Bilateral Parieto-occipital Cortex Research Articles

Tau epicenter identification and connectivity in clinically heterogeneous Alzheimer’s disease variants

AbstractBackgroundWhile the spread of tau throughout the brain is well‐characterized in amnestic Alzheimer’s disease (AD), tau staging remains less clear for those suffering from clinically heterogeneous variants including logopenic variant primary progressive aphasia (lvPPA) and posterior cortical atrophy (PCA). We created a method to identify local maxima of tau SUVR (“epicenters”) in participants with early‐stage clinically heterogeneous AD with the goal of classifying participant subtypes based on the functional connectivity of these epicenters.MethodWe obtained 18F‐MK‐6240 tau PET scans from 10 participants with diagnoses of early‐stage clinically heterogeneous AD (5 lvPPA, 5 PCA, Clinical Dementia Rating 0.5‐1.0). We identified three local maxima of tau SUVR with a minimum specified distance of 20mm between them for each participant (Fig. 1). We then derived each epicenter’s functional connectivity in 1000 healthy controls using Neurosynth and sorted participants into subtypes based on the overlap of these functional connectivity maps.ResultParticipants with lvPPA showed highest tau burden in the posterior temporoparietal and temporoocciptal regions, left side predominant, and participants with PCA displayed highest tau burden in the bilateral parietooccipital cortex, frontal eye fields, and fusiform gyrus. We identified nine distinct subtypes of functional connectivity and most participants’ epicenters participated in more than one subtype. All subtypes highlight functional connectivity networks that have been associated with language and, or visuospatial processing. The most common subtype (seen in 7 of the 10 participants and 11 of the 30 epicenters) features connectivity within the bilateral occipital lobule, fusiform gyrus, and superior parietal lobule (Fig. 2).ConclusionWe used a novel method to identify tau “epicenters” in the brains of participants with early‐stage clinically heterogeneous AD. Using these epicenters, we derived functional connectivity maps, which we then grouped into nine subtypes across participants. We will shortly begin collecting longitudinal tau PET in these clinically heterogeneous individuals with AD, allowing us to assess the extent to which tau spreads along the functional connectivity maps predicted by each participant’s epicenters and whether individually tailored epicenters outperform subtype classification. This work could serve as the basis for patient‐specific biomarkers of expected disease spread in clinically heterogeneous AD.

Is there a link between COVID-19 and Creutzfeldt-Jakob Disease? a Case Report

Creutzfeldt-Jakob Disease (CJD) is a rare rapidly progressive neurodegenerative disease. The diagnosis of CJD is based on magnetic resonance imaging (MRI) findings, electro-encephalography (EEG), or 14-3-3 protein detection. We report a case of a previously-healthy 72 years old woman, with evidence of coronavirus disease 2019 (COVID-19), who complained of behavioral changes and rapidly progressive dementia. While hospitalization, she didn't have orientation to time and place and repeated an irrelevant sentence in response to questions. Also, anomia and impaired comprehension was observed. Myoclonic jerks, abnormal signal intensity at bilateral parieto-occipital cortices in MRI, periodic sharp wave complexes in EEG, and increased lactate dehydrogenase in cerebrospinal fluid (CSF), highly recommended CJD for her. This is the second case of CJD after COVID-19 during this pandemic, which can be an alarm to clinicians about the silent impact of COVID-19 on the central nervous system.

Metabolic patterns across core features in dementia with lewy bodies.

To identify brain regions whose metabolic impairment contributes to dementia with Lewy bodies (DLB) clinical core features expression and to assess the influence of severity of global cognitive impairment on the DLB hypometabolic pattern. Brain fluorodeoxyglucose positron emission tomography and information on core features were available in 171 patients belonging to the imaging repository of the European DLB Consortium. Principal component analysis was applied to identify brain regions relevant to the local data variance. A linear regression model was applied to generate core-feature-specific patterns controlling for the main confounding variables (Mini-Mental State Examination [MMSE], age, education, gender, and center). Regression analysis to the locally normalized intensities was performed to generate an MMSE-sensitive map. Parkinsonism negatively covaried with bilateral parietal, precuneus, and anterior cingulate metabolism; visual hallucinations (VH) with bilateral dorsolateral-frontal cortex, posterior cingulate, and parietal metabolism; and rapid eye movement sleep behavior disorder (RBD) with bilateral parieto-occipital cortex, precuneus, and ventrolateral-frontal metabolism. VH and RBD shared a positive covariance with metabolism in the medial temporal lobe, cerebellum, brainstem, basal ganglia, thalami, and orbitofrontal and sensorimotor cortex. Cognitive fluctuations negatively covaried with occipital metabolism and positively with parietal lobe metabolism. MMSE positively covaried with metabolism in the left superior frontal gyrus, bilateral-parietal cortex, and left precuneus, and negatively with metabolism in the insula, medial frontal gyrus, hippocampus in the left hemisphere, and right cerebellum. Regions of more preserved metabolism are relatively consistent across the variegate DLB spectrum. By contrast, core features were associated with more prominent hypometabolism in specific regions, thus suggesting a close clinical-imaging correlation, reflecting the interplay between topography of neurodegeneration and clinical presentation in DLB patients. Ann Neurol 2019;85:715-725.

