| Name | Dario |
| Surname | Grossi |
| Institution | Università degli Studi della Campania Luigi Vanvitelli |
| dario.grossi@unicampania.it | |
| Address | Villa Camaldoli Foundation Clinic, Naples, Italy; Department of Psychology, University of Campania "Luigi Vanvitelli", Napoli, Italy |
We aimed at verifying whether the hemispheric specialisation for categorical/coordinate spatial judgements also applies to the spatial imagery domain by the use of whole-brain fMRI. In a block-design experiment we used the "coordinate" mental clock test, contrasting it with a "categorical" task applied to the same clock stimuli; as a control task we used a syllable counting task requiring a verbal-phonological judgement on the same material of the two imagery tasks. Our results showed that categorical and coordinate spatial judgements on imagined stimuli rely on the activation of a set of cortical areas, centred upon the superior parietal lobule (SPL) bilaterally. These regions, together with other parietal and prefrontal areas, showed a pattern of relative lateralization, with the left hemisphere being mainly activated during the categorical task and the right in the coordinate task. These data confirm the strong involvement of the SPL in spatial processing. Moreover, our findings suggest that different interconnected neural networks are activated to comply with specific test requirements, giving rise to functional imaging patterns compatible with psychological theories on hemispheric specialization.
In this article we describe a child affected by right parieto-occipital lesion due to head injury. The patient showed left hemianopia, but not unilateral spatial neglect on traditional paper-and-pencil tests and on "ecological" tests. However, his parents reported frequent collisions with obstacles on the left side. A specific test was set up: The patient had to kick down skittles put on both sides of a route traced on the floor. He kicked down 89% of skittles on the right, but only 38% on the left side. These findings are discussed in light of recent theories on unilateral neglect.
Cognitive models for developmental dyslexia are nowadays centered on the hypothesis of a specific deficit within the phonologic module of the language system. To ascertain whether defects of spatial cognition are associated with developmental reading disability, we investigated a sample of 43 school children (aged 8-9 years) found to be reading impaired during a wide screening survey for developmental dyslexia in the province of Naples, Italy. After one year all children were tested again and only 9/43 still presented reading impairment, while the remaining had achieved a variable range of spontaneous recovery. A detailed analysis was performed on all children to characterize their cognitive performances using on one hand classical conventional tests for constructional praxis, visuospatial cognition, and visuospatial memory and on the other a specific neuropsychological battery for constructional disorders. The results of our study demonstrated that children with long-lasting reading impairment exhibited normal performances on spatial cognition tasks. Moreover, one single child was found with relevant visuospatial deficits pointing to the possible existence of a visuospatial subtype for developmental dyslexia.
The present study aimed to investigate the acquisition of visuospatial and graphomotor capacities during the pre-school and early schooling years in order to follow the normal development of drawing-related abilities and spatial cognition. Eighty children aged 3-5 years, divided in four subgroups each different for a 6-month period, and 80 children aged 8-9 years were administered a neuropsychological battery for visuospatial and visuoconstructional analysis. The battery explored five cognitive domains: visual scanning, visuospatial perceptual and representational abilities, visuomotor control and graphomotor skills. Results showed that the total scores significantly improved in each group of children with respect to the previous one, but the pattern of skill acquisition was not homogeneous. We observed a gradient from explorative and visuomotor to perceptive, representational and graphomotor abilities. Explorative and visuomotor abilities were almost mature at a time when visuoperceptual capacities began to develop. On the contrary, at that time we found very low performances at representational and constructional tasks. Our findings could suggest that constructional abilities need both perceptual and representational competences to develop properly.
Do spatial operations on mental images and those on visually presented material share the same neural substrate? We used the high spatial resolution of functional magnetic resonance imaging to determine whether areas in the parietal lobe that have been implicated in the spatial transformation of visual percepts are also activated during the generation and spatial analysis of imagined objects. Using a behaviourally controlled mental imagery paradigm, which did not involve any visual stimulation, we found robust activation in posterior parietal cortex in both hemispheres. We could thus identify the subset of spatial analysis-related activity that is involved in spatial operations on mental images in the absence of external visual input. This result clarifies the nature of top-down processes in the dorsal stream of the human cerebral cortex and provides evidence for a specific convergence of the pathways of imagery and visual perception within the parietal lobes.
