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Neural correlates of lexicon and grammar: evidence from the production, reading, and judgment of inflection in aphasia.

Are the linguistic forms that are memorized in the mental lexicon and those that are specified by the rules of grammar subserved by distinct neurocognitive systems or by a single computational system with relatively broad anatomic distribution? On a dual-system view, the productive -ed-suffixation of English regular past tense forms (e.g., look-looked) depends upon the mental grammar, whereas irregular forms (e.g., dig-dug) are retrieved from lexical memory. On a single-mechanism view, the computation of both past tense types depends on associative memory. Neurological double dissociations between regulars and irregulars strengthen the dual-system view. The computation of real and novel, regular and irregular past tense forms was investigated in 20 aphasic subjects. Aphasics with non-fluent agrammatic speech and left frontal lesions were consistently more impaired at the production, reading, and judgment of regular than irregular past tenses. Aphasics with fluent speech and word-finding difficulties, and with left temporal/temporo-parietal lesions, showed the opposite pattern. These patterns held even when measures of frequency, phonological complexity, articulatory difficulty, and other factors were held constant. The data support the view that the memorized words of the mental lexicon are subserved by a brain system involving left temporal/temporo-parietal structures, whereas aspects of the mental grammar, in particular the computation of regular morphological forms, are subserved by a distinct system involving left frontal structures.

Adult↗

Verbal memory compensation: application to left and right temporal lobe epileptic patients.

This study investigates the compensatory impact of cognitive aids on left and right temporal lobe epileptic patients suffering from verbal memory disorders, who were candidates for surgery. Cognitive aids are defined in the levels-of-processing framework and deal with the depth of encoding, the elaboration of information, and the use of retrieval cues. Results indicate differential compensatory impact for left and right epileptic patients and are discussed according to the HERA model and the compensation framework.

Adult↗

Effects of transcutaneous electrical nerve stimulation (TENS) on memory in elderly with mild cognitive impairment.

In previous studies, transcutaneous electrical nerve stimulation (TENS) was shown to have a positive effect on memory in Alzheimer's disease (AD) patients. Moreover, the reported effects appeared to be more beneficial in early stages of Alzheimer's disease compared to later stage intervention. Based on this stage-dependency, the present study examined the effects of TENS on memory in a preclinical stage of AD, i.e. in subjects with mild cognitive impairment (MCI). Our results suggest that TENS did not improve memory in a MCI population. Mechanisms that might underlie the absence of positive effects of the TENS treatment in a MCI population are discussed.

Aged↗

Functional magnetic resonance imaging during auditory verbal working memory in nonpsychotic relatives of persons with schizophrenia: a pilot study.

BACKGROUND: First-degree relatives of persons with schizophrenia carry elevated genetic risk for the illness and show deficits on high-load information processing tasks. We used functional magnetic resonance imaging (fMRI) to test whether nonpsychotic relatives show altered functional activation in the prefrontal cortex (PFC), thalamus, hippocampus, and anterior cingulate during a working memory task requiring interference resolution. METHODS: Twelve nonpsychotic relatives of persons with schizophrenia and 12 healthy control subjects were administered an auditory, verbal working memory version of the Continuous Performance Test during fMRI. An asymmetric, spin-echo, T2*-weighted sequence (15 contiguous, 7-mm axial slices) was acquired on a full-body MR scanner. Data were analyzed by Statistical Parametric Mapping (SPM). RESULTS: Compared with control subjects, relatives showed greater task-elicited activation in the PFC and the anterior and dorsomedial thalamus. When task performance was controlled, relatives showed significantly greater activation in the anterior cingulate. When effects of other potentially confounding variables were controlled, relatives generally showed significantly greater activation in the dorsomedial thalamus and anterior cingulate. CONCLUSIONS: This pilot study suggests that relatives of persons with schizophrenia have subtle differences in brain function in the absence of psychosis. These differences add to the growing literature identifying neurobiological vulnerabilities to schizophrenia.

