Occipitotemporal Cortex Research Articles

Potential effects of peripheral neuropathy on brain function in patients with type 2 diabetes mellitus

BackgroundThe mechanisms associated between diabetic peripheral neuropathy (DPN) and various brain function abnormalities in patients remains unclear. This study attempted to indirectly evaluate the effect of DPN on brain function in patients with type 2 diabetes mellitus (T2DM) by characterizing the resting-state functional connectivity (FC) of the lower limb sensorimotor cortex (LSM).MethodsForty-four T2DM patients with diabetic peripheral neuropathy (DPN), 39 T2DM patients without diabetic peripheral neuropathy (ND), and 43 healthy controls (HCs) underwent a neuropsychological assessment and resting-state functional magnetic resonance imaging examinations to examine the differences in FC between the LSM and the whole brain. The relationships of FC with clinical/cognitive variables were examined.ResultsIn comparison with the HCs group, the ND group showed reduced FC of the LSM with the right lateral occipitotemporal cortex (LOTC) and increased FC with the medial superior frontal gyrus (SFGmed), while the DPN group showed reduced FC of the LSM with the right cerebellar lobule VI, the right LOTC, the rostral prefrontal cortex (rPFC), and the anterior cingulate gyrus (ACC). Moreover, in comparison with the ND group, the DPN group showed reduced FC of the LSM with the ACC, SFGmed, and rPFC. In the DPN group, the FC between the LSM and right cerebellar lobule VI was significantly correlated with fasting blood glucose levels (r = -0.490, p = 0.001), and that between the LSM and ACC was significantly correlated with the Montreal Cognitive Assessment score (r = 0.479, p = 0.001).ConclusionsPatients with T2DM may show abnormal motion-related visual perceptual function before the appearance of DPN. Importantly, DPN can influence the brain regions that maintain motion and motor control, and this effect is not limited to motor function, which may be the central neuropathological basis for diabetic peripheral neuropathy.

Activity in Occipito-Temporal Cortex Is Involved in Tool-Use Planning and Contributes to Tool-Related Semantic Neural Representations

Abstract Tool use and language are highly refined human abilities which may show neural commonalities due to their potential reciprocal interaction during evolution. Recent work provided evidence for shared neural resources between tool use and syntax. However, whether activity within the tool-use network also contributes to semantic neural representations of tool nouns remains untested. To this aim, we identified the tool-use planning network with functional magnetic resonance imaging while participants used pliers. The very same participants underwent a semantic priming task including two categories, tool nouns and animal nouns, to highlight the respective underlying networks. With multivariate analyses of the activation neural patterns, we tested whether activity in tool-use brain clusters takes part in the neural representation of tool nouns as compared with animal nouns. The results revealed that word semantic categories were decoded within the left occipito-temporal cortex activated by preparing to use a tool, with similar patterns of brain activity for words within the same category. In addition, in the same area, neural activations for tool nouns were found to be higher than those for animal nouns. These findings suggest that activity in tool-use related brain areas encodes semantic information separately for tool nouns and animal nouns, thus supporting the embodiment of tool-noun processing in the tool-use sensorimotor network.

A 7T fMRI investigation of hand and tool areas in the lateral and ventral occipitotemporal cortex.

Previous studies demonstrated the existence of hand and tool areas in lateral and ventral occipitotemporal cortex (OTC), as well as an overlap between them. We reinvestigated this organization using 7T fMRI, benefiting from a higher signal-to-noise ratio than 3T. This enabled us to include a wider array of categories to achieve a more holistic perspective, and to omit certain spatial preprocessing steps. Despite these improvements, univariate analysis confirmed the existence of hand-tool overlap across OTC, which is striking given the omission of the spatial preprocessing steps that can influence overlap. There was significantly more overlap between hands and tools, compared to other overlap types in the left hemisphere of OTC. The overlap was also larger in the left lateral OTC as compared to the right lateral OTC. We found in all hand areas a differentiation between tools and other types of objects, although they still responded more to bodies than to tools. Regarding the tool areas, we observed a differentiation between hands and other categories such as faces and non-tool objects. Left hemisphere tool areas also differentiated between hands and bodies. When excluding the overlapping voxels from the hand and tool areas, they still showed a significant response to tools or hands (compared to objects or faces) respectively. Multi-voxel pattern analysis indicated that neural representations in the hand areas showed greater similarity between hands and tools than between hands and other objects. In the tool areas, the neural representations between tools and hands and between tools and other type of objects were all equally similar. To summarize, capitalizing on the benefits of 7T fMRI, we further substantiate the evidence in favor of hand-tool overlap in several regions of occipitotemporal cortex.

