Auditory-verbal Short-term Memory Research Articles

The 10-Word Auditory Verbal Learning Test and Vocabulary Performance in 4- and 5-Year-Old Children.

Understanding the different factors that determine vocabulary development in young children is essential for the diagnosis and rehabilitation of language disorders in children. Language development is closely related to other cognitive processes such as auditory verbal learning and memory. This research focuses on the development of a novel auditory verbal learning test (AVLT) for 4- and 5-year-old children within the Dutch population. This new test is an adaptation of the common AVLT for both older children and adults, usually including a list of 15 words. Considering the lower attention span and limited executive functioning in young children, the word list of this new instrument is reduced to 10 words. Besides, a second recognition form has been developed to improve the ability to distinguish between possible underlying learning and memory deficits. Ninety-five preschool children (ages 4;0-5;12 [years;months]) were tested with this new AVLT 10-word test for kids (10WT-K), yielding different measures of verbal auditory memory. Forty-eight of 95 children received a recognition task with semantically unrelated items, and 47 of 95 received a recognition task with semantically related items. Three additional language skills were assessed to establish test validation: receptive and expressive vocabulary performance and nonword repetition. Outcome of the 10WT-K was related to scores on the language measures. Positive correlations were found between the total score of the 10WT-K and all three aforementioned language skills. We found no correlations between frequency of error types (intrusions and repetitions) and language measures. Furthermore, children who were administered the recognition list with semantically related items showed fewer correct answers and more false-positive and false-negative responses than children who received a recognition list with semantically unrelated items. The 10WT-K for young children can be used to (a) measure different aspects of auditory verbal learning and memory, (b) clarify the nature of possible verbal learning difficulties, and (c) identify a possible nature of language disorders. The word recognition task tested with semantically related items provides a more accurate measurement of individual differences, namely, in distinguishing retrieval and storage abilities. The significant relation found between auditory verbal short-term memory capacity and vocabulary performance in preschool children is a first step toward establishing test validity.

Perks of blindness: Enhanced verbal memory span in blind over sighted adults

Blind individuals commonly use verbal encoding (i.e. text-to-speech) and memory-based strategies (i.e. serial recall) for situations in which sighted individuals use vision (i.e. finding items). These strategies may serve to train cognitive systems responsible for maintaining and manipulating verbal information. To test this hypothesis, we investigate whether early visual deprivation is linked to improved verbal short-term and working memory abilities, and thus might illustrate experience-dependent plasticity in memory systems. We also test whether the sensory modality for encoding information influences performance. Our data show that blind adults recalled more items on a verbal short-term memory span task than sighted participants. Furthermore, blind individuals performed equally well on auditory forward and backward conditions despite the fact that recalling items in reverse order is more difficult for the general population. However, the benefits of recalling items in reverse order did not extend to the tactile domain, specifically, a braille version of the short-term memory digit span task in blind individuals. Furthermore, we observed no differences between blind and sighted individuals on a more demanding auditory n-back task evaluating more complex working memory processes. We conclude that the memory benefits associated with blindness might be restricted to auditory-verbal short-term memory and likely reflect strategy use and practice.

Canonical Sentence Processing and the Inferior Frontal Cortex: Is There a Connection?

