Blog Archives

Working memory and response inhibition in children and adolescents: Age and organization issues

The aim of the present study was to examine the role of age in the organization of verbal working memory, visuospatial working memory and inhibition; specifically whether these constructs could be considered unitary or separate in children aged 7 to 12 years (n = 164) and in adolescents aged 13 to 16 years (n = 75) using a multi-group confirmatory factor analysis. Results suggested that verbal working memory, visuospatial working memory and inhibition improved from childhood to adolescence. However, improvement was not followed by a change in the organization of these components. Verbal working memory, visuospatial working memory and inhibition constituted separable but associated constructs in children and in adolescents.

from Development and Aging

Individual Differences in Working Memory Capacity Determine the Effects of Oculomotor Task Load on Concurrent Word Recall Performance

In this study, the interaction between individual differences in working memory capacity, which were assessed by the Korean version of the California Verbal Learning Test (K-CVLT), and the effects of oculomotor-task load on word-recall performance are examined in a dual-task experiment. We hypothesized that varying levels of oculomotor-task load should result in different demands on cognitive resources. The verbal working memory task used in this study involved a brief exposure to seven words to be remembered, followed by a 30-second delay during which the subject carried out an oculomotor task. Then, memory performance was assessed by having the subjects recall as many words as possible. Forty healthy normal subjects with no vision-related problems carried out four separate dual-tasks over four consecutive days of participation, wherein word-recall performances were tested under unpredictable random SPEM (smooth pursuit eye movement), predictive SPEM, fixation, and eyes-closed conditions. The word recall performance of subjects with low K-CVLT scores was significantly enhanced under predictive SPEM conditions as opposed to the fixation and eyes-closed conditions, but performance was reduced under the random SPEM condition, thus reflecting an inverted-U relationship between the oculomotor-task load and word recall performance. Subjects with high K-CVLT scores evidenced steady word recall performances, regardless of the type of oculomotor task performed. The concurrent oculomotor performance measured by velocity error did not differ significantly among the K-CVLT groups. However, the high-scoring subjects evidenced smaller phase errors under predictive SPEM conditions than did the low-scoring subjects; this suggests that different resource allocation strategies may be adopted, depending on individuals’ working memory capacity.

from Brain Research

Exploring the Outcomes of a Novel Computer-Assisted Treatment Program Targeting Expressive-Grammar Deficits in Preschoolers with SLI

: Results suggested that treatments designed to directly address expressive-grammar deficits were better than no treatment for preschool SLI. Further, use of a C-AT program may be another feasible treatment method for this disorder population.

from the Journal of Communication Disorders

Beyond Capacity Limitations II: Effects of Lexical Processes on Word Recall in Verbal Working Memory Tasks in Children With and Without Specific Language Impairment

Conclusions: Performance on verbal working memory span tasks for both SLI and CA children is influenced by word frequency, lexical cohorts, and semantic representations. Future studies need to examine the extent to which verbal working memory capacity is a cognitive construct independent of extant language knowledge representations.

from the Journal of Speech, Language, and Hearing Research

Modality specific cerebro-cerebellar activations in verbal working memory: An fMRI study

Verbal working memory (VWM) engages frontal and temporal/parietal circuits subserving the phonological loop, as well as, superior and inferior cerebellar regions which have projections from these neocortical areas. Different cerebro-cerebellar circuits may be engaged for integrating aurally- and visually-presented information for VWM. The present fMRI study investigated load (2, 4, or 6 letters) and modality (auditory and visual) dependent cerebro-cerebellar VWM activation using a Sternberg task. FMRI revealed modality-independent activations in left frontal (BA 6/9/44), insular, cingulate (BA 32), and bilateral inferior parietal/supramarginal (BA 40) regions, as well as in bilateral superior (HVI) and right inferior (HVIII) cerebellar regions. Visual presentation evoked prominent activations in right superior (HVI/CrusI) cerebellum, bilateral occipital (BA19) and left parietal (BA7/40) cortex while auditory presentation showed robust activations predominately in bilateral temporal regions (BA21/22). In the cerebellum, we noted a visual to auditory emphasis of function progressing from superior to inferior and from lateral to medial regions. These results extend our previous findings of fMRI activation in cerebro-cerebellar networks during VWM, and demonstrate both modality dependent commonalities and differences in activations with increasing memory load.

from Behavioural Neurology

The contributions of cerebro-cerebellar circuitry to executive verbal working memory

