a small red fixation cross. Participants were instructed to fixate for the entire experiment and to press a response key with the right index finger at the termination of each stimulation period (varying in duration 1.5 to 2 s). MEG data was first analyzed using synthetic aperture magnetometry (SAM) and then by performing time-frequency analysis of SAM source waveforms at SAM peak locations from right primary visual cortices. Consistent with previous findings, gamma oscillations show considerable inter-individual variability in terms of frequency, and amplitude. However, our results demonstrate a significant negative correlation between the observed gamma oscillation frequency and the participant’s age (r = -0.53, p < 0.0005). A recent report [1] assessing both MEG visual gamma and MRS GABA indicate that gamma frequency is also correlated with GABA concentration. Thus, the reduction of visual gamma frequency may be in part due to the known decrease of GABA with increasing age [2, 3].