The role of left inferior frontal cortex (LIFC) in canonical sentence comprehension is controversial. Many studies have found involvement of LIFC in sentence production or complex sentence comprehension, but negative or mixed results are often found in comprehension of simple or canonical sentences. We used voxel-, region-, and connectivity-based lesion symptom mapping (VLSM, RLSM, CLSM) in left-hemisphere chronic stroke survivors to investigate canonical sentence comprehension while controlling for lexical-semantic, executive, and phonological processes. We investigated how damage and disrupted white matter connectivity of LIFC and two other language-related regions, the left anterior temporal lobe (LATL) and posterior temporal-inferior parietal area (LpT-iP), affected sentence comprehension. VLSM and RLSM revealed that LIFC damage was not associated with canonical sentence comprehension measured by a sensibility judgment task. LIFC damage was associated instead with impairments in a lexical semantic similarity judgment task with high semantic/executive demands. Damage to the LpT-iP, specifically posterior middle temporal gyrus (pMTG), predicted worse sentence comprehension after controlling for visual lexical access, semantic knowledge, and auditory-verbal short-term memory (STM), but not auditory single-word comprehension, suggesting pMTG is vital for auditory language comprehension. CLSM revealed that disruption of left-lateralized white-matter connections from LIFC to LATL and LpT-iP was associated with worse sentence comprehension, controlling for performance in tasks related to lexical access, auditory word comprehension, and auditory-verbal STM. However, the LIFC connections were accounted for by the lexical semantic similarity judgment task, which had high semantic/executive demands. This suggests that LIFC connectivity is relevant to canonical sentence comprehension when task-related semantic/executive demands are high.

Workplace stress and cognitive functions (a population based study of adults aged 25—44 years)

Objective: to investigate the effect of workplace stress on cognitive functions of younger men and women (25—44 years) in an open population of Novosibirsk.Patients and methods. The study included a representative sample of Novosibirsk population aged 25—44 years (2013—2016 screening) within the budgetary theme №0541-2014-0004. We screened individuals aged 25—44years: 463 men, mean age 35.94±5.957years, and 546 women, mean age 36.17±5.997 years. Association of workplace stress with cognitive functions were assessed with standardized questions such as: «Has your specialty changed over the past 12 years?», «Do you like your job?» and «How do you rate your work responsibility over the past 12 months?». Cognitive evaluation during screening period included: A.R. Luria 10-words learning task (immediate and delayed recall), Burdon's test, exclusion of concepts «5th extra», animal naming test.Results and discussion. We observed a decrease in semantic associations number among the respondents who did not change their occupation over the past year and among respondents who assess their work responsibility as «low». Verbal logical reasoning was lower in the respondents who assumed that they «did not like» or «did not like at all» their job and also assessed their work responsibility as «low». Auditory verbal shortterm memory, long-term memory, memorization productivity, and attention were worse in the participants who had either «insignificant» or «average» work responsibility.Conclusion. Younger adults experiencing workplace stress have a decrease in cognitive functions.

The impact of lexical skills and executive functioning on L1 and L2 phonological awareness in bilingual kindergarten

This study investigated the role of lexical skills and executive functioning on L1 Dutch and L2 English phonological awareness in children enrolled in bilingual Dutch/English kindergarten in The Netherlands (n = 95) and monolingual Dutch kindergarten (n = 83). Participants had an average age of 5 years and 10 months and completed tasks on phonological awareness, lexical skills (vocabulary and lexical specificity), and executive functioning (sustained visual and auditory attention, behavioural self-regulation, and verbal short-term memory) in the L1 Dutch and the L2 English. Dutch phonological awareness was predicted by self-regulation and verbal short-term memory. English phonological awareness was directly predicted by Dutch phonological awareness and visual sustained attention. The results highlight the importance of executive functioning such as sustained attention, behavioural self-regulation and short-term memory in first and second language learning in kindergarten, and support cross-language transfer effects from L1 to L2 phonological awareness among bilingual learners.

Autonomic and Cognitive Function Response to Normobaric Hyperoxia Exposure in Healthy Subjects. Preliminary Study.

