Biomedical subjects

C Incoccia

Publications and source records attributed to C Incoccia.

7 recordsLinked to original sources

PubMed2005

Abnormal motor preparation in severe traumatic brain injury with good recovery.

Movement-related cortical potentials (MRCPs) were examined in seven patients with severe traumatic brain injury (TBI) and 12 matched control subjects. All patients had clinically established good recovery by the time of testing. Flexion movements of the index finger of the left or right hand were recorded in two (alternating and repetitive) self-paced conditions and in one externally triggered condition. In control subjects, the bereitschaftspotential (BP) component of MRCP was detected approximately 2000 msec prior to movement onset in the self-paced conditions and was larger and earlier in the alternating compared to the repetitive condition. The BP component was absent in the externally triggered condition. In TBI patients, the BP was greatly reduced and no difference between the alternating-repetitive conditions was detected; in contrast, only small differences were present in the controls for the negative slope (NS) and MP components and no difference for the reafferent positivity (RAP) component. A dipole analysis indicated the supplementary motor area and the premotor area as the likely generators of BP and NS' components, respectively. Gradientrecalled echo magnetic resonance imaging allowed the detection of a number of small hypointense lesions primarily located in the frontal lobes, as in diffuse axonal injury. This pattern of results indicates a selective deficit in motor preparation and a relatively spared pattern of activation during and following movement in these patients. Imaging data appear generally consistent with the pattern of MRCPs observed in the patient group. Implications of these results for the problem of slowness in TBI patients are discussed.

Adult↗

PubMed1999

The endpoints' task: an analysis of length reproduction in unilateral neglect.

When patients with left hemineglect are shown the centre of a memorised line and are asked to mark both the endpoints, they place the left one significantly farther. This contralesional bias appears to be incoherent with respect to most current interpretations of neglect [7]. In the present study, ten patients with left hemineglect and two control groups were presented the centre of a line and one of its endpoints and had to mark the missing one at the correct distance. With this modification, subjects had not to rely on stored information about the line, but simply to reproduce a distance either to the left or to the right separately. The task was performed in three different spatial locations with respect to subjects' body midline. Similarly to the original endpoints' task, neglect patients showed a leftward bias, placing the left endpoint significantly farther than the right one. However, this was not associated with a paradoxical contralesional over-extension with respect to the distance to reproduce. Indeed, when marking the left endpoint, patients were accurate (when performing in the right hemispace) or even underestimated the distance to reproduce (when performing centrally and in the left hemispace). Instead, the leftward bias was due to severe underestimation errors when marking the right endpoint, which were independent of the stimulus location. These results demonstrate that the leftward bias in the endpoints' task is relative rather than absolute and does not reflect a paradoxical overestimation in length reproduction towards the left side.

Adult↗

PubMed1998

Seeing only the right half of the forest but cutting down all the trees?

Unilateral neglect following damage to the right hemisphere of the brain can be characterized by failure of the global attentional mechanisms of the right hemisphere to direct the local detail processors of the left hemisphere towards the contralesional left hemispace. This is suggested by patients who recognize the global form of the left side of shapes (the forest) but fail to cancel out its local details (the trees). Here we report the opposite behavioural dissociation in a patient (Q.M.) with damage to the right hemisphere of the brain. Q.M. detected local details (such as the tail of a dog) on the left or right side of visual shapes, regardless of whether these details belonged to predefined target shapes (a dog in this case) or to distractor shapes differing on the opposite side (a dog with a swan's neck and head, for example). Psychological testing showed an abnormal tendency of this patient to respond to local features, but perfect accuracy in interpreting global features when the local features could not interfere in global processing. The results indicate that the left hemisphere can integrate multiple local features simultaneously but loses global awareness as soon as local features individually compete for response selection. However, awareness of the whole is not necessary for the sequential processing of the parts.

Attention↗

PubMed1997

Neural control of fast-regular saccades and antisaccades: an investigation using positron emission tomography.

Regional cerebral blood flow changes related to the performance of two oculomotor tasks and a central fixation task were compared in ten healthy human subjects. The tasks were: (a) performance of fast-regular saccades; (b) performance of voluntary antisaccades away from a peripheral cue; (c) passive maintenance of central visual fixation in the presence of irrelevant peripheral stimulation. The saccadic task was associated with a relative increase in activity in a number of occipitotemporal areas. Compared with both the fixation and the saccadic task, the performance of antisaccades activated a set of areas including: the superior and inferior parietal lobules, the precentral and prefrontal cortex, the cingulate cortex, and the supplementary motor area. The results of the present study suggest that: (a) compared with self-determined saccadic responses the performance of fast regular, reflexive saccades produces a limited activation of the frontal eye fields; (b) in the antisaccadic task the inferior parietal lobes subserve operations of sensory-motor integration dealing with attentional disengagement from the initial peripheral cue (appearing at an invalid spatial location) and with the recomputation of the antisaccadic vector on the basis of the wrong (e.g., spatially opposite) information provided by the same cue.

Adult↗

PubMed1995

Amplitude and speed change of the optokinetic response in patients with and without neglect.

The present study quantitatively investigated the slow and quick phases of optokinetic nystagmus (OKN) in four groups of patients: right unilateral brain-damaged patients with neglect, left and right patients without neglect or hemianopia and patients with left or right retrogeniculate lesions and lateral homonymous hemianopia. Our results indicate that only neglect patients show a perturbation of both components of OKN. A comparison among MRI images of different patients shows that a region involving area 37 and adjacent areas 39 and 19, was impaired in all patients with neglect, but not in any other patient with either right or left lesions.

Adolescent↗

PubMed1991

SPECT, MRI and cognitive functions in multiple sclerosis.

Seventeen patients with relapsing remitting multiple sclerosis (MS) and mild physical disability had neuropsychological testing, magnetic resonance imaging (MRI) and single photon emission computerised tomography (SPECT) using technetium 99m (99mTc) hexamethyl-propyleneamine oxime (HMPAO). Performance in verbal fluency, naming and memory testing appeared to be impaired in MS patients compared with 17 age-sex and education matched normal controls. Weighted periventricular and confluent lesion scores and the width of the third ventricle, proved to be the most sensitive MRI measures in differentiating more cognitively impaired patients from those who were relatively unimpaired. Ratios of regional to whole brain activity, measured by SPECT, showed significant reduction in the frontal lobes and in the left temporal lobe of MS patients. A relationship was found between left temporal abnormality in 99mTc-HMPAO uptake and deficit in verbal fluency and verbal memory. Finally, asymmetrical lobar activity indicated a predominant left rather than right temporo-parietal involvement.

Brain↗

PubMed1990

Effect of optokinetic stimulation in patients with visual neglect.

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.

Attention↗