Adult↗

Striatal volume on magnetic resonance imaging and repetitive behaviors in autism.

BACKGROUND: The repetitive behaviors seen in autism phenotypically resemble those seen in obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), disorders in which structural and functional abnormalities of the basal ganglia (BG) are present and correspond to the severity of repetitive behaviors. METHODS: Seventeen subjects with autism by DSM-IV and Autism Diagnostic Interview (ADI) and 17 matched controls completed a 1.5 T magnetic resonance image (MRI) of the brain. Two blinded researchers, with good inter-rater reliability, outlined the right and left caudate and putamen. Autistic and control BG volumes covaried for total brain volume were compared using analysis of covariance. BG volumes within the autistic group were correlated with the ADI Repetitive Behavior scores (ADI-C domain). RESULTS: Right caudate volume controlled for total brain volume was significantly larger in autistic subjects than in controls. In addition, right caudate and total putamen volumes correlated positively with repetitive behavior scores on the ADI-C domain, particularly the higher order OCD-like repetitive behaviors. CONCLUSIONS: Increased right caudate volume in autism is of interest, since this has also been observed in OCD patients. Increased volume of the right caudate and total putamen positively correlated with greater repetitive behaviors, supporting the hypothesis of BG dysfunction associated with repetitive behaviors in autistic adults.

Adolescent↗

The neural organization of semantic memory: Electrophysiological activity suggests feature-based segregation.

Despite decades of research, it remains controversial whether semantic knowledge is anatomically segregated in the human brain. To address this question, we recorded event-related potentials (ERPs) while participants viewed pictures of animals and tools. Within the 200-600-ms epoch after stimulus presentation, animals (relative to tools) elicited an increased anterior negativity that, based on previous ERP studies, we interpret as associated with semantic processing of visual object attributes. In contrast, tools (relative to animals) evoked an enhanced posterior left-lateralized negativity that, according to prior research, might reflect accessing knowledge of characteristic motion and/or more general functional properties of objects. These results support the hypothesis of the neuroanatomical knowledge organization at the level of object features: the observed neurophysiological activity was modulated by the features that were most salient for object recognition. The high temporal resolution of ERPs allowed us to demonstrate that differences in processing animals and tools occurred specifically within the time-window encompassing semantic analysis.

Adolescent↗

Characteristic functional networks in high- versus low-proficiency second language speakers detected also during native language processing: an explorative EEG coherence study in 6 frequency bands.

An EEG coherence study was performed with a twofold objective: first, to scrutinize the theoretical concept of "cortical efficiency" in connection with second language (L2) acquisition and, second, to detect cooperations between cortical areas in specific frequency bands indicative for highly proficient L2 processing. Two groups differing only in their level of L2 proficiency were contrasted during presentation of natural language videos in English (L2) and German (native language, L1), with explorative coherence analysis in 6 frequency bands (0.5-31.5 Hz). The coherence brain maps revealed more pronounced and widespread increases in coherences in the alpha1-band (8-10 Hz) in low-proficiency than in the high-proficiency L2 speakers. Surprisingly, this difference was obtained also during L1 processing and corroborated for both languages by multivariate permutation tests. These tests revealed additional differences between the low- and the high-proficiency group also for coherences within the beta1- (13-18 Hz) and the beta2-band (18.5-31.5 Hz), again during L2 and L1 processing. Since the same group differences were observed during L1 and L2 processing, our high-proficiency group might have profited from a more generic advantage in language or text processing strategy. This strategic advantage was most evident at alpha1 frequencies, possibly related to a specific way of processing internal mental states (top-down processing).

Acoustic Stimulation↗

Early syntactic productivity: evidence from dative shift.

