Medial Parietal Lobe Research Articles

Gray and white matter changes in Alzheimer's disease: A diffusion tensor imaging study

To investigate microstructural changes in cortical and white matter pathways in patients with Alzheimer's disease using diffusion tensor imaging (DTI). Measures of mean diffusivity (MD) and fractional anisotropy (FA) were compared in the brains of 13 Alzheimer's disease (AD) patients and a group of 13 aged-matched control participants employing an optimized DTI technique involving a fully automated, voxel-based morphometric (VBM) analysis. After rigorous control for anatomical variation and confounding partial volume effects, we found significantly elevated MD measures within the hippocampus, amygdala, and medial temporal, parietal, and frontal lobe gray matter regions in the AD participants. The largest number of pixels with increased MD was localized bilaterally, within the posterior cingulate gyrus. The FA was significantly reduced within the thalamus, parietal white matter, and posterior limbs of the internal capsule, indicating significant involvement of corticothalamic and thalamocortical radiations. This study demonstrates that rigorous VBM analysis of DTI data can be used to investigate microstructural changes in cortical, subcortical, and white matter regions in AD.

Treatment monitoring and response prediction with proton MR spectroscopy in AD

In this proton magnetic resonance spectroscopy ((1)H-MRS) study, the authors correlated cognitive improvement after 3 months of treatment with donepezil with changes of N-acetylaspartate (NAA) level and NAA/Creatine (Cr) ratio in the medial temporal and parietal lobe of 17 patients with Alzheimer disease. Treatment response was associated with an increase of NAA and NAA/Cr in the parietal lobe. Low baseline NAA/Cr in the parietal lobe predicted positive treatment outcome.

White matter integrity of the whole brain is disrupted in first-episode schizophrenia

Diffusion tensor imaging studies in schizophrenia have demonstrated lower diffusion anisotropy within white matter that provides information about brain white matter integrity. We have examined whether white matter is abnormal in first-episode schizophrenia by using diffusion tensor imaging. Twenty-one schizophrenic patients and healthy controls underwent diffusion tensor imaging scans that analyzed by using a rigorous voxel-based approach. We found that fractional anisotropy in white matter of the patients was lower than that in controls at the cerebral peduncle, frontal regions, inferior temporal gyrus, medial parietal lobes, hippocampal gyrus, insula, right anterior cingulum bundle and right corona radiata. These results suggested that white matter integrity of the whole brain was disrupted in early illness onset of schizophrenia.

Neural substrates for functionally discriminating self-face from personally familiar faces.

Understanding the neurobiological substrates of self-recognition yields important insight into socially and clinically critical cognitive functions such as theory of mind. Experimental evidence suggests that right frontal and parietal lobes preferentially process self-referent information. Recognition of one's own face is an important parameter of self-recognition, but well-controlled experimental data on the brain substrates of self-face recognition is limited. The goal of this study was to characterize the activation specific to self-face in comparison with control conditions of two levels of familiarity: unknown unfamiliar face and the more stringent control of a personally familiar face. We studied 12 healthy volunteers who made "unknown," "familiar," and "self" judgments about photographs of three types of faces: six different novel faces, a personally familiar face (participant's fraternity brother), and their own face during an event-related functional MRI (fMRI) experiment. Contrasting unknown faces with baseline showed activation of the inferior occipital lobe, which supports previous findings suggesting the presence of a generalized face-processing area within the inferior occipital-temporal region. Activation in response to a familiar face, when contrasted with an unknown face, invoked insula, middle temporal, inferior parietal, and medial frontal lobe activation, which is consistent with an existing hypothesis suggesting familiar face recognition taps neural substrates that are different from those involved in general facial processing. Brain response to self-face, when contrasted with familiar face, revealed activation in the right superior frontal gyrus, medial frontal and inferior parietal lobes, and left middle temporal gyrus. The contrast familiar vs. self produced activation only in the anterior cingulate gyrus. Our results support the existence of a bilateral network for both perceptual and executive aspects of self-face processing that cannot be accounted for by a simple hemispheric dominance model. This network is similar to those implicated in social cognition, mirror neuron matching, and face-name matching. Our findings also show that some regions of the medial frontal and parietal lobes are specifically activated by familiar faces but not unknown or self-faces, indicating that these regions may serve as markers of face familiarity and that the differences between activation associated with self-face recognition and familiar face recognition are subtle and appear to be localized to lateral frontal, parietal, and temporal regions.

