Complementary hemispheric asymmetries in object naming and recognition: A voxel-based correlational study

Dual-Process Model in Semantic Priming: A Functional Imaging Perspective

Objectives: We aimed to investigate whether an inter-voxel diffusivity metric (local diffusion homogeneity, LDH), can provide supplementary information to traditional intra-voxel metrics (i.e., fractional anisotropy, FA) in white matter (WM) abnormality detection for type 2 diabetes mellitus (T2DM).Methods: Diffusion tensor imaging was acquired from 34 T2DM patients and 32 healthy controls. Voxel-based group-difference comparisons based on LDH and FA, as well as the association between the diffusion metrics and T2DM risk factors [i.e., body mass index (BMI) and systolic blood pressure (SBP)], were conducted, with age, gender and education level controlled.Results: Compared to the controls, T2DM patients had higher LDH in the pons and left temporal pole, as well as lower FA in the left superior corona radiation (p < 0.05, corrected). In T2DM, there were several overlapping WM areas associated with BMI as revealed by both LDH and FA, including right temporal lobe and left inferior parietal lobe; but the unique areas revealed only by using LDH included left inferior temporal lobe, right supramarginal gyrus, left pre- and post-central gyrus (at the semiovale center), and right superior radiation. Overlapping WM areas that associated with SBP were found with both LDH and FA, including right temporal pole, bilateral orbitofrontal area (rectus gyrus), the media cingulum bundle, and the right cerebellum crus I. However, the unique areas revealed only by LDH included right inferior temporal lobe, right inferior occipital lobe, and splenium of corpus callosum.Conclusion: Inter- and intra-voxel diffusivity metrics may have different sensitivity in the detection of T2DM-related WM abnormality. We suggested that LDH could provide supplementary information and reveal additional underlying brain changes due to diabetes.

Preserved mid-fusiform activation for visual words in a patient with a visual word recognition impairment

Combined treatment with escitalopram and memantine increases gray matter volume and cortical thickness compared to escitalopram and placebo in a pilot study of geriatric depression.

a:2:{s:4:"lang";s:2:"en";s:7:"content";s:1392:"<h3>Background/Objectives</h3> Alexia without agraphia is a disorder of reading inability with intact writing, usually caused by infarction in the left occipital lobe involving the splenium. A significantly rarer form arises following lesions in the left inferior temporal lobe, affecting the visual word form area (VWFA), a specialised region responsible for word recognition. We describe a 51-year-old male with alexia without agraphia due to a strategic infarction affecting the VWFA, with complete recovery several weeks later. <h3>Methods</h3> The patient‘s history and examination findings are reported, with imaging findings presented, and a discussion of the literature. <h3>Results</h3> The patient demonstrated selective impairment in whole-word reading, with preserved writing and letter-by-letter reading, and no visual field defects. MR brain demonstrated VWFA infarction. The patient experienced complete recovery. <h3>Discussion</h3> This case illustrates a ‘cortical’ variant of alexia without agraphia due to strategic infarction in the VWFA, distinct from the better-recognised ‘disconnection syndrome’ involving the occipital lobe and splenium. This report further evidences the VWFA’s role in word recognition, providing valuable insights into the functional localisation of reading and writing abilities. andrewmacphie{at}gmail.com ";}

We report the case of a 76-year-old woman who presented with recurrent episodes of complex visual hallucinations in her right visual field without an anopsia. The electroencephalogram showed sharp transients in the left parietotemporal region with phase reversals at T5 and P3. FLAIR MRI revealed hyperintense lesions in the left temporo-occipital lobe, located mainly in the left inferior temporal lobe. Cerebral angiography revealed an arteriovenous shunt from the left occipital artery to the left transverse sinus with cortical venous reflux. The complex visual hallucinations were resolved after transarterial embolization. We therefore hypothesize that this patient's complex visual hallucinations were caused by epileptic seizures or changes in cortical blood flow caused by the cortical venous reflux from the arteriovenous fistula. In general, epileptic hallucinations expand into the bilateral visual field. We reveal that in rare cases, complex visual hallucinations can also be limited to the unilateral visual field without an anopsia. Additionally, we reveal that a dural arteriovenous fistula can cause visual hallucinations without hemianopia.

The inferior, anterior temporal lobes and semantic memory clarified: Novel evidence from distortion-corrected fMRI

<h3>To the Editor.—</h3> We recently had a patient who had postanoxic action myoclonus (Lance-Adams syndrome). This severe movement disorder was completely suppressed with the oral administration of valproate sodium (Epilim [Britain]; Depakene, comparable US product) at a dosage of 1,000 mg daily, with corresponding serum levels of 50 to 80 μg/mL. At these serum levels and while receiving no other therapy, severe uncontrollable yawning developed. This was occurring every two to three minutes. Lowering the dosage of the valproate sodium abolished the yawning, and its reinstitution at the previous level led to its return. Pimozide (Orap), 400 mg daily, was added to the regimen of full dosage of valproate sodium, and the yawning disappeared within one day. Withdrawal of the pimozide caused the yawning to reappear. Computerized tomography of the brain demonstrated mild generalized cortical atrophy with an area of infarction in the left inferior temporal lobe. Serotonin deficiency was