The abstractness of children's early syntactic representations has been questioned in the recent acquisition literature. While some research has suggested that children's knowledge of basic constructions such as the transitive is robust and abstract at a very young age, other work has proposed that young children only have constructions that are specific to individual lexical items. The present paper seeks to resolve this discrepancy by examining children's abstract knowledge of the English dative alternation via a production study. The studies ask whether young children who hear a sentence like I pilked the cup to Petey know that the same meaning can be expressed with the sentence I pilked Petey the cup. This generalization is well-attested in the language that children hear and represents a strong test-case for determining the nature of children's early syntactic representations. The results indicate that three-year-old children have productive knowledge of the English dative alternation, but that their performance can be influenced by small changes in the nature of the task. A preference for the prepositional dative form is also found and the possible reasons for this preference are discussed.

Age Factors↗

Infant-directed speech supports phonetic category learning in English and Japanese.

Across the first year of life, infants show decreased sensitivity to phonetic differences not used in the native language [Werker, J. F., & Tees, R. C. (1984). Cross-language speech perception: evidence for perceptual reorganization during the first year of life. Infant Behaviour and Development, 7, 49-63]. In an artificial language learning manipulation, Maye, Werker, and Gerken [Maye, J., Werker, J. F., & Gerken, L. (2002). Infant sensitivity to distributional information can affect phonetic discrimination. Cognition, 82(3), B101-B111] found that infants change their speech sound categories as a function of the distributional properties of the input. For such a distributional learning mechanism to be functional, however, it is essential that the input speech contain distributional cues to support such perceptual learning. To test this, we recorded Japanese and English mothers teaching words to their infants. Acoustic analyses revealed language-specific differences in the distributions of the cues used by mothers (or cues present in the input) to distinguish the vowels. The robust availability of these cues in maternal speech adds support to the hypothesis that distributional learning is an important mechanism whereby infants establish native language phonetic categories.

Canada↗

Causal relations drive young children's induction, naming, and categorization.

A number of recent models and experiments have suggested that evidence of early category-based induction is an artifact of perceptual cues provided by experimenters. We tested these accounts against the prediction that different relations (causal versus non-causal) determine the types of perceptual similarity by which children generalize. Young children were asked to label, to infer novel properties, and to project future appearances of a novel animal that varied in two opposite respects: (1) how much it looked like another animal whose name and properties were known, and (2) how much its parents looked like parents of another animal whose name and properties were known. When exemplar origins were known, children generalized to exemplars with similar origins rather than with similar appearances; when origins were unknown, children generalized to exemplars with similar appearances. Results indicate even young children possess the cognitive control to choose the similarities that best predict accurate generalizations.

Avoidance Learning↗

Subjective versus objective behavioral ratings following two analogue tasks: a comparison of socially phobic and non-anxious adolescents.

Although results regarding objective social skills deficits in adults are inconsistent, research with youth have consistently demonstrated such deficits. Furthermore, research has consistently demonstrated subjective appraisal of social skill deficit in both youth and adults with social phobia or social anxiety. As a result, research has begun to examine the presence of a negative perceptual bias in individuals with social phobia and social anxiety. The purpose of the present study was to extend the findings of social skill deficits to an adolescent sample by investigating differences between adolescents with social phobia and non-anxious peers with regard to objective and subjective behavioral ratings. In addition, the presence of a negative perceptual bias was investigated by examining discrepancy scores between these ratings. The results of the current study provide support for the presence of social skill deficits in a socially phobic adolescent population and are the first to suggest that a limited negative bias exists in this population.

Adolescent↗

Using case study methods to investigate the effects of interactive intervention for children with autism spectrum disorders.

