Hemispheric alpha asymmetry and self-rated originality of ideas.

The generation of highly original ideas in divergent thinking tasks has been found to be associated with task-related changes in the alpha band. The goal of the current study was to determine if exposure to brainwave entrainment (BWE) at the alpha centre frequency before and during performance of a divergent thinking task would result in increases in task-related, event-related synchrony and the production of more highly original ideas. We found that alpha entrainment interfered with the oscillatory dynamics associated with divergent thinking such that only the control group showed greater right hemispheric engagement. Furthermore, the control group showed greater self-rated originality. These findings provide confirmation of the importance of hemispheric asymmetry in alpha power to successful divergent thinking and indicate that refinements are required in order for BWE to be used effectively to improve divergent thinking performance.

Short-term memory after all: comment on Sederberg, Howard, and Kahana (2008).

P. B. Sederberg, M. W. Howard, and M. J. Kahana have proposed an updated version of the temporal-context model (TCM-A). In doing so, they accepted the challenge of developing a single-store model to account for the dissociations between short- and long-term recency effects that were reviewed by E. J. Davelaar, Y. Goshen-Gottstein, A. Ashkenazi, H. J. Haarmann, and M. Usher (2005). In this commentary, the authors argue that the success of TCM-A in addressing the dissociations is dependent not only on an episodic encoding matrix but--critically--also on its implicit use of a short-term memory store--albeit exponential rather than buffer-like. The authors also highlight some difficulties of TCM-A in accounting for these dissociations, and they argue that TCM-A fails to account for critical data--the presentation-rate effect--that dissociates exponential and buffer-like models.

Probing culture in the head: the neural correlates of relational models.

Relational Models Theory or RMT proposes that there are four universal ways in which socio-economic relations can be organized. According to the RMT, each of its four relational models (Communal Sharing, Authority Ranking, Equality Matching, and Market Pricing) is associated with a distinct cognitive representation, with a cumulative pattern in which each relational model is a superset of the next lower model. This report for the first time uses a combination of cognitive and the social neuroscience to put this model to the test. RMT proposes that members of every culture use all four relational models, just in different proportions. It should therefore be possible to study their neural correlates in a mono-cultural sample. In this study, thirty-nine European-American students were imaged in a 3T Siemens Trio with a 24-channel head coil while rating the extent to which each relational model organized relationships with each of thirty-two acquaintances/friend/relatives in a boxcar design. FreeSurfer Functional Analysis Stream (FS-FAST) analyses revealed distinct patterns of activation for each of the relational models. The activations did not follow a cumulative hierarchical pattern, suggestive that this aspect of the RMT model should be revised.

Language performance under sustained work and sleep deprivation conditions.

INTRODUCTION: Although substantial research has been completed on the effects of sleep deprivation on performance, very little research has focused on language-based tasks. The purpose of the current study was two-fold: 1) to determine the extent to which short-term sleep deprivation affects language performance; and 2) to examine whether relatively short and easy-to-administer "probe" tasks could signal decrements in language performance under sleep deprivation conditions. METHODS: There were 38 non-native English-speaking students who were paid to complete a 28-h sleep deprivation study. The participants completed several potential cognitive and vigilance probe tasks and a variety of language-based tasks. Each task was administered four times, once in each testing session during the night (18:30-22:30, 23:00-03:00, 03: 30-07:30, and 08:00-12:00). All tasks were counterbalanced across the testing sessions. RESULTS: Repeated-measures ANOVAs indicated that language tasks that required sustained attention and higher level processing (e.g., reading comprehension) were negatively affected by sleep deprivation, whereas other tasks that relied primarily on more basic language processing (e.g., antonym identification) were not affected. Hierarchical linear modeling analyses assessed how well the probe tasks predicted language performance. These results indicated that performance accuracy and/or speed on many of the probe tasks predicted decrements in language performance. CONCLUSIONS: These findings suggest that sustained work conditions and sleep deprivation negatively affect some types of language performance. Moreover, the use of probe tasks indicates that easy-to-administer tasks may be useful to identify when detriments are likely to occur in language-based performance under sleep deprivation conditions.

The demise of short-term memory revisited: empirical and computational investigations of recency effects.

In the single-store model of memory, the enhanced recall for the last items in a free-recall task (i.e., the recency effect) is understood to reflect a general property of memory rather than a separate short-term store. This interpretation is supported by the finding of a long-term recency effect under conditions that eliminate the contribution from the short-term store. In this article, evidence is reviewed showing that recency effects in the short and long terms have different properties, and it is suggested that 2 memory components are needed to account for the recency effects: an episodic contextual system with changing context and an activation-based short-term memory buffer that drives the encoding of item-context associations. A neurocomputational model based on these 2 components is shown to account for previously observed dissociations and to make novel predictions, which are confirmed in a set of experiments.

Active maintenance of sentence meaning in working memory: evidence from EEG coherences.

