1,720,976 research outputs found
The Neural Network of Spatial Cognition and its Modulation by Biological and Environmental Factors
No full textUsing functional magnetic resonance imaging (fMRI), we investigated the question, if the neural spatial cognition network is modulated by biological (Sex) and environmental factors ( Experience, Spatial Component). Sex and Experience modulate response selection and motor imagery. Both Spatial Component and Experience are strongly related to brain activity in visual areas. The interaction between Spatial Component and Experience revealed that high spatial experience and significant better performance in the mental rotation task are related to task-specific neural changes. We conclude that brain areas involved in perceptual and motor processes are associated with the investigated factors Sex, Spatial Component, and Experience. The neural activity in core regions of the spatial cognition network seems to be associated with specific performance changes. Further studies should examine whether these results are specific to our spatial tasks or can be generalized to other cognitive tasks
Different cortical activations for subjects using allocentric or egocentric strategies in a virtual navigation task
No full textSubjects were required to navigate through a virtual 3D labyrinth presented on a screen while fMRI images were obtained. Contrasting the fMRI images obtained during the navigation trials with appropriate control conditions revealed a bilateral network comprising the parietal lobe (including the intraparietal sulcus) and various lateral and medial premotor areas. The subjects using an allocentric strategy showed stronger activation in the medial temporal areas including the parahippocampal region, the hippocampus, and the thalamus. In addition, the cerebellum was also active in those subjects. We believe that this activation pattern is related to visually guided memory retrieval based on generalized spatial maps. The stronger activation in the thalamic–basal ganglia–cerebellar–loop points to a more automatic support of memory and attentional processes possibly supporting memorization of spatial maps
Neurological soft signs and brain morphology in first-episode schizophrenia
No full textBackground. Although minor motor and sensory deficits, or neurological soft signs (NSS), are a well-established finding in schizophrenia, the cerebral changes underlying these signs are only partly understood. We therefore investigated the cerebral correlates of NSS by using magnetic resonance imaging (MRI) in patients with schizophrenia and healthy controls. Method. Forty-two patients, all receiving atypical neuroleptics, with first-episode schizophrenia or schizophreniform disorder and 22 healthy controls matched for age and gender were included. NSS were examined on the Heidelberg Scale after remission of the acute symptoms before discharge and correlated to density values by using optimized voxel-based morphometry (VBM). Results. NSS scores were significantly higher in patients than healthy controls. Within the patient group NSS were significantly associated with reduced grey or white-matter densities in the pre- and post-central gyrus, pre-motor area, middle and inferior frontal gyri, cerebellum, caudate nucleus and thalamus. These associations did not apply for the control group, in whom only the associations between NSS and reduced frontal gyri densities could be confirmed. Conclusions. The pattern of cerebral changes associated with NSS clearly supports the model of 'cognitive dysmetria' with a disrupted cortico-cerebellar-thalamic-cortical circuit in schizophrenia. The variety of sites may correspond with the clinical diversity of NSS, which comprises both motor and sensory signs, and with the putative heterogeneity of the pathogenetic changes involved. That the respective associations did not apply for the healthy control group indicates that NSS in patients and controls refer to different pathogenetic factors.Stanley Medical Research Institut
Structural changes of the corpus callosum in Mild Cognitive Impairment and Alzheimer's disease
No full textScanning silence: Mental imagery of complex sounds
No full textIn this functional magnetic resonance imaging (fMRI) study, we investigated the neural basis of mental auditory imagery of familiar complex sounds that did not contain language or music. In the first condition (perception), the subjects watched familiar scenes and listened to the corresponding sounds that were presented simultaneously. In the second condition (imagery), the same scenes were presented silently and the subjects had to mentally imagine the appropriate sounds. During the third condition (control), the participants watched a scrambled version of the scenes without sound. To overcome the disadvantages of the stray acoustic scanner noise in auditory FMRI experiments, we applied sparse temporal sampling technique with five functional clusters that were acquired at the end of each movie presentation. Compared to the control condition, we found bilateral activations in the primary and secondary auditory cortices (including Hesehl's gyrus and planum temporale) during perception of complex sounds. In contrast, the imagery condition elicited bilateral hemodynamic responses only in the secondary auditory cortex (including the planum temporale). No significant activity was observed in the primary auditory cortex. The results show that imagery and perception of complex sounds that do not contain language or music rely on overlapping neural correlates of the secondary but not primary auditory cortex. (c) 2005 Elsevier Inc. All rights reserved
The neural basis of the egocentric and allocentric spatial frame of reference
No full textThe present study examines the functional and anatomical underpinnings of egocentric and allocentric coding of spatial coordinates. For this purpose, we set up a functional magnet resonance imaging experiment using verbal descriptions of spatial relations either with respect to the listener (egocentric) or without any body-centered relations (allocentric) to induce the two different spatial coding strategies. We aimed to identify and distinguish the neuroanatomical correlates of egocentric and allocentric spatial coding without any possible influences by visual stimulation. Results from sixteen participants show a general involvement of a bilateral fronto-parietal network associated with spatial information processing. Furthermore, the egocentric and allocentric conditions gave rise to activations in primary visual areas in both hemispheres. Moreover, data show separate neural circuits mediating different spatial coding strategies. While egocentric spatial coding mainly recruits the precuneus, allocentric coding of space activates a network comprising the right superior and inferior parietal lobe and the ventrolateral occipito-temporal cortex bilaterally. Furthermore, bilateral hippocampal involvement was observed during allocentric, but not during egocentric spatial processing. Our results demonstrate that the processing of egocentric spatial relations is mediated by medial superior-posterior areas, whereas allocentric spatial coding requires an additional involvement of right parietal cortex, the ventral visual stream and the hippocampal formation. These data suggest that a hierarchically organized processing system exists in which the egocentric spatial coding requires only a subsystem of the processing resources of the allocentric condition. (c) 2006 Elsevier B.V. All rights reserved
Structural changes of the corpus callosum in Mild Cognitive Impairment and Alzheimer's disease
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