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Purpose: To investigate the neural correlates associated with recovery from acute spatial neglect resulting from right hemispheric stroke. Methods: Four neglect patients were investigated both behaviourally and by fMRI at an acute (18 ± 5 days) and at a chronic stage (123 ± 18 days) post stroke. Results: At the second assessment all patients showed substantial behavioural improvements. These were associated with an increase of neural activity in the right middle frontal gyrus, right inferior parietal cortex, right inferior temporal gyrus/fusiform gyrus, left superior temporal gyrus/angular gyrus and left anterior cingulate gyrus. Decreased neural activity at the second assessment was found in the right parahippocampal gyrus and left fusiform gyrus. Conclusions: The pattern of neural reorganisation comprises areas of a right hemisphere fronto-parietal attentional network and corresponding left hemisphere areas suggesting a compensatory recruitment of analogous contralesional areas. Interestingly, a more complex pattern of neural changes was observed in the fusiform gyri which have previously been implicated in lateralised directed spatial attention. There was an increase in the right hemisphere and a decrease in the left hemisphere. This pattern of recovery is reminiscent of a "push-pull" pattern previously described for the dorsal parietal cortex by Corbetta et al. (2005) in the recovery from spatial neglect. [ABSTRACT FROM AUTHOR]

Abstract: The cholinergic agonist nicotine facilitates detection of invalidly cued trials in location-cueing paradigms and reduces the associated neural activity in human inferior parietal cortex. By using functional magnetic resonance imaging we test the hypothesis that the nicotinic modulation of attentional reorienting may result from reduced use of top-down information derived from prior cues. In a within subjects design non-smoking volunteers were given either placebo or nicotine (Nicorette® 2 mg gum) prior to performing a cued target discrimination task. Attention was either validly (80%) or invalidly (20%) cued to the right or left visual hemifield. The difference in reaction times to invalidly and validly cued targets is termed the ‘validity effect’ and indicates the costs for attentional reorienting. Nicotine reduced the validity effect and reorienting-related neural activity in right inferior parietal cortex. Further regions consistently modulated in their activity by nicotine were the right middle temporal gyrus, left middle frontal gyrus, left parahippocampal gyrus and right cerebellum. The effects of nicotine upon top-down modulation were investigated by comparing occipital activity when attending to the right vs. left visual hemifield under placebo and nicotine. If nicotine reduced the use of top-down information attentional modulation in occipital cortex should be smaller under nicotine as compared with placebo. Even though an attention-related modulation of neural activity was observed in the fusiform and middle occipital gyrus we found no evidence for differences in attentional modulation under placebo and nicotine. Our data support a role of nicotinic cholinergic receptors in facilitating several subcomponents of attentional reorienting via modulation of right inferior parietal, temporal and frontal brain activity. In contrast, the findings in the occipital cortex do not support the hypothesis that the effects of nicotine on attentional reorienting are due to reduced reliance on top-down information derived from prior cues. [Copyright &y& Elsevier]

Abstract: It has been suggested that the processing of action-related words involves activation of the motor circuitry. Using fMRI (functional magnetic resonance imaging), the current study further explored the interaction between action and language by investigating whether the linguistic context, in which an action word occurs, modulates motor circuitry activity related to the processing of action words. To this end, we examined whether the presentation of hand action-related verbs as positive or negative imperatives, for example, “Do grasp” or “Don''t write,” modulates neural activity in the hand area of primary motor cortex (M1) or premotor cortex (Pm). Subjects (n = 19) were asked to read silently the imperative phrases, in which both meaningful action verbs and meaningless pseudo-verbs were presented, and to decide whether they made sense (lexical decision task). At the behavioral level, response times in the lexical decision task were significantly longer for negative, compared to positive, imperatives. At the neural level, activity was differentially decreased by action verbs presented as negative imperatives for the premotor and the primary motor cortex of both hemispheres. The data suggest that context (here: positive vs. negative imperatives), in which an action verb is encountered, modulates the neural activity within key areas of the motor system. The finding implies that motor simulation (or motor planning) rather than semantic processing per se may underlie previously observed motor system activation related to action verb processing. Furthermore, the current data suggest that negative imperatives may inhibit motor simulation or motor planning processes. [Copyright &y& Elsevier]

Abstract: Presence of the apolipoprotein E (APOE) ε4 allele is linked to an increased risk to develop Alzheimer''s dementia (AD). However, there are controversial data concerning the impact of the APOE genotype on cognitive functioning and brain activity in healthy subjects. We used event-related functional magnetic resonance imaging (fMRI) to investigate the effects of APOE genotype on spatial contextual memory encoding and retrieval success in healthy older adults. Eighteen subjects (eight APOE4 heterozygotes (ε4+) and 10 non-carriers (ε4−), mean age 60.0±5.0 years) were included in the present analysis. Behaviorally, ε4+ subjects performed significantly worse than ε4− subjects in item memory and spatial context retrieval. fMRI data revealed that ε4+ subjects, compared to ε4-subjects, predominantly showed an increase of neural activity specific to encoding of items and their spatial context in prefrontal, temporal and parietal regions. In contrast, ε4+ subjects showed activity decreases in the right amygdala during successful item recognition and in the prefrontal cortex bilaterally during spatial context retrieval when compared to ε4− subjects. While the activity increases during encoding may reflect compensatory activity in the attempt to maintain normal performance, the decreases during retrieval indicate incipient neural decline in ε4+ subjects. These data highlight that preclinical ApoE-related changes in neural activity are not unidirectional but dissociate depending on the memory phase, i.e., encoding or retrieval. [Copyright &y& Elsevier]

Abstract: The integration of spatial and temporal information is a prerequisite for skilled movements. Likewise, spatial and temporal information must be integrated to predict the potential collision (or otherwise) of two moving objects. In a previous blocked functional magnetic resonance imaging (fMRI) study [Neuroimage 20 (2003) S82] we showed that collision judgments (relative to size judgments) provoked a significant increase in neural activity in the left inferior parietal cortex (supramarginal gyrus). This result suggests that this region is involved in the integration of perceptual spatiotemporal information in addition to its known involvement in programming skilled actions. To further investigate the impact of the integration of temporal and spatial information on the left parietal cortex we conducted an event-related fMRI study in which we varied the difficulty of the collision (and the size) judgment tasks parametrically. Reaction times and error rates were used as behavioral measures of increasing task demands. There was a significant linear increase in reaction times and error rates during the collision and the size tasks over the four levels of task difficulty. A linear increase of the blood oxygen level-dependent signal in the left inferior parietal cortex was found only for the collision, not for the size, conditions. Neural activation in the left inferior parietal cortex thus paralleled the increasing demands on spatiotemporal integration. This result confirms that the left supramarginal gyrus integrates spatial and temporal information irrespective of motor demands. [Copyright &y& Elsevier]