Altered Effective Connectivity of Children and Young Adults With Unilateral Amblyopia: A Resting-State Functional Magnetic Resonance Imaging Study

The altered functional connectivity (FC) in amblyopia has been investigated by many studies, but the specific causality of brain connectivity needs to be explored further to understand the brain activity of amblyopia. We investigated whether the effective connectivity (EC) of children and young adults with amblyopia was altered. The subjects included 16 children and young adults with left eye amblyopia and 17 healthy controls (HCs). The abnormalities between the left/right primary visual cortex (PVC) and the other brain regions were investigated in a voxel-wise manner using the Granger causality analysis (GCA). According to the EC results in the HCs and the distribution of visual pathways, 12 regions of interest (ROIs) were selected to construct an EC network. The alteration of the EC network of the children and young adults with amblyopia was analyzed. In the voxel-wise manner analysis, amblyopia showed significantly decreased EC between the left/right of the PVC and the left middle frontal gyrus/left inferior frontal gyrus compared with the HCs. In the EC network analysis, compared with the HCs, amblyopia showed significantly decreased EC from the left calcarine fissure, posterior cingulate gyrus, left lingual gyrus, right lingual gyrus, and right fusiform gyrus to the right calcarine fissure. Amblyopia also showed significantly decreased EC from the right inferior frontal gyrus and right lingual gyrus to the left superior temporal gyrus compared with the HCs in the EC network analysis. The results may indicate that amblyopia altered the visual feedforward and feedback pathway, and amblyopia may have a greater relevance with the feedback pathway than the feedforward pathway. Amblyopia may also correlate with the feedforward of the third visual pathway.

Alterations in the Expression of the Genes Responsible for the Synthesis of Heparan Sulfate in Brains With Alzheimer Disease

The saccharide chains of heparan sulfate appear to be involved in several aspects Alzheimer disease (AD) pathogenesis. Their structural complexity is due to the expression of different isoenzymes. We studied the differential transcription of heparan sulfate chain biosynthesis in AD brains, analyzing different brain regions in patients with different extents of AD pathology. The transcriptomic study was performed by RT-PCR using samples of amygdala, anterior hippocampus, posterior hippocampus, claustrum, calcarine fissure, globus pallidus and cerebellum from patients with mild, moderate, or severe AD, as well as healthy individuals. Certain heparan sulfate epitopes were also detected by immunohistochemistry. Several genes, across all stages of heparan sulfate synthesis, showed altered transcription in different brain regions of AD patients. The numbers of alterations were greater in in moderate versus mild AD patients. In severe patients, there were fewer alterations in genes related to early stages of biosynthesis, and overexpression of genes involved in late stages. The alterations correlated with progressive brain atrophy, although alterations were more common in the cerebellum. Detection of some heparan sulfate epitopes by immunohistochemistry was consistent with previous studies. In conclusion, transcriptional alterations in the biosynthetic genes of heparan sulfate depend on the brain region and the degree of AD pathology.

Left Occipital Craniotomy for Resection of Arteriovenous Malformation: 2-Dimensional Operative Video

Medial parieto-occipital arteriovenous malformations (AVMs) are fed by distal cortical posterior cerebral artery branches and are generally considered eloquent given the proximity to the calcarine fissure and paracentral lobule. This patient was a neurologically intact 12-yr-old girl with an incidentally discovered left occipital AVM. The patient underwent preoperative angiographic evaluation with embolization of a dominant posterior cerebral artery feeding vessel. The AVM was removed in the standard manner using circumdissection. Indocyanine green angiography was utilized to demonstrate disconnection of the AVM before sacrificing the draining veins. The AVM was removed entirely, as evidenced on postoperative angiography. The patient had a partial right hemianopsia after the operation but was otherwise neurologically intact. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Preserved repetition in thalamic afasia. A pathophysiological hypothesis

ABSTRACT. The ability to repeat words is almost always preserved in thalamic aphasia. The pathophysiology of both thalamic aphasia and preservation of repetition are not fully understood. In a case of severe aphasia with preserved repetition after a left thalamic hemorrhage, MRI disclosed left thalamic lesion and loss of fractional anisotropy in the left centrum semiovale. FDG-PET showed severe hypometabolism in the left cerebral hemisphere, except for superior and transverse temporal gyri, calcarine fissure and frontopolar regions. Primary sensory function may be less functionally dependent on thalamic connections than heteromodal and paralimbic areas, which have connections with several thalamic nuclei. The extensive cortical hypometabolism due to diaschisis may have been responsible for the severity of the aphasia, whereas the less severe reduction of metabolism in the superior and transverse temporal gyri, and also, albeit less evident, in Broca’s area, might explain the preservation of repetition.

