Biology subjects

Margulies, D.

Publications and source records attributed to Margulies, D..

22 records · Page 2Linked to original sources

bioRxiv2020

Missing the forest because of the trees: Slower alternations during binocular rivalry are associated with lower levels of visual detail

Conscious awareness of the world fluctuates, either through variation in the quality with which we perceive the environment, or, when attention switches to information generated using imagination rather than the external environment. Our study combined individual differences in experience sampling, psychophysical reports of perception, and neuroimaging descriptions of structural connectivity, to better understand these changes in conscious awareness. In particular, we (a) examined if aspects of ongoing thought, as measured by multi-dimensional experience sampling during a sustained attention task, are associated with the white matter fibre organization of the cortex as reflected by their relative degree of anisotropic diffusion, and (b) whether these neuro-cognitive descriptions of ongoing experience are related to a more constrained measure of visual consciousness provided by the analysis of bistable perception during binocular rivalry. Individuals with greater fractional anisotropy (FA) in right hemisphere white matter regions involving the inferior fronto-occipital fasciculus, the superior longitudinal fasciculus and the cortico-spinal tract, described their ongoing thoughts as lacking external details. Subsequent analysis indicated that the combination of low FA in these right hemisphere regions, with reports of high level external details, was associated with the shortest periods of dominance during binocular rivalry. Since variation in binocular rivalry reflects differences between bottom-up and top-down influences on vision, our study suggests that reports of ongoing thoughts with vivid external details may occur when conscious precedence is given to bottom-up representation of perceptual information and that this may partly be rooted in the white matter fibre organization of the cortex.

neuroscience↗

bioRxiv2018

Dissociations between microstructural and functional hierarchies within regions of transmodal cortex

While the role of cortical microstructure in organising neural function is well established, it remains unclear how structural constraints can give rise to more flexible elements of cognition. While non-human primate research has demonstrated a close structure-function correspondence, the relationship between microstructure and function remains poorly understood in humans, in part because of the reliance on post mortem analyses which cannot be directly related to functional data. To overcome this barrier, we developed a novel approach to model the similarity of microstructural profiles sampled in the direction of cortical columns. Our approach was initially formulated based on an ultra-high-resolution 3D histological reconstruction of an entire human brain and then translated to myelin-sensitive MRI data in a large cohort of healthy adults. This novel method identified a system-level gradient of microstructural differentiation traversing from primary sensory to limbic regions that followed shifts in laminar differentiation and cytoarchitectural complexity. Importantly, while microstructural and functional gradients described a similar hierarchy, they became increasingly dissociated in transmodal default mode and fronto-parietal networks. Meta analytic decoding of these topographic dissociations highlighted involvement in higher-level aspects of cognition such as cognitive control and social cognition. Our findings demonstrate a relative decoupling of macroscale functional from microstructural gradients in transmodal regions, which likely contributes to the flexible role these regions play in human cognition.

neuroscience↗

bioRxiv2017

Scaffolding imagination: A role for medial frontal cortex in the expression of off-task thought

We often think about people, places and events that are outside of our immediate environment. Although prior studies have explored how we can reduce the occurrence of these experiences, the neurocognitive process through which they are produced are less understood. The current study builds on developmental and evolutionary evidence that language helps organise and express our thoughts. Behaviorally, we found the occurrence of task unrelated thought (TUT) in easy situations was associated with thinking in words. Using experience sampling data, in combination with online measures of neural function, we established that activity in a region of anterior cingulate cortex / medial-prefrontal cortex (mPFC) tracked with changes in the expression of TUT. This region is at the intersection of two mPFC clusters identified through their association with variation in aspects of spontaneous thought: thinking in words (dorsal) and mental time travel (ventral). Finally, using meta-analytic decoding we confirmed the dorsal/ventral distinction within mPFC corresponding to a functional difference between domains linked to language and meaning and those linked to memory and scene construction. This evidence suggests a role for mPFC in the expression of TUT that may emerge from interactions with distributed neural signals reflecting processes such as language and memory.

animal behavior and cognition↗

bioRxiv2017

Isolated from input: Transmodal cortex in the default mode network supports perceptually-decoupled and conceptually-guided cognition

The default mode network supports a variety of mental operations such as semantic processing, episodic memory retrieval, mental time travel and mind-wandering, yet the commonalities between these functions remains unclear. One possibility is that this system supports cognition that is independent of the immediate environment; alternatively or additionally, it might support higher-order conceptual representations that draw together multiple features. We tested these accounts using a novel paradigm that separately manipulated the availability of perceptual information to guide decision-making and the representational complexity of this information. Using task based imaging we established regions that respond when cognition combines both stimulus independence with multi-modal information. These included left and right angular gyri and the left middle temporal gyrus. Although these sites were within the default mode network, they showed a stronger response to demanding memory judgements than to an easier perceptual task, contrary to the view that they support automatic aspects of cognition. In a subsequent analysis, we showed that these regions were located at the extreme end of a macroscale gradient, which describes gradual transitions from sensorimotor to transmodal cortex. This shift in the focus of neural activity towards transmodal, default mode, regions might reflect a process of isolation from specific sensory inputs that enables conceptually rich cognitive states to be generated in the absence of input.\n\nHighlights O_LIBrain regions supporting meaning overlap with stimulus independence.\nC_LIO_LIBilateral angular gyri and left MTG respond strongly to both features of cognition.\nC_LIO_LIThese patterns reflect a shift in activity towards regions of transmodal cortex.\nC_LIO_LIComplex memory representations may emerge in cortical areas distant from input.\nC_LI

neuroscience↗