IMPACT OF PLASMA GLUCOSE ON THE PATTERN OF BRAIN FDG UPTAKE IN COGNITIVELY NORMAL ELDERLY SUBJECTS

Several studies reported increased blood glucose levels (BGL) to be associated with alterations of regional uptake of F-18-fluorodeoxyglucose (FDG) in the brain that mimic the characteristic pattern of Alzheimer's disease (AD)-related hypometabolism. Aim of the present study was to test this relationship in well characterized normal controls of the Alzheimer's Disease Neuroimaging Initiative (ADNI). The study included all ADNI control subjects with baseline FDG-PET that were cognitively stable for at least 36 months (n=87, 74.2±5.3y, 40 females). Pre-processed FDG-PET data was downloaded and stereotactically normalized to MNI space using SPM8. The mean signal in brain parenchyma was used for intensity scaling. Voxelwise multiple regression was used to test the effect of BGL on scaled FDG uptake, using a cluster-defining voxel-level threshold of p=0.05, uncorrected. Resulting clusters were considered statistically significant if the family-wise error corrected p-value of the cluster was 0.05 or less. BGL ranged between 59 and 149 mg/dl (98±16 mg/dl). There was a significant cluster of negative correlation between scaled FDG uptake and BGL comprising precuneus and bilateral parieto-occipital cortex (cluster volume 123 ml, p=0.020). The cluster did not include the posterior cingulate. Positive correlation was detected in a large cluster of white matter in the centrum semiovale (245 ml, p<0.0005). A piecewise linear broken stick model used to fit mean FDG uptake in the cluster of negative correlation as a function of BGL identified a breaking point at 94 mg/dl. Unexpectedly, the decline of scaled FDG uptake in this cluster was steeper below the breaking point than above. The broken stick provided a better fit of the data than a straight line (Akaike Information Criterion).

Progressive Posterior Encephalopathy Syndrome Related with Drug-refractory Hypertension in a Patient with Pheochromocytoma

Background: Posterior reversible encephalopathy syndrome (PRES) is a neuroradiological syndrome characterized by headache, altered mental status, visual disturbance, and seizures with diagnostic MRI features, especially in the territories of posterior circulation. Reversibility of clinical and radiologic findings is generally regarded as a defining feature of PRES. Case Report: A 72-year old man who had a history of hypertension presented with subacute and progressive visual disturbance, dizziness, limb ataxia, and finally non-convulsive status epilepticus. Magnetic resonance imaging (MRI) showed extensive lesions in bilateral parieto-occipital cortex and subcortex. Due to his marked fluctuation of blood pressure, we detected a pheochromocytoma of left adrenal gland. In spite of administration with several types of antihypertensive medication, the patient presented with clinical deterioration, leading to death. MRI demonstrated the progression of lesions. Conclusion: This case report highlights the clinical and radiological progression of posterior encephalopathy syndrome caused by pheochromocytoma despite appropriate treatment of blood pressure. J Neurocrit Care 2014;7(2):141-144

Coherent Activity in Bilateral Parieto-Occipital Cortices during P300-BCI Operation.

The visual P300 brain–computer interface (BCI), a popular system for electroencephalography (EEG)-based BCI, uses the P300 event-related potential to select an icon arranged in a flicker matrix. In earlier studies, we used green/blue (GB) luminance and chromatic changes in the P300-BCI system and reported that this luminance and chromatic flicker matrix was associated with better performance and greater subject comfort compared with the conventional white/gray (WG) luminance flicker matrix. To highlight areas involved in improved P300-BCI performance, we used simultaneous EEG–fMRI recordings and showed enhanced activities in bilateral and right lateralized parieto-occipital areas. Here, to capture coherent activities of the areas during P300-BCI, we collected whole-head 306-channel magnetoencephalography data. When comparing functional connectivity between the right and left parieto-occipital channels, significantly greater functional connectivity in the alpha band was observed under the GB flicker matrix condition than under the WG flicker matrix condition. Current sources were estimated with a narrow-band adaptive spatial filter, and mean imaginary coherence was computed in the alpha band. Significantly greater coherence was observed in the right posterior parietal cortex under the GB than under the WG condition. Re-analysis of previous EEG-based P300-BCI data showed significant correlations between the power of the coherence of the bilateral parieto-occipital cortices and their performance accuracy. These results suggest that coherent activity in the bilateral parieto-occipital cortices plays a significant role in effectively driving the P300-BCI.