PURPOSE: The purpose of this multiple case study was to describe outcomes for three parents and their children following participation in a social interactive model of language intervention. More specifically, this study sought to clarify if changes in children's participation, engagement, and initiation of social interaction could be observed following an 11-week intervention. METHOD: Three preschool children with autism spectrum disorders and their mothers participated in an 11-week intervention program. The intervention taught parents to follow the children's lead, promote children's participation in routines, and model language at the children's level. Outcome measures included estimates of parents' responsive language input, and measures of children's rate of communication, number of engagements in social interaction, and initiations. RESULTS: The results indicated that all three mothers increased their responsive comments during play interactions and were rated as being more responsive on a rating scale. All three children evidenced positive outcomes in vocabulary and the number of engagements in social interaction. In addition, improvement was observed in social initiation skills for all three children. CONCLUSIONS: Increases in mothers' responsiveness and children's engagement in social interactions are consistent with the theoretical mechanisms of the social interaction model of language intervention. The results suggest that further randomized control trials of this intervention approach are warranted.

Autistic Disorder↗

Hypervigilance and attentional fixedness in chronic musculoskeletal pain: consistency of findings across modified stroop and dot-probe tasks.

UNLABELLED: Results from modified Stroop and dot-probe tasks have provided mixed evidence regarding attentional biases for sensory and affect pain stimuli in chronic pain patients. No studies have compared the same groups of chronic pain and healthy control participants on both tasks. We tested 36 patients with chronic musculoskeletal pain and 29 healthy control subjects on the modified Stroop and dot-probe tasks. Stimuli comprised affect pain, sensory pain, physical catastrophe, and neutral words. There was no evidence to suggest differential processing of threat cues by patients and control subjects on the modified Stroop task. All participants did, however, show differential processing of affect pain words. This was evident on both masked and unmasked presentation formats. There were no significant interactions between clinical status and threat word type observed for any of the indices of selective attention derived from the dot-probe task, but all participants had difficulty disengaging attention from affective pain and health catastrophe words. Findings were not influenced by individual differences in mood, anxiety, or fear of pain. Correlational analyses of the standard (unmasked) Stroop interference index and dot-probe indices of selective attention revealed a consistent lack of significant association, suggesting that the 2 tasks might be measuring different phenomena. Taken together, these findings provide evidence that chronic pain patients and healthy control participants do not differ in the way they attend to threatening linguistic stimuli. PERSPECTIVE: Some patients with chronic pain might have trouble paying attention to anything other than the affective components of pain and associated catastrophic health consequences. Interventions that specifically target this attentional fixedness might facilitate shifting attention to other targets and thereby reduce pain-specific anxiety and fear.

Adolescent↗

Temporal processing in poor adult readers.

The aim of this study was to investigate the relationships between two different temporal processing tasks and word identification performance in skilled, dyslexic and poor adult readers. In Experiment 1 spatial and temporal sequencing tasks were conducted. It was found that adult dyslexics were significantly less accurate than skilled readers across all conditions in the temporal sequencing task, and when higher numbers of stimuli were presented in the spatial task. Experiment 2 replicated Experiment 1 in the temporal sequencing task and also found that poor readers had significantly higher motion coherence thresholds than those found in the skilled reader group. Ten percent of the variance in coherence thresholds was accounted for by performance on the temporal sequencing task. Multiple regression analyses determined that performance on the two temporal tasks could explain seventy percent of the variance in word identification scores, with the temporal sequencing task making the larger independent contribution. Experiment 3 replicated the findings of Experiment 2, while taking into account IQ, verbal memory and processing speed. Three things were concluded. First, the temporal tasks measure different aspects of temporal processing. The contribution to performance of higher-level perceptual and attentional components of the temporal sequencing task accounts for the relatively weak correlation found between the two measures. While sensory sensitivity to motion is measured at MT, the involvement of this area and PPC in higher-level perceptual and attentional processes is suggested by the findings of this study. Second, the association between temporal sequencing and reading skills may provide a stronger link between neural processing and poor reading skills than basic sensory processing measures alone, suggesting that a sensory magnocellular (M) system deficit cannot fully explain the relationship found between reading and visual neural processing. Third, problems with rapid sequential processing are predicted to be a generalised problem in poor adult readers, whether they are formally classified as dyslexic, or are poor performers on measures of word identification. Temporal processing may follow a distribution similar to that found for word identification skills.

