Semantic representations during language comprehension are affected by context

The meaning of words in natural language depends crucially on context. However, most neuroimaging studies of word meaning use isolated words and isolated sentences with little context. Because the brain may process natural language differently from how it processes simplified stimuli, there is a pressing need to determine whether prior results on word meaning generalize to natural language. We investigated this issue by directly comparing the brain representation of semantic information across four conditions that vary in context. fMRI was used to record human brain activity while four subjects (two female) read words presented in four different conditions: narratives (Narratives), isolated sentences (Sentences), blocks of semantically similar words (Semantic Blocks), and isolated words (Single Words). Using a voxelwise encoding model approach, we find two clear and consistent effects of increasing context. First, stimuli with more context (Narratives, Sentences) evoke brain responses with substantially higher SNR across bilateral visual, temporal, parietal, and prefrontal cortices compared to stimuli with little context (Semantic Blocks, Single Words). Second, increasing context increases the representation of semantic information across bilateral temporal, parietal, and prefrontal cortices at the group level. However, in individual subjects, only natural language stimuli (Narratives) consistently evoke widespread representation of semantic information across the cortical surface. These results show that context has large effects on both the quality of neuroimaging data and on the representation of meaning in the brain, and they imply that the results of neuroimaging studies that use stimuli with little context may not generalize well to the natural regime.

Decreased frontotemporal connectivity in patients with parkinson’s disease experiencing face pareidolia

The precise neural underpinnings of face pareidolia in patients with Parkinson’s disease (PD) remain unclear. We aimed to clarify face recognition network abnormalities associated with face pareidolia in such patients. Eighty-three patients with PD and 40 healthy controls were recruited in this study. Patients with PD were classified into pareidolia and nonpareidolia groups. Volumetric analyses revealed no significant differences between the pareidolia (n = 39) and nonpareidolia (n = 44) patient groups. We further observed decreased functional connectivity among regions of interest in the bilateral frontotemporal lobes in patients with pareidolia. Seed-based analysis using bilateral temporal fusiform cortices as seeds revealed significantly decreased connectivity with the bilateral inferior medial prefrontal cortices in the pareidolia group. Post hoc regression analysis further demonstrated that the severity of face pareidolia was negatively correlated with functional connectivity between the bilateral temporal fusiform and medial prefrontal cortices. Our findings suggest that top-down modulation of the face recognition network is impaired in patients with PD experiencing face pareidolia.

Increased Connectivity of Thalamocortical Tract/Occipital Cortex Concurrent with Recovery of Impaired Consciousness in a Stroke Patient: A Diffusion Tensor Tractography Study: A Case Report

Background: Little has been reported about the role of the occipital cortex in the recovery from impaired consciousness. In this case report, we report on a stroke patient who showed increased connectivity of the thalamocortical tract (TCT), including the occipital cortex, on follow-up diffusion tensor tractography (DTT) that was concurrent with recovery of impaired consciousness. Case presentation: A 64-year-old male patient underwent craniectomy and hematoma removal for spontaneous intracerebral hemorrhage (ICH) in the left fronto-parieto-temporal lobes and extraventricular catheterization for intraventricular hemorrhage (IVH). When he started rehabilitation eight weeks after onset, he was in a minimally conscious state with a Coma Recovery Scale-Revised (CRS-R) score of 14. On 8-week DTT, decreased connectivity of the TCT between the thalamic intralaminar nuclei and the cerebral cortex was observed in both medial prefrontal cortices (mPFCs), the occipital cortex, and the left parietal cortex. By contrast, on 12-week DTT, TCT connectivity had increased to include both medial prefrontal cortices and the right occipital cortex. Conclusion: Increased neural connectivity of the TCT to the mPFC and the occipital cortex, as shown by DTT, contributed to the recovery of impaired consciousness in a stroke patient. The results suggest that increased neural connectivity to the occipital cortex might contribute to the recovery of impaired consciousness in stroke patients.

