Intersubject Regularity in the Intrinsic Shape of Human V1

Previous studies have reported considerable intersubject variability in the three-dimensional geometry of the human primary visual cortex (V1). Here we demonstrate that much of this variability is due to extrinsic geometric features of the cortical folds, and that the intrinsic shape of V1 is similar across individuals. V1 was imaged in ten ex vivo human hemispheres using high-resolution (200 μm) structural magnetic resonance imaging at high field strength (7 T). Manual tracings of the stria of Gennari were used to construct a surface representation, which was computationally flattened into the plane with minimal metric distortion. The instrinsic shape of V1 was determined from the boundary of the planar representation of the stria. An ellipse provided a simple parametric shape model that was a good approximation to the boundary of flattened V1. The aspect ration of the best-fitting ellipse was found to be consistent across subject, with a mean of 1.85 and standard deviation of 0.12. Optimal rigid alignment of size-normalized V1 produced greater overlap than that achieved by previous studies using different registration methods. A shape analysis of published macaque data indicated that the intrinsic shape of macaque V1 is also stereotyped, and similar to the human V1 shape. Previoud measurements of the functional boundary of V1 in human and macaque are in close agreement with these results

Asymmetry of the Frontal Aslant Tract is Associated with Lexical Decision

The frontal aslant tract (FAT) is a recently documented white matter tract that connects the inferior and superior frontal gyri with a tendency to be more pronounced in the left hemisphere. This tract has been found to play a role in language functions, particularly verbal fluency. However, it is not entirely clear to what extent FAT asymmetry is related to performance benefits in language-related tasks. In the present study, we aimed to fill this gap by examining the correlations between asymmetric micro- and macro-structural properties of the FAT and performance on verbal fluency and lexical decision tasks. The results showed no correlation between the FAT and verbal fluency; however, lexical decision was correlated with FAT laterality. Specifically, greater left lateralization in both micro- and macro-structural properties was related to faster lexical decision response times. The results were not due merely to motor or decision-making processes, as responses in a simple discrimination task showed no correlation with laterality. These data are the first to suggest a role for the FAT in mediating processes underlying lexical decision

Unravelling the Intrinsic Functional Organization of the Human Lateral Frontal Cortex: A Parcellation Scheme Based on Resting State fMRI

Human and nonhuman primates exhibit flexible behavior. Functional, anatomical, and lesion studies indicate that the lateral frontal cortex (LFC) plays a pivotal role in such behavior. LFC consists of distinct subregions exhibiting distinct connectivity patterns that possibly relate to functional specializations. Inference about the border of each subregion in the human brain is performed with the aid of macroscopic landmarks and/or cytoarchitectonic parcellations extrapolated in a stereotaxic system. However, the high interindividual variability, the limited availability of cytoarchitectonic probabilistic maps, and the absence of robust functional localizers render the in vivo delineation and examination of the LFC subregions challenging. In this study, we use resting state fMRI for the in vivo parcellation of the human LFC on a subjectwise and data-driven manner. This approach succeeds in uncovering neuroanatomically realistic subregions, with potential anatomical substrates includingBA46, 44, 45, 9 and related (sub)divisions. Ventral LFC subregions exhibit different functional connectivity (FC), which can account for different contributions in the language domain, while more dorsal adjacent subregions mark a transition to visuospatial/sensorimotor networks. Dorsal LFC subregions participate in known large-scale networks obeying an external/internal information processing dichotomy. Furthermore, we traced “families” of LFC subregions organized along the dorsal–ventral and anterior–posterior axis with distinct functional networks also encompassing specialized cingulate divisions. Similarities with the connectivity of macaque candidate homologs were observed, such as the premotor affiliation of presumed BA 46. The current findings partially support dominant LFC models

Improved Language in a Chronic Nonfluent Aphasia Patient After Treatment With CPAP and TMS

Objective: To present pretreatment and post-treatment language data for a nonfluent aphasia patient who received 2 treatment modalities: (1) continuous positive airway pressure (CPAP) for his sleep apnea, starting 1-year poststroke; and (2) repetitive transcranial magnetic brain stimulation (TMS), starting 2 years poststroke. Background: Language data were acquired beyond the spontaneous recovery period of 3 to 6 months poststroke onset. CPAP restores adequate oxygen flow throughout all stages of sleep, and may improve cognition. A series of slow, 1 Hz repetitive TMS treatments to suppress a posterior portion of right pars triangularis has been shown to improve phrase length and naming in chronic nonfluent aphasia. Method: The Boston Diagnostic Aphasia Examination and Boston Naming Test were administered pre-CPAP, and after 2 to 5 months of CPAP. These same tests were administered pre-TMS, and at 3 and 6 months post-TMS, and again 2.4 years later. Results: Post-CPAP testing showed increased Phrase Length, Auditory Comprehension, and naming Animals and Tools/Implements (Boston Diagnostic Aphasia Examination). Testing at 3 and 6 months post-TMS showed significant increase in Phrase Length, Auditory Comprehension, and Boston Naming Test compared with pre-TMS. These gains were retained at 2.4 years post-TMS. CPAP use continued throughout.Conclusions: Physiologic treatment interventions may promote language recovery in chronic aphasia

On the selection of words and oral motor responses : evidence of a response-independent fronto-parietal network

Several brain areas including the medial and lateral premotor areas, and the prefrontal cortex, are thought to be involved in response selection. It is unclear, however, what the specific contribution of each of these areas is. It is also unclear whether the response selection process operates independent of response modality or whether a number of specialized processes are recruited depending on the behaviour of interest. In the present study, the neural substrates for different response selection modes (volitional and stim- ulus-driven) were compared, using sparse-sampling functional magnetic resonance imaging, for two different response modalities: words and comparable oral motor gestures. Results demonstrate that response selection relies on a network of prefrontal, premotor and parietal areas, with the pre-supplementary motor area (pre-SMA) at the core of the process. Overall, this network is sensitive to the manner in which responses are selected, despite the absence of a medio-lateral axis, as was suggested by Goldberg (1985). In contrast, this network shows little sensitivity to the modality of the response, suggesting of a domain-general selection process. Theoretical implications of these results are discussed

