Neuropsychologia
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Accessing the meaning of words, objects, people and facts is a human ability, made possible thanks to semantic processing. Although studies concerning its cortical organization are proficient, the subcortical connectivity underlying this semantic network received less attention. We used intraoperative direct electrostimulation, which mimics a transient virtual lesion during brain surgery for glioma in eight awaken patients, to map the anatomical white matter substrate subserving the semantic system. ⋯ These transient disorders were highly reproducible, and concerned verbal as well as non-verbal output. Our results highlight for the first time the essential role of the left inferior fronto-occipital fascicle in multimodal (and not only in verbal) semantic processing. On the basis of these original findings, and in the lights of phylogenetic considerations regarding this fascicle, we suggest its possible implication in the monitoring of the human level of consciousness related to semantic memory, namely noetic consciousness.
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This paper describes the progressive performance of JD, a patient with semantic dementia, on acronym categorisation, recognition and reading aloud over a period of 18 months. Most acronyms have orthographic and phonological configurations that are different from English words (BBC, DVD, HIV). While some acronyms, the majority, are regularly pronounced letter by letter, others are pronounced in a more holistic, and irregular, way (NASA, AWOL). ⋯ The decline in JD's semantic system led to increasingly impaired semantic categorisation and lexical decision for acronyms relative to healthy controls. However, her accuracy for reading aloud regular acronyms (i.e. those pronounced letter by letter such as BBC) remained near ceiling while reading irregular acronyms (i.e. those pronounced as mainstream words such as NASA) demonstrated impairment. It is therefore argued that consequences of semantic impairment vary across acronym types, a finding that informs our understanding of any reading account of this growing class of words.
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Randomized Controlled Trial
Dopaminergic contributions to distance estimation in Parkinson's disease: a sensory-perceptual deficit?
Recent research has found that perceptual deficits exist in Parkinson's disease (PD), yet the link between perception and movement impairments is not well understood. Inaccurate estimation of distance has the potential to be an underlying cause of movement impairments. Alternatively, those with PD may not be able to perceive their own movements accurately. ⋯ Individuals with PD demonstrated distance estimation deficits only when required to actively move through their environment. In contrast to estimations made with movement, neither static perception (laser) nor passive dynamic perceptions (wheelchair) revealed significant differences in the magnitude of error between the two groups. Thus perceptual estimation deficits appear to be amplified during movement, which may be suggestive of an underlying sensory processing deficit which leads to a problem integrating vision and self-motion information.
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A growing body of evidence suggests that a different hemispheric specialization may exist for different modalities of person identification, with a prevalent right lateralization of the sensory-motor systems allowing face and voice recognition and a prevalent left lateralization of the name recognition system. Data supporting this claim concern, however, much more disorders of familiar people recognition observed in patients with focal brain lesions than results of experimental studies conducted in normal subjects. ⋯ Results of this survey indicate that: (a) recognition of familiar faces and voices show a prevalent right lateralization, whereas recognition of familiar names is lateralized to the left hemisphere; (b) the right hemisphere prevalence is greater in tasks involving familiar than unfamiliar faces and voices, and the left hemisphere superiority is greater in the recognition of familiar than unfamiliar names. Taken together, these data suggest that hemispheric asymmetries in the recognition of faces, voices and names are not limited to their perceptual processing, but also extend to the domain of their cortical representations.
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The item-specific proportion congruent (ISPC) effect in a Stroop task - the observation of reduced interference for color words mostly presented in an incongruent color - has attracted growing interest since the original study by Jacoby, Lindsay, and Hessels [(2003) Psychonomic Bulletin & Review, 10(3), 638-644]. Two mechanisms have been proposed to explain the effect: associative learning of contingencies and item-specific control through word reading modulation. Both interpretations have received empirical support from behavioral data. ⋯ Results showed that the ISPC effect is associated with increased activity in the anterior cingulate (ACC), dorsolateral prefrontal (DLPFC), and inferior and superior parietal cortex. Importantly, behavioral and fMRI analyses specifically addressing the respective contribution of associative learning and item-specific control mechanisms brought support for the contingency learning account of the ISPC effect. Results are discussed in reference to task and procedure characteristics that may influence the extent to which item-specific control and/or contingency learning contribute to the ISPC effect.