Neural Networks Involved in Spatial and Temporal Pattern Separation

Critical to episodic memory is pattern separation (PS), the storage of similar inputs as distinct and nonoverlapping. Spatial and temporal PS have been shown to be related to disparate subfields of the hippocampus (HC) in rodents. Extra-HC structures involved have not yet been elucidated. The current work provides an exploratory investigation into the neural correlates of spatial and temporal PS, employing functional magnetic resonance imaging and univariate and multivariate analysis techniques. In Experiment 1, behavioural spatial and temporal memory tasks were developed that assess varying PS demands. Objectives for the experiment were met, in that accuracy was lower and reaction time higher for conditions requiring more engagement of PS. In Experiment 2, whole-brain regions as well as the neural networks involved in spatial and temporal PS were examined, and functional connectivity of the HC was observed. Univariate data revealed unique areas of activation based on information type being encoded (i.e., spatial vs. temporal). The cuneus and HC were uniquely involved in the spatial task, while a wider area of regions including middle occipital and medial frontal areas were activated in the temporal task. Multivariate analyses were convergent with the spatial and temporal context memory literature. The HC, parahippocampal gyri, prefrontal cortices, and precuneus were part of a correlated network in the spatial task. Bilateral prefrontal cortices, including the orbitofrontal cortex were involved in the temporal task. Further, the multivariate analysis revealed qualitatively distinct networks based on memory processing stage (i.e., encoding vs. retrieval). Interestingly, the network included anterior HC in spatial encoding, and posterior HC in spatial and temporal retrieval, consistent with an influential theory positing a rostrocaudal gradient along the HC for encoding and retrieval. Functional connectivity analyses revealed connectivity of the posterior HC seed with temporal and superior parietal areas in the spatial task, and with frontal areas in the temporal task, suggesting the right posterior HC interacts with regions differently based on information type. Results confirm and extend findings from previous literature demonstrating HC involvement in PS, and also suggest HC and extra-HC involvement varies based on processing stage and information type.

Neural Networks Involved in Spatial and Temporal Pattern Separation

Critical to episodic memory is pattern separation (PS), the storage of similar inputs as distinct and nonoverlapping. Spatial and temporal PS have been shown to be related to disparate subfields of the hippocampus (HC) in rodents. Extra-HC structures involved have not yet been elucidated. The current work provides an exploratory investigation into the neural correlates of spatial and temporal PS, employing functional magnetic resonance imaging and univariate and multivariate analysis techniques. In Experiment 1, behavioural spatial and temporal memory tasks were developed that assess varying PS demands. Objectives for the experiment were met, in that accuracy was lower and reaction time higher for conditions requiring more engagement of PS. In Experiment 2, whole-brain regions as well as the neural networks involved in spatial and temporal PS were examined, and functional connectivity of the HC was observed. Univariate data revealed unique areas of activation based on information type being encoded (i.e., spatial vs. temporal). The cuneus and HC were uniquely involved in the spatial task, while a wider area of regions including middle occipital and medial frontal areas were activated in the temporal task. Multivariate analyses were convergent with the spatial and temporal context memory literature. The HC, parahippocampal gyri, prefrontal cortices, and precuneus were part of a correlated network in the spatial task. Bilateral prefrontal cortices, including the orbitofrontal cortex were involved in the temporal task. Further, the multivariate analysis revealed qualitatively distinct networks based on memory processing stage (i.e., encoding vs. retrieval). Interestingly, the network included anterior HC in spatial encoding, and posterior HC in spatial and temporal retrieval, consistent with an influential theory positing a rostrocaudal gradient along the HC for encoding and retrieval. Functional connectivity analyses revealed connectivity of the posterior HC seed with temporal and superior parietal areas in the spatial task, and with frontal areas in the temporal task, suggesting the right posterior HC interacts with regions differently based on information type. Results confirm and extend findings from previous literature demonstrating HC involvement in PS, and also suggest HC and extra-HC involvement varies based on processing stage and information type.

Preserving Right Pre-motor and Posterior Prefrontal Cortices Contribute to Maintaining Overall Basic Emotion

Basic emotions such as happiness, sadness, and anger are universal, regardless of the human species, and are governed by specific brain regions. A recent report revealed that mentalizing, which is the ability to estimate other individuals’ emotional states via facial expressions, can be preserved with the help of awake surgery. However, it is still questionable whether we can maintain the ability to understand others’ emotions by preserving the positive mapping sites of intraoperative assessment. Here, we demonstrated the cortical regions related to basic emotions via awake surgery for patients with frontal glioma and investigated the usefulness of functional mapping in preserving basic emotion. Of the 56 consecutive patients with right cerebral hemispheric glioma who underwent awake surgery at our hospital, intraoperative assessment of basic emotion could be successfully performed in 22 patients with frontal glioma and were included in our study. During surgery, positive responses were found in 18 points in 12 patients (54.5%). Of these, 15 points from 11 patients were found at the cortical level, mainly the premotor and posterior part of the prefrontal cortices. Then, we focused on cortical 15 positive mappings with 40 stimulations and investigated the types of emotions that showed errors by every stimulation. There was no specific rule for the region-emotional type, which was beyond our expectations. In the postoperative acute phase, the test score of basic emotion declined in nine patients, and of these, it decreased under the cut-off value (Z-score ≤ −1.65) in three patients. Although the total score declined significantly just after surgery (p = 0.022), it recovered within 3 months postoperatively. Our study revealed that through direct electrical stimulation (DES), the premotor and posterior parts of the prefrontal cortices are related to various kinds of basic emotion, but not a single one. When the region with a positive mapping site is preserved during operation, basic emotion function might be maintained although it declines transiently after surgery.