When ‘glaucomatous fields’ are not glaucoma: bilateral calcarine fissure strokes masquerading as glaucoma in a normal tension glaucoma suspect

A 78-year-old man with vascular risk factors and a family history of glaucoma presents with bilateral superior arcuate visual field loss. MRI brain was reported normal. Intraocular pressure (IOP) and optical coherence tomography of the retinal nerve fibre layer (RNFL) were within normal limits. A tentative diagnosis of normal tension glaucoma was made. Over the next 5 years, IOP remained stable without treatment, serial visual fields noted repeatable bilateral superior depressions with normal RNFL. Referral to a glaucoma subspecialist and subsequently neuro-ophthalmologist prompted repeat MRIs, which demonstrated mild small vessel ischaemia. Standard visual evoked potentials (VEPs) were normal. Multifocal VEPs identified poor response across the entire visual field in both eyes. The combination of visual defects, unremarkable RNFL and reduced multifocal VEPs raised suspicion of bilateral inferior calcarine fissure change. Retrospective review of MRI’s in a multidisciplinary meeting confirmed extensive microvascular changes with bilateral inferior calcarine fissure ischaemia.

Neural correlates of oral word reading, silent reading comprehension, and cognitive subcomponents

The ability to read is essential for cognitive development. To deepen our understanding of reading acquisition, we explored the neuroanatomical correlates (cortical thickness; CT) of word-reading fluency and sentence comprehension efficiency in Chinese with a group of typically developing children ( N = 21; 12 females and 9 males; age range 10.7–12.3 years). Then, we investigated the relationship between the CT of reading-defined regions and the cognitive subcomponents of reading to determine whether our study lends support to the multi-component model. The results demonstrated that children’s performance on oral word reading was positively correlated with CT in the left superior temporal gyrus (LSTG), left inferior temporal gyrus (LITG), left supramarginal gyrus (LSMG) and right superior temporal gyrus (RSTG). Moreover, CT in the LSTG, LSMG and LITG uniquely predicted children’s phonetic representation, phonological awareness, and orthography–phonology mapping skills, respectively. By contrast, children’s performance on sentence-reading comprehension was positively correlated with CT in the left parahippocampus (LPHP) and right calcarine fissure (RV1). As for the subcomponents of reading, CT in the LPHP was exclusively correlated with morphological awareness, whereas CT in the RV1 was correlated with orthography–semantic mapping. Taken together, these findings indicate that the reading network of typically developing children consists of multiple sub-divisions, thus providing neuroanatomical evidence in support of the multi-componential view of reading.

Reorganization of Auditory Cortex in Early-deaf People: Functional Connectivity and Relationship to Hearing Aid Use

Cross-modal reorganization after sensory deprivation is a model for understanding brain plasticity. Although it is a well-documented phenomenon, we still know little of the mechanisms underlying it or the factors that constrain and promote it. Using fMRI, we identified visual motion-related activity in 17 early-deaf and 17 hearing adults. We found that, in the deaf, the posterior superior temporal gyrus (STG) was responsive to visual motion. We compared functional connectivity of this reorganized cortex between groups to identify differences in functional networks associated with reorganization. In the deaf more than the hearing, the STG displayed increased functional connectivity with a region in the calcarine fissure. We also explored the role of hearing aid use, a factor that may contribute to variability in cross-modal reorganization. We found that both the cross-modal activity in STG and the functional connectivity between STG and calcarine cortex correlated with duration of hearing aid use, supporting the hypothesis that residual hearing affects cross-modal reorganization. We conclude that early auditory deprivation alters not only the organization of auditory regions but also the interactions between auditory and primary visual cortex and that auditory input, as indexed by hearing aid use, may inhibit cross-modal reorganization in early-deaf people.