Increased Alpha-Band Power during the Retention of Shapes and Shape-Location Associations in Visual Short-Term Memory

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.

Neural oscillatory correlates of duration maintenance in working memory

“…It is still debated whether alpha oscillation is related to successful maintenance of item information Palva and Palva, 2007;Hsieh et al, 2011;Johnson et al, 2011), or whether it reflects inhibition of task-irrelevant information (Jokisch and Jensen, 2007;Klimesch et al, 2007;Tuladhar et al, 2007;Manza et al, 2014). Our study provided three pieces of evidence to support the maintenance rather than inhibition.…”

“…However, the precise role of the alpha band in WM is still under debate. Some scholars have proposed that oscillatory alpha activity reflects the inhibition of cortical areas representing task-irrelevant information (Jokisch and Jensen, 2007;Klimesch et al, 2007;Tuladhar et al, 2007;Manza et al, 2014), while others have suggested that alpha oscillation is related to successful maintenance of item information Palva and Palva, 2007;Hsieh et al, 2011;Johnson et al, 2011). Duration maintenance in WM has received much less attention compared with non-temporal stimulus properties, and the relationship between neural oscillation and duration maintenance in WM has yet to be identified.…”

“…As the theta band reflects the organization of sequentially ordered WM items (Hsieh et al, 2011;Roberts et al, 2013;Roux and Uhlhaas, 2014), the temporal order was equal for four duration conditions; thus, we predicted that the amplitude of the theta band would not be modulated by the length of duration retained in WM. As previously stated, we hypothesized that different internal representations would be retained in WM for durations below and above about 3 s. We inferred that if alpha oscillation is related to successful maintenance of item information (Palva and Palva, 2007;Hsieh et al, 2011;Johnson et al, 2011), then the alpha band activity would reflect different internal representations of durations below and above about 3 s retained in WM. If alpha oscillation reflects inhibition of task-irrelevant information (Jokisch and Jensen, 2007;Klimesch et al, 2007;Tuladhar et al, 2007;Manza et al, 2014), and there is no relationship between alpha band activity and internal representation of duration retained in WM, we would observe no significant alpha band difference between durations above and below about 3 s.…”

“…Research shows that theta oscillation reflects the organization of sequentially ordered WM items (Hsieh et al, Roberts et al, 2013;Roux and Uhlhaas, 2014). Alpha band activity (8-12 Hz) over the parieto-occipital region increases with the number of items maintained in WM, such as locations (Gevins et al, 1997;Johnson et al, 2011), letters , digits (Meltzer et al, 2007), shapes (Johnson et al, 2011), and faces (Jokisch and Jensen, 2007;Tuladhar et al, 2007). However, the precise role of the alpha band in WM is still under debate.…”

Correlation of EEG with neuropsychological status in children with epilepsy

“…Hypotheses regarding the alpha rhythm include: (1) an electrophysiological marker of an “idling” state of the brain (Pfurtscheller et al, 1996), (2) suppression of unattended sensory information (Worden et al, 2000; Kelly et al, 2006; Thut et al, 2006), especially in the suppression of task-irrelevant information (Klimesch et al, 2007; Jokisch, Jensen, 2007; Jensen, Mazaheri, 2010), and (3) retention and processing of task-relevant information (Palva, Palva 2007; Johnson et al, 2011). The fascinating and complex roles that alpha range rhythms play in cognitive function have been reviewed (Palva, Palva, 2007; Klimesch, 2012).…”