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PubMed1994

Micrographia associated with a parietal lobe lesion in multiple sclerosis.

The occurrence of micrographia in a 52 year old women two years after an isolated episode of painful sensory disturbance led to the diagnosis of multiple sclerosis. Her handwriting returned to normal after a course of intravenous methylprednisolone. Previous reports of movement disorders occurring in the context of multiple sclerosis are briefly reviewed. The finding on MRI studies of an enhancing lesion in the dominant parietal white matter supports Kinnier Wilson's suggestion that the anatomical origin of micrographia lies in the cerebral hemisphere rather than the corpus striatum.

Brain Diseases↗
PubMed1987

An experimental investigation of the parietal lobes and temperature discrimination in monkeys.

Seven groups of 3 monkeys each were given preoperative training over a series of thermal discrimination tasks of increasing difficulty to use eventually their left hands to detect a 1 degree C difference. One group served as an unoperated control (C), and the others were subjected to the following lesions: bilateral SI-bilateral SII; bilateral SI; bilateral SI-contralateral SII; bilateral SII-bilateral posterior parietal; bilateral parietal lobectomy; and contralateral parietal lobectomy. The groups were then tested again on the same tasks. No group showed any difficulty with differences larger than 12 degrees C, and groups 2, 4, 6 and C showed no statistical differences in their preoperative and postoperative number of trials to criteria for any of the temperature tasks. However, groups 1, 3 and 5 had considerable difficulty making discriminations ranging between 3 and 12 degrees C; and, although their postoperative performances were not significantly different from one another, they took statistically more trials to discriminate the 1 degree C difference in post- than in preoperative testing. Following extensive retraining, all but one of the subjects in the latter groups were able to detect the 1 degree C difference. It was concluded that the bilateral SI and contralateral SII areas play important roles in the monkey's ability to discriminate fine temperature differences with its hand, but that these areas are not essential to this capacity. It was also concluded that the monkey's parietal cortex plays little or no role in perceiving and reacting to noxious thermal stimulation applied to the hand.

Animals↗
PubMed1998

Alzheimer's disease with asymmetric parietal lobe atrophy: a case report.

A 52-year-old, right-handed female presented with visuospatial dysfunction including left hemineglect, incomplete Balint's syndrome, and environmental agnosia, together with left-sided motor symptoms such as unskillful movement, dystonic postures, and myoclonus in the left hand, without significant dementia. Symptoms progressed to akinetic mutism prior to her death 10 years after onset of illness. Imaging studies such as MRI, SPECT, and PET studies showed severe, predominantly right-sided involvement of parietal and parieto-occipital areas. The motor signs might originate from the right parietal lesions such as area five or somatosensory area. Neuropathologic studies including immunocytochemistry showed tau-positive neurofibrillary tangles and abundant neuritic plaques with amyloid deposits, confirming the diagnosis of Alzheimer's disease. An analysis of serum apolipoprotein E revealed epsilon3/epsilon3 homozygosity. This case represents a variant of Alzheimer's disease conspicuous for progressive motor signs and visuospatial dysfunction with a striking laterality, reflecting asymmetric parietal involvement. Alzheimer's disease with asymmetric parietal atrophy is difficult to be clinically distinguished from corticobasal degeneration characterized by progressive unilateral motor signs and focal cortical signs.

Agnosia↗
PubMed2004

Parietal lobe lesions disrupt saccadic remapping of inhibitory location tagging.

Maintaining a coherent percept of the visual scene while eye position continuously changes requires that saccades be accompanied by remapping of the visual environment. We studied saccadic remapping in patients with unilateral lesions in the intraparietal sulcus and healthy controls, using inhibition of return (IOR)-an inhibitory tag that enables efficient visual search. In healthy controls, IOR was found at both retinal and environmental locations of the cue, indicating that the inhibitory tag had been remapped into environmental coordinates. In contrast, right parietal patients demonstrated IOR only at the retinal location of the cue, indicating that the intraparietal sulcus is involved in remapping of the environment after eye movements to afford a stable, environmentally based reference frame. Note that patients did not show environmental IOR in either visual field. These results also suggest that this region may be the neural substrate for encoding inhibitory spatial tags in an environmentally based reference frame.

Adult↗
PubMed1997

Four legs. Illusory reduplication of the lower limbs after bilateral parietal lobe damage.

OBJECTIVE: To report an unusual disorder of body schema and its neurologic and neuropsychological correlates. DESIGN AND METHODS: We describe a patient with a reduplicative phantom illusion of her lower limbs. Motor and sensory functions, as well as mental representation of body and space, were studied during the reduplication experience until its resolution. SETTING: Clinical neurology department in a primary care hospital. PATIENT: A 64-year-old, left-handed woman who experienced the uncontrollable and distressing feeling of having 4 legs, without delusional belief, after surgical removal of a right-predominant parasagittal parietal meningioma. This phenomenon spontaneously resolved after 2 weeks. INTERVENTION: None. MAIN OUTCOME MEASURES: Clinical neurologic examinations and standardized neuropsychological tests, with emphasis on tests assessing orientation to body parts, right-left discrimination, and mental orientation in space. RESULTS: The patient had severe weakness and proprioceptive sensory loss in both lower limbs. She had no disturbances of body schema knowledge but a striking impairment in tasks requiring mental orientation in space, particularly for right-left laterality discrimination. Resolution of the reduplication experience correlated with improvement in the affected spatial abilities, while motor, sensory, and other cognitive functioning did not significantly change. CONCLUSION: This patient's reduplicative phantom illusion might be related to the combination of the severe somatosensory loss with an underlying impaired mental representation of relative positions in space.

