Preparing for the unknown: How working memory provides a link between perception and anticipated action.

What mechanisms underlie the transfer of a working memory representation into a higher-level code for guiding future actions? Electrophysiological correlates of attentional selection and motor preparation processes within working memory were investigated in two retrospective cuing tasks. In the first experiment, participants stored the orientation and location of a grating. Subsequent feature cues (selective vs. neutral) indicated which feature would be the target for later report. The oscillatory response in the mu and beta frequency range with an estimated source in the sensorimotor cortex contralateral to the responding hand was used as correlate of motor preparation. Mu/beta suppression was stronger following the selective feature cues compared to the neutral cue, demonstrating that purely feature-based selection is sufficient to form a prospective motor plan. In the second experiment, another retrospective cue was included to study whether knowledge of the task at hand is necessary to initiate motor preparation. Following the feature cue, participants were cued to either compare the stored feature(s) to a probe stimulus (recognition task) or to adjust the memory probe to match the target feature (continuous report task). An analogous suppression of mu oscillations was observed following a selective feature cue, even ahead of task specification. Further, a subsequent selective task cue again elicited a mu/beta suppression, which was stronger after a continuous report task cue. This indicates that working memory is able to flexibly store different types of information in higher-level mental codes to provide optimal prerequisites for all required action possibilities.

Pattern reinstatement and attentional control overlap during episodic long-term memory retrieval.

Episodic long-term memory (eLTM) retrieval involves the reinstatement of neural patterns from the encoding phase. However, recent evidence suggests that comparable cortical activity patterns can also be linked to attentional control processes on the level of memory representations. The current investigation assesses these two processes independently based on alpha-beta-band activity in the electroencephalogram (EEG). During encoding, subjects were presented with an object on a certain position on the screen and had to imagine it on a new position. In each trial, either the task-irrelevant presentation position or the task-relevant imagination position was lateralized. In the retrieval phase, subjects first made an old/new judgement based on centrally presented objects and then reported the imagination position. Pattern reinstatement should be reflected in similar lateralized alpha-beta activity during encoding and retrieval. Conversely, the influence of attentional control processes during retrieval would be associated with the suppression of alpha-beta power contralateral to the to-be-reported imagination position and with the increase of activity contralateral to the irrelevant presentation position. Our results support this latter pattern. This shows that an experimental differentiation between selective attention and pattern reinstatement processes is necessary when studying the neural basis of eLTM retrieval.

Aging impairs primary task resumption and attentional control processes following interruptions.

Attentional selection of working memory content is impaired after an interruption. Here we investigate the neural correlates underlying attentional selection within working memory. We focus especially on how older and younger adults differ in attentional selection processes during primary task resumption. Participants performed a working memory task, while being frequently interrupted with either a cognitively low- or high-demanding arithmetic task. Afterwards, a retrospective cue (retro-cue) indicated the working memory content required for later report. The detrimental effect of the interruption was evident in both age groups, but while younger adults were more strongly affected by a high- than by a low-demanding interruption, the performance deficit appeared independently of the cognitive requirements of the interruption task in older adults. A similar pattern was found regarding frontal-posterior connectivity in the theta frequency range, suggesting that aging decreases the ability to selectively maintain relevant information within working memory. The power of mid-frontal theta oscillations (~4-9 Hz) featured a comparable effect of interruptions in both age groups. However, posterior alpha/beta power (~8-30 Hz) following the retro-cue was more diminished by a preceding interruption in older adults. These results suggest an age-related deficit in the attentional selection and maintenance of primary task information following an interruption that appeared independent from the cognitive requirements of the interrupting task.

How to refocus attention on working memory representations following interruptions-Evidence from frontal theta and posterior alpha oscillations.

Interruptions lead to a deterioration of primary task performance. Applied research usually describes a delay in primary task resumption as an essential component of this performance deficit. Here, we investigate this approach using electrophysiological correlates of the focusing of attention within working memory, a process that is fundamental to switching between different tasks. A lateralized working memory task was frequently interrupted by either a high- or low-demanding arithmetic task and a subsequent retrospective cue indicated the working memory item required for later report. The detrimental effect of interruptions on primary task performance was most pronounced for high-demanding interruptions. After retro-cue presentation, fronto-central theta power (4-7 Hz) was lowest following high-demanding interruptions and posterior alpha power (8-14 Hz) was less suppressed in the two interruption conditions. These effects might be related to a deficit in attentional control processes following the retrospective cue. Furthermore, we introduce the suppression of posterior alpha power contralateral to the remembered primary task stimuli during the interruption phase as a temporal marker for primary task resumption. Especially for cognitively demanding interruption tasks, this effect seems to overlap in time with the processing of the interruption, which should contribute to the primary task performance deficit.