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PubMed2002

Children with dyslexia and right parietal lobe dysfunction: event-related potentials in response to words and pseudowords.

Hari and Renvall (Trends Cogn. Sci., 5 (2001) 525) proposed that dyslexic children suffer from sluggish attention deployment due to a right parietal lobe dysfunction. To examine this hypothesis, good and poor readers (12, 11-year-old boys in each group) had to read familiar words (low attentional demand) and pseudowords (high attentional demand). The amplitude of the event-related potential at around 100 ms post-stimulus (N1) in response to words and pseudowords was used as measure of attention deployment. Consistent with the attention deficit/right parietal lobe dysfunction hypothesis, poor readers showed lower N1 amplitudes in response to pseudowords, but not in response to words at central sites of the right hemisphere. However, poor readers also showed lower N1 amplitudes to both words and pseudowords at left frontal sites suggestive of an early deficit in activating phonological codes.

Attention↗
PubMedDate not supplied

Cortical networks for visual reaching: physiological and anatomical organization of frontal and parietal lobe arm regions.

The functional and structural properties of the dorsolateral frontal lobe and posterior parietal proximal arm representations were studied in macaque monkeys. Physiological mapping of primary motor (MI), dorsal premotor (PMd), and posterior parietal (area 5) cortices was performed in behaving monkeys trained in an instructed-delay reaching task. The parietofrontal corticocortical connectivities of these same areas were subsequently examined anatomically by means of retrograde tracing techniques. Signal-, set-, movement-, and position-related directional neuronal activities were distributed nonuniformly within the task-related areas in both frontal and parietal cortices. Within the frontal lobe, moving caudally from PMd to the MI, the activity that signals for the visuo-spatial events leading to target localization decreased, while the activity more directly linked to movement generation increased. Physiological recordings in the superior parietal lobule revealed a gradient-like distribution of functional properties similar to that observed in the frontal lobe. Signal- and set-related activities were encountered more frequently in the intermediate and ventral part of the medial bank of the intraparietal sulcus (IPS), in area MIP. Movement-and position-related activities were distributed more uniformly within the superior parietal lobule (SPL), in both dorsal area 5 and in MIP. Frontal and parietal regions sharing similar functional properties were preferentially connected through their association pathways. As a result of this study, area MIP, and possibly areas MDP and 7m as well, emerge as the parietal nodes by which visual information may be relayed to the frontal lobe arm region. These parietal and frontal areas, along with their association connections, represent a potential cortical network for visual reaching. The architecture of this network is ideal for coding reaching as the result of a combination between visual and somatic information.

Animals↗
PubMed1999

An angiographically occult arteriovenous malformation in the medial parietal lobe presenting as seizures of medial temporal lobe origin.

We present an unusual case of a patient who was diagnosed with temporal lobe epilepsy and whose seizures were reduced markedly after excision of an angiographically occult arteriovenous malformation (AVM) located in the left medial parietal lobe. A 38-year-old man had complex partial seizures characterized by motionless staring with oroalimentary and behavioral automatisms since the age of 15 years. Magnetic resonance imaging (MRI) demonstrated a small lesion extending from the left posterior cingulate gyrus to the precuneus. There was no MRI evidence of mesial temporal sclerosis. Intracranial EEG recordings showed ictal onset from the left medial parietal lobe propagating to the medial temporal lobes. Clinical signs appeared when these discharges reached the temporal lobes. After excision of the lesion (which was histologically confirmed as an AVM), together with the marginal cortex, seizures were reduced significantly. Careful diagnostic evaluation of lesions such as the this one may reveal an epileptogenic lesion (zone) far from the region where scalp ictal discharges seem to arise. In our case, we hypothesize that false localization was due to propagation of ictal discharges from the parietal focus through the limbic system.

Adult↗
PubMed2005

Functional coupling between frontal and parietal lobes during recognition memory.

Neuroimaging studies have suggested that the frontal and parietal lobes may be important for the process by which we remember information. However, little is known about how these regions exchange information during memory retrieval. We measured EEG synchronisation in the gamma-band (25-55 Hz), a putative measure of functional coupling between brain regions, while human subjects performed a recognition memory task. Fronto-parietal synchrony was increased for true old memories relative to false memories and new items. Our results suggest that synchronization of neuronal responses in the gamma-band may be an important mechanism by which frontal and parietal regions exchange information during the recognition of past events.

Adult↗
PubMed2001

Damage to the parietal lobe impairs bimanual coordination.

Moving the upper limbs at a common tempo according to a mirror or parallel mode represents elementary coordination dynamics. Previously, the role of the medial wall areas have been emphasized for successful production of these bimanual patterns. The involvement of the parietal lobe is less clear despite its importance for the representation of motor skill and sensorimotor integration. The objective of this study was to investigate temporal control in patients with parietal pathology when performing isofrequency configurations. As compared to control subjects, these patients showed desynchronization of movement trajectories that was most apparent during parallel patterns. These observations suggest the significant role of the parietal lobe for bimanual coordination which becomes increasingly relevant as a function of task complexity.