Brain Neoplasms↗
PubMed1986

Components of visual attention. Alterations in response pattern to visual stimuli following parietal lobe infarction.

The contribution of attentional factors per se in response to visual stimuli was studied in patients with unilateral lesions of the left or right cerebral hemispheres. Subjects were required to respond to visual targets that were presented tachistoscopically, and were preceded by spatial cues that served to manipulate the spatial locus of attention. On 'valid' cue trials, the cue directed attention to the target's spatial coordinates; on 'invalid' cue trials, the cue misdirected attention. It was determined that damage to either the left or right hemisphere results in a general slowing of reaction times to visual stimuli irrespective of where such stimuli appear, and that patients with right parietal lesions are further impaired at shifting attention within the left visual field.

Adult↗
PubMed2006

Parietal lobe source localization and sensitivity to hyperventilation in a patient with subclinical rhythmic electrographic discharges of adults (SREDA).

OBJECTIVE: Subclinical rhythmic electrographic discharges of adults (SREDA) is currently considered a benign EEG pattern of uncertain significance. The underlying cortical sources and generating mechanisms are unknown. We performed a source localization analysis of SREDA with the aim of better understanding this unusual EEG pattern. METHODS: Multiple spontaneous episodes of typical SREDA were recorded in a patient during continuous EEG monitoring. Additional SREDA episodes were induced by hyperventilation. Source localization was carried out using statistical non-parametric mapping (SNPM) of low resolution electromagnetic tomography (LORETA). RESULTS: SNPM of both time- and frequency-domain LORETA revealed a widespread biparietal cortical origin of SREDA, the anatomical distribution of which included the parietal operculum and the known vascular watershed areas between anterior, middle and posterior cerebral arteries. Vigorous deep hyperventilation induced SREDA on three of four attempts. Mean duration of the hyperventilation-induced SREDA was approximately three times longer than spontaneous events. CONCLUSIONS: Investigations in this patient with typical SREDA revealed hyperventilation sensitivity and a posterior hemispheric source localization maximal in the parietal cortex bilaterally, in large part overlying the anatomical distribution of the vascular watershed areas. SIGNIFICANCE: The source localization results and sensitivity to hyperventilation suggest some sort of association between cerebral vascular supply and SREDA, as originally proposed by Naquet et al. [Naquet R, Louard C, Rhodes J, Vigouroux M. A propos de certaines décharges paroxystiques du carrefour temporo-pariéto-occipital. Leur activation par l'hypoxie. Rev Neurol 1961;105:203-207.].

Aged↗
PubMed2006

Discrete and analogue quantity processing in the parietal lobe: a functional MRI study.

The human intraparietal sulcus (IPS) is implicated in processing symbolic number information and possibly in nonsymbolic number information. Specific IPS activity for discrete quantities (numerosities) as compared with continuous, analogue quantity has not been demonstrated. Here we use a stimulus-driven paradigm to distinguish automatic estimation of "how many things" from "how much" and "how long." The discrete analogue response task (DART) uses the perception of hues which can change either abruptly (discrete, numerous stimuli) or smoothly (analogue, nonnumerous stimuli) in space or in time. Subjects decide whether they saw more green or more blue. A conjunction analysis of spatial and temporal conditions revealed that bilateral IPS was significantly more active during the processing of discrete stimuli than during analogue stimuli, as was a parietal-occipital transition zone. We suggest that processing numerosity is a distinct process from processing analogue quantity, whether extended in space or time, and that an intraparietal network connects objects' segmentation to the estimation of their numerosity.

Adolescent↗
PubMed1984

Transient inaccuracy in reaching caused by a posterior parietal lobe lesion.

A transient disturbance of manual reaching in both hemispaces associated with a small contralateral posterior perietal lobe (area 7) lesion is described. This defect was increased when the patient tried to reach without viewing of the affected arm. Inaccurate reaching is a distinct syndrome from visuomotor or optic ataxia, and is interpreted as a failure in guiding the arm towards specific sites of the space.

Aged↗
PubMed2006

Motion standstill leads to activation of inferior parietal lobe.

Previous studies on motion perception revealed motion-processing brain areas sensitive to changes in luminance and texture (low-level) and changes in salience (high-level). The present functional magnetic resonance imaging (fMRI) study focused on motion standstill. This phenomenon, occurring at fast presentation frequencies of visual moving objects that are perceived as static, has not been previously explored by neuroimaging techniques. Thirteen subjects were investigated while perceiving apparent motion at 4 Hz, at 30 Hz (motion standstill), isoluminant static and flickering stimuli, fixation cross, and blank screen, presented randomly and balanced for rapid event-related fMRI design. Blood oxygenation level-dependent (BOLD) signal in the occipito-temporal brain region MT/V5 increased during apparent motion perception. Here we could demonstrate that brain areas like the posterior part of the right inferior parietal lobule (IPL) demonstrated higher BOLD-signal during motion standstill. These findings suggest that the activation of higher-order motion areas is elicited by apparent motion at high presentation rates (motion standstill). We interpret this observation as a manifestation of an orienting reaction in IPL towards stimulus motion that might be detected but not resolved by other motion-processing areas (i.e., MT/V5).

Adult↗
PubMed2002

Solitary parietal lobe histoplasmoma mimicking a brain tumor.

We describe a rare case of Histoplasma infection, which manifested only as a brain histoplasmoma, in a previously healthy woman who had no underlying predisposing conditions. Only a few cases of such intracranial histoplasmomas have been reported but this entity can mimic a brain neoplasm and should be a diagnostic consideration during the evaluation of ring-enhancing brain lesions.

Antifungal Agents↗