Recovery of orthographic processing after stroke: A longitudinal fMRI study

There is a paucity of high-level evidence for endovascular thrombectomy (EVT) in posterior cerebral artery (PCA) strokes. The MEDLINE, Embase, and Web of Science databases were queried for well-conducted cohort studies comparing EVT vs medical management (MM) for PCA strokes. Outcomes of interest included 90-day functional outcomes, symptomatic intracranial hemorrhage (sICH), and death. The level of evidence was determined per the Oxford Centre for Evidence-Based Medicine criteria. We also conducted a propensity score matched (PSM) analysis of the 2016-2020 National Inpatient Sample (NIS) to provide support for our findings with real-world data. A total of 2,095 patients (685 EVT and 1,410 MM) were identified across 5 well-conducted cohort studies. EVT was significantly associated with higher odds of no disability at 90 days (odds ratio [OR] 1.25, 95% CI 1.04-1.50, p = 0.015) but not functional independence (OR 0.87, 95% CI 0.72-1.07, p = 0.18). EVT was also associated with higher odds of sICH (OR 2.48, 95% CI 1.55-3.97, p < 0.001) and numerically higher odds of death (OR 1.32, 95% CI 0.73-2.38; p = 0.35). PSM analysis of 95,585 PCA stroke patients in the NIS showed that EVT (n = 1,540) was associated with lower rates of good discharge outcomes (24.4% vs 30.7%, p = 0.037), higher rates of in-hospital mortality (8.8% vs 4.9%, p = 0.021), higher rates of ICH (18.2% and 11.7%, p = 0.008), and higher rates of subarachnoid hemorrhage (3.9% vs 0.6%, p < 0.001). Among patients with moderate to severe strokes (NIH Stroke Scale 5 or greater), EVT was associated with significantly higher rates of good outcomes (21.7% vs 13.8%, p = 0.023) with similar rates of mortality (7.6% vs 6.6%, p = 0.67) and ICH (17.8% vs, 13.1%, p = 0.18). Our meta-analysis revealed that while EVT may be effective in alleviating disabling deficits due to PCA strokes, it is not associated with different odds of functional independence and may be associated with higher odds of sICH. These findings were corroborated by our large propensity score matched analysis of real-world data in the United States. Thus, the decision to pursue PCA thrombectomies should be carefully individualized for each patient. Future randomized trials are needed to further explore the efficacy and safety of EVT for the treatment of PCA strokes. This study provides Class III evidence that in patients with acute PCA ischemic stroke, treatment with EVT compared with MM alone was associated with higher odds of no disabling deficit at 90 days and higher odds of sICH.

Visual word recognition has been proposed to have a functional and spatial organization corresponding to hierarchical language-like word forms in the left fusiform gyrus (FG) during visual word recognition in alphabetic languages. However, it is still unclear whether the similar functional gradients of word-like representation exist during Chinese character recognition. In this study, we adopted univariate activation analysis and representational similarity analysis (RSA) methods to investigate the functional organization in the FG for Chinese character recognition using task fMRI data. Native Chinese readers were visually presented with four types of character-like stimuli (i.e., real characters, pseudo-characters, false characters, and stroke combinations). After analysis, we observed a posterior-to-anterior functional gradient in the left FG corresponding to the degree of likeness of stimuli to character. Additionally, distinct subregions of the left FG harbor different orthographic codes. The middle part of the left FG was involved in abstract orthographic processing, while the anterior part of the left FG was involved in lexical orthographic processing (i.e., mapping orthography onto phonology or semantics). Notably, for the right FG, we did not find similar coding pattern for selectivity to character likeness, indicating the asymmetry of the functional hierarchical organization in favor of the left hemisphere. In conclusion, our findings revealed that the left FG presents a posterior-to-anterior gradient functional processing for Chinese character recognition, which expands our understanding of the psychological, neural, and computational theories of word reading.

