Positron emission tomography (PET) was used to investigate the functional brain anatomy associated with the short-term maintenance of linguistic information. Subjects were asked to retain five related words, unrelated words, or pseudowords silently for the duration of a 40 sec PET scan. When brain activity during these short-term maintenance tasks was compared with a visual fixation control task, increases were found bilaterally in the dorsolateral prefrontal cortex and cerebellum, and medially in the supplementary motor area. Furthermore, effects of stimulus condition and recall performance were found in the left frontal operculum. To investigate the role of articulatory systems in the maintenance of verbal information, regional activation was compared across the maintenance tasks and a covert articulation task (silent counting). The cerebellum was active in both task conditions, whereas activation in prefrontal regions was specific to the maintenance condition. Conversely, greater activation was found in a left middle insular region in the silent counting than in the maintenance tasks. Based on converging results in this and previous studies, dorsolateral prefrontal cortical areas appear to contribute to the maintenance of both verbal and nonverbal information, whereas left frontal opercular regions appear to be involved specifically in the rehearsal of verbal material. Contrary to results found in other studies of working memory, activation was not found in the inferior parietal cortex, suggesting that this area is involved in aspects of stimulus encoding and retrieval, which were minimized in the present study.

Wakeful rest is a brief (e.g., 10 minutes), quiet period of minimal stimulation, which has been shown to facilitate memory performance, compared to a distractor task. Researchers have argued that this benefit is driven by automatic consolidation during the wakeful rest period.However, prior studies have not fully ruled out a controlled rehearsal mechanism, which might also occur during wakeful rest. In the current study, we attempted to replicate the wakeful rest effect under conditions that more strictly limit the possibility of rehearsal. Across six experiments, we manipulated parameters of a standard wakeful rest paradigm, including the type of target materials (word lists or abstract shapes), intentionality of encoding (incidental or intentional), and final retrieval delay (immediate or delayed). Additionally, we tested both younger and older adults to test whether these effects are consistent across the adult lifespan.Importantly, we observed the expected wakeful rest memory benefit in recall for verbal targets, which are easily rehearseable, but not for abstract shapes, which cannot be readily rehearsed.This pattern occurred in both younger and older adults. These results place constraints on the generalizability of wakeful rest memory benefits and suggest that the effect may be at least partly driven by rehearsal processes, rather than an automatic consolidation process. Wakeful Rest 3Memory consolidation has been viewed as involving neurological processes, ranging from the molecular to the systems levels, acting to stabilize memory traces over time (for review, see 1-5; but also see 6,7). These consolidation processes are theorized to ultimately transfer the storage of a memory trace from hippocampal to neocortical areas, resulting in a stronger longterm trace that is less prone to forgetting. Evidence for consolidation, comes from a wide, interdisciplinary range of sources including studies of amnestic individuals (e.g., 9,10), animal lesion experiments (e.g., 11), computational modeling of lesioned memory performance (12), experimental manipulations of sleep (for review, see 13), pharmacological manipulations of specific neurotransmitter agonists and antagonists (e.g., 14,15), as well as studies of neural replay in animals (16) and humans (17). Despite this broad interest within the domains of neuroscience and computational modeling, there have been relatively few attempts to manipulate consolidation processes within the span of a behavioral laboratory experiment. Hence, many cognitive questions about consolidation processes remain unaddressed. For instance, does consolidation require supra-threshold reactivation of a memory trace? Is consolidation influenced by motivational states or intentionality? Does consolidation demand attentional capacity?In pursuit of such cognitive questions, researchers have more recently developed an intriguing experimental paradigm using "wakeful rest," a brief period (roughly 10 minutes) of minimal stimulation while individuals are awake. In a typical wakeful rest paradigm...