Brain Neoplasms↗
PubMed2001

A severe frontal-parietal lobe syndrome following cerebellar damage.

We report a case study of a frontal and parietal lobe syndrome with memory loss after unilateral left-sided cerebellar damage caused by a stroke in a patient with right cerebellar unusual developmental agenesis. The syndrome consisted of severe deficits in planning an organized sequence of events, in visuo-constructive abilities and inappropriate jocularity. These changes are ascribed in part to cerebellar-pontine lesions with resulting frontal lobe diaschisis as documented by single-photon emission computed tomography in the absence of morphological damage to the neocortex.

Adult↗
PubMed1976

Personality disorder and parietal lobe dysfunction.

An inability to relate transitionally is a major feature of personality disorder. The developmental independence of transitional relatedness from verbal-symbolic growth, its orienting function, and the nature of its visual and tactile components support the conclusion that it is a function of the nondominant parietal lobe. Therefore it can be hypothesized that dysfunction of this area is the cerebral analogue of personality disorder. The fact that unawareness of illness ("anosognosia") in conjunction with grossly intact intellectual function is common to both personality disorder and minor parietal lobe dysfunction further supports this hypothesis.

Adult↗
PubMed1994

Non-spatial extinction following lesions of the parietal lobe in humans.

Efficient behaviour in the visual environment requires selection between stimuli competing for control of action. Many current models of selection are spatial: relevant objects are chosen by attending to their locations. The unilateral stimulus extinction observed following lesions of the parietal lobe provides evidence for spatial selection. Such patients may identify a single stimulus presented in their contralesional field, but can fail to detect the same stimulus when a competing stimulus is shown simultaneously on the ipsilesional side. Here we demonstrate that extinction need not be spatial in nature, but may be determined by characteristics of the objects to be selected. In two patients with parietal lobe lesions and poor spatial localization, pictures extinguished words and closed shapes extinguished open shapes. This object-based extinction indicates the existence of biases within non-spatial selection mechanisms which are independent of biases produced by spatial selection mechanisms. We suggest that selection of objects for action requires that the 'winners' produced by the independent competitive biases for selection are bound together within distinct neural areas concerned with object properties and space.

Brain Diseases↗
PubMed1977

Ictal tonic postural changes and automatisms of the upper limb during epileptic parietal lobe discharges.

Tonic postural changes of the upper limb accompanied by epileptic parietal lobe discharges are not well known. The authors report 3 such cases. In the 3 patients, a total of 18 spontaneous seizures were recorded, 12 by telemetry, from either scalp electrodes or stereotactically implanted electrodes. Of these 18 seizures, 14 included tonic postural changes of the upper limb accompanied by a contralateral parietal discharge. Combining these 3 cases with the 4 such cases in the literature, the authors found that the clinical pattern consisted of a tonic postural change in one upper limb associated with automatisms of the opposite upper limb. It was also found that the same patient might have automatisms involving the upper limb in some seizures and upper limb postural changes in other seizures, both accompanied by the same electrical discharge. It is concluded that tonic postural changes and automatisms in the upper limb may be interchangeable.

Adult↗
PubMed1997

False lateralization of seizure perceived by a patient with infarction of the right parietal lobe who showed the neglect syndrome.

A 66-year-old right-handed man developed seizures characterized by an electric sensation and convulsive movements involving the left arm, which sometimes secondarily generalized. The patient, however, reported that the seizures occurred in his right arm. Neurological examination showed many features of left hemineglect, including allesthesia, secondary to acute infarction of the right parietal lobe. Although allesthetic response was not documented during the seizure, it is likely that sensory symptoms of the seizures were localized inappropriately or that he had false memory for lateralization of seizures. In this case, the neglect syndrome caused by infarction of the right parietal lobe extended to symptoms of the seizure itself.

Aged↗
PubMed1987

Deep left parietal lobe syndrome: conduction aphasia and other neurobehavioural disorders due to a small subcortical lesion.

A patient with sudden onset of conduction aphasia in the context of an ischaemic stroke is reported. Other neurological and neuropsychological findings included bilateral ideomotor apraxia, right hemisensory defect and paradoxical left ear extinction on a dichotic listening test. Lesion location, as inferred from magnetic resonance imaging, involved a restricted subcortical area in the left parietal lobe, near the lateral wall of the cerebral ventricle. The anatomical correlate for each of the clinical findings is discussed in the light of classical anatomo-clinical correlations. It is concluded that this tetrad constitutes a specific syndrome which may be easily recognised and ascribed to a single lesion in the deep white matter of the left parietal lobe.

