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PubMed1980

Optokinetic nystagmus and parietal lobe lesions.

In an attempt to define better the mechanism of impaired optokinetic nystagmus (OKN) caused by parietal lobe lesions, we recorded the eye movements of two patients. One had a slowly enlarging parietal glioma, and the other, an infarction involving the parietal and occipital lobes. In both patients, ipsilateral foveal pursuit and full-field pursuit of a surrounding optokinetic drum were impaired while voluntary and involuntary saccades (fast components) were normal. Foveal pursuit was impaired more than full-field pursuit, suggesting the existence of two separate pathways by which visual signals for OKN slow phases reach the oculomotor centers in the brainstem. We conclude that the ipsilateral slow phase OKN deficit seen in our patients resulted from damage to the foveal pursuit pathway that runs from the occipitoparietal association area to the ipsilateral brainstem horizontal gaze center.

Adult↗
PubMed2003

The role of the parietal lobe in borderline personality disorder.

Many patients with a diagnosis of borderline personality disorder describe multi-modal hallucinations. A likely cortical origin for multi-modal hallucinations is the inferior parietal lobule. Neuropsychological testing of borderline personality disorder reveals deficits of visuospatial capacity; a function which is also localised to the inferior parietal lobule. It is hypothesised that this brain area is likely to be dysfunctional in those patients with borderline personality disorder who have multi-modal hallucinations. A deficit in the inferior parietal lobe could plausibly explain a number of other clinical features; the gender dimorphism of this disorder, the lack of expressive gesture and the specific response to clozapine. More speculatively; the increased concern over this disorder over the past 40 years could result from the normal population showing an increase in functional ability in the parietal lobe, leaving patients with parietal deficits relatively more disabled.

Borderline Personality Disorder↗
PubMed1977

Visual input to the visuomotor mechanisms of the monkey's parietal lobe.

A newly identified class of neurons of the parietal cortex, studied in waking monkeys (Macaca mulatta), is activated by visual stimuli, perhaps via the retino-collicular visual pathway. This afferent input is thought to provide the visual cues activating the visuomotor mechanisms of the parietal lobe for the direction of visual attention.

Action Potentials↗
PubMed2005

Distribution of cerebral cortical lesions in diffuse neurofibrillary tangles with calcification: a clinicopathological study of four autopsy cases showing prominent parietal lobe involvement.

We investigated clinicopathologically four Japanese autopsy cases of diffuse neurofibrillary tangles with calcification (DNTC), which has been believed to be characterized by temporal or temporofrontal circumscribed lobar atrophy, and examined the distribution of their cerebral cortical lesions using hemisphere specimens. The lesions were classified into three categories (slight, moderate, and severe). Severe lesions were present in the temporal lobes and insular gyri of all four cases, consistent with the studies reported to date. In contrast, severe lesions were encountered in the parietal lobe of case 1 and moderate lesions were found in the parietal lobes of cases 2-4. Furthermore, moderate lesions of the precentral gyrus were present in cases 2-4, and moderate lesions of the postcentral gyrus were encountered in all four cases. We postulate that the distribution of cerebral cortical lesions in DNTC is more widespread than previously assumed. Our data also indicate that the unusual clinical signs of DNTC reported by several Japanese researchers, including parietal signs such as apraxia and agnosia, are roughly consistent with the topographic distribution of cerebral cortical lesions in DNTC elucidated in this study.

Brain Diseases↗
PubMed1995

Tumoural parietal lobe epilepsy. Clinical manifestations and outcome in 34 patients treated between 1934 and 1988.

Between 1934 and 1988, 34 patients with tumoural parietal lobe epilepsy were treated surgically at the Montreal Neurological Institute (MNI). Fifteen had right-sided and 16 left-sided resections. The remaining three patients had biopsies only. Follow-up ranging from 1 to 40 years (mean 12.3 years) was available for 28 patients. Seventy-five percent (21 out of 28) became seizure free or had rare seizures. Permanent post-operative sensory deficits were described in 12% of patients. An aura was described by 79%. 62% had somatosensory symptoms, contralateral to the epileptogenic region in all but one. Visual illusions (12%), aphasia (9%) and disturbances of body image (6%), were much less common at the beginning of the attacks. Intra-operative cortical stimulation reproduced the habitual aurae in 10 out of 25 (40%) of the patients. The clinical manifestations suggested different spread patterns: 21% had tonic posturing of the extremities, 82% focal clonic activity, 15% head deviation, 9% automatisms and 6% difficulty speaking. Eleven (32%) had Todd's paralysis and 18% postictal dysphasia. Almost half the patients had impaired two-point discrimination in contralateral fingers; two of these also had impaired stereognosis, but only one had astereognosis without coexisting primary cortical sensory deficit. Review of this, now historical, series shows that parietal lobe tumours can be resected with good control of previously intractable seizures. Such an approach is preferable to postponing resection until the lesion is shown to increase in volume.