Adolescent↗

A category-specific advantage for numbers in verbal short-term memory: evidence from semantic dementia.

This study explored possible reasons for the striking difference between digit span and word span in patients with semantic dementia. Immediate serial recall (ISR) of number and non-number words was examined in four patients. For every case, the recall of single-digit numbers was normal whereas the recall of non-number words was impaired relative to controls. This difference extended to multi-digit numbers, and remained even when frequency, imageability, word length, set size and size of semantic category were matched for the numbers and words. The advantage for number words also applied to the patients' reading performance. Previous studies have suggested that semantic memory plays a critical role in verbal short-term memory (STM) and reading: patients with semantic dementia show superior recall and reading of words that are still relatively well known compared to previously known but now semantically degraded words. Additional assessments suggested that this semantic locus was the basis of the patients' category-specific advantage for numbers. Comprehension was considerably better for number than non-number words. Number knowledge may be relatively preserved in semantic dementia because the cortical atrophy underlying the condition typically spares the areas of the parietal lobes thought to be crucial in numerical cognition but involves the inferolateral temporal-lobes known to support general conceptual knowledge.

Aged↗

Qualitative aspects of verbal fluency in HIV-associated dementia: a deficit in rule-guided lexical-semantic search processes?

HIV-associated dementia (HAD) is widely considered a "subcortical" dementia that involves a disruption of frontal-basal ganglia circuits. Deficits in verbal fluency are common in HAD; however, the cognitive underpinnings of these deficits are not well understood. To elucidate the cognitive mechanisms underlying the diminished verbal fluency output in HAD, we examined several qualitative aspects of letter fluency in 21 individuals with HAD, 51 nondemented persons with HIV infection (HIV+), and 30 healthy controls (HC) who were comparable for age, education, sex, ethnicity, and estimated premorbid verbal intelligence. The verbal fluency protocols were scored to obtain the total number of correct words, average phonemic cluster size, total number of switches between phonemic clusters, and the proportion of error responses (i.e., intrusions, perseverations, and variants). Consistent with prior research, HAD participants produced significantly fewer total correct words relative to the HC and nondemented HIV+ groups. The HAD group also demonstrated fewer switches and a higher proportion of response errors (especially intrusion errors), but no differences were observed in average cluster size. Findings are interpreted as reflecting a disruption of rule-guided lexical-semantic search strategies in HAD, perhaps mediated by prefrontal-striatal circuit dysfunction, rather than depleted lexical-semantic memory stores.

AIDS Dementia Complex↗

Cortical organization for receptive language functions in Chinese, English, and Spanish: a cross-linguistic MEG study.

Chinese differs from Indo-European languages in both its written and spoken forms. Being a tonal language, tones convey lexically meaningful information. The current study examines patterns of neurophysiological activity in temporal and temporoparietal brain areas as speakers of two Indo-European languages (Spanish and English) and speakers of Mandarin-Chinese were engaged in a spoken-word recognition task that is used clinically for the presurgical determination of hemispheric dominace for receptive language functions. Brain magnetic activation profiles were obtained from 92 healthy adult volunteers: 30 monolingual native speakers of Mandarin-Chinese, 20 Spanish-speaking, and 42 native speakers of American English. Activation scans were acquired in two different whole-head MEG systems using identical testing methods. Results indicate that (a) the degree of hemispheric asymmetry in the duration of neurophysiological activity in temporal and temporoparietal regions was reduced in the Chinese group, (b) the proportion of individuals who showed bilaterally symmetric activation was significantly higher in this group, and (c) group differences in functional hemispheric asymmetry were first noted after the initial sensory processing of the word stimuli. Furthermore, group differences in the degree of hemispheric asymmetry were primarily due to greater degree of activation in the right temporoparietal region in the Chinese group, suggesting increased participation of this region in the spoken word recognition in Mandarin-Chinese.

Adolescent↗