Episodic retrieval activates the precuneus irrespective of the imagery content of word pair associates. A PET study.
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The aim of this study was to evaluate further the role of the precuneus in episodic memory retrieval. The specific hypothesis addressed was that the precuneus is involved in episodic memory retrieval irrespective of the imagery content. Two groups of six right-handed normal male volunteers took part in the study. Each subject underwent six [15O]butanol-PET scans. In each of the six trials, the memory task began with the injection of a bolus of 1500 MBq of [15O]butanol. For Group 1, 12 word pair associates were presented visually, for Group 2 auditorily. The subjects of each group had to learn and retrieve two sets of 12 word pairs each. One set consisted of highly imaginable words and another one of abstract words. Words of both sets were not related semantically, representing 'hard' associations. The presentations of nonsense words served as reference conditions. We demonstrate that the precuneus shows consistent activation during episodic memory retrieval. Precuneus activation occurred in visual and auditory presentation modalities and for both highly imaginable and abstract words. The present study therefore provides further evidence that the precuneus has a specific function in episodic memory retrieval as a multimodal association area. (+info)
Language outcome following multiple subpial transection for Landau-Kleffner syndrome.
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Landau-Kleffner syndrome is an acquired epileptic aphasia occurring in normal children who lose previously acquired speech and language abilities. Although some children recover some of these abilities, many children with Landau-Kleffner syndrome have significant language impairments that persist. Multiple subpial transection is a surgical technique that has been proposed as an appropriate treatment for Landau-Kleffner syndrome in that it is designed to eliminate the capacity of cortical tissue to generate seizures or subclinical epileptiform activity, while preserving the cortical functions subserved by that tissue. We report on the speech and language outcome of 14 children who underwent multiple subpial transection for treatment of Landau-Kleffner syndrome. Eleven children demonstrated significant postoperative improvement on measures of receptive or expressive vocabulary. Results indicate that early diagnosis and treatment optimize outcome, and that gains in language function are most likely to be seen years, rather than months, after surgery. Since an appropriate control group was not available, and that the best predictor of postoperative improvements in language function was that of length of time since surgery, these data might best be used as a benchmark against other Landau-Kleffner syndrome outcome studies. We conclude that multiple subpial transection may be useful in allowing for a restoration of speech and language abilities in children diagnosed with Landau-Kleffner syndrome. (+info)
Infants' learning about words and sounds in relation to objects.
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In acquiring language, babies learn not only that people can communicate about objects and events, but also that they typically use a particular kind of act as the communicative signal. The current studies asked whether 1-year-olds' learning of names during joint attention is guided by the expectation that names will be in the form of spoken words. In the first study, 13-month-olds were introduced to either a novel word or a novel sound-producing action (using a small noisemaker). Both the word and the sound were produced by a researcher as she showed the baby a new toy during a joint attention episode. The baby's memory for the link between the word or sound and the object was tested in a multiple choice procedure. Thirteen-month-olds learned both the word-object and sound-object correspondences, as evidenced by their choosing the target reliably in response to hearing the word or sound on test trials, but not on control trials when no word or sound was present. In the second study, 13-month-olds, but not 20-month-olds, learned a new sound-object correspondence. These results indicate that infants initially accept a broad range of signals in communicative contexts and narrow the range with development. (+info)
Cognitive deficits in spinocerebellar ataxia 2.
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This is one of the first studies assessing the pattern of cognitive impairment in spinocerebellar ataxia 2 (SCA2). Cognitive function was studied in 17 patients with genetically confirmed SCA2 and 15 age- and IQ- matched controls using a neuropsychological test battery comprising tests for IQ, attention, verbal and visuospatial memory, as well as executive functions. Twenty-five percent of the SCA2 subjects showed evidence of dementia. Even in non-demented SCA2 subjects, there was evidence of verbal memory and executive dysfunction. Tests of visuospatial memory and attention were not significantly impaired in the non-demented group compared with controls. There was no relationship between test performance and motor disability, repeat length or age of onset, while disease duration was shown to be inversely correlated with two tests reflecting the progression of cognitive deficits during the course of the disease. Intellectual impairment should therefore not be interpreted as a secondary effect of progressive motor disability, but represents an important and independent part of the SCA2 phenotype. (+info)
Learning-related neuronal responses in prefrontal cortex studied with functional neuroimaging.