A Functional MRI and Magneto/Electro Source Imaging Procedure for Cognitive and Pre-surgical Evaluation

AbstractAnalysis of normal/pathological brain activity using neuroimaging methods is necessary to avoid operation risks, and the outcome serves as prior information for surgical neuronavigation. We present an fMRI/MEG/EEG-based methodology for tasks demanding mainly sensorimotor and visual/cognitive responses. This consists of carefully selected/designed stimulation paradigms and statistical parametric mapping methods that demonstrate the practicability of these techniques for clinical applications. The results replicate known findings in the brain-imaging field, with the improvement that our analyses are restricted to grey matter tissue. The latter enhance computations, which is advantageous for the massive data analyses that are typical of clinical and radiological functional brain “checkup” services

Right Neural Substrates of Language and Music Processing Left Out: Activation Likelihood Estimation (ALE) and Meta-Analytic Connectivity Modelling (MACM)

Introduction: Language and music processing have been investigated in neuro-based research for over a century. However, consensus of independent and shared neural substrates among the domains remains elusive due to varying neuroimaging methodologies. Identifying functional connectivity in language and music processing via neuroimaging meta-analytic methods provides neuroscientific knowledge of higher cognitive domains and normative models may guide treatment development in communication disorders based on principles of neural plasticity. Methods: Using BrainMap software and tools, the present coordinate-based meta-analysis analyzed 65 fMRI studies investigating language and music processing in healthy adult subjects. We conducted activation likelihood estimates (ALE) in language processing, music processing, and language + music (Omnibus) processing. Omnibus ALE clusters were used to elucidate functional connectivity by use of meta-analytic connectivity modelling (MACM). Paradigm Class and Behavioral Domain analyses were completed for the ten identified nodes to aid functional MACM interpretation. Results: The Omnibus ALE revealed ten peak activation clusters (bilateral inferior frontal gyri, left medial frontal gyrus, right superior temporal gyrus, left transverse temporal gyrus, bilateral claustrum, left superior parietal lobule, right precentral gyrus, and right anterior culmen). MACM demonstrates an interconnected network consisting of unidirectional and bidirectional connectivity. Subsequent analyses demonstrated nodal involvement across 44 BrainMap paradigms and 32 BrainMap domains. Discussion: These findings demonstrate functional connectivity among Omnibus areas of activation in language and music processing. We analyze ALE and MACM outcomes by comparing them to previously observed roles in cognitive processing and functional network connectivity. Finally, we discuss the importance of translational neuroimaging and need for normative models guiding intervention

Structural correlates of spoken language abilities : a surface-based region-of interest morphometry study

Brain structure can predict many aspects of human behavior, though the extent of this relationship in healthy adults, particularly for language-related skills, remains largely unknown. The objective of the present study was to explore this relation using magnetic resonance imaging (MRI) on a group of 21 healthy young adults who completed two language tasks: (1) semantic fluency and (2) sentence generation. For each region of interest, cortical thickness, surface area, and volume were calculated. The results show that verbal fluency scores correlated mainly with measures of brain morphology in the left inferior frontal cortex and bilateral insula. Sentence generation scores correlated with structure of the left inferior parietal and right inferior frontal regions. These results reveal that the anatomy of several structures in frontal and parietal lobes is associated with spoken language performance. The presence of both negative and positive correlations highlights the complex relation between brain and language

A case of pure apraxia of speech after left hemisphere stroke: behavioral findings and neural correlates

IntroductionApraxia of speech (AOS) is a motor speech disorder impairing the coordination of complex articulatory movements needed to produce speech. AOS typically co-occurs with a non-fluent aphasia, or language disorder, making it challenging to determine the specific brain structures that cause AOS. Cases of pure AOS without aphasia are rare but offer the best window into the neural correlates that support articulatory planning. The goal of the current study was to explore patterns of apraxic speech errors and their underlying neural correlates in a case of pure AOS.MethodsA 67-year-old right-handed man presented with severe AOS resulting from a fronto-insular lesion caused by an ischemic stroke. The participant’s speech and language were evaluated at 1-, 3- and 12-months post-onset. High resolution structural MRI, including diffusion weighted imaging, was acquired at 12 months post-onset.ResultsAt the first assessment, the participant made minor errors on the Comprehensive Aphasia Test, demonstrating mild deficits in writing, auditory comprehension, and repetition. By the second assessment, he no longer had aphasia. On the Motor Speech Evaluation, the severity of his AOS was initially rated as 5 (out of 7) and improved to a score of 4 by the second visit, likely due to training by his SLP at the time to slow his speech. Structural MRI data showed a fronto-insular lesion encompassing the superior precentral gyrus of the insula and portions of the inferior and middle frontal gyri and precentral gyrus. Tractography derived from diffusion MRI showed partial damage to the frontal aslant tract and arcuate fasciculus along the white matter projections to the insula.DiscussionThis pure case of severe AOS without aphasia affords a unique window into the behavioral and neural mechanisms of this motor speech disorder. The current findings support previous observations that AOS and aphasia are dissociable and confirm a role for the precentral gyrus of the insula and BA44, as well as underlying white matter in supporting the coordination of complex articulatory movements. Additionally, other regions including the precentral gyrus, Broca’s area, and Area 55b are discussed regarding their potential role in successful speech production