Background and objective: This is the first study to investigate the effect of high-flow oxygen therapy, using a normobaric chamber on cognitive, biochemical (oxidative stress parameters and the level of neurotrophins), cardiovascular and autonomic functioning. Materials and methods: 17 healthy volunteers, eight males and nine females, with a mean age of 37.5 years, were examined. The experimental study involved ten two-hour exposures in a normobaric chamber with a total pressure of 1500 hPa, in air adjusted to 37% oxygen, 1.079% carbon dioxide and 0.44% hydrogen. Cognitive function was assessed by using Trail Making Test parts A, B and difference in results of these tests (TMT A, TMT B and TMT B-A); California Verbal Learning Test (CVLT); Digit symbol substitution test (DSST); and Digit Span (DS). Fatigue (Fatigue Severity Scale (FSS)), cardiovascular, autonomic and baroreceptor functioning (Task Force Monitor) and biochemical parameters were measured before and after intervention. Results: After 10 sessions in the normobaric chamber, significant decreases in weight, caused mainly by body fat % decrease (24.86 vs. 23.93%, p = 0.04 were observed. TMT part A and B results improved (p = 0.0007 and p = 0.001, respectively). In contrast, there was no statistically significant influence on TMT B-A. Moreover, decrease in the number of symbols left after a one-minute test in DSST was noted (p = 0.0001). The mean number of words correctly recalled in the CVLT Long Delay Free Recall test improved (p = 0.002), and a reduction in fatigue was observed (p = 0.001). Biochemical tests showed a reduction in levels of malondialdehyde (p < 0.001), with increased levels of Cu Zn superoxide dismutase (p < 0.001), Neurotrophin 4 (p = 0.0001) and brain-derived neurotrophic factor (p = 0.001). A significant increase in nitric oxide synthase 2 (Z = 2.29, p = 0.02) and Club cell secretory protein (p = 0.015) was also noted. Baroreceptor function was significantly improved after normobaric exposures (p = 0.003). Significant effect of normobaric exposures and BDNF in CVLT Long Delay Free Recall was noted. Conclusions: This study demonstrates that 10 exposures in a normobaric chamber have a positive impact on visual information and set-shifting processing speed and increase auditory-verbal short-term memory, neurotrophic levels and baroreceptor function. A response of the respiratory tract to oxidative stress was also noted. There is a need to rigorously examine the safety of normobaric therapy. Further studies should be carried out with physician examination, both pre and post treatment.

The peculiarities of cognitive and emotional-volitional spheres of the patients with post-stroke neurological dysfunctions

The subject of this research is the peculiarities of cognitive (memory, attention) and emotional-volitional (manifestations of anxiety and depression, motivation towards recovery) spheres of the patients with severe dysfunctions of cerebral circulation of ischemic type in the early and late rehabilitation period. The relevance of this topic is defined by commonness of the ischemic stroke, growing number of incapacitating consequences, and mortality rate in Russia. Ischemic stroke leads to the change of physical, social and psychological status of a patient, worsening of quality of life, and unfavorable prognosis for recovery. The scientific novelty consists in assessment of the dynamics of indicators in cognitive and emotional-volitional spheres of the post-stroke patients at various states of rehabilitation treatment. It is determined that the highest positive dynamics in cognitive and emotional-volitional spheres is observed at the early stage of rehabilitation. The resource and deficiency characteristics, which are most important for selecting the target of psychological interventions, are determined for each group of patients. In the cognitive sphere are noted veracious differences in the capacity of auditory-verbal short-term and long-term memory, memory for images, allocation and shifting of attention. In the emotional-volitional sphere &amp;ndash; the indicators of depression and anxiety, motivation towards recovery. The presented data underlines the need for simultaneous provision of psychological rehabilitation and medication interventions for fullest readaptation of a patient to life at all stages of rehabilitation. &amp;nbsp;

Pitch-specific contributions of auditory imagery and auditory memory in vocal pitch imitation.

Vocal imitation guides both music and language development. Despite the developmental significance of this behavior, a sizable minority of individuals are inaccurate at vocal pitch imitation. Although previous research suggested that inaccurate pitch imitation results from deficient sensorimotor associations between pitch perception and vocal motor planning, the cognitive processes involved in sensorimotor translation are not clearly defined. In the present research, we investigated the roles of basic cognitive processes in the vocal imitation of pitch, as well as the degree to which these processes rely on pitch-specific resources. In the present study, participants completed a battery of pitch and verbal tasks to measure pitch perception, pitch and verbal auditory imagery, pitch and verbal auditory short-term memory, and pitch imitation ability. Information on participants' music background was collected, as well. Pitch imagery, pitch short-term memory, pitch discrimination ability, and musical experience were unique predictors of pitch imitation ability. Furthermore, pitch imagery was a partial mediator of the relationship between pitch short-term memory and pitch imitation ability. These results indicate that vocal imitation recruits cognitive processes that rely on at least partially separate neural resources for pitch and verbal representations.

