"Examining the role of feedback to early visual cortex in visual awareness"

Abstract:
Early visual cortex plays a critical role in visual awareness; however, it is unclear whether that role stems purely from its function as a critical input to the visual system or whether it is also necessary during continued cortical dynamics. These two possibilities have been difficult to assess, in part because it is difficult to dissociate input from later processing. Here, we bypass V1 input functions by using single-pulse transcranial magnetic stimulation (TMS) over left posterior parietal cortex (PPC) to produce visual experiences in the form of a phosphene. We simultaneously recorded activity in bilateral occipital cortex and under the TMS coil using the event-related optical signal (EROS) to examine whether activity in early visual areas or in PPC is predictive of visual awareness.