Adolescent↗
PubMed2004

[Borderline personality disorder associated with psychotic symptoms and parietal lobe abnormalities].

OBJECTIVE: We explore a case of a forensic patient with severe personality disorder, borderline type, and additional psychotic symptoms. Furthermore, she showed parietal lobe abnormalities. METHOD: We describe a case report and the relevant theoretical deliberations. CONCLUSIONS: Attempts to categorize patients with severe borderline personality disorder and psychotic symptoms have been made since the beginning of the 20th century. We show that in our patient neuroimaging such as SPECT scan can prove parietal lobe abnormalities. We describe possible links between these findings and her symptoms.

Adult↗
PubMed1995

Anatomy of the parietal lobe: mapping the individual pattern.

Using magnetic resonance imaging with planes of section tangential to the left or right perietal convexity, we studied the sulcus pattern of the parietal lobes in 50 healthy subjects. The postcentral sulcus and the intraparietal sulcus were easily identified. As a characteristic landmark, and corresponding to postmortem findings, both sulci joined in 77% of the 100 hemispheres. The presurgical recognition of individual parietal lobe anatomy may improve surgical planning, in particular with an intended persulcal approach.

Adult↗
PubMed2001

A review of the evidence for a disengage deficit following parietal lobe damage.

We review the literature on response times to ipsilesional and contralesional targets following spatial precues in patients with damage involving the left- and right-parietal lobes with the aim of appraising the 'disengage deficit' reported initially by Posner and colleagues (Posner MI, Cohen A, Rafal RD. Neural systems control of spatial orienting. Proceedings of the Royal Society of London, B 1982;298:187-98). The data of individual subjects from a sub-sample of studies were submitted to analyses of variance, and data from all studies meeting our selection criteria were submitted to meta-analytic procedures (Hunter JE, Schmidt FL. Methods of meta-analysis: correcting error and bias in research. Newberg Park: Sagge Publications, 1990). Findings from both types of analysis conducted on data from patients with right-hemisphere lesions indicate that: (1) the disengage deficit phenomenon is robust following peripheral cues, but not following central cues; (2) the disengage deficit is large at shorter cue-target stimulus onset asynchronies (SOAs), and decreases as SOA increases; (3) the disengage deficit is larger in patients with a diagnosis of hemispatial neglect; and (4) although the magnitude of the disengage deficit appears to increase with increases in lesion size, multilobar vs unilobar involvement did not significantly alter the pattern of the disengage deficit. We also show that responses to validly cued targets in the contralesional hemispace were significantly slower than for validly cued targets in ipsilesional hemispace. Similar, but usually smaller, effects were observed in patients with homologous left-hemisphere damage. The implications of these results for current models of the role of the parietal lobes in attentional orienting are discussed.

Animals↗
PubMed2001

The parietal lobe as a sensorimotor interface: a perspective from clinical and neuroimaging data.

Lesion studies show a wide range of sensorimotor functions that can be selectively disturbed in patients with parietal lobe damage. This is illustrated by the selective impairment of unimodal or polymodal sensorimotor transformations in patients with apraxia. These clinically apparent deficits of goal-directed motor behavior are complimented by more subtle sensorimotor transformation disorders such as mirror agnosia and ataxia that can only be disclosed by special tests. Imaging studies further exemplify the prominent role of the parietal cortex as a sensorimotor interface and provide new information about the interrelationship between perception and action. Action observation activates premotor cortex, but parietal cortex is also recruited whenever an action involves objects. This emphasizes the significance of parietal cortex for goal-directed motor behavior. The intact comprehension of the meaning of gestures or of tool use shows the preservation of the cognitive aspects of motor behavior as long as lesions are restricted to the parietal lobe.

Apraxia, Ideomotor↗
PubMed2006

Coming unbound: disrupting automatic integration of synesthetic color and graphemes by transcranial magnetic stimulation of the right parietal lobe.

