The lateral premotor cortex (PM) of the macaque monkey is an anatomically multifaceted area, which serves multiple sensorimotor and cognitive functions. While evidence for the functional organization of human premotor cortex accumulates, much less is known about the underlying anatomical properties of this brain region. We used diffusion tractography and functional magnetic resonance imaging (fMRI) to investigate whether the precentral gyrus in humans can be segregated on the basis of anatomical connectivity and of functional activation in a set of cognitive and motor tasks. Tractographic data suggested a distinction between ventral and dorsal premotor cortex, and furthermore inferior and superior subparcellation of both. Functional MRI data corroborated these four areas, showing that anatomical parcellation predicts the distribution of functional activation and vice versa (preliminary evidence). These results may encourage the application of combining diffusion tractography and fMRI in vivo in order to shed light on the correspondence of brain function and anatomy.

Anatomical and functional parcellation of the human lateral premotor cortex

An atlas of white matter anatomy, its variability, and reproducibility based on constrained spherical deconvolution of diffusion MRI

White matter integrity and structural connectivity may be altered in mild cognitive impairment (MCI), and these changes may closely reflect decline in specific cognitive domains. Multi-shell diffusion data in healthy control (HC, n = 31) and mild cognitive impairment (MCI, n = 19) cohorts were downloaded from the ADNI3 database. The data were analyzed using an advanced approach to assess both white matter microstructural integrity and structural connectivity. Compared with HC, lower intracellular compartment (IC) and higher isotropic (ISO) values were found in MCI. Additionally, significant correlations were found between IC and Montreal Cognitive Assessment (MoCA) scores in the MCI cohort. Network analysis detected structural connectivity differences between the two groups, with lower connectivity in MCI. Additionally, significant differences between HC and MCI were observed for global network efficiency. Our results demonstrate the potential of advanced diffusion MRI biomarkers for understanding brain changes in MCI. 

Analysis of Brain Structural Connectivity Networks and White Matter Integrity in Patients With Mild Cognitive Impairment

Atypical meta-memory evaluation strategy in schizophrenia patients

Conversion of concept-specific decision confidence into integrative introspection in primates.

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition.

Metacognition as the capacity of monitoring one’s own cognition operates across domains. Here, we addressed whether metacognition in different cognitive domains rely on common or distinct neural substrates with combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) techniques. After acquiring DTI and resting-state fMRI data, we asked participants to perform a temporal-order memory task and a perceptual discrimination task, followed by trial-specific confidence judgments. DTI analysis revealed that the structural integrity (indexed by fractional anisotropy) in the anterior portion of right superior longitudinal fasciculus (SLF) was associated with both perceptual and mnemonic metacognitive abilities. Using perturbed mnemonic metacognitive scores produced by inhibiting the precuneus using TMS, the mnemonic metacognition scores did not correlate with individuals’ SLF structural integrity anymore, revealing the relevance of this tract in memory metacognition. In order to further verify the involvement of several cortical regions connected by SLF, we took the TMS-targeted precuneus region as a seed in a functional connectivity analysis and found the functional connectivity between precuneus and two SLF-connected regions (inferior parietal cortex and precentral gyrus) differentially mediated mnemonic but not perceptual metacognition performance. These results illustrate the importance of SLF and a putative white-matter grey-matter circuitry that supports human metacognition.

https://www.biorxiv.org/content/biorxiv/early/2020/04/21/2020.03.17.994574.full.pdf

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition

Atypical meta-memory evaluation strategy in schizophrenia patients.

Knowing when confidence computations take place is critical for building mechanistic understanding of the neural and computational bases of metacognition. Yet, even though substantial amount of research has focused on revealing the neural correlates and computations underlying human confidence judgments, very little is known about the timing of confidence computations. Subjects judged the orientation of a briefly presented visual stimulus and provided a confidence rating regarding the accuracy of their decision. We delivered single pulses of transcranial magnetic stimulation (TMS) at different times after stimulus presentation. TMS was delivered to either dorsolateral prefrontal cortex (DLPFC) in the experimental group or to vertex in the control group. We found that TMS to DLPFC, but not to vertex, led to increased confidence in the absence of changes to accuracy or metacognitive ability. Critically, equivalent levels of confidence increase occurred for TMS delivered between 200 and 500 ms after stimulus presentation. These results suggest that confidence computations occur during a broad window that begins before the perceptual decision has been fully made and thus provide important constraints for theories of confidence generation.

/pdf/the-timing-of-confidence-computations-in-human-prefrontal-cpon7afz.pdf

Yunxuan Zheng

Papers

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition.

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition

Atypical meta-memory evaluation strategy in schizophrenia patients.

The timing of confidence computations in human prefrontal cortex