Differential Neural Activation for Updating Rule versus Stimulus Information in Working Memory

BackgroundIschemic stroke caused by infarction in the territory of the posterior cerebral artery (PCA) has not been studied as extensively as infarctions in other vascular territories. This single centre, retrospective clinical study was conducted a) to describe salient characteristics of stroke patients with PCA infarction, b) to compare data of these patients with those with ischaemic stroke due to middle cerebral artery (MCA) and anterior cerebral artery (ACA) infarctions, and c) to identify predictors of PCA stroke.FindingsA total of 232 patients with PCA stroke were included in the "Sagrat Cor Hospital of Barcelona Stroke Registry" during a period of 19 years (1986-2004). Data from stroke patients are entered in the stroke registry following a standardized protocol with 161 items regarding demographics, risk factors, clinical features, laboratory and neuroimaging data, complications and outcome. The characteristics of these 232 patients with PCA stroke were compared with those of the 1355 patients with MCA infarctions and 51 patients with ACA infarctions included in the registry.Infarctions of the PCA accounted for 6.8% of all cases of stroke (n = 3808) and 9.6% of cerebral infarctions (n = 2704). Lacunar infarction was the most frequent stroke subtype (34.5%) followed by atherothrombotic infarction (29.3%) and cardioembolic infarction (21.6%). In-hospital mortality was 3.9% (n = 9). Forty-five patients (19.4%) were symptom-free at hospital discharge. Hemianopia (odds ratio [OR] = 6.43), lacunar stroke subtype (OR = 2.18), symptom-free at discharge (OR = 1.92), limb weakness (OR = 0.10), speech disorders (OR = 0.33) and cardioembolism (OR = 0.65) were independent variables of PCA stroke in comparison with MCA infarction, whereas sensory deficit (OR = 2.36), limb weakness (OR = 0.11) and cardioembolism as stroke mechanism (OR = 0.43) were independent variables associated with PCA stroke in comparison with ACA infarction.ConclusionsLacunar stroke is the main subtype of infarction occurring in the PCA territory. Several clinical features are more frequent in stroke patients with PCA infarction than in patients with ischaemic stroke due to infarction in the MCA and ACA territories. In-hospital mortality in patients with PCA territory is low.

Motivation: Microstructural changes of white matter tracts on ventral stream function deficits after posterior cerebral artery (PCA) stroke remain poorly understood. Goal(s): This study investigates the association between the integrity of six essential white matter tracts and residual ventral stream functions in PCA stroke survivors. Approach: We used tractography and diffusion tensor imaging (DTI) to assess microstructural integrity along tracts of interest, with principal component analysis to capture significant spatial variations for white matter microstructure. Results: White matter integrity correlates with residual ventral stream functions, specifically in colour perception, fine shape discrimination, and face recognition. Impact: This study demonstrates that applying principal component analysis to along-tract DTI metrics is an effective approach to evaluate white matter integrity, aiding in the assessment of ventral stream function loss after stroke.

We examined (a) how rapid automatized naming (RAN) components—articulation time and pause time—predict reading accuracy and reading fluency in Grades 4 and 5, and (b) what cognitive-processing skills (phonological processing, orthographic processing, or speed of processing) mediate the RAN–reading relationship. Sixty children were followed from Grade 3 to Grade 5 and were administered RAN (Letters and Digits), phonological processing, lexical and sublexical orthographic processing, speed of processing, reading accuracy, and fluency tasks. Pause time was highly correlated with reading fluency and shared more of its predictive variance with lexical orthographic processing and speed of processing than with phonological processing. Articulation time also predicted reading fluency, and its contribution was mostly independent from other cognitive-processing skills. Implications for the relationship between RAN and reading are discussed.