The neural correlates of auditory-verbal short-term memory: a voxel-based lesion-symptom mapping study on 103 patients after glioma removal.

The relationship between verbal-auditory short-term memory (STM) and language is an open area of debate and contrasting hypotheses have been proposed, suggesting either that STM would strongly rely on language-related processes, or that it depends on a dedicated system related to language, but independent from it. In this study we examined 103 patients undergoing surgery for glioma resection in the left or right hemisphere, and we conducted a VLSM analysis on their behavioral performance on auditory-verbal STM, as well as on more general verbal and nonverbal tasks. The aim was to investigate whether the anatomical correlates of auditory-verbal STM were part of the language system or they were spatially segregated from it. VLSM results showed that digit span scores were linked to lesions in both the left supramarginal gyrus and superior-posterior temporal areas, as reported in the literature on patients with a selective deficit of auditory-verbal STM. Conversely, other verbal tasks involved areas only partly overlapping with those found for digit span, with repetition being affected by lesions in more anterior regions in the parietal, temporal, and frontal lobes, and word comprehension by lesions in a network including cortical and subcortical pathways in the temporal lobe. The present results, thus, show that auditory-verbal STM neural correlates are only partially overlapping with those supporting comprehension and production: while the left posterior-superior temporal cortex, involved in speech perception, takes part in both functions, the left supramarginal gyrus has a consistent and specific role only in STM, supporting the hypothesis of interacting but segregated networks.

Neurocognitive basis of repetition deficits in primary progressive aphasia

Previous studies indicate that repetition is affected in primary progressive aphasia (PPA), particularly in the logopenic variant, due to limited auditory-verbal short-term memory (avSTM). We tested repetition of phrases varied by length (short, long) and meaning (meaningful, non-meaningful) in 58 participants (22 logopenic, 19 nonfluent, and 17 semantic variants) and 21 healthy controls using a modified Bayles repetition test. We evaluated the relation between cortical thickness and repetition performance and whether sub-scores could discriminate PPA variants.Logopenic participants showed impaired repetition across all phrases, specifically in repeating long phrases and any phrases that were non-meaningful. Nonfluent, semantic, and healthy control participants only had difficulty repeating long, non-meaningful phrases. Poor repetition of long phrases was associated with cortical thinning in left temporo-parietal areas across all variants, highlighting the importance of these areas in avSTM. Finally, Bayles repetition phrases can assist classification in PPA, discriminating logopenic from nonfluent/semantic participants with 89% accuracy.

Neural correlates of auditory verbal short-term memory deficits in vascular and neurodegenerative aphasia

Neural correlates of auditory verbal short-term memory deficits in vascular and neurodegenerative aphasia

RTMS evidence for a dissociation in short-term memory for spoken words and nonwords

Differing patterns of verbal short-term memory (STM) impairment have provided unique insights into the relationship between STM and broader language function. Lexicality effects (i.e., better recall for words than nonwords) are larger in patients with phonological deficits following left temporoparietal lesions, and smaller in patients with semantic impairment and anterior temporal damage, supporting linguistic accounts of STM. However, interpretation of these patient dissociations are complicated by (i) non-focal damage and (ii) confounding factors and secondary impairments. This study addressed these issues by examining the impact of inhibitory transcranial magnetic stimulation (TMS) on auditory-verbal STM performance in healthy individuals. We compared the effects of TMS to left anterior supramarginal gyrus (SMG) and left anterior middle temporal gyrus (ATL) on STM for lists of nonwords and random words. SMG stimulation disrupted nonword recall, in a pattern analogous to that observed in patients, compatible with a role for this site in processing speech sounds without support from long-term lexical-semantic representations. Stimulation of ATL, a semantic site, disrupted the recall of words but not nonwords. A visual pattern memory task indicated that these effects of TMS were restricted to the verbal domain. These data provide convergent evidence for the conclusions of neuropsychological studies that support linguistic accounts of verbal STM.