Within-individual BOLD signal variability in the N-back task and its associations with vigilance and working memory

The learning of perceptual skills is thought to rely upon multiple regions in the cerebral cortex, but imaging studies have not yet provided evidence about the changes in neural activity that accompany visual skill learning. Functional magnetic resonance imaging (fMRI) was used to examine changes in activation of posterior brain regions associated with the acquisition of mirror-reading skill for novel and practiced stimuli. Multiple regions in the occipital lobe, inferior temporal cortex, superior parietal cortex and cerebellum were involved in the reading of mirror-reversed compared to normally oriented text. For novel stimuli, skilled mirror-reading was associated with decreased activation in the right superior parietal cortex and posterior occipital regions and increased activation in the left inferior temporal lobe. These results suggest that learning to read mirror-reversed text involves a progression from visuospatial transformation to direct recognition of transformed letters. Reading practiced, relative to unpracticed, stimuli was associated with decreased activation in occipital visual cortices, inferior temporal cortex and superior parietal cortex and increased activation in occipito-parietal and lateral temporal regions. By examining skill learning and item-specific repetition priming in the same task, this study demonstrates that both of these forms of learning exhibit shifts in the set of neural structures that contribute to performance.

We report a patient with bilateral independent temporal lobe seizures in whom two [99mTc]HMPAO single photon emission computed tomograph (SPECT) scans were performed during two different seizures. In the first periictal SPECT, [99mTc]HMPAO was injected in the interval between two closely spaced seizures (one localized in the left temporal lobe and the other in the right temporal lobe). SPECT images showed hypoperfusion in the left lateral temporal lobe, hyperperfusion of the left mesial temporal region, and pronounced hyperperfusion in the right anterior temporal lobe. These results suggest both a postictal left temporal SPECT pattern and an ictal right temporal pattern. In the second periictal SPECT, [99mTc]HMPAO was injected immediately after a right temporal lobe seizure and showed right lateral temporal lobe hypoperfusion and right mesial hyperperfusion, suggesting a postictal right temporal SPECT pattern. Interpretation of the periictal SPECT should take into account EEG changes at the time or in the minutes immediately after injection of [99mTc]HMPAO.

Clinical Neurophysiology: EEG–Video Monitoring

It has been proposed that isolation of the inferior temporal cortex and medial temporal lobe from their cholinergic afferents results in a severe anterograde amnesia. To test this hypothesis directly, seven rhesus monkeys received a unilateral immunotoxic lesion of the cholinergic cells of the basal forebrain with an ipsilesional section of the fornix. In a second surgery, inferior temporal cortex was ablated in the opposite hemisphere. All animals were severely impaired at learning visual scenes and object-reward associations. The impairment in learning scenes was correlated with cholinergic cell loss in the basal forebrain, but not with generalized tissue damage. Two monkeys served as surgical controls with saline injection in place of the immunotoxin, but all other procedures the same, and were not as severely impaired as those with immunotoxic lesions. Previous work has shown that monkeys with bilateral section of the anterior temporal stem (white matter of the temporal lobe), amygdala and fornix show a severe new learning impairment, and provide a model of human medial temporal lobe amnesia. One effect of this combined ablation is to isolate inferior temporal cortex and medial temporal lobe from their cholinergic afferents, possibly in addition to a direct disruption of the hippocampal system. The results of the present study, then, provide a novel link between the mechanisms of medial temporal lobe amnesia and Alzheimer's disease in which the cholinergic basal forebrain shows pathology. We propose that in both cases the mnemonic impairments result from isolating inferior temporal cortex and medial temporal lobe from their cholinergic afferents, possibly in addition to a direct disruption of the hippocampal system.

It is generally accepted that the anterior temporal lobes support knowledge of famous people. The specific roles of the right and left temporal lobe remain a subject of debate, with some studies suggesting differential roles based on modality (visual versus verbal information) and others category (person knowledge versus general semantics). The present study re-examined performance of semantic dementia patients with predominantly right and predominantly left temporal lobe atrophy on famous face, famous name and general semantic tasks, with the specific aim of testing the hypothesis that the right temporal lobe has a privileged role for person knowledge and the left temporal lobe for general semantic knowledge. Comparisons of performance rankings across tasks showed no evidence to support this hypothesis. By contrast, there was robust evidence from naming, identification and familiarity measures for modality effects: right-sided atrophy being associated with relatively greater impairment for faces and visual tasks and left-sided atrophy for names and verbal tasks. A double dissociation in test scores in two patients reinforced these findings. The data present a challenge for the influential ‘semantic hub’ model, which views the anterior temporal lobes as an area of convergence in which semantic information is represented in amodal form.

Mesial temporal lobe Cho to Cr(PCr) ratio asymmetry in chronic schizophrenics