Biomedical subjects
Publications and source records attributed to C Guariglia.
Dissociation between personal and extrapersonal neglect has rarely been observed in man. In this study we present a case of severe personal neglect in the absence of a deficit for extrapersonal space. An extensive neuropsychological assessment demonstrates the absence of cognitive impairments in visuo-spatial processing and confirms the selective presence of a severe representational deficit of the left side of the body.
A patient with hemineglect disturbance (N.G.) due to a right hemispheric lesion was admitted to rehabilitative training which featured the use of procedures devised in a previous study (Pizzamiglio et al., 1990) both in a standard way and with the addition of optokinetic stimulation. This latter paradigm produces an automatic reaction which favors the spatial orienting of the patient toward his (left) neglected side. N.G. showed good recovery in visual scanning and, by the end of training, reached a level of recovery similar to other neglect patients. However, his recovery was particularly slow and no change was observed in his attitude toward the visual disturbance. The conclusion is reached that recovery in visual scanning also can be obtained in patients with persistent anosognosic disturbances. Stimulations such as the optokinetic condition which influence patients' behavior at an automatic level may play an important role in this recovery. CBF studies obtained before and after training showed a CBF improvement mainly in the right temporoparietal regions, behind the lesion, and in the left frontal cortex. The implications of these findings on various theoretical interpretations of the hemineglect disturbance are briefly discussed.
The CBF was assessed in seven patients before and after rehabilitation for visuospatial neglect. Two months of treatment produced an increased perfusion both in the right posterior and left anterior areas of the brain. However, only the left anterior CBF increase was correlated with the neglect disorders. The left anterior improvement in CBF was inversely correlated with right-left cerebellum asymmetry in pre- and post-treatment. The present data suggest the role of the frontal eye-fields in the mechanism of recovery of visual exploration in patients with severe neglect.
Contrasting hypotheses have been proposed about the functional equivalence between waking saccades and REMs. Patients with left visual hemi-inattention showed dissociation between the direction of waking saccades and that of REMs. REMs directed toward the left were virtually absent, while waking inspective saccades directed in both lateral directions were present, but confined to the right hemispace. It is concluded that: a) the cortical areas regulating attention are relevant in the production of REMs; b) two separate attentional mechanisms have to be considered in relation to the hemi-inattentive syndrome, one is involved in the cognitive control of visual exploration and plays little or no role in the modulation of REMs, the other deals with REMs during sleep and with reflex-like orienting responses to peripheral stimuli during waking.
Contrast sensitivity for sinusoidal gratings of different spatial frequencies and low spatial frequency discrimination of high contrast squarewave gratings were measured in 26 right brain damaged patients, 15 of whom showed symptoms of spatial hemi-neglect. No difference was present between neglect and non-neglect patients in either task. A difference in contrast sensitivity restricted to low spatial frequencies was present between controls and patients, independent of neglect. Overall, results indicated that spatial vision at threshold and suprathreshold levels is not selectively impaired in patients with hemi-neglect, a finding consistent with theories which postulate a post-perceptual locus of impairment in this syndrome.
Three groups of subjects, normal controls, right brain damaged patients with and without heminattention, were required to bisect a line in presence of a fixed or a moving background. The stimulus moving horizontally toward the left or the right induced an optokinetic nystagmus with a slow phase coherent with the direction of the movement: together with the optokinetic nystagmus, a displacement of the subjective midpoint, as compared to the condition with a fixed background, was observed in all three groups of subjects. Within the right brain damaged with heminattention the displacement of the line bisection was great for stimuli moving toward the right, but a significant reduction of the left bias was present. In the same group of patients the effect of the optokinetic stimulation was present in a very large proportion of cases and proved to be relatively stable in a test-retest presentation. Theoretical relevance of these data and their potential importance for rehabilitation are discussed.
Shape, size and relative position in space perception were tested in 17 right brain damaged (RBD) patients with neglect symptoms, 10 RBD patients without neglect and 11 controls. Simultaneous pair comparison task in free vision was used. Two arrangements of the visual display were used: side by side and top-bottom. Neglect patients' performance was comparable to RBD and controls in the shape and size test, but was below the other groups in the relative space position test. The selective failure of neglect patients in the position task did not depend on the spatial arrangement of the visual display, which may indicate a general perceptual deficit, rather than a deficit restricted to the neglect hemifield.
The possible dissociation of unilateral neglect in far and near extra-personal space was systematically investigated using a modified version of the Wundt-Jastrow area illusion test. This task, which requires no motor response, has been shown to be sensitive to unilateral neglect. Stimuli were presented at two different distances (near and far) to a group of 70 patients with right hemispheric lesion (18 in acute and 52 in chronic stage). Twenty-eight patients evidenced unilateral neglect; that is, they displayed unexpected (i.e., contrary to the known illusory effect) responses when the stimuli were perceived as oriented toward the left side. However, performances in the two conditions were highly correlated and there were no individual instances of dissociation. These results suggest that the presence of a motor response may be necessary to show behavioral dissociations between different parts of extra-personal space.
The effects of congenital deficiency of gonadal hormones on verbal and spatial performance and on the establishment of hemispheric asymmetries were investigated in a group of patients with idiopathic hypogonadotropic hypogonadism. The patients showed a left hemispheric advantage for verbal material and were mildly impaired, mainly on tasks involving a short-term memory load, in comparison with a matched control group. These results do not indicate a specific role of gonadal hormones on the establishment of hemispheric asymmetries. Lack of exposure during brain development results in a decrease in memory functions which is not specific for verbal or spatial material.