Biology subjects

Frank, S. M.

Publications and source records attributed to Frank, S. M..

5 recordsLinked to original sources

bioRxiv2025

Excitatory signal processing in early visual areas based on task-relevance and perceptual salience modulates visual perceptual learning

Adaptive visual perceptual learning (VPL) should occur primarily for visual signals relevant to an observers task but not for task-irrelevant signals. However, it is unclear which neural mechanisms reduce VPL for task-irrelevant signals. Here, we repeatedly exposed participants to a task-irrelevant visual signal (coherent motion in one direction) that was perceptually salient (suprathreshold for coherent motion detection) or weak (near threshold for coherent motion detection). The processing of the task-irrelevant signal in early visual areas during the first and final exposure sessions was measured using functional magnetic resonance spectroscopy (fMRS). The behavioral results showed that discrimination sensitivity for the exposed coherent motion direction increased to a greater extent after near threshold than after suprathreshold exposure. The fMRS results showed that excitatory processing in