Neural representations of phonological information in bilingual language production.

Previous research has explored the neural mechanisms of bilinguals' language production, but most studies focused on neural mechanisms of cognitive control during language production. Therefore, it is unclear which brain regions represent lexical information (especially phonological information) during production and how they are affected by language context. To address those questions, we used representational similarity analysis to explore neural representations of phonological information in native (L1) and second languages (L2) in the single- and mixed-language contexts, respectively. Results showed that Chinese-English bilinguals behaviorally performed worse and exhibited more activations in brain regions associated with language processing and cognitive control in the mixed-language context relative to the single-language context. Further representational similarity analysis revealed that phonological representations of L1 were detected in the left pars opercularis, middle frontal gyrus, and anterior supramarginal gyrus, while phonological representations of L2 were detected in the bilateral occipitotemporal cortex regardless of the target language. More interestingly, robust phonological representations of L1 were observed in brain areas related to phonological processing during L2 production regardless of language context. These results provide direct neuroimaging evidence for the nonselective processing hypothesis and highlight the superiority of phonological representations in the dominant language during bilingual language production.

The 2024 Richardson Lecture: Prosopagnosia - A Classic Neurologic Deficit Meets the Modern Era.

Acquired prosopagnosia is a rare disorder, but it serves as a model for impairments in expert-level visual processing. This review discusses five key observations made over the past 30 years. First, there are variants, an apperceptive type linked to damage to the inferior occipitotemporal cortex and an amnestic type associated with anterior temporal lesions, both either right or bilateral. Second, these variants are clustered in syndromes with other perceptual deficits, the apperceptive type with field defects, dyschromatopsia and topographagnosia, and the amnestic type with topographagnosia and the auditory disorders of phonagnosia and acquired amusia. Third, extensive testing often shows additional problems with recognizing exemplars of other objects, especially when degrees of expertise are taken into account. Fourth, the prosopagnosic impairment does not affect all facial information. For example, the perception of expression and lip-reading likely depends on other neural substrates than those for processing facial identity. Last, face perception in prosopagnosia is not immutable but can improve with extensive training, though as yet this does not represent a cure for the condition. Continuing work with neural networks and animal models will enhance our understanding of this intriguing condition and what it tells us about how our brains process vision.

Orthographic and phonological processing in the left ventral occipitotemporal cortex during Chinese word reading.

The left ventral occipitotemporal cortex (lvOT) has been consistently identified as a crucial structure in word reading, and its function varies across subregions. Nevertheless, the specific function of the lvOT and its subregions remains controversial because the obvious grapheme-to-phoneme correspondence rules of alphabetic languages make it difficult to disentangle the contributions of orthography and phonology to neural activations. To explore information processing in lvOT subregions, the present study manipulated the orthography and phonology in a factorial design and used the fMRI rapid adaptation paradigm. The results revealed a posterior-to-anterior functional gradient in lvOT in Chinese word reading and specified that the functional transition from sublexical to lexical processing occurred in the middle subregion close to the classic VWFA. More importantly, we found that the middle and posterior subregions of lvOT are responsible for processing both orthographic and phonological information during Chinese word reading. These results elaborated the function of the lvOT in Chinese word reading.

Differential Mnemonic Contributions of Cortical Representations during Encoding and Retrieval.