Aged↗
PubMed2001

EEG abnormalities in dementia reflect the parietal lobe syndrome.

The aim of this study was to investigate to what extent the examination of regional syndromes can improve EEG diagnostics in dementia. The study was based on 77 patients, aged between 47 and 83 years, with a dementia disease in accordance with the DSM-III-R criteria. The clinical examination was refined using a so-called stepwise clinical status analysis to estimate the occurrence and intensity of the parietal lobe syndrome, the frontal lobe syndrome, the subcortical syndrome and the less-regionalised global syndrome. In the same time period, the patients were examined electroencephalographically and the recordings were assessed both visually and by means of spectrum analysis. It was found that the intensity of the parietal lobe syndrome was correlated more strongly to the EEG slow activity as compared to the other regional syndromes. Thus, it can be expected that the EEG will be most valuable in the early-onset type of Alzheimer's disease, in which the parietal syndrome is dominant, giving information regarding the degree of dementia and suggesting a possible interference with depression. The results of the study can probably explain some discrepancies between the EEG findings and the results of clinical examination in other forms of dementia.

Aged↗
PubMed1980

Focal histiocytosis X of the parietal lobe. Case report.

The authors describe a case of histiocytosis X of the parietal lobe presenting as a space-occupying lesion on a computerized tomography scan of the brain. The clinical, radiographic, and therapeutic aspects of the case are discussed. A brief review of the literature is presented.

Brain Diseases↗
PubMed1998

Maintaining internal representations: the role of the human superior parietal lobe.

In sensorimotor integration, sensory input and motor output signals are combined to provide an internal estimate of the state of both the world and one's own body. Although a single perceptual and motor snapshot can provide information about the current state, computational models show that the state can be optimally estimated by a recursive process in which an internal estimate is maintained and updated by the current sensory and motor signals. These models predict that an internal state estimate is maintained or stored in the brain. Here we report a patient with a lesion of the superior parietal lobe who shows both sensory and motor deficits consistent with an inability to maintain such an internal representation between updates. Our findings suggest that the superior parietal lobe is critical for sensorimotor integration, by maintaining an internal representation of the body's state.

Body Image↗
PubMed2002

Selective reduction of N-acetylaspartate in medial temporal and parietal lobes in AD.

BACKGROUND: Both AD and normal aging cause brain atrophy, limiting the ability of MRI to distinguish between AD and age-related brain tissue loss. MRS imaging (MRSI) measures the neuronal marker N-acetylaspartate (NAA), which could help assess brain change in AD and aging. OBJECTIVES: To determine the effects of AD on concentrations of NAA, and choline- and creatine-containing compounds in different brain regions and to assess the extent NAA in combination with volume measurements by MRI improves discrimination between AD patients and cognitively normal subjects. METHODS: Fifty-six patients with AD (mean age: 75.6 +/- 8.0 years) and 54 cognitively normal subjects (mean age: 74.3 +/- 8.1 years) were studied using MRSI and MRI. RESULTS: NAA concentration was less in patients with AD compared with healthy subjects by 21% (p < 0.0001) in the medial temporal lobe and by 13% to 18% (p < 0.003) in parietal lobe gray matter (GM), but was not changed significantly in white matter and frontal lobe GM. In addition to lower NAA, AD patients had 29% smaller hippocampi and 11% less cortical GM than healthy subjects. Classification of AD and healthy subjects increased significantly from 89% accuracy using hippocampal volume alone to 95% accuracy using hippocampal volume and NAA together. CONCLUSION: In addition to brain atrophy, NAA reductions occur in regions that are predominantly impacted by AD pathology.

Aged↗
PubMed1991

Primary embryonal-cell carcinoma of the parietal lobe. Case report.

A case of primary embryonal-cell carcinoma of the parietal lobe is reported. The unusually chronic presentation of such a malignant tumor is described. The atypical computerized tomography and magnetic resonance imaging characteristics of this lesion are presented. Review of the literature yielded no previous reports of a lobar embryonal-cell carcinoma. The rarity of intracranial germ-cell tumors presenting off the midline is discussed.

Brain Neoplasms↗
PubMed1998

A case of parietal lobe epilepsy with distinctive clinical and neuroradiological features.

We present a case of parietal lobe epilepsy, the epileptogenic focus of which was conspicuously demonstrated on magnetoencephalography (MEG). The remarkable fluctuation in the seizure frequency and the presence of atonic seizures were suggestive of atypical partial benign epilepsy of childhood (APBEC). An interictal positron emission tomography (PET) scan performed during the cluster of fits revealed hypermetabolism around the epileptogenic focus, which might be related to the marked tendency of clustering of seizures in this patient.

Electroencephalography↗