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Free keywords:
short-term memory, alpha band, oscillations, electroencephalography, inhibition
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 delayed-recognition short-term memory
tasks. These increases have been proposed to reflect the inhibition, for example, of cortical
areas representing task-irrelevant information, or of potentially interfering representations from
previous trials. Another possibility, however, is that elevated delay-period alpha-band power
(DPABP) reflects the selection and maintenance of information, rather than, or in addition to,
the inhibition of task-irrelevant information. In the present study, we explored these possibilities
using a delayed-recognition paradigm in which the presence and task relevance of shape
information was systematically manipulated across trial blocks and electroencephalographic was
used to measure alpha-band power. In the first trial block, participants remembered locations
marked by identical black circles. The second block featured the same instructions, but locations
were marked by unique shapes. The third block featured the same stimulus presentation as
the second, but with pretrial instructions indicating, on a trial-by-trial basis, whether memory
for shape or location was required, the other dimension being irrelevant. In the final block,
participants remembered the unique pairing of shape and location for each stimulus. Results
revealed minimal DPABP in each of the location-memory conditions, whether locations were
marked with identical circles or with unique task-irrelevant shapes. In contrast, alpha-band
power increases were observed in both the shape-memory condition, in which location was
task irrelevant, and in the critical final condition, in which both shape and location were task
relevant. These results provide support for the proposal that alpha-band oscillations reflect
the retention of shape information and/or shape–location associations in short-term memory.