Age differences in the neural systems supporting human allocentric spatial navigation

Age-related declines in spatial navigation are well-known in human and non-human species. Studies in non-human species suggest that alteration in hippocampal and other neural circuitry may underlie behavioral deficits associated with aging but little is known about the neural mechanisms of human age-related decline in spatial navigation. The purpose of the present study was to examine age differences in functional brain activation during virtual environment navigation. Voxel-based analysis of activation patterns in young subjects identified activation in the hippocampus and parahippocampal gyrus, retrosplenial cortex, right and left lateral parietal cortex, medial parietal lobe and cerebellum. In comparison to younger subjects, elderly participants showed reduced activation in the hippocampus and parahippocampal gyrus, medial parietal lobe and retrosplenial cortex. Relative to younger participants elderly subjects showed increased activation in anterior cingulate gyrus and medial frontal lobe. These results provide evidence of age specific neural networks supporting spatial navigation and identify a putative neural substrate for age-related differences in spatial memory and navigational skill.

Three‐dimensional stereotactic surface projection SPECT analysis in Parkinson's disease with and without dementia

We investigated regional cerebral blood flow (rCBF) using three-dimensional stereotactic surface projection (3D-SSP) analysis in 30 patients initially diagnosed as Parkinson's disease (PD), and compared differences in rCBF between patients with and without PD-related manifestations. 3D-SSP analysis of cerebral perfusion was performed by use of a control database. Compared to age-matched controls, there were multiple hypoperfusion areas in cases where the original diagnosis was PD. Temporal bases showed the lowest perfusion; frontal bases and medial parietal lobes the second; visual cortices the third; and parietal association areas exhibited the fourth lowest. During the clinical course, 10 of the patients suffered dementia, 9 had fluctuating cognition, and 19 experienced repeated visual hallucinations. Significant negative correlations were observed between dementia and the bilateral posterior cingulate area, and among fluctuating cognition and bilateral medial parietal lobes, parietal association areas, and dorsal occipital lobes. Repeated visual hallucinations did not show any correlation with any region of interest. We concluded that multiple hypoperfusion areas were observed in the 3D-SSP SPECT analysis. Although the presence of dementia showed a significant relationship with the bilateral posterior cingulate areas, perfusion in the frontal bases, temporal bases, or parietal lobes was markedly more reduced than that seen in the bilateral posterior cingulate areas.

Reduced medial temporal lobe N -acetylaspartate in cognitively impaired but nondemented patients

N-acetylaspartate (NAA) in the medial temporal lobe (MTL) and parietal lobe gray matter (GM) is diminished in Alzheimer disease (AD). Because NAA is considered a marker of neuronal integrity, reduced medial temporal and parietal lobe NAA could be an early indication of dementia-related pathology in elderly individuals. 1) To determine whether cognitively impaired but nondemented (CIND) elderly individuals exhibit a similar pattern of reduced medial temporal and parietal lobe NAA as AD patients. 2) To compare regional NAA patterns, hippocampal and neocortical gray matter (GM) volumes in CIND patients who remained cognitively stable and those who became demented over 3.6 years of follow-up. 3) To examine the relationship between memory performance, medial temporal lobe NAA, and hippocampal volume. Seventeen CIND, 24 AD, and 24 cognitively normal subjects were studied using MRSI and MRI. Relative to controls, CIND patients had reduced MTL NAA (19 to 21%, p = 0.005), hippocampal (11 to 14%, p < or = 0.04), and neocortical GM (5%, p = 0.05) volumes. CIND patients who later became demented had less MTL NAA (26%, p = 0.01), hippocampal (17 to 23%, p < or = 0.05), and neocortical GM (13%, p = 0.02) volumes than controls, but there were no significant differences between stable CIND patients and controls. MTL NAA in combination with hippocampal volume improved discrimination of CIND and controls over hippocampal volume alone. In AD and CIND patients, decreased MTL NAA correlated significantly with impaired memory performance. Reduced medial temporal lobe N-acetylaspartate, together with reduced hippocampal and neocortical gray matter volumes, may be early indications of dementia-related pathology in subjects at high risk for developing dementia.

Common Ground for Spatial Cognition? A Behavioral and fMRI Study of Sex Differences in Mental Rotation and Spatial Working Memory

