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PubMed1991

Paroxysmal choreoathetosis precipitated by movement, sound and photic stimulation in a case of arterio-venous malformation in the parietal lobe.

A patient is presented with paroxysmal choreoathetosis precipitated by movement, sound and photic stimulation associated with an arterio-venous malformation (AVM) who responded to carbamazepine treatment. Hemodynamic circulatory disorder of the sensory-motor cortices having AVM may alter striatal function and produce paroxysmal choreoathetosis. This finding supports the concept that paroxysmal choreoathetosis results from an abnormality at the connections between basal ganglia and cerebral cortices.

Acoustic Stimulation↗
PubMed2004

Left parietal lobe activation to auditory mismatch?

The original article to which this Commentary refers was published in the November, 2002 issue of Human Brain Mapping (Park H-J, Kwon JS, Youn T, Pae JS, Kim J-J, Kim M-S, Ha K-S. Statistical Parametric Mapping of LORETA Using High-Density EEG and Individual MRI: Application to Mismatch Negativities in Schizophrenia. Hum Brain Mapp 2002;17:168-178).

Acoustic Stimulation↗
PubMed2001

The priming method: imaging unconscious repetition priming reveals an abstract representation of number in the parietal lobes.

Most of the current brain imaging methods are limited by the low spatial resolution of neuroimaging techniques and remain unable to measure activity at the scale of single neurons or small columns of neurons, which are the coding elements of the nervous system. In this work we have adapted the priming method, an emerging research strategy that can overcome some of these spatial limitations, to investigate the coding of numerical quantities in the human brain. This approach combines the logic of psychological priming experiments with the recently discovered neurophysiological phenomenon called repetition suppression (RS). In each trial, while subjects perform a constant task, a subliminal prime is presented prior to each target. By varying the relationship between prime and target, one can detect which brain areas present RS specifically for any given level of prime-target repetition. We first expose the general logic, potential and limitations of the priming method and then illustrate it by demonstrating that a region of parietal cortex is coding for numbers at the quantity level, independently of other stimulus attributes, and that this region processes both consciously and unconsciously perceived stimuli.

Adult↗
PubMed1978

[Amyotrophy due to parietal lobe lesions].

A bibliographical revision about Silverstein's amyotrophy, with a historical sight analizing the physiopathogeny and its clinical manifestations is reported. The authors discussed the possible cause of the few references in the literature about the matter and relate three cases; they leave a blank in one of them with amyotrophy in the other side and the same side of the lesion, that got better with surgical treatment. This was not found in the bibliographical revision that has been looked for.

Adult↗
PubMed1987

Non-pyramidal neurons of layers I-III in the dog's cerebral cortex (parietal lobe). A Golgi survey.

In an attempt to classify neurons in the upper layers of the cerebral cortex according to modern nomenclature based on Golgi impregnations, non-pyramidal neurons in layers II and III of the dog's cerebral cortex have been categorized into thirteen types: large double-bouquet cells with long ascending and descending axons (type I double-bouquet cells); bipolar neurons; multipolar neurons with long tufted descending axons (type II double-bouquet cells); neurons with long ascending axons; neurons with superficial axon plexuses; elongated large multipolar neurons with extended generalized axonal arborizations; neurons with long descending axons; small bi-tufted neurons with short ascending, descending or local axons; small multipolar neurons with short ascending, descending or local axons; multipolar neurons with local or extended axonal arborizations usually forming arcades (some of them also with a long descending axon); basket cells; neurogliaform neurons, and chandelier cells. Neurons in the molecular layer were horizontal cells and multipolar neurons with short axons. These data have been compared with those described in other species to provide a provisional classification of non-pyramidal neurons located in the upper layers of the cerebral cortex.

Animals↗
PubMed2005

Egocentric disorientation following bilateral parietal lobe damage.