Several recent fMRI studies of episodic and working memory representations converge on the finding that visual information is most strongly represented in occipito-temporal cortex during the encoding phase but in parietal regions during the retrieval phase. It has been suggested that this location shift reflects a change in the content of representations, from predominantly visual during encoding to primarily semantic during retrieval. Yet, direct evidence on the nature of encoding and retrieval representations is lacking. It is also unclear how the representations mediating the encoding-retrieval shift contribute to memory performance. To investigate these two issues, in the current fMRI study, participants encoded pictures (e.g., picture of a cardinal) and later performed a word recognition test (e.g., word "cardinal"). Representational similarity analyses examined how visual (e.g., red color) and semantic representations (e.g., what cardinals eat) support successful encoding and retrieval. These analyses revealed two novel findings. First, successful memory was associated with representational changes in cortical location (from occipito-temporal at encoding to parietal at retrieval) but not with changes in representational content (visual vs. semantic). Thus, the representational encoding-retrieval shift cannot be easily attributed to a change in the nature of representations. Second, in parietal regions, stronger representations predicted encoding failure but retrieval success. This encoding-retrieval "flip" in representations mimics the one previously reported in univariate activation studies. In summary, by answering important questions regarding the content and contributions to the performance of the representations mediating the encoding-retrieval shift, our findings clarify the neural mechanisms of this intriguing phenomenon.

Music literacy shapes the specialization of a right hemispheric word reading area

This study aimed to examine differences in the brain activity of professional musicians and non-musicians, particularly in relation to neuroplastic changes that may be associated with musical training. Specifically, we investigated whether the ability to read complex musical notation might be linked to neurofunctional adaptations that could influence word reading mechanisms. The study involved 80 participants (half of which were musicians). High-density EEG recordings and swLORETA inverse solutions were employed to analyze brain activity related to word processing and orthographic analysis. The electromagnetic signals were analyzed in the temporal window corresponding to the latency of N170 component (150–190 ms). Musicians and musically naïve people (controls) were matched based on native language, sociocultural and educational status, age, and laterality preference. Behavioural data and reading proficiency tests demonstrated higher reading skills (for words, non-words and text), and faster RTs to target letters embedded in words, in musicians. Source reconstruction showed fundamental differences in word reading mechanisms between musicians and non-musicians, including a larger involvement of the right occipitotemporal cortex, in the former than the latter. In particular, musicians showed a bilateral activation of the middle occipital gyrus (BA19, Visual Word Form Area), which was strongly lateralized to the left hemisphere in controls, during word orthographic analysis. A relationship is proposed between music literacy, enhanced reading skills and the development of a right-sided reading area for notation recognition in musicians, which could serve as a potential protective factor for ‘surface’ dyslexia.

Visual self-face and self-body recognition in a left-brain-damaged prosopagnosic patient.

The present case study describes the patient N.G., who reported prosopagnosia along with difficulty in recognising herself in the mirror following a left-sided temporo-occipital hemispheric stroke. The neuropsychological and experimental investigation revealed only a mild form of apperceptive prosopagnosia, without visual agnosia, primarily caused by an impaired visual processing of face-parts and body parts but not of full faces. Emotional expressions did not modulate her face processing. On the other hand, N.G. showed a marked impairment of visual self-recognition, as assessed with visual matching-to-sample tasks, both at the level of body-part and face-part processing and at a full-face level, featured by a deficit in the perceptual discrimination of her own face and body, as compared to the others' face and body. N.G.'s lesion mapping showed damage to the left inferior occipito-temporal cortex, affecting the inferior occipital gyrus and compromising long-range connections between the occipital/temporo-occipital areas and the anterior fronto-temporal areas. Overall, the present case report documents that visual processing of the person's own face may be selectively compromised by a left-sided hemispheric lesion disconnecting extra-striate body- and face-selective visual areas to self-representation regions. Moreover, others' (full) face processing may be preserved, as compared with the impaired ability to discriminate others' body and face parts.

Training-Induced Functional Homogenization in the Occipitotemporal Cortex: Differential Cross-Modal Mechanisms in Blindness vs. Severe Low Vision

Training-Induced Functional Homogenization in the Occipitotemporal Cortex: Differential Cross-Modal Mechanisms in Blindness vs. Severe Low Vision

Ventral Variant Posterior Cortical Atrophy with Occipito-temporal Accumulation of Tau Proteins/Astrocyte Gliosis.