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We assessed time-dependent neuronal activity accompanying learning using functional magnetic resonance imaging (fMRI). An artificial grammar learning paradigm enabled us to dissociate activations associated with individual item learning from those involved in learning the underlying grammar system. We show that a localized region of right prefrontal cortex (PFC) is preferentially sensitive to individual item learning during the early stages of the experiment, while the left PFC region is sensitive to grammar learning which occurred across the entire course of the experiment. In addition to dissociating these two types of learning, we were able to characterize the effect of rule acquisition on neuronal responses associated with explicit learning of individual items. This effect was expressed as modulation of the time-dependent right PFC activations such that the early increase in activation associated with item learning was attenuated as the experiment progressed. In a further analysis we used structural equation modelling to explore time-dependent changes in inter-regional connectivity as a function of both item and grammar rule learning. Although there were no significant effects of item learning on the measured path strengths, rule learning was associated with a decrease in right fronto-parietal connectivity and an increase in connectivity between left and right PFC. Further fronto-parietal path strengths were observed to change, with an increase in left fronto-parietal and a decrease in right fronto-parietal connectivity path strength from right PFC to left parietal cortex. We interpret our findings in terms of a left frontal system mediating the semantic analysis of study items and directly influencing a right fronto-parietal system associated with episodic memory retrieval. (+info)
A comparison of language achievement in children with cochlear implants and children using hearing aids.
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English language achievement of 29 prelingually deaf children with 3 or more years of cochlear implant (CI) experience was compared to the achievement levels of prelingually deaf children who did not have such CI experience. Language achievement was measured by the Rhode Island Test of Language Structure (RITLS), a measure of signed and spoken sentence comprehension, and the Index of Productive Syntax (IPSyn), a measure of expressive (signed and spoken) English grammar. When the CI users were compared with their deaf age mates who contributed to the norms of the RITLS, it was found that CI users achieved significantly better scores. Likewise, we found that CI users performed better than 29 deaf children who used hearing aids (HAs) with respect to English grammar achievement as indexed by the IPSyn. Additionally, we found that chronological age highly correlated with IPSyn levels only among the non-CI users, whereas length of CI experience was significantly correlated with IPSyn scores for CI users. Finally, clear differences between those with and without CI experience were found by 2 years of post-implant experience. These data provide evidence that children who receive CIs benefit in the form of improved English language comprehension and production. (+info)
Direct comparison of the neural substrates of recognition memory for words and faces.
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For the purpose of identifying the relatively specific brain regions related to word and face recognition memory on the one hand and the regions common to both on the other, regional cerebral blood flow associated with different cognitive tasks for recognition memory was examined using [H215O]PET in healthy volunteers. The tasks consisted of recognizing two types of stimuli (faces and words) in two conditions (novel and familiar), and two baseline tasks (reading words and gender classification). The statistical analyses used to identify the specific regions consisted of three subtractions: novel words minus novel faces, familiar words minus familiar faces, and reading words minus gender classification. These analyses revealed relative differences in the brain circuitry used for recognizing words and for recognizing faces within a defined level of familiarity. In order to find the regions common to both face and word recognition, overlapping areas in four subtractions (novel words minus reading words, novel faces minus gender classification, familiar words minus reading words, and familiar faces minus gender classification) were identified. The results showed that the activation sites in word recognition tended to be lateralized to the left hemisphere and distributed as numerous small loci, and particularly included the posterior portion of the left middle and inferior temporal gyri. These regions may be related to lexical retrieval during written word recognition. In contrast, the activated regions for face recognition tended to be lateralized to the right hemisphere and located in a large aggregated area, including the right lingual and fusiform gyri. These findings suggest that strikingly different neural pathways are engaged during recognition memory for words and for faces, in which a critical role in discrimination is played by semantic cueing and perceptual loading, respectively. In addition, the investigation of the regions common to word and face recognition indicates that the anterior and posterior cingulate have dissociable functions in recognition memory that vary with familiarity, and that the cerebellum may serve as the co-ordinator of all four types of recognition memory processes. (+info)
Isolating the contributions of familiarity and source information to item recognition: a time course analysis.
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Recognition memory may be mediated by the retrieval of distinct types of information, notably, a general assessment of familiarity and the recovery of specific source information. A response-signal speed-accuracy trade-off variant of an exclusion procedure was used to isolate the retrieval time course for familiarity and source information. In 2 experiments, participants studied spoken and read lists (with various numbers of presentations) and then performed an exclusion task, judging an item as old only if it was in the heard list. Dual-process fits of the time course data indicated that familiarity information typically is retrieved before source information. The implications that these data have for models of recognition, including dual-process and global memory models, are discussed. (+info)