Aguirre and D'Esposito (1999) suggested a taxonomy and theoretical framework for understanding topographical disorders. One of the problems they described involved egocentric disorientation, in which deficits are not strictly confined to the topographical sphere but are seen on a wide variety of visuo-spatial paradigms. Here, we report a neuropsychological investigation of MU, a person with egocentric disorientation. To test the usefulness of Aguirre and D'Esposito's framework, we administered tests which were predicted to be easy or difficult for people with egocentric disorientation to show that MU was impaired on tasks sensitive to egocentric disorientation and that he showed adequate performance on tests sensitive to other types of topographical representation. Thus MU showed normal performance on a test of recognition of famous landmarks and he could identify photographs of personally familiar places in his home town, yet he could not say how to get from a recognised building to another place in his environment. His performance fulfils the criteria for egocentric disorientation and fits the predictions derived from Aguirre and D'Esposito's views.

Adult↗
PubMed1981

Environmental reduplication associated with right frontal and parietal lobe injury.

Four patients with environmental reduplication, a specific form of spatial disorientation and confabulation are described. The patients maintained that their hospital rooms were located in their homes. Each patients had evidence of right frontal or right parietal injury based upon computed tomography, neurosurgery, and neuropsychological testing. The factors associated with environmental reduplication were: impaired spatial perception and visual memory, inability of the patients to recognise the inconsistency between their believed location and their actual location, confusion soon after admission to hospital, and a strong desire to be at home.

Adult↗
PubMed1988

The effects of lesions of superior temporal gyrus and inferior parietal lobe on temporal and vertex components of the human AEP.

We recorded auditory evoked potentials (AEPs) to 1 kHz tone bursts in controls and patients with unilateral lesions centered in posterior superior temporal gyrus and adjacent caudal inferior parietal lobule (STG) or in rostral inferior parietal lobule (IPL). Controls generated a vertex maximal N94 (N1b) and P200 (P2) and additional P45, N78 and N127 temporal AEP components (P45, N1a, N1c). Similar to prior reports, in controls the N1a was most prominent over the left temporal lobe and the P45 was largest over the right temporal lobe consistent with behavioral and anatomical data indicating differential organization of left and right human temporal lobe. The N1c was recorded equally from both T3 and T4 electrodes and was enhanced in the temporal site contralateral to the ear of stimulation. The patient groups had differential effects on AEPs. Unilateral STG lesions resulted in bilateral reductions of the N1b and P45 and marked unilateral reductions of the N1a and N1c over lesioned hemisphere. IPL lesions resulted in bilateral but non-significant reductions of the N1b and N1c. The scalp topography results in normal subjects combined with the effects of unilateral STG lesions provide supportive evidence that the temporal maximal components of the human AEP (P45, N1a, N1c) are generated by radially oriented neuronal dipole sources located in STG. The bilateral reduction of the N1b vertex response by unilateral STG lesions is compatible with a unilateral disruption of a vertically oriented dipole situated in the posterior superior temporal plane. The results emphasize the critical role of the superior temporal plane and lateral superior temporal gyrus in generation of human long latency AEPs.

Brain Diseases↗
PubMed1998

Multimodal imaging of residual function and compensatory resource allocation in cortical atrophy: a case study of parietal lobe function in a patient with Huntington's disease.

In a case of Huntington's disease (HD) with dementia and pronounced parieto-frontal atrophy, the functional state of the affected regions was investigated using functional magnetic resonance imaging (fMRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET). It was observed that although parietal areas showed extensive atrophy and reduced resting glucose metabolism, the patient performed with similar accuracy but with longer response time in a visuospatial task compared with healthy control subjects. At the same time, the blood oxygen level-dependent (BOLD) fMRI signal in these areas, which are involved in visuospatial processing, showed a similar task-dependent modulation as in control subjects. The signal amplitude (signal percent change) of the task-dependent activation was even higher for the HD patient than in the control group. This residual functionality of parietal areas involved in visuospatial processing could account for the patient's performance in the task concerned, which contrasted with his poor performance in other cognitive tasks. The increased percent-signal change suggests that a higher neuronal effort was necessary to reach a similar degree of accuracy as in control subjects, fitting well with the longer reaction time. We propose that fMRI should be considered as a tool for the assessment of functionality of morphologically abnormal cortex and for the investigation of compensatory resource allocation in neurodegenerative disorders.

Adult↗
PubMed2003

Material-dependent and material-independent selection processes in the frontal and parietal lobes: an event-related fMRI investigation of response competition.