A 73-year-old woman with posterior cortical atrophy (PCA) presented with progressive apperceptive visual agnosia, alexia, agraphia, ventral simultanagnosia, prosopagnosia, and allocentric (stimulus-centered) left-sided hemispatial neglect. All of these symptoms were attributed to damage to the bilateral occipito-temporal cortices, consistent with ventral variant PCA. While the Pittsburgh compound B uptake was extensively distributed throughout the occipito-parietal (dorsal) and occipito-temporal (ventral) areas, the THK5351 (ligand binding to tau aggregates/astrocyte gliosis) accumulation was limited to the ventral area. These findings suggest that local accumulation of tau proteins and/or astrocyte gliosis over the occipito-temporal cortices can result in ventral variant PCA.

Conjunctive representation of colors and shapes in human occipitotemporal and posterior parietal cortices

Conjunctive representation of colors and shapes in human occipitotemporal and posterior parietal cortices

Quantification of reading circuits in the ventral occipitotemporal cortex

Quantification of reading circuits in the ventral occipitotemporal cortex

Intracerebral recordings evidence that unfamiliar face-identity recognition is supported by face-selective neural populations in the human ventral occipito-temporal cortex

Intracerebral recordings evidence that unfamiliar face-identity recognition is supported by face-selective neural populations in the human ventral occipito-temporal cortex

A radial template space reveals organization of feature and task-selective regions in lateral occipitotemporal cortex

A radial template space reveals organization of feature and task-selective regions in lateral occipitotemporal cortex

Using imagination and the contents of memory to create new scene and object representations: A functional MRI study

Humans can use the contents of memory to construct scenarios and events that they have not encountered before, a process colloquially known as imagination. Much of our current understanding of the neural mechanisms mediating imagination is limited by paradigms that rely on participants' subjective reports of imagined content. Here, we used a novel behavioral paradigm that was designed to systematically evaluate the contents of an individual's imagination. Participants first learned the layout of four distinct rooms containing five wall segments with differing geometrical characteristics, each associated with a unique object. During functional MRI, participants were then shown two different wall segments or objects on each trial and asked to first, retrieve the associated objects or walls, respectively (retrieval phase) and then second, imagine the two objects side-by-side or combine the two wall segments (imagination phase). Importantly, the contents of each participant's imagination were interrogated by having them make a same/different judgment about the properties of the imagined objects or scenes. Using univariate and multivariate analyses, we observed widespread activity across occipito-temporal cortex for the retrieval of objects and for the imaginative creation of scenes. Interestingly, a classifier, whether trained on the imagination or retrieval data, was able to successfully differentiate the neural patterns associated with the imagination of scenes from that of objects. Our results reveal neural differences in the cued retrieval of object and scene memoranda, demonstrate that different representations underlie the creation and/or imagination of scene and object content, and highlight a novel behavioral paradigm that can be used to systematically evaluate the contents of an individual's imagination.

Functional interactions underlying visuospatial orthographic processes in Chinese reading.

As a logographic writing system, Chinese reading involves the processing of visuospatial orthographic (ORT) properties. However, this aspect has received relatively less attention in neuroimaging research, which has tended to emphasize phonological (PHO) and semantic (SEM) aspects in processing Chinese characters. Here, we compared the functional correlates supporting all these three processes in a functional MRI single-character reading study, in which 35 native Chinese adults were asked to make ORT, PHO, and SEM judgments in separate task-specific activation blocks. Our findings revealed increased involvement of the right hemisphere in processing Chinese visuospatial orthography, particularly evident in the right ventral occipito-temporal cortex (vOTC). Additionally, time course analysis revealed that the left superior parietal gyrus (SPG) was initially involved in SEM processing but contributed to the visuospatial processing of words in a later time window. Finally, ORT processing demonstrated stronger recruitment of left vOTC-SPG-middle frontal gyrus (MFG) functional connectivity compared to SEM processing. This functional coupling correlated with reduced regional engagement of the left vOTC and MFG, highlighting that visuospatial ORT processes in reading Chinese rely on functional interactions among key regions rather than local regional processes. In conclusion, these findings underscore visuospatial ORT processes as a distinctive feature of reading logographic characters.

Retinotopy drives the variation in scene responses across visual field map divisions of the occipital place area.

