Gain Changes in Response to Full Field Flicker

Gain control is a core feature of cortical processing that provides neurons with an increased effective dynamic response range and may play a role in cognitive processes such as selective attention. Deficits in gain control are associated with psychiatric disorders such as schizophrenia, affecting about 1% of the population. The goal of this project is to understand gain control better and to develop an intervention that improves gain control. We previously showed that exposure to full-field flicker increases neuronal gain in the primary visual cortex of non-human primates (NHP). The current study investigated whether full-field flicker changes gain in the human brain. We exposed human volunteers to periods of visual flicker at frequencies (0, 5, 10, 20, and 40 Hz) and recorded whole-brain responses using 256-channel high-density EEG. We mapped these responses to cortical regions using source localization based on individual structural MRIs. Corroborating our findings in NHP, we found that exposure to full-field flicker increases gain in human visual cortex in a frequency-tuned manner. In addition, the EEG recordings' whole-brain coverage revealed strong responses and gain changes extending well beyond visual cortex. We conclude that full-field flicker is a potent driver of cortical activity in primates and that prolonged exposure to this stimulus can substantially increase the gain of a wide range of cortical networks.