Biology subjects

Labek, K.

Publications and source records attributed to Labek, K..

5 recordsLinked to original sources

bioRxiv2024

Cognitive effort and reward. Functional imaging of time on task and the involvement of dopaminergic and cholinergic substrates

Neuroimaging studies have identified the neural substrates associated with sustained cognitive efforts and control and their modulation by rewards. Different lines of evidence implicate the prefrontal cortex (especially the anterior cingulate cortex, ACC), dopaminergic, and cholinergic substrates in this modulation. We studied here the activity of these substrates at increasing time on task (requiring increasing levels of cognitive effort) in trials within blocks with differing reward levels. In the cortex, while peaking in the ACC, activity associated with time on task was extensive, also including activity decrements outside the default mode network, primarily involving motor and somatosensory regions. Information about reward levels was carried in the ventral striatum, consistent with its motivational role, but did not reflect trade-offs with increasing efforts during time on task. Instead, the ventral tegmental area and parts of the basal forebrain (BF) corresponding to the cholinergic Ch4 nuclei increased in activity with time on task and were sensitive to reward levels. This BF activity is consistent with a cholinergic role in driving compensatory efforts modulated by reward levels. These findings identify the BF as a neuroimaging phenotype associated with sustaining task sets and cognitive efforts.

neuroscience↗

bioRxiv2024

The neural correlates of social rejection in the cyberball paradigm: An arterial spin labelling study

Background/ObjectivesThe cyberball paradigm has been used in numerous neuroimaging studies to elicit activation in neural substrates of social exclusion, which have been interpreted in terms of activity associated with "social pain". The objectives of the study were to assess not only the replicability but also the specificity of the areas activated by this paradigm. MethodsFunctional imaging with arterial spin labelling, an approach to image longer mental states. Resultswe replicated findings of previous meta-analyses of this paradigm in the inferior frontal gyrus and ventral cingular cortex. However, these areas were also active in a watch condition (in which participants were not excluded), although less so. ConclusionsThese findings relativize a simple and specific interpretation of these areas as the neural substrates of social exclusion and social pain, as in previous studies. In a broader experimental context, similar activations have been reported by neuroimaging studies when semantic disambiguation and evaluation of action goals are required, an interpretation that may apply also to the effects elicited by this paradigm.

neuroscience↗

bioRxiv2024

The fMRI global signal and its association with the signal from cranial bone

The nature of the global signal, i.e. the average signal from sequential functional imaging scans of the brain or the cortex, is not well understood, but is thought to include vascular and neural components. Using resting state data, we report on the strong association between the global signal and the average signal from the part of the volume that includes the cranial bone and subdural vessels and venous collectors, separated from each other and the subdural space by multispectral segmentation procedures. While subdural vessels carried a signal with a phase delay relative to the cortex, the association with the cortical signal was strongest in the parts of the scan corresponding to the laminae of the cranial bone, reaching 80% shared variance in some individuals. These findings suggest that in resting state data vascular components may play a prominent role in the genesis of fluctuations of the global signal. Evidence from other studies on the existence of neural sources of the global signal suggests that it may reflect the action of multiple mechanisms (including cerebrovascular reactivity and autonomic control) concurrently acting to regulate global cerebral perfusion.

neuroscience↗

bioRxiv2021

The gradient model of brain organization in decisions involving 'empathy for pain'

Influential models of cortical organization propose a close relationship between heteromodal association areas and highly connected hubs in the default mode network. The gradient model of cortical organization proposes a close relationship between these areas and highly connected hubs in the default mode network, a set of cortical areas deactivated by demanding tasks. Here, we used a decision-making task and representational similarity analysis with classic empathy for pain stimuli to probe the relationship between high-level representations of imminent pain in others and these areas. High-level representations were co-localized with task deactivations or the transitions from activations to deactivations. These loci belonged to two groups: those that loaded on the high end of the principal cortical gradient and were associated by meta-analytic decoding with the default mode network, and those that appeared to accompany functional repurposing of somatosensory cortex in the presence of visual stimuli. In contrast to the nonspecific meta-analytic decoding of these loci, low-level representations, such as those of body parts involved in pain or of pain itself, were decoded with matching topics terms. These findings suggest that task deactivations may set out cortical areas that host high-level representations. We anticipate that an increased understanding of the cortical correlates of high-level representations may improve neurobiological models of social interactions and psychopathology.

neuroscience↗

bioRxiv2020

Segregation, connectivity, and gradients of deactivation in neural correlates of evidence in social decision making

Functional imaging studies of sensory decision making have detected a signal associated with evidence for decisions that is consistent with data from single-cell recordings in laboratory animals. However, the generality of this finding and its implications on our understanding of the organization of the fMRI signal are not clear. In the present functional imaging study, we investigated decisions in an elementary social cognition domain to identify the neural correlates of evidence, their segregation, connectivity, and their relationship to task deactivations. Besides providing data in support of an evidence-related signal in a social cognition task, we were interested in embedding these neural correlates in models of supramodal associative cortex placed at the top of a hierarchy of processing areas. Participants were asked to decide which of two depicted individuals was saddest based on information rich in sensory features (facial expressions) or through contextual cues suggesting the mental state of others (stylized drawings of mourning individuals). The signal associated with evidence for the decision was located in two distinct networks differentially recruited depending on the information type. Using the largest peaks of the signal associated with evidence as seeds in a database of connectivity data, these two networks were retrieved. Furthermore, the hubs of these networks were located near or along a ribbon of cortex located between task activations and deactivations between areas affected by perceptual priming and the deactivated areas of the default network system. In associative cortex, these findings suggest gradients of progressive relative deactivation as a possible neural correlate of the cortical organization envisaged by structural models of cortical organization and by predictive coding theories of cortical function.

neuroscience↗