The occipital place area (OPA) is a scene-selective region on the lateral surface of human occipitotemporal cortex that spatially overlaps multiple visual field maps, as well as portions of cortex that are not currently defined as retinotopic. Here we combined population receptive field modeling and responses to scenes in a representational similarity analysis (RSA) framework to test the prediction that the OPA's visual field map divisions contribute uniquely to the overall pattern of scene selectivity within the OPA. Consistent with this prediction, the patterns of response to a set of complex scenes were heterogeneous between maps. To explain this heterogeneity, we tested the explanatory power of seven candidate models using RSA. These models spanned different scene dimensions (Content, Expanse, Distance), low- and high-level visual features, and navigational affordances. None of the tested models could account for the variation in scene response observed between the OPA's visual field maps. However, the heterogeneity in scene response was correlated with the differences in retinotopic profiles across maps. These data highlight the need to carefully examine the relationship between regions defined as category-selective and the underlying retinotopy, and they suggest that, in the case of the OPA, it may not be appropriate to conceptualize it as a single scene-selective region.

Incidental learning of predictive temporal context within cortical representations of visual shape.

Abstract Incidental learning of spatio-temporal regularities and consistencies— also termed ‘statistical learning’— may be important for discovering the causal principles governing the world. We studied statistical learning of temporal structure simultaneously at two time-scales: the presentation of synthetic visual objects (3 s) and predictive temporal context (30 s) in the order of appearance of such objects. Visual objects were complex and rotated in three dimensions about varying axes. Observers viewed fifteen (15) objects recurring many times each, intermixed with other objects that appeared only once, while whole-brain BOLD activity was recorded. Over three successive days, observers grew familiar with the recurring objects and reliably distinguished them from others. As reported elsewhere (Kakaei & Braun, 2023), representational similarity analysis (RSA) of multivariate BOLD activity revealed 124 ‘object-selective’ brain parcels with selectivity for recurring objects, located mostly in the ventral occipitotemporal cortex and the parietal cortex. Here we extend RSA to the representation of predictive temporal context, specifically “temporal communities” formed by objects that tended to follow each other. After controlling for temporal proximity, we observed 27 ‘community-sensitive’ brain parcels, in which pairwise distances between multivariate responses reflected community structure, either positively (smaller distances within than between communities) or negatively (larger distances within). Among object-selective parcels, 11 parcels were positively community-sensitive in the primary visual cortex (2 parcels), the ventral occipital, lingual, or fusiform cortex (8 parcels), and the inferior temporal cortex (1 parcel). Among non-object-selective parcels, 12 parcels were negatively community-sensitive in the superior, middle, and medial frontal cortex (6 parcels), the insula (2 parcels), the putamen (1 parcel), and in the superior temporal or parietal cortex (3 parcels). We conclude that cortical representations of object shape and of predictive temporal context are largely coextensive along the ventral occipitotemporal cortex.

Gradual change of cortical representations with growing visual expertise for synthetic shapes

Abstract Objective: Visual expertise for particular categories of objects (e.g., mushrooms, birds, flowers, minerals, and so on) is known to enhance cortical responses in parts of the ventral occipitotemporal cortex. How is such additional expertise integrated into the prior cortical representation of life-long visual experience? To address this question, we presented synthetic visual objects rotating in three dimensions and recorded multivariate BOLD responses as initially unfamiliar objects gradually became familiar. Main results: An analysis of pairwise distances between multivariate BOLD responses (“representational similarity analysis,” RSA) revealed that visual objects were linearly discriminable in large parts of the ventral occipital cortex, including the primary visual cortex, as well as in certain parts of the parietal and frontal cortex. These cortical representations were present from the start, when objects were still unfamiliar, and even though objects were shown from different sides. As shapes became familiar with repeated viewing, the distribution of responses expanded to fill more of the available space. In contrast, the distribution of responses to novel shapes (which appeared only once) contracted and shifted to the margins of the available space. Conclusion: Our results revealed cortical representations of object shape and gradual changes in these representations with learning and consolidation. The cortical representations of once-viewed shapes that remained novel diverged dramatically from repeatedly viewed shapes that became familiar. This disparity was evident in both the similarity and the diversity of multivariate BOLD responses.