The active maintenance of sentence meaning in working memory was investigated using event-related electroencephalogram (EEG) coherences. Participants read a sentence, retained it for 2.5 s, and then verified a statement about its meaning. The sentences contained either three semantically related nouns or unrelated nouns and started either with a what phrase (WH sentences) or not (non-WH sentences), imposing either a high or low demand on verbal working memory. Comprehension accuracy showed an interaction of semantic relatedness and sentence type due to the presence of a relatedness effect (lower accuracy in the unrelated condition) in WH sentences but not in non-WH sentences. During the post-sentence retention interval, EEG coherences also displayed this interaction of relatedness and sentence type. A semantic relatedness effect was obtained in the WH sentences (high demand) but not in the non-WH sentences (low demand). In addition, compared to a pre-sentence baseline and sentence presentation, coherences increased in the 10-14 Hz band during retention and decreased in the 4-6 Hz band. These coherence changes spanned prefrontal and posterior brain regions, possibly reflecting increased synchronization in projection loops between attention control systems in prefrontal cortex and activated meaning representations in semantic memory in posterior cortex. These findings suggest that short-term retention of the meaning of a sentence involves active maintenance in a capacity-limited working memory, accompanied by a heightened inner direction of attention after sentence presentation.

Short-term semantic retention during on-line sentence comprehension. Brain potential evidence from filler-gap constructions.

In filler-gap sentences, a phrase ('filler') is separated by intervening words from a subsequent phrase ('gap') with which it is integrated. The filler-gap interval provides a useful model for the study of short-term retention processes during sentence comprehension. Kluender and Kutas [J. Cogn. Neurosci. 5 (1993) 29] used event-related brain potentials (ERPs) to show that a filler phrase places a demand on short-term retention processes in the filler-gap interval, but left the processing level at which this demand arises unspecified. Here we use ERPs to address the issue of whether the filler places a demand on the semantic component of short-term retention processes in the filler-gap interval. Participants read filler-gap sentences, which began with a filler phrase and, in the filler-gap interval, contained a subject and object that were either semantically related or unrelated. There was also a control condition in which the filler phrase was absent (i.e. less memory demand). The main result was that during the filler-gap interval, bilateral posterior electrodes displayed a larger positivity for unrelated than related words. Moreover, during the same interval, posterior electrodes displayed a larger positivity for filler-gap sentences than for control sentences. In the control condition (non-filler gap sentences), manipulation of semantic relatedness did not produce differences in ERP activity. Our results suggest that a filler phrase places a demand on the semantic component of verbal working memory during on-line sentence comprehension.

Semantic similarity dissociates short- from long-term recency effects: testing a neurocomputational model of list memory.

The finding that recency effects can occur not only in immediate free recall (i.e., short-term recency) but also in the continuous-distractor task (ie., long-term recency) has led many theorists to reject the distinction between short- and long-term memory stores. Recently, we have argued that long-term recency effects do not undermine the concept of a short-term store, and we have presented a neurocomputational model that accounts for both short- and long-term recency and for a series of dissociations between these two effects. Here, we present a new dissociation between short- and long-term recency based on semantic similarity, which is predicted by our model. This dissociation is due to the mutual support between associated items in the short-term store, which takes place in immediate free recall and delayed free recall but not in continuous-distractor free recall.

Age-related declines in context maintenance and semantic short-term memory.

This study reports age-related declines in context maintenance (Braver et al., 2001) and semantic short-term memory (STM) and evidencc for a relation between the two. A group of younger and older adults completed a context maintenance task (AX-CPT), a semantically oriented STM task (conceptual span), a phonologically oriented STM task (digit span), and a meaning integration task (semantic anomaly judgement). In the AX-CPT task, a target response is required to the probe letter "X" but only when it is preceded by the letter "A" (the context). Either three (short interference) or six distractor letters (long interference) were presented between the cue and the probe. Results indicated an age-related deficit in context maintenance. Age-related declines were also observed for conceptual span and semantic anomaly judgement but not for digit span. Context maintenance was correlated with conceptual span and semantic anomaly judgement but not with digit span. These correlations were largely mediated by age differences, which also explained variance that was unique to (and not shared among) context maintenance, conceptual span, and semantic anomaly judgement.

Long-term memory is the representational basis for semantic verbal short-term memory.

The present study supports activation models of verbal short-term memory that include a semantic contribution to the retention process. Event-related brain potentials were used to probe the level of activation of semantic representations of a series of words in a delay interval following their presentation. The levels of activation were compared in two tasks: (1) a short-term memory task that involved a semantic judgment in the recall phase following the delay interval, and (2) a nonmemory control task. The level of semantic activation during the delay interval was higher in the short-term memory task, indicating that enhanced activation of semantic representations is involved in the short-term storage of verbal information. This result implies that activated long-term memory provides a representational basis for semantic verbal short-term memory, and hence supports theories that postulate that short- and long-term stores are not separate.

Neural synchronization mediates on-line sentence processing: EEG coherence evidence from filler-gap constructions.

This study investigated cognitive and neural processes involved in gap filling during on-line sentence comprehension. Electroencephalogram (EEG) coherences were used to demonstrate that increases in the synchronization of neural activity in different cortical regions occur during gap filling when load in semantic working memory is high due to semantically unrelated words in the filler-gap interval. Sentences could either require gap filling at a verb or not, and the nouns preceding the verb could be either semantically related or unrelated. In the unrelated but not related condition, coherences in the beta band were larger during verb processing for sentences requiring gap filling compared to sentences not requiring gap filling. The coherence changes involved linkages between frontal and posterior temporal-parietal sites in both hemispheres. These results further indicate that semantic working memory is involved in the process of gap filling.