The present study used the flanker task [Percept. Psychophys. 16 (1974) 143] to identify neural structures that support response selection processes, and to determine which of these structures respond differently depending on the type of stimulus material associated with the response. Participants performed two versions of the flanker task while undergoing event-related functional magnetic resonance imaging (fMRI). Both versions of the task required participants to respond to a central stimulus regardless of the responses associated with simultaneously presented flanking stimuli, but one used colored circle stimuli and the other used letter stimuli. Competition-related activation was identified by comparing Incongruent trials, in which the flanker stimuli indicated a different response than the central stimulus, to Neutral stimuli, in which the flanker stimuli indicated no response. A region within the right inferior frontal gyrus exhibited significantly more competition-related activation for the color stimuli, whereas regions within the middle frontal gyri of both hemispheres exhibited more competition-related activation for the letter stimuli. The border of the right middle frontal and inferior frontal gyri and the anterior cingulate cortex (ACC) were significantly activated by competition for both types of stimulus materials. Posterior foci demonstrated a similar pattern: left inferior parietal cortex showed greater competition-related activation for the letters, whereas right parietal cortex was significantly activated by competition for both materials. These findings indicate that the resolution of response competition invokes both material-dependent and material-independent processes.

Adolescent↗
PubMed1992

Decreases in frontal and parietal lobe regional cerebral blood flow related to habituation.

We previously reported decreased mean CBF between consecutive resting conditions, ascribed to habituation. Here we address the regional specificity of habituation over three consecutive flow studies. Regional CBF (rCBF) was measured in 55 adults (12 right-handed men, 12 right-handed women, 14 left-handed men, 17 left-handed women), with the 133Xe inhalation technique, during three conditions: resting, verbal tasks (analogies), and spatial tasks (line orientation). Changes in rCBF attributable to the cognitive tasks were eliminated by correcting these values to a resting equivalent. There was a progressive decrease in mean rCBF over time, reflecting habituation. This effect differed by region, with specificity at frontal (prefrontal, inferior frontal, midfrontal, superior frontal) and inferior parietal regions. In the inferior parietal region, habituation was more marked in the left than the right hemisphere. Right-handers showed greater habituation than did left-handers. There was no sex difference in global habituation, but males showed greater left whereas females showed greater right hemispheric habituation. The results suggest that habituation to the experimental setting has measurable effects on rCBF, which are differently lateralized for men and women. These effects are superimposed on task activation and are most pronounced in regions that have been implicated in attentional processes. Thus, regional decrement in brain activity related to habituation seems to complement attentional effects, suggesting a neural network for habituation reciprocating that for attention.

Adult↗
PubMed2004

Frontal and temporo-parietal lobe contributions to theory of mind: neuropsychological evidence from a false-belief task with reduced language and executive demands.

A model of the functional and anatomical basis of belief reasoning is essential for understanding the relationship between belief reasoning and other cognitive processes in both normal development and pathology. Studies of brain-damaged patients can give valuable insights into the nature of belief processing but pose unique methodological problems. The current study addresses these problems by using a nonlinguistic belief-reasoning task with substantially reduced executive demands. A case series of 12 brain-damaged patients is presented. The belief-reasoning errors of four patients with damage to the prefrontal cortex appeared to arise from these patients' executive function problems. The belief-reasoning errors of three patients with damage to the temporo-parietal junction could not easily be accounted for in this way, raising the possibility that this brain region has a necessary role in representing beliefs, rather than handling the executive demands of belief-reasoning tasks. We discuss the importance of gaining empirical evidence about the scope of ''theory of mind'' impairments, and the important role for neuropsychological studies in this project.

Adult↗
PubMed2000

Methylphenidate enhances working memory by modulating discrete frontal and parietal lobe regions in the human brain.