Short-term memory span in aphasia: Insights from speech-timing measures.

Auditory-verbal short-term memory impairments are part and parcel of aphasia and interfere with linguistic processing. To date, the science about short-term memory impairments in aphasia has been generated and dominated by studying measures of accuracy, that is, span length. Because accuracy is expressed through speech, examining the speech-timing characteristics of persons with aphasia as they engage in spoken recall could reveal insights about the manner in which accuracy is achieved. Six speech-timing measures (e.g., response durations, pause durations) were elicited from the speech waveform of word span tasks from twelve people with aphasia. Speech-timing measures were compared to neuro-typical control participants. Speech-timing performance between erroneous and correct responses in the aphasia group was also examined. Across all measures, people with aphasia produced considerably longer speech-timing patterns in comparison to control participants. Memory load affected some measures in people with aphasia and control participants. Speech-timing in correct response trials was shorter than responses in erroneous trials. Memory span correlated only with one measure, namely, speech time (defined as the sum of each individual word duration in a response). Speech time also correlated with the following measures: Aphasia severity (Aphasia Quotient of the Western Aphasia Battery), spontaneous speech, and language comprehension (also measured by the Western Aphasia Battery). Some protracted speech-timing patterns in the aphasia group may be explained by a deregulation of activation-decay patterns. However, in the absence of further evidence from people with aphasia, possible issues around the sensitivity of some speech-timing measures limit firmer conclusions. Speech-timing measures are response-time measures, which have not been systematically studied in studies of short-term or working memory in aphasia and as such, can push the current boundaries of knowledge of short-term and working memory impairments in aphasia, not only in stroke related aphasia but also other neurological conditions.

Temporal precision and the capacity of auditory-verbal short-term memory.

The capacity of serially ordered auditory-verbal short-term memory (AVSTM) is sensitive to the timing of the material to be stored, and both temporal processing and AVSTM capacity are implicated in the development of language. We developed a novel "rehearsal-probe" task to investigate the relationship between temporal precision and the capacity to remember serial order. Participants listened to a sub-span sequence of spoken digits and silently rehearsed the items and their timing during an unfilled retention interval. After an unpredictable delay, a tone prompted report of the item being rehearsed at that moment. An initial experiment showed cyclic distributions of item responses over time, with peaks preserving serial order and broad, overlapping tails. The spread of the response distributions increased with additional memory load and correlated negatively with participants' auditory digit spans. A second study replicated the negative correlation and demonstrated its specificity to AVSTM by controlling for differences in visuo-spatial STM and nonverbal IQ. The results are consistent with the idea that a common resource underpins both the temporal precision and capacity of AVSTM. The rehearsal-probe task may provide a valuable tool for investigating links between temporal processing and AVSTM capacity in the context of speech and language abilities.

Cognitive symptoms in mayor depression: A study with vortioxetina

IntroductionThe major depression is associated with decreased cognitive functions in a range of areas, including attention, memory and executive functions. The cognitive symptoms of depression can have a profound effect on the ability of patients to keep out the tasks of daily living, and are significant factors that affect the ability to function both interpersonal and occupational level.AimsVortioxetina have a multimodal action acting on various serotonin receptors in addition to inhibiting serotonin reuptake. Vortioxetina, is a new therapeutic tool seems to have shown efficacy in the treatment of cognitive symptoms of depression.MethodsTo evaluate this action we have evaluated the cognitive decline in patients with major depression before receiving treatment vortioxetina (whether state or not previously treated with other antidepressants) and at 2, 6 and 12 months after starting treatment with the drug. For that, we’ve used the Verbal Hearing Test King (RAVLT), which evaluates the auditory verbal short-term memory, the learning rate, the retention of information, and the differences between learning and recovery, and testing Digit substitution by symbols (DSST) that perform quick detection of brain dysfunctions by a conventional task.ResultsThe results of this study are still under analysis.Disclosure of interestThe authors have not supplied their declaration of competing interest.