Contributions of cerebro-cerebellar function to executive verbal working memory were examined using event-related functional magnetic resonance imaging (fMRI) while 16 subjects completed two versions of the Sternberg task. In both versions subjects were presented with two or six target letters during the encoding phase, which were held in memory during the maintenance phase. A single probe letter was presented during the retrieval phase. In the “match condition”, subjects decided whether the probe matched the target letters. In the “executive condition”, subjects created a new probe by counting two alphabetical letters forward (e.g., f→h) and decided whether the new probe matched the target letters. Neural activity during the match and executive conditions was compared during each phase of the task. There were four main findings. First, cerebro-cerebellar activity increased as a function of executive load. Second, the dorsal cerebellar dentate co-activated with the supplementary motor area (SMA) during encoding. This likely represented the formation of an articulatory (motor) trajectory. Third, the ventral cerebellar dentate co-activated with anterior prefrontal regions Brodmann Area (BA) 9/46 and the pre-SMA during retrieval. This likely represented the manipulation of information and formation of a response. A functional dissociation between the dorsal “motor” dentate and “cognitive” ventral dentate agrees with neuroanatomical tract tracing studies that have demonstrated separate neural pathways involving each region of the dentate: the dorsal dentate projects to frontal motor areas (including the SMA), and the ventral dentate projects to frontal cognitive areas (including BA 9/46 and the pre-SMA). Finally, activity during the maintenance phase in BA 9, anterior insula, pre-SMA and ventral dentate predicted subsequent accuracy of response to the probe during the retrieval phase. This finding underscored the significant contribution of the pre-SMA/ventral dentate pathway – observed several seconds prior to any motor response to the probe – to executive verbal working memory.

from Cortex

Functional activation in the cerebellum during working memory and simple speech tasks

Verbal working memory is the ability to temporarily store and manipulate verbal information. This study tested the predictions of a neuroanatomical model of how the cerebellum contributes to verbal working memory (Desmond et al., 1997). In this model, a large bilateral region in the superior cerebellum is associated with articulatory rehearsal and a right-lateralized region in the inferior cerebellum is associated with the correction of errors within the working memory system. The Desmond et al. (1997) model was based on neuroimaging findings using item recognition tasks and comparisons between working memory and covert rehearsal tasks, whereas in this functional magnetic resonance imaging (fMRI) study we used a delayed serial recall (DSR) task because it relies more heavily on articulatory rehearsal, and our comparison tasks included both overt and covert speech tasks. Our results provide some support for the Desmond et al. (1997) model. In particular, we found multiple activation foci within the superior and inferior sectors of the cerebellum and evidence that these regions show different patterns of activation across working memory and speech tasks. However, the specific patterns of activation were not fully consistent with those reported by Desmond et al. (1997). Namely, our results indicate that activation in the superior sector should be functionally subdivided into a medial focus involved in speech processing and a lateral focus more specific to verbal working memory; the results also indicate that activation in the inferior sector is not uniquely right lateralized. These complex findings speak to the need for future studies to consider the speech-motor aspects of tasks, to investigate the functional significance of adjacent peaks of activation within large regions of cerebellar activation, and to use analysis procedures that support regional distinctions through direct statistical tests. Such studies would help to refine our understanding of how the cerebellum contributes to speech and verbal working memory.

from Cortex

Phonetic recalibration does not depend on working memory

Listeners use lipread information to adjust the phonetic boundary between two speech categories (phonetic recalibration, Bertelson et al. 2003). Here, we examined phonetic recalibration while listeners were engaged in a visuospatial or verbal memory working memory task under different memory load conditions. Phonetic recalibration was—like selective speech adaptation—not affected by a concurrent verbal or visuospatial memory task. This result indicates that phonetic recalibration is a low-level process not critically depending on processes used in verbal- or visuospatial working memory.

from Experimental Brain Research

In search of decay in verbal short-term memory.

Is forgetting in the short term due to decay with the mere passage of time, interference from other memoranda, or both? Past research on short-term memory has revealed some evidence for decay and a plethora of evidence showing that short-term memory is worsened by interference. However, none of these studies has directly contrasted decay and interference in short-term memory in a task that rules out the use of rehearsal processes. In this article the authors present a series of studies using a novel paradigm to address this problem directly, by interrogating the operation of decay and interference in short-term memory without rehearsal confounds. The results of these studies indicate that short-term memories are subject to very small decay effects with the mere passage of time but that interference plays a much larger role in their degradation. The authors discuss the implications of these results for existing models of memory decay and interference. (PsycINFO Database Record (c) 2009 APA, all rights reserved)

from the Journal of Experimental Psychology: Learning, Memory, and Cognition