The indirect catecholamine agonist methylphenidate (Ritalin) is the drug treatment of choice in attention deficit/hyperactivity disorder (AD/HD), one of the most common behavioral disorders of childhood (DSM-IV), although symptoms may persist into adulthood. Methylphenidate can enhance cognitive performance in adults and children diagnosed with AD/HD (Kempton et al., 1999; Riordan et al., 1999) and also in normal human volunteers on tasks sensitive to frontal lobe damage, including aspects of spatial working memory (SWM) performance (Elliott et al., 1997). The present study investigated changes in regional cerebral blood flow (rCBF) induced by methylphenidate during performance of a self-ordered SWM task to define the neuroanatomical loci of the beneficial effect of the drug. The results show that the methylphenidate-induced improvements in working memory performance occur with task-related reductions in rCBF in the dorsolateral prefrontal cortex and posterior parietal cortex. The beneficial effects of methylphenidate on working memory were greatest in the subjects with lower baseline working memory capacity. This is to our knowledge the first demonstration of a localization of a drug-induced improvement in SWM performance in humans and has relevance for understanding the treatment of AD/HD.

Adrenergic Uptake Inhibitors↗
PubMed2002

Frontal and parietal lobe activation during transitive inference in humans.

Cortical areas engaged in knowledge manipulation during reasoning were identified with functional magnetic resonance imaging (MRI) while participants performed transitive inference (TI) on an ordered list of 11 items (e.g. if A < B and B < C, then A < C). Initially, participants learned a list of arbitrarily ordered visual shapes. Learning occurred by exposure to pairs of list items that were adjacent in the sequence. Subsequently, functional MR images were acquired as participants performed TI on non-adjacent sequence items. Control tasks consisted of height comparisons (HT) and passive viewing (VIS). Comparison of the TI task with the HT task identified activation resulting from TI, termed 'reasoning', while controlling for rule application, decision processes, perception, and movement, collectively termed 'support processes'. The HT-VIS comparison revealed activation related to support processes. The TI reasoning network included bilateral prefrontal cortex (PFC), pre-supplementary motor area (preSMA), premotor area (PMA), insula, precuneus, and lateral posterior parietal cortex. By contrast, cortical regions activated by support processes included the bilateral supplementary motor area (SMA), primary motor cortex (M1), somatic sensory cortices, and right PMA. These results emphasize the role of a prefrontal-parietal network in manipulating information to form new knowledge based on familiar facts. The findings also demonstrate PFC activation beyond short-term memory to include mental operations associated with reasoning.

Adult↗
PubMed2004

Linguistic and gait disturbance in a child with Laurence-Moon-Biedl syndrome: left temporal and parietal lobe hypoplasia.

Laurence-Moon-Biedl syndrome is an autosomal recessive disorder characterized by retinitis pigmentosa, obesity, polydactyly, hypogenitalism, mental retardation, and renal abnormalities. We report the linguistic and gait disorders in a child with Laurence-Moon-Biedl syndrome associated with left temporal and parietal hypoplasia as determined by magnetic resonance imaging. Our patient was mildly mentally retarded, scoring better on the performance subtest than on the verbal subtest. He received serial assessments for developmental, language, speech, and gait functions, before and after rehabilitation, at age 4.5 and 6 yr, respectively. After comprehensive rehabilitation, the boy achieved improvement in speech, language, fine motor, and gait functions. Early comprehensive rehabilitation programs seem beneficial for improving functional development for children with Laurence-Moon-Biedl syndrome.

Child, Preschool↗
PubMed1998

Effects of beta-amyloid peptides on the fluidity of membranes from frontal and parietal lobes of human brain. High potencies of A beta 1-42 and A beta 1-43.

beta-amyloid peptide (A beta) and several A beta-fragments decrease the fluidity of human cortex membranes in a concentration dependent fashion. The effect of A beta on membrane fluidity increases with peptide length, is most pronounced for A beta 1-43 and can be seen at concentrations as low as 100 nmol/l. While the fragment A beta 25-35 is active, scrambled peptide (A beta 35-25) when investigated under similar conditions shows no effects on membrane fluidity. The effect of A beta peptides on fluidity of the phospholipid bilayer is more pronounced in the hydrocarbon core (labeled with the fluorescence probe 1,6-diphenylhexa-1,3,5-triene) than in the region of the hydrophilic heads (labeled with the fluorescence probe 1-[4'-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene). It is suggested that the effect of A beta on neuronal membranes is probably a major initial mechanism in a cascade of events finally leading to neurotoxicity and cell death in Alzheimer's disease.

Alzheimer Disease↗