In some individuals, a visually presented letter or number automatically evokes the perception of a specific color, an experience known as color-grapheme synesthesia. It has been suggested that parietal binding mechanisms play a role in the phenomenon. We used a noninvasive stimulation technique, transcranial magnetic stimulation (TMS), to determine whether the posterior parietal lobe is critical for the integration of color and shape in color-grapheme synesthesia, as it appears to be for normal color-shape binding. Using a color-naming task with colored letters that were either congruent or incongruent with the synesthetic photism, we demonstrate that inhibition of the right posterior parietal lobe with repetitive TMS transiently attenuates synesthetic binding. These findings suggest that synesthesia (the induction of color from shape) relies on similar mechanisms as found in normal perception (where the perception of color is induced by wavelength).

Adult↗
PubMed1980

Left medial parietal lobe and receptive language functions: mixed transcortical aphasia after left anterior cerebral artery infarction.

Three aphasic patients with infarctions involving the left anterior cerebral artery have been studied. Two had trancortical motor aphasia, and one had mixed transcortical (or isolation) aphasia. Based on computerized tomography in two patients and whole-brain sections in one, the patient with mixed transcortical aphasia had a lesion that went beyond the rolandic fissure to involve the anterior precuneus lobule of the left medial parietal lobe. In the patients with transcortical motor aphasia, the lesion was confined to the frontal lobe. From these cases and other data, it seems likely that the left medial parietal lobe has receptive language functions analogous to the motor language functions of the left medial frontal lobe, thus accounting for the mixed transcortical aphasia observed in the patient whose left anterior cerebral artery infarction involved both the medial parietal and medial frontal lobes.

Aged↗
PubMedDate not supplied

EEG findings in dementia are related to the parietal lobe syndrome.

EEG indicators were correlated with clinical items in 174 patients with dementia diagnoses based on the DSM-III-R criteria. The patients' clinical symptomatologies were presented as regional brain syndromes, i.e. parietal lobe, frontal lobe, subcortical and global (nonregional) syndromes. The EEGs were abnormal in 87% of the cases. The typical abnormalities consisted of diffusely distributed slow wave activity. A significant correlation was found between the degree of slow wave abnormality and the degree of dementia. The results of the statistical analysis also suggest that EEG slow wave activity in dementia primarily reflects parietal lobe dysfunction. No association seems to exist between EEG slow wave activity and frontal lobe dysfunction.

Aged↗
PubMed1989

Parietal lobe mechanisms of spatial attention: modality-specific or supramodal?

Is the spatial attention system divided into separate, modality-specific subsystems, or is there a supramodal spatial attention system? More specifically, does the role of the parietal lobe in spatial attention involve modality-specific or supramodal mechanisms? We addressed this question using a variant of Posner's spatial cuing task. Parietal-lesioned patients performed a simple reaction time task to lateralized visual target stimuli, preceded on each trial by either non-predictive lateralized visual cue stimuli or non-predictive lateralized auditory cue stimuli. With both types of cues, we found disproportionate slowness in responding to invalidly cued contralesional targets, indicative of an impairment in disengaging attention from the ipsilesional to the contralesional side of space. The finding of an attentional disengagement impairment for visual targets with auditory cues implies that the parietal lobe's attentional mechanism operates on a representation of space in which both visual and auditory stimuli are represented, in other words, a supramodal representation of space.

Adult↗
PubMed1999

Mirror agnosia and mirror ataxia constitute different parietal lobe disorders.

We describe two new clinical syndromes, mirror agnosia and mirror ataxia, both characterized by the deficit of reaching for an object through a mirror in association with a lesion of either parietal lobe. Clinical investigation of 13 patients demonstrated that the impairments affected both sides of the body. In mirror agnosia, the patients always reached toward the virtual object in the mirror and they were not capable of changing their behavior even after presentation of the position of the object in real visual space. In mirror ataxia (resembling optic ataxia) although some patients initially tended to reach for the virtual object in the mirror, they soon learned to guide their arms toward the real object, all of them producing many directional errors. Both patient groups performed poorly on mental rotation, but only the patients with mirror agnosia were impaired in line orientation. Only 1 of the patients suffered from neglect and 3 from apraxia. Magnetic resonance imaging showed that in mirror agnosia the common zone of lesion overlap was scattered around the posterior angular gyrus/superior temporal gyrus and in mirror ataxia around the postcentral sulcus. We propose that both these clinical syndromes may represent different types of dissociation of retinotopic space and body scheme, or likewise, of allocentric and egocentric space normally adjusted in the parietal lobe.

Adult↗