Sex differences in spatial cognition are well documented; males typically outperform females on tasks dealing with mental rotation and spatial navigation, while females tend to outperform males on tasks dealing with object location, relational object location memory, or spatial working memory. Here we investigated both behavioral and neural sex differences in sex-specific spatial abilities. In Experiment 1, sixty-six (30 males, 36 females) participants completed computerized mental rotation (MR) and spatial working memory (SWM) tasks. In Experiment 2, twelve (6 males, 6 females) participants were given slightly modified versions of the same tasks during functional magnetic resonance imaging (fMRI). In both experiments, males outperformed females on the MR task, but no behavioral sex difference was observed on the SWM task. Males showed more activation in left parahippocampal gyrus, right medial frontal gyrus, inferior parietal lobe, inferior frontal gyrus in the MR task. Females showed activation in the left parahippocampal gyrus only. For the study condition of the spatial working memory task, females showed activation in left inferior frontal gyrus, while males activated left inferior parietal and medial frontal areas. In the test conditions, females showed activation in the right inferior frontal gyrus, left middle temporal gyrus, and left parahippocampal gyrus. Males activated right medial frontal gyrus and inferior parietal lobe. Interestingly, similar regions – parahippocampal gyrus, inferior parietal lobe, and middle temporal gyrus - were found to be active when males solved mental rotation tasks and females solved spatial working memory tasks. Further, performance was modulated by activation in the parahippocampal gyrus and middle temporal gyrus for males and the middle temporal gyrus and inferior frontal gyrus for females. These data extend previous claims for sex differences in sex specific spatial cognitive abilities by demonstrating both behavioral and neural sex differences consistent with an evolutionary model, which suggests sexual selection may have favored sex-differences in such abilities and the neural substrates that sub-serve those processes.

Effects of thiamylal, sevoflurane and isoflurane on the cortically recorded somatosensory evoked potentials

Effects of thiamylal, sevoflurane and isoflurane on the cortically recorded somatosensory evoked potentials

Mapping the evolution of regional atrophy in Alzheimer's disease: unbiased analysis of fluid-registered serial MRI.

Alzheimer's disease (AD) is characterized by progressive cerebral atrophy, which may be assessed by using volumetric MRI. We describe a voxel-based analysis of nonlinear-registered serial MRI to demonstrate the most statistically significant (P < 0.001) regions of change at different stages of the disease. We compared presymptomatic (n = 4), mild (n = 10), and moderately affected (n = 12) patients with early- and late-onset AD, with age- and sex-matched controls, and demonstrated increasing global atrophy with advancing disease. Significantly increased rates of hippocampal atrophy were seen in presymptomatic and mildly affected patients. There was a shift in the distribution of temporal lobe atrophy with advancing disease; the inferolateral regions of the temporal lobes showed the most significantly increased rates of atrophy by the time the patients were mildly or moderately affected. Significantly increased rates of medial parietal lobe atrophy were seen at all stages, with frontal lobe involvement occurring later in the disease. Our results suggest that the sites showing the most significant rates of atrophy alter as the disease advances, and that regional atrophy is already occurring before the onset of symptoms. This technique provides insights into the natural history of AD, and may be a valuable tool in assessing the efficacy of disease-modifying treatments, especially if these treatments were to have region-specific effects.

Encoding and retrieval related cerebral activation in continuous verbal recognition

The differential neuronal activation related to encoding of novel and recognition of previously studied items and the effect of retrieval effort on neuronal activation were assessed in a event-related functional magnetic resonance imaging experiment. A verbal continuous recognition task with two repetitions of the target items was used. The interpretation of the results was focused on brain areas that have been previously reported to be involved in explicit memory. Encoding of novel words in comparison with the first repetition was associated with a stronger activation in the left parahippocampal and inferior frontal gyrus. Encoding of novel words compared to the second repetition was related to a greater bifrontal activation. Recognition of studied items was associated with greater activation in the medial and bilateral inferior parietal lobe at first repetition and in the medial and left inferior parietal lobe at second repetition in comparison with encoding of the novel items. Recognition at first repetition compared to recognition at second repetition was associated with greater bilateral frontal activation. The results are discussed in relation to current concepts of spatial differentiation of memory function and findings from event-related potentials studies of continuous recognition.

Contribution of the Supplementary Motor Area and Anterior Cingulate Gyrus to Pathological Grasping Phenomena

To investigate the relationship between the site of brain damage and characteristics of the pathological grasping phenomena, we examined different varieties of the reaction in a consecutive series of 28 patients with unilateral hemispheric damage due to stroke. Patients with a lesion relatively confined to the supplementary motor area (n = 4) constantly exhibited a grasp reflex, mainly in the hand contralateral to the lesion, but they never showed a groping reaction. By contrast, patients with damage primarily involving the anterior cingulate gyrus (n = 3) developed the groping reaction in the hand contralateral to the lesion, but they had only a very mild grasp reflex in that hand. Patients with damage involving both the supplementary motor area and the anterior cingulate gyrus (n = 12) showed the grasp reflex and groping reaction mainly in the hand contralateral to the lesion. Patients with damage to the medial parietal lobe (n = 2), those with damage to the lateral convexity of the hemisphere (n = 6), and a patient with damage confined to the corpus callosum did not exhibit such grasping phenomena. From these observations, we conclude that the grasp reflex is closely related to a lesion of the supplementary motor area, whereas the groping reaction is bound to a lesion of the anterior cingulate gyrus.