The Effects of Cognitive Training for Elderly: Results from My Mind Project.

Cognitive decline and dementia represent very important public health problems that impact the ability to maintain social function and independent living. The aim of this study was to investigate the effects of a nonpharmacological intervention consisting of comprehensive cognitive training in elderly people having one of three different cognitive statuses. In all, 321 elderly people with a diagnoses of mild–moderate Alzheimer's disease (AD), with mild cognitive impairment (MCI) and without cognitive decline were randomly assigned to two groups: experimental group (EG, who underwent intervention) and control group (CG), according to a prospective randomized intervention study. In the three groups, immediately after the end of the intervention, we observed a significant effect on some cognitive and noncognitive outcomes in the EGs. At the end of the intervention, we found an intermediate intervention effect on the Alzheimer's Disease Assessment Scale (ADAS) score of subjects with AD, as well as on functional status, as measured by using the Instrumental Activities of Daily Living scale. A significant intervention effect was also observed on enhancement of auditory verbal short-term memory and subjective memory complaints of subjects with MCI. The group of subjects without cognitive decline obtained a significant intervention effect on subjective complaints outcomes. The obtained results demonstrated that participation in the intervention could improve performance with respect to specific cognitive functions and psychological statuses. The role of healthy lifestyle programs, such as the use of comprehensive interventions, has been shown to be efficient for enhancing memory and other abilities in aged individuals with and without cognitive decline.

Effects of semantic context on access to words of low imageability in deep-phonological dysphasia: a treatment case study

ABSTRACTBackground: Deep dysphasia is a relatively rare subcategory of aphasia, characterised by word repetition impairment and a profound auditory-verbal short-term memory (STM) limitation. Repetition of words is better than nonwords (lexicality effect) and better for high-image than low-image words (imageability effect). Another related language impairment profile is phonological dysphasia, which includes all of the characteristics of deep dysphasia except for the occurrence of semantic errors in single word repetition. The overlap in symptoms of deep and phonological dysphasia has led to the hypothesis that they share the same root cause, impaired maintenance of activated representation of words, but that they differ in severity of that impairment, with deep dysphasia being more severe.Aims: We report a single-subject multiple baseline, multiple probe treatment study of a person who presented with a pattern of repetition that was consistent with the continuum of deep-phonological dysphasia: imageability and lexicality effects in repetition of single and multiple words and semantic errors in repetition of multiple-word utterances. The aim of this treatment study was to improve access to and repetition of low-imageability words by embedding them in modifier-noun phrases that enhanced their imageability.Methods & Procedures: The treatment involved repetition of abstract noun pairs. We created modifier-abstract noun phrases that increased the semantic and syntactic cohesiveness of the words in the pair. For example, the phrases “long distance” and “social exclusion” were developed to improve repetition of the abstract pair “distance-exclusion”. The goal of this manipulation was to increase the probability of accessing lexical and semantic representations of abstract words in repetition by enriching their semantic -syntactic context. We predicted that this increase in accessibility would be maintained when the words were repeated as pairs, but without the contextual phrase.Outcomes & Results: Treatment outcomes indicated that increasing the semantic and syntactic cohesiveness of low-imageability and low-frequency words later improved this participant’s ability to repeat those words when presented in isolation.Conclusions: This treatment approach to improving access to abstract word pairs for repetition was successful for our participant with phonological dysphasia. The approach exemplifies the potential value in manipulating linguistic characteristics of stimuli in ways that improve access between phonological and lexical-semantic levels of representation. Additionally, this study demonstrates how principles of a cognitive model of word processing can be used to guide treatment of word processing impairments in aphasia.