Five neglect patients without diffuse cognitive impairment or overt constructional disabilities were asked to bisect lines and rectangles and to copy rectangles bisected in their midplane. As a group, patients showed the usual rightward bias in bisecting lines and a milder deviation in bisecting horizontally-aligned rectangles, but showed a leftward deviation of the subjective midline in the copying task. This was due to drawing the left half shorter with respect to normal controls but three patients also drew the right half longer (the total length was the same as that of controls). A possible interpretation of rectangle copying results in these three patients is that they could create a representation of the stimulus to be copied accurately enough to reproduce its total length correctly but the subjective distribution of right and left space within that representation was unbalanced. However, specific experimental work is needed to verify why our patients with mild to moderate unilateral spatial neglect overrepresented the left side in a line bisection task and underrepresented it in a copying task.
A patient is described who was affected by degenerative dementia and who developed severe constructional apraxia. She showed a dissociation between the construction of horizontal lines (impaired) and oblique or vertical lines (spared) which has never been reported previously. A battery of tests disclosed that this phenomenon was consistent across a range of experimental conditions and that a similar dissociation was evident in perceptual and representational domains. This peculiar clinical finding suggests that mental representations of horizontal and vertical spatial relations in an egocentric coordinate system are functionally dissociated.
We assessed neuropsychological performances of 22 patients affected by Autosomal Dominant Cerebellar Ataxia type 1. All subjects completed a comprehensive battery of standardized tests requiring a verbal response, without time constraints. In order to verify the hypothesis that disease severity is the major factor in determining the cognitive status in this syndrome, patients were divided into three groups according to the severity of the clinical picture, as evaluated by the Inherited Ataxias Progression Scale (IAPS). Statistical analysis of the three groups' raw scores showed a significant decrement in patients with more severe clinical pictures on verbal short-term memory tasks. A similar trend, but not significant, was seen for general intelligence tests and verbal learning tasks. The decrement of verbal short-term memory could be related to motor speech problems. On the other hand, the decline of cognitive abilities over the course of the Autosomal Dominant Cerebellar Ataxia type 1 was not homogeneous enough to ensure statistically reliable trends. Therefore, this cross-sectional study suggests that the progression of the disease is a necessary factor in determining cognitive decline, but it is not sufficient. Other disease-related factors (age at onset, genotypic variety) could play a critical role: among these, the size of the expanded CAG repeats is significantly related to a decline of verbal intelligence and short-term memory in SCA2 patients.
We report on a patient affected by selective drawing disabilities. The patient could correctly reproduce and draw simple geometric figures on request, but when he tried to reproduce more complex drawings or to draw common objects he performed very poorly. To identify the cognitive impairment in this patient, we adopted two test batteries based on recent information-processing models of drawing. Results showed that the patient's drawing disabilities were independent of visuo-perceptual and executive impairments. These findings support recent cognitive models of drawing abilities: some intermediate stages of drawing exist at which information is processed to prepare and guide motor output, and which may be selectively disrupted after discrete cerebral lesions.
We describe a simple, three-dimensional constructional test (the Box test), which reflects common daily-living activities, to be used for the assessment of constructional disability in elderly brain-lesioned patients. Subjects are required to put as may of 12 objects of varied shape and volume as they can into a box. To carry out the task successfully subjects have to arrange the items according to an efficient constructional strategy. We administered this test to 68 normal subjects and to 50 brain-damaged patients. Analysis indicated the Box test is easy and simple to administer and can be used without difficulty by elderly patients having focal brain damage. Performance correlated well with general intelligence and other bidimensional, conventional constructional tasks. Right or left brain lesions have a similar, significant detrimental effect on performance but probably through different mechanisms.