In the present study, we aimed at examining selective neural changes after task-switching training in old age by not only considering the spatial location but also the timescale of brain activation changes (i.e., sustained/block-related or transient/trial-related timescales). We assigned a sample of 50 older adults to a task-switching training or an active single-task control group. We administered two task paradigms, either sensitive to transient (i.e., a context-updating task) or sustained (i.e., a delayed-recognition working-memory task) dynamics of cognitive control. These dynamics were captured by utilizing an appropriate event-related or block-related functional magnetic resonance imaging design. We captured selective changes in task activation during the untrained tasks after task-switching training compared to an active control group. Results revealed changes at the neural level that were not evident from only behavioral data. Importantly, neural changes in the transient-sensitive context updating task were found on the same timescale but in a different region (i.e., in the left inferior parietal lobule) than in the task-switching training task (i.e., ventrolateral PFC, inferior frontal junction, superior parietal lobule), only pointing to temporal overlap, while neural changes in the sustained-sensitive delayed-recognition task overlapped in both timescale and region with the task-switching training task (i.e., in the basal ganglia), pointing to spatio-temporal overlap. These results suggest that neural changes after task-switching training seem to be critically supported by the temporal organization of neural processing.

P10. ‘Clustered sparse’ fMRI using simultaneous multislice excitation in language mapping

Editorial

Purpose: To investigate the neural correlates associated with recovery from acute spatial neglect resulting from right hemispheric stroke. Methods: Four neglect patients were investigated both behaviourally and by fMRI at an acute (18 ± 5 days) and at a chronic stage (123 ± 18 days) post stroke. Results: At the second assessment all patients showed substantial behavioural improvements. These were associated with an increase of neural activity in the right middle frontal gyrus, right inferior parietal cortex, right inferior temporal gyrus/fusiform gyrus, left superior temporal gyrus/angular gyrus and left anterior cingulate gyrus. Decreased neural activity at the second assessment was found in the right parahippocampal gyrus and left fusiform gyrus. Conclusions: The pattern of neural reorganisation comprises areas of a right hemisphere fronto-parietal attentional network and corresponding left hemisphere areas suggesting a compensatory recruitment of analogous contralesional areas. Interestingly, a more complex pattern of neural changes was observed in the fusiform gyri which have previously been implicated in lateralised directed spatial attention. There was an increase in the right hemisphere and a decrease in the left hemisphere. This pattern of recovery is reminiscent of a "push-pull" pattern previously described for the dorsal parietal cortex by Corbetta et al. (2005) in the recovery from spatial neglect.

Regional profiles of cortical gray matter volume deficits in schizophrenia and alcoholism

The concepts of the representation of visual field in primary visual cortex are based on studies of war wounds and correlations with brain imaging in small cohorts. Because of the difficulty of judging brain lesion extent and the small number of studied patients, there is lingering controversy as to whether the central 15° of visual field are mapped onto the posterior 25% of primary visual cortex or onto a larger area. To improve the delineation of MRI lesion extent, we have studied only patients with posterior cerebral artery (PCA) ischemic strokes. We accrued a cohort of 92 patients with PCA strokes from an electronic medical records search between 2009 and 2020 at a single tertiary care academic institution. Patients had reliable static perimetry demonstrating homonymous hemianopias and high-definition reviewable brain imaging. We divided the primary visual cortex on the MRI T1 sagittal sequence into 8 equal segments in right and left cerebral hemispheres and located lesions according to the segments they occupied. We correlated lesion locations with 3 visual field defects (VFDs): macular-sparing homonymous quadrantanopias, macular-splitting homonymous quadrantanopias, and homonymous paracentral scotomas. Among 25 cases with macular sparing, 13 had lesion-sparing confined to the posterior 25% of visual cortex. Among 6 cases with homonymous paracentral scotomas, 2 had lesions confined to the posterior 25% of visual cortex. Macular-splitting quadrantanopia did not occur in any patients with lesions confined to the posterior 25% of visual cortex, but did occur in 3 patients with lesions confined to the posterior 50% of visual cortex. These phenomena would not be expected if the central 15° of visual field were mapped onto a region extending beyond the posterior 25% of visual cortex. In patients with PCA strokes that involved the retrogeniculate visual pathway proximal to visual cortex, the visual cortex lesions were often less extensive than predicted by the VFDs, perhaps because of widespread damage to axons before they reached their destination in visual cortex. These results support the concept that the central 15° of the visual field are represented in the posterior 25% of visual cortex. Although this study contributes a larger cohort of patients with better-defined lesion borders than in past reports, its conclusions must be tempered by the variability of patient attention during visual field testing, the subjectivity in the interpretation of the defect patterns, and the difficulty in judging MRI lesion extent even on diffusion-weighted and precontrast T1 sagittal sequences.

