Abstract not found

The control of routine action is a complex process subject both to minor lapses in normals and to more severe breakdown followingcertain forms of neurological damage. A number of recent empirical studies (e.g. Humphreys & Ford, 1998; Schwartz et al., 1991, 1995, 1998) have examined the details of breakdown in certain classes of patient, and attempted to relate the findings to existing psychological theory. This paper complements those studies by presenting a computational model of the selection of routine actions based on competitive activation within a hierarchically organised network of action schemas (cf. Norman & Shallice, 1980, 1986). Simulations are reported which demonstrate that the model is capable of organised sequential action selection in a complex naturalistic domain. It is further demonstrated that, after lesioning, the model exhibits behaviour qualitatively equivalent to that observed by Schwartz et al., in their action disorganisation syndrome patients.

The article contributes to the quest to relate global data on brain and behavior (e.g. from PET, Positron Emission Tomography, and fMRI, functional Magnetic Resonance Imaging) to the underpinning neural networks. Models tied to human brain imaging data often focus on a few "boxes" based on brain regions associated with exceptionally high blood flow, rather than analyzing the cooperative computation of multiple brain regions. For analysis directly at the level of such data, a schema-based model may be most appropriate. To further address neurophysiological data, the Synthetic PET imaging method uses computational models of biological neural circuitry based on animal data to predict and analyze the results of human PET studies. This technique makes use of the hypothesis that rCBF (regional cerebral blood flow) is correlated with the integrated synaptic activity in a localized brain region. We also describe the possible extension of the Synthetic PET method to fMRI. The second half of the...

Selective deficits in aphasics patients ’ grammatical production and comprehension are often cited as evidence that syntactic processing is modular and localizable in discrete areas of the brain (e.g., Y. Grodzinsky, 2000). The authors review a large body of experimental evidence suggesting that morphosyntactic deficits can be observed in a number of aphasic and neurologically intact populations. They present new data showing that receptive agrammatism is found not only over a range of aphasic groups, but is also observed in neurologically intact individuals processing under stressful conditions. The authors suggest that these data are most compatible with a domain-general account of language, one that emphasizes the interaction of linguistic distributions with the properties of an associative processor working under normal or suboptimal conditions. The primary purpose of this article is to provide empirical arguments in support of a new view of language deficits and their neural correlates, particularly in the realm of syntax. Selective syntactic deficits are often cited as evidence that the human brain contains a bounded and well-defined faculty or module dedicated exclusively to the representation and/or processing of syntax (Caplan & Waters, 1999; Grodzinsky, 1995a,

“Origins of communicative disorders ” to Elizabeth Bates, and by a grant from the John D. and Catherine T. MacArthur Foundation. We are grateful to Larry Juarez and Meiti Opie The effects of focal brain injury are investigated in the first stages of language development, during the passage from first words to grammar. Parent report and/or free speech data are reported for 53 infants and preschool children between 10- 44 months of age. All children had suffered a single, unilateral brain injury to the left or right hemisphere, incurred before six months of age (usually in the pre- or perinatal period). This is the period in which we should expect to see maximal plasticity, but it is also the period in which the initial specializations of particular cortical regions ought to be most evident. In direct contradiction of hypotheses based on the adult aphasia literature, results from 10- 17 months suggest that children with righthemisphere injuries are at greater risk for delays in word comprehension, and in the gestures that normally precede and accompany language onset. Although there were no differences between left- vs. right-hemisphere injury per se on expressive language, children whose lesions include the left temporal lobe did show significantly greater delays in expressive vocabulary and

s a predictor of decits in processing for both speech and environmental sounds. The lesion mapping and further statistical assessments reliably revealed a posterior superior temporal region (Wernicke's area, traditionally considered a language-specic region) as being differentially more important for processing nonverbal sounds compared with verbal sounds. These results suggest that, in most cases, processing of meaningful verbal and nonverbal auditory information break down together in stroke and that subsequent recovery of function applies to both domains. This suggests that language shares neural resources with those used for processing information in other domains. Keywords: aphasia; auditory agnosia; environmental sounds; Wernicke's area; lesion mapping Abbreviations: AQ = aphasia quotient; ERD = event-related desynchronization; ERP = event-related potentials; fMRI = functional MRI; IPL = inferior parietal lobule; LHD = left hemisphere-damaged; pMTG = posterior middle temporal

Abstract not found

Abstract. This chapter describes the characteristics and preliminary evaluation of The Virtual Environment for Body Image Modification (VEBIM), a set of tasks aimed at treating body image disturbances and body dissatisfaction associated with eating disorders. Two methods are commonly used to treat body image: (1) a cognitive/behavioural therapy to influence patients ' feelings of dissatisfaction; (2) a visual/motorial therapy with the aim of influencing the level of bodily awareness. VEBIM tries to integrate these two therapeutic approaches within an immersive virtual environment. This choice would not only make it possible to intervene simultaneously on all of the forms of bodily representations, but also to use the psycho-physiological effects provoked on the body by the virtual experience for therapeutic purposes. The chapter, together with the description of the VEBIM theoretical approach, it also presents a study on two preliminary samples (71 normal subjects, uncontrolled study, 48 normal subjects, controlled study) to test its efficacy. 1.

We tested aphasic patients ’ comprehension of actions to examine processing deficits in the linguistic and non-linguistic domains and their lesion correlates. 29 left-hemisphere injured patients and 18 age-matched control subjects matched pictured actions (with the objects missing) or their linguistic equivalents (printed sentences with the object missing) to one of two visually-presented pictures of objects. Aphasic patients performed poorly not only in the linguistic domain but also in the non-linguistic domain. A subset of the patients, largely consisting of severe and non-fluent aphasics, showed a greater deficit in the linguistic domain compared with the non-linguistic domain and across the patient group, deficits in the linguistic and non-linguistic domains were not tightly correlated. Poor performance in pantomime interpretation was associated with lesions in the inferior frontal, premotor and motor cortex, a portion of somatosensory cortex, and the caudate, while poor reading comprehension of actions was associated with lesions around the anterior superior temporal lobe, the anterior insula and the anterior portion of the inferior parietal lobe. Lesion size did not correlate with deficits. The lesion results for pantomime interpretation deficits demonstrate that lesions in the frontal component of the human analog of the “mirror neuron system ” are associated with deficits in non-linguistic action understanding. For reading comprehension deficits, the

Although neuropsychological localization constitutes the principal approach to the study of language disorders, there is reason to think it may not be entirely correct. Recent anatomical studies suggest that cognitive brain functions do not localize to precise anatomical locations. Connectionist (parallel distributed processing) approaches to the study of language, which emphasize the distributed nature of computational processes, may help explain the variability found in these anatomical studies, and provide a new way to approach the neurological study of language. This combined computational and empirical method focuses on the interplay between a computational model and the appropriate neurological, neuropsychological, and speech and language data, the whole couched in connectionist mechanisms that map naturally to what is known of the neurophysiological structure of the brain. This paper introduces the concepts of connectionist modeling, with emphasis on their use in understanding language disorders.