1,720,982 research outputs found
Una via parieto- temporo mediale per i processi visuo-spaziali: uno studio di connettività funzionale
No full textNeuropsychology of environmental navigation in humans: review and meta-analysis of FMRI studies in healthy participants.
No full textIn the past 20 years, many studies in the cognitive neurosciences have analyzed human ability to navigate in recently learned and familiar environments by
investigating the cognitive processes involved in successful navigation. In this
study, we reviewed the main experimental paradigms and made a cognitive-oriented
meta-analysis of fMRI studies of human navigation to underline the importance of
the experimental designs and cognitive tasks used to assess navigational skills.
We performed a general activation likelihood estimation (ALE) meta-analysis of 66
fMRI experiments to identify the neural substrates underpinning general aspects
of human navigation. Four individual ALE analyses were performed to identify the
neural substrates of different experimental paradigms (i.e., familiar vs.
recently learned environments) and different navigational strategies (allocentric
vs. egocentric). Results of the general ALE analysis highlighted a wide network
of areas with clusters in the occipital, parietal, frontal and temporal lobes,
especially in the parahippocampal cortex. Familiar environments seem to be
processed by an extended temporal-frontal network, whereas recently learned
environments require activation in the parahippocampal cortex and the parietal
and occipital lobes. Allocentric strategy is subtended by the same areas as
egocentric strategy, but the latter elicits greater activation in the right
precuneus, middle occipital lobe and angular gyrus. Our results suggest that
different neural correlates are involved in recalling a well-learned or recently
acquired environment and that different networks of areas subtend egocentric and
allocentric strategies.In the past 20 years, many studies in the cognitive neurosciences have analyzed
human ability to navigate in recently learned and familiar environments by
investigating the cognitive processes involved in successful navigation. In this
study, we reviewed the main experimental paradigms and made a cognitive-oriented
meta-analysis of fMRI studies of human navigation to underline the importance of
the experimental designs and cognitive tasks used to assess navigational skills.
We performed a general activation likelihood estimation (ALE) meta-analysis of 66
fMRI experiments to identify the neural substrates underpinning general aspects
of human navigation. Four individual ALE analyses were performed to identify the
neural substrates of different experimental paradigms (i.e., familiar vs.
recently learned environments) and different navigational strategies (allocentric
vs. egocentric). Results of the general ALE analysis highlighted a wide network
of areas with clusters in the occipi
Where am I? A new case of developmental topographical disorientation.
No full textRecently, developmental topographical disorientation (DTD) was described (Bianchini et al., 2010, J Clin Exp Neuropsychol, 20, 807-27; Iaria & Barton, 2010, Exp Brain Res, 206, 189-96; Iaria, Bogod, Fox, & Barton, 2009, Neuropsychologia, 47, 30-40) as a navigational deficit in the absence of neurological or psychiatric disorders. Here, we reported the case of a healthy subject who presented this disorder. Dr. WAI was a 29-year-old right-handed man with normal development and no clinical history of neurological or psychiatric diseases who was affected by a very pervasive topographical orientation and navigational disorder. A neuroradiological exam confirmed the absence of structural and anatomical alterations of the brain. Dr. WAI was submitted to an extensive neuropsychological examination and to a battery of tests specifically developed to assess developmental topographical disorder. Using this battery, we analysed Dr. WAI's acquisition of navigational information and re-orientation processes. He showed severe DTD accompanied by deficits of different cognitive processes directly or indirectly involved in navigational skills. Dr. WAI showed a deficit in developing cognitive maps, already found in previous cases, plus difficulties in evaluating distances and computing metric environmental features. He represents a further confirmation of the existence of DTD suggesting dissociations within the disorder related to the level of development of the ability to build cognitive maps and the association of different imagery deficits. Dr. WAI can help in shedding some light on the mechanisms underlying lack of development of navigational skills
Un penny per i tuoi pensieri! I pattern di attivazione fMRI rivelano il contenuto delle immagini mentali visuo-spaziali
No full textLooking for the compass in a case of developmental topographical disorientation: A behavioral and neuroimaging study.
No full textDevelopmental topographical disorientation (DTD) is the presence of navigational deficits in the context of normal intellectual ability and in the absence of any perinatal, neurological, or psychiatric disorder. As only three cases of DTD have been fully described thus far, we are still unable to draw definitive conclusions about its nature and relationship with other visuospatial competencies, such as mental rotation. The case of Mr. L.A., a 38-year-old man with no history of neurological or psychiatric disorders, sheds some light on these open questions. A neuropsychological assessment including IQ, memory, visuospatial, visuoconstructive, and navigational tests showed that Mr. L.A. has pure navigational deficits affecting both route knowledge and cognitive map processing. Unlike previously described cases of DTD, Mr. L.A. was not affected by any other visuospatial or visuoconstructive deficits. In a functional magnetic resonance imaging (fMRI) task involving the recall of route knowledge, Mr. L.A. showed activation in the occipital areas, involved in low-level perceptual analysis of the stimuli, and showed no activation in the areas activated in controls with regard to route knowledge. The present case suggests that different types of DTD exist, which are characterized by different navigational difficulties and anomalous/lacking functional brain activities in specific navigational networks
A penny for your thoughts! patterns of fMRI activity reveal the content and the spatial topography of visual mental images.
No full textVisual mental imagery is a complex process that may be influenced by the content of mental images. Neuropsychological evidence from patients with hemineglect suggests that in the imagery domain environments and objects may be represented separately and may be selectively affected by brain lesions. In the present study, we used functional magnetic resonance imaging (fMRI) to assess the possibility of neural segregation among mental images depicting parts of an object, of an environment (imagined from a first-person perspective), and of a geographical map, using both a mass univariate and a multivariate approach. Data show that different brain areas are involved in different types of mental images. Imagining an environment relies mainly on regions known to be involved in navigational skills, such as the retrosplenial complex and parahippocampal gyrus, whereas imagining a geographical map mainly requires activation of the left angular gyrus, known to be involved in the representation of categorical relations. Imagining a familiar object mainly requires activation of parietal areas involved in visual space analysis in both the imagery and the perceptual domain. We also found that the pattern of activity in most of these areas specifically codes for the spatial arrangement of the parts of the mental image. Our results clearly demonstrate a functional neural segregation for different contents of mental images and suggest that visuospatial information is coded by different patterns of activity in brain areas involved in visual mental imagery
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Finding my own way: an fMRI single case study of a subject with developmental topographical disorientation
No full textDevelopmental topographical disorientation (DTD) causes impaired spatial orientation and navigation from early childhood with no evidence of cerebral damage. Using fMRI and a landmark sequencing task, we investigated the hypothesis that Dr Wai's abnormal cerebral activation pattern was related to his peculiar behavioral profile. Although Dr Wai was able to correctly perform landmark sequencing, he showed a lack of activity in regions activated in all control subjects and activity in areas that were not activated in any control subject. These results are discussed in light of cognitive and functional model of navigation, with relevant implications for DTD physiology
Finding my own way: an fMRI single case study of a subject with developmental topographical disorientation.
No full textevelopmental topographical disorientation (DTD) causes impaired spatial orientation and navigation from early childhood with no evidence of cerebral damage. Using fMRI and a landmark sequencing task, we investigated the hypothesis that Dr Wai's abnormal cerebral activation pattern was related to his peculiar behavioral profile. Although Dr Wai was able to correctly perform landmark sequencing, he showed a lack of activity in regions activated in all control subjects and activity in areas that were not activated in any control subject. These results are discussed in light of cognitive and functional model of navigation, with relevant implications for DTD physiology
- …