Are the neural correlates of subitizing and estimation dissociable? An fNIRS investigation

Human performance in visual enumeration tasks typically shows two distinct patterns as a function of set size. For small sets, usually up to 4 items, numerosity judgments are extremely rapid, precise and confident, a phenomenon known as subitizing. When this limit is exceeded and serial counting is precluded, exact enumeration gives way to estimation: performance becomes error-prone and more variable. Surprisingly, despite the importance of subitizing and estimation in numerical cognition, only few neuroimaging studies have examined whether the neural activity related to these two phenomena can be dissociated. In the present work, we used multi-channel near-infrared spectroscopy (fNIRS) to measure hemodynamic activity of the bilateral parieto-occipital cortex during a visual enumeration task. Participants had to judge the numerosity of dot arrays and indicate it by means of verbal response. We observed a different hemodynamic pattern in the parietal cortex, both in terms of amplitude modulation and temporal profile, for numerosities below and beyond the subitizing range. Crucially, the neural dissociation between subitizing and estimation was strongest at the level of right IPS. The present findings confirm that fNIRS can be successfully used to detect subtle temporal differences in hemodynamic activity and to produce inferences on the neural mechanisms underlying cognitive functions.

Discordance in the anatomical locations between morphological and perfusion changes occurring with the progression of Alzheimer’s disease

The aim of this study was to clarify the difference between the morphological and perfusion changes occurring with the progression of Alzheimer's disease (AD). The study focused on 37 patients who were clinically diagnosed with AD and were examined by both MRI and perfusion SPECT twice during a 1- to 2-year clinical observation period. Twenty-four of the 37 patients showed a progression of cognitive deterioration during the 1.2(±0.4)-year period of clinical observation (rapidly progressing group: initial mean MMSE score = 23.3; second mean MMSE score = 20.2), while 13 patients showed no apparent progression of cognitive deterioration (slowly progressing group: initial mean MMSE score = 21.2; second mean MMSE score = 22.2). The morphological changes were evaluated using a voxel-based morphometric technique with segmented MRI images. Cerebral perfusion was measured by Tc-99m ECD SPECT. Data analysis was performed by SPM on a MATLAB work space (2007.a). There was no significant difference in either the perfusion or gray matter density between the rapidly progressing and slowly progressing groups at the initial examination. The rapidly progressing group showed an interval decrease of perfusion in the bilateral parieto-occipital cortex and a decrease of gray matter density in the bilateral temporal and cingulate cortex. The slowly progressing group did not show a significant interval change in either the cerebral perfusion or gray matter density. These results suggest that rapid symptomatic progression in AD patients accompanies rapid progression of both morphological and perfusion changes, although the regions of the changes differ between them.

Motion direction tuning in human visual cortex

A number of electrophysiological studies have been conducted in recent years in order to clarify the dynamics of visual motion processing in the human brain. Using a variety of event-related potential (ERP) measures, several parameters such as onset, offset, contrast and velocity have been investigated, while a critical aspect of visual motion, that of direction, has received less attention. Here we used multichannel electroencephalography and distributed source localization to study brain activity for different directions of visual motion using random dot stimuli. Our data reveal differential extrastriate activation at 164-226 ms after motion onset that coded for motion direction with different ERP maps and underlying electrical generators for each tested direction. This activation was paralleled initially (164-186 ms) by a distinct extrastriate activation encoding whether the motion stimulus consisted of directed motion stimuli (as above) or contained undirected incoherent motion (control stimulus). Application of a linear inverse solution localized the brain activity for each tested motion direction to distinct brain regions within the same larger network of extrastriate brain regions. These regions included bilateral temporo-occipital and bilateral parieto-occipital cortex. The present data in healthy subjects are compatible with extrastriate activity that is tuned to different directions of visual motion. This extends previous clinical data and suggests the presence of distributed macroscopic motion direction tuning in primate extrastriate cortex that may complement the classical microscopic motion tuning at the columnar level.

Cerebral injury in association with profound iatrogenic hyperglycemia in a neonate

The adverse effect of hyperglycemia on neurological outcome following cerebral ischemia has been established in both experimental and adult human studies. However, there is a paucity of data to assess this risk in the human infant. This case is the first to describe severe and prolonged iatrogenic hyperglycemia in association with ischemia in an infant who sustained a major cerebral lesion. The topography of the predominant cerebral injury, i.e., bilateral parieto-occipital cortex and subcortical white matter, shown by magnetic resonance imaging was similar to that documented in the hypoglycemic infant, suggesting a similarity in regional cerebral vulnerability to altered glucose metabolism. This case extends recognition of the risk of severe hyperglycemia in association with cerebral ischemia to the newborn and suggests also that the posterior cerebral predilection for injury is similar in both hypoglycemia and hyperglycemia.

産じょく期に生じた皮質盲の１例

A 19-year-old woman, status post an uneventful pregnancy and delivery, developed a severe migranous headache and visual loss at 2 hours post partum. Computed tomography demonstrated ischemia and edema in the bilateral parietooccipital cortices. Magnetic resonance imaging (MRI) ruled out cerebral sinus thrombosis. Magnetic resonance imaging angiography (MRA) did not reveal remarkable abnormal findings in the major arteries. Cerebral angiography revealed circulation disorder of the bilateral posterior cerebral arteries in the capillary phase. The patient recovered with conservative therapy. The ischemic lesion associated with eclampsia often affects the parieooccipital cortices and basal ganglia. In such cases, the ischemic lesions are often reversible, and the symptoms resolve quickly, usually within a week. Conservative therapy is warranted when major artery stenosis or venous thrombosis can be excluded. Careful follow-up is essetial, however, as cases in which the vasospasm worsened and the patient died have been reported.