Reduced cortical activation in inferior frontal junction in Unverricht–Lundborg disease (EPM1) – A motor fMRI study

Multitasking (MT) constitutes engaging in two or more cognitive activities at the same time. MT‐training improves performance on untrained MT tasks and alters the functional activity of the brain during MT. However, the effects of MT‐training on neural mechanisms beyond MT‐related functions are not known. We investigated the effects of 4 weeks of MT‐training on regional gray matter volume (rGMV) and functional connectivity during rest (resting‐FC) in young human adults. MT‐training was associated with increased rGMV in three prefrontal cortical regions (left lateral rostral prefrontal cortex (PFC), dorsolateral PFC (DLPFC), and left inferior frontal junction), the left posterior parietal cortex, and the left temporal and lateral occipital areas as well as decreased resting‐FC between the right DLPFC and an anatomical cluster around the ventral anterior cingulate cortex (ACC). Our findings suggest that participation in MT‐training is as a whole associated with task‐irrelevant plasticity (i.e., neural changes are not limited to certain specific task conditions) in regions and the network that are assumed to play roles in MT as well as diverse higher‐order cognitive functions. We could not dissociate the effects of each task component and the diverse cognitive processes involved in MT because of the nature of the study, and these remain to be investigated. Hum Brain Mapp 35:3646–3660, 2014. © 2013 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.

Objective To investigate the characteristics of hypomanic symptoms (HS) to the brain neural activity in the resting-state of the patients with major depressive disorder (MDD). Methods Twenty-three patients from 54 patients with MDD were defined as MDD with HS because their HCL-32 scores were higher than or equal to 12. The rest 31 patients were defined as MDD patients without HS because of the lower scores. After checking the match of the factors such as gender and age et al, there were 19 MDD patients with HS, 19 patients without HS and 19 healthy controls in the final analysis. We analyzed the impact of HS to the regional brain function of the patients with MDD by amplitude of low-frequency fluctuation (ALFF). Results The patients with MDD had abnormal resting-state brain activity in a diffuse brain areas compared to healthy controls by the ALFF analysis. Compared to the patients without HS, the ALFF of the depressed MDD patients with HS were significantly higher in the bilateral orbitofrontal cortex (OFC; left OFC: MNI(x,y,z): - 34,56,- 10; t=5.26; right OFC: MNI(x,y,z): 20, 66, - 2; t=493) and superior frontal cortex (SFC; left SFC: MNI(x,y,z): -4, 66, 8; t=4.12; right SFC: MNI(x,y,z): 14, 56, 18, t=3.97, all P< 0.05); while lower in bilateral thalamus and left fusiform gyrus (P<0.05). Correlation analysis of ALFF at each voxel in the whole brain against the HCL-32 in the patients with MDD revealed significantly positive correlation in OFC (r=0.363, 0.426, 0.405, all P<0.05), negative correlation in left thalamus and left fusiform gyrus (r=- 0.352, P<0.05; r=- 0.468, P<0.01). Conclusions The study suggested that there were differences between the two subgroups patients with MDD defined by the HCL-32. Compared to the MDD without HS patients, MDD with HS patients showed increase ALFF in bilateral frontal cortex (especially the OFC), and decrease ALFF in left thalamus and left fusiform gyrus. These features may be regarded as the biomarker of the MDD patients who were positive to HCL-32 screening. Key words: Major depressive disorder; Hypomanic symptoms; Resting state; Functional magnetic resonance imaging; Amplitude of low-frequency fluctuation