The Effects of Aging on the Components of Auditory - Verbal Short-Term Memory.

This study aimed at exploring the effects of aging on the multiple components of the auditory-verbal short-term memory (STM). Participants of 45–54, 55–64, 65–74 and 75–84 years of age were presented STM tasks assessing short-term retention of order and item information, and of phonological and lexical-semantic information separately. Because older participants often present reduced hearing levels, we sought to control for an effect of hearing status on performance on STM tasks. Participants’ hearing thresholds were measured with a pure-tone audiometer. The results showed age-related effects on all STM components. However, after hearing status was controlled for in analyses of covariance, the age-related differences became non-significant for all STM processes. The fact that age-related hearing loss may in large part explain decreases in performance on STM tasks with aging is discussed.

Verbal and musical memory: Selectivity of auditory disorders after stroke

Neuropsychological consequences of stroke have important social, professional, and private life impacts. Deficits affecting language processing are well documented unlike musical disorders. Yet, according to Sarkamo et al. (Neuropsychologia, 2009), the incidence of acquired amusia after stroke is 60% after a delay of one week and 42% after 3 months. The goal of this study is to compare verbal and musical auditory memory in patients with stroke history, using a short-term memory paradigm. The goal is to evaluate the interest of testing non-verbal memory in neuropsychological assessment after stroke, as it could guide the choice of reeducation methods. Patients included in the study have been hospitalized in the stroke unit of the neurological hospital in Lyon for a stroke in the MCA (middle cerebral artery) territory. Several months after stroke, they were assessed with a test battery including cognitive evaluation, speech evaluation and audiometry. Acquired amusia was diagnosed with the MBEA (Montreal Battery of Evaluation of Amusia, Peretz et al., Ann N Y Acad Sci, 2003). The auditory musical and verbal short-term memory was tested with a paradigm involving a comparison of short word sequences or tone sequences, separated by a delay of 1000 ms. Performance in the auditory short-term memory task were significantly decreased for the verbal task in patients with left hemisphere lesions, and for the musical task in patients with right hemisphere lesions, in comparison with controls. These results suggest separated cerebral networks for speech and music, for auditory short-term memory, with a preference of the left hemisphere for speech and the right hemisphere for music. To correlate behavioral results and cerebral lesions, analyses of cerebral imaging data will be conducted using voxel based lesion symptom mapping and DTI.

Memory load effect in auditory-verbal short-term memory task: EEG fractal and spectral analysis.

The objective of this preliminary study was to quantify changes in complexity of EEG using fractal dimension (FD) alongside linear methods of spectral power, event-related spectral perturbations, coherence, and source localization of EEG generators for theta (4-7 Hz), alpha (8-12 Hz), and beta (13-23 Hz) frequency bands due to a memory load effect in an auditory-verbal short-term memory (AVSTM) task for words. We examined 20 healthy individuals using the Sternberg's paradigm with increasing memory load (three, five, and seven words). The stimuli were four-letter words. Artifact-free 5-s EEG segments during retention period were analyzed. The most significant finding was the increase in FD with the increase in memory load in temporal regions T3 and T4, and in parietal region Pz, while decrease in FD with increase in memory load was registered in frontal midline region Fz. Results point to increase in frontal midline (Fz) theta spectral power, decrease in alpha spectral power in parietal region-Pz, and increase in beta spectral power in T3 and T4 region with increase in memory load. Decrease in theta coherence within right hemisphere due to memory load was obtained. Alpha coherence increased in posterior regions with anterior decrease. Beta coherence increased in fronto-temporal regions. Source localization delineated theta activity increase in frontal midline region, alpha decrease in superior parietal region, and beta increase in superior temporal gyrus with increase in memory load. In conclusion, FD as a nonlinear measure may serve as a sensitive index for quantifying dynamical changes in EEG signals during AVSTM tasks.