Publication Date


Document Type


Committee Members

Sherif Elbasiouny, Ph.D. (Advisor); Subhashini Ganapathy, Ph.D. (Committee Member); Assaf Harel, Ph.D. (Committee Member)

Degree Name

Master of Science in Biomedical Engineering (MSBME)


The posterior alpha rhythm, seen in human electroencephalograms (EEG), is posited to originate from cycling inhibitory/excitatory states of visual relay cells in the thalamus, which could result in discrete sampling of visual information. Here, we tested this hypothesis by presenting light flashes at perceptual threshold intensity through closed eyelids to 20 participants during times of spontaneous alpha oscillations. Alpha phase and amplitude were calculated relative to each individual’s retina-to-V1 conduction delay, estimated by the individuals’ C1 visual-evoked potential latency. Our results show that an additional 20.96% of stimuli are observed when afferenting at V1 during an alpha wave trough (272.41°) than at peak (92.41°) phase. Additionally, the perception-phase relationship is observed at high, but not low alpha amplitudes. These results support the visual sampling hypothesis and, considering the alpha rhythm’s negative correlation with attention, suggests that the alpha rhythm facilitates attention by down-sampling task-irrelevant information.

Page Count


Department or Program

Department of Biomedical, Industrial and Human Factors Engineering

Year Degree Awarded