Neuroimaging findings in Alzheimer's disease

In the present article, the neuroimaging findings in Alzheimer's disease are summarized and experimental data from animals relating to metabolic changes in Alzheimer's disease (AD), particularly in the frontobasal cholinergic projections onto the cerebral cortex, are reviewed. Changes in glucose metabolism as well as in cerebral blood flow (CBF) are specific for AD, in which the parietotemporal association cortex shows metabolic suppression. This finding is used as a diagnostic aid in the clinical application of single photon emission computed tomography. In rare cases, limited suppression of metabolism and blood flow is also found in the unilateral medial temporal lobe or parietal lobe. Statistically, approximately 80% of cases of AD show a typical parietotemporal suppression pattern of CBF. This cortical metabolic and circulatory suppression has been attributed to cholinergic deprivation from the basal forebrain Mynert nucleus. Animal experiments have revealed transient cortical suppression of glucose metabolism in the frontal cortex after destruction of the basal forebrain cholinergic neurons by ibotenic acid. This suppression persists for approximately 1 week and returns to normal 1 month after operation. Thus, the typical neuroimaging findings in AD would not be due to deficient cholinergic projections from the basal forebrain.

Pure Topographical Disorientation Related to Dysfunction of the Viewpoint Dependent Visual System

A 70-year-old woman presented with pure topographical disorientation following haemorrhage in the right medial parietal lobe. She could not navigate in the real world despite good ability to draw maps, describe routes, and identify objects and buildings. Her performance on mental rotation, visual memory, and spatial learning tests also was normal. In contrast, she failed totally in a locomotor map test and in a task in which she was requested to judge viewpoints of buildings. Her highly selective topographical disorientation was probably caused by the inability to identify a viewpoint of a particular building. The lesion may have disconnected the association between the spatial information processed in the lateral parietal lobe and the visual memory mediated by the limbic system, which seems to be important for viewpoint dependent analysis.

Hippocampal involvement in human topographical memory: evidence from functional imaging.

Functional brain imaging in humans is beginning to reveal a network of brain regions that subserve topographical learning: the medial parietal lobe, the posterior cingulate gyrus, occipitotemporal areas, the parahippocampal gyrus and the right hippocampus. These findings illuminate the patient lesion literature where all of these brain regions have been implicated at one time or another in cases of topographical disorientation. Once topographical information is acquired, the neuroanatomy that supports its use from either episodic or semantic memory is similar to that activated during encoding. The specific contributions of extrahippocampal regions within the topographical memory system are being revealed, such as the role of the right parahippocampal gyrus in object-in-place encoding. The right hippocampus is clearly involved in processing spatial layouts over long as well as short time-courses, and participates in both the encoding and the retrieval of topographical memory. The ventromedial orbitofrontal cortex is recruited when information in the topographical memory system is not sufficient to produce direct navigation to a goal place.

The distribution of posterior parietal fibers in the corpus callosum of the rhesus monkey.

The distribution of posterior parietal fibers in the corpus callosum of the rhesus monkey was analyzed using autoradiographic techniques. Posterior parietal fibers are located in the posterior half of the body of the corpus callosum. There is some segregation of fibers with respect to their place of origin within the posterior parietal lobe. However, there is also overlap, particularly between fibers coming from the caudal inferior parietal lobule and the medial parietal lobe.

Left medial parietal lobe and receptive language functions

Left medial parietal lobe and receptive language functions

Anticoagulants in Acute Myocardial Infarction

<h3>Abstract</h3> Our memories form a rich, colorful tapestry of emotions, events, people, and places, woven across the decades of our lives. However, research has typically been limited in its ability to assess the multidimensional nature of episodic memory, given the short time scales and artificial stimulus sets often required in experiments. In an era when people are constantly recording their lives through social media, we can now examine key questions about the behavioral and neural underpinnings of diverse and extensive real-world memories. Here, we tested the neural representations of episodic memory in a naturalistic setting, specifically focusing on the age, location, subjective memory strength, and emotional content of memories. We recruited 23 users of a video diary app (“1 Second Everyday”), who had recorded a total of 9,266 daily memory videos spanning up to 7 years prior to our study. During a 3T fMRI scan, participants viewed a set of 300 of their own memory videos intermixed with 300 videos from another individual. We identified key areas specifically engaged for one’s own memories versus another’s. Delving into the multidimensional nature of these memories, we find that their features are tightly interrelated, highlighting the need to consider these features in conjunction when conducting memory research. Importantly, when looking at the distinct contributions of these features, we find a topography of memory content extending across the medial parietal lobe with separate representations of a memory’s age, it’s strength, and the familiarity of the people and places involved.