Abstract
Studies exploring the role of neural oscillations in cognition have revealed sustained increases in alpha-band (~8-14 Hz) power during the delay period of verbal and visual short term memory (STM) tasks. Such increases have been proposed to gate the flow of information from cortical areas representing potentially disruptive, task irrelevant information. In keeping with this possibility, alpha-band increases have been observed over cortical regions representing task-irrelevant properties of remembered stimuli (e.g., over the dorsal stream during the retention of face-identity vs. face-orientation information; Jokisch & Jensen, 2007). However, similar increases have also been observed when all remembered stimulus features are task relevant, and therefore inhibitory gating would presumably not be required (Johnson, et al. 2011). This suggests that alpha-band oscillations may play a role in the active retention of information in STM. In the present study, we explore a third possibility: that alpha-band oscillations reflect the gating of incoming sensory inputs, even when no task-irrelevant information is being retained. To test this possibility, we recorded the electroencephalogram (EEG) while subjects performed a change detection task that required the retention of varying numbers of colored squares on each trial. Importantly, on a portion of trials, a series of task-irrelevant checkerboard probes were presented bilaterally to assess the excitability of visual cortex. We reasoned that, if load-dependent alpha-band power increases represent the gating of sensory inputs, they should be associated with modulations of components of the visual evoked potential (VEP) on a subject-by-subject basis. Although we did observe group level load-dependent increases in the magnitude of the N1 VEP and in delay-period alpha-band power, these changes were not correlated at the individual subject level. We conclude that load-dependent changes in alpha-band power are not associated with the gating of task-irrelevant sensory inputs in the standard change detection task with bilateral stimulus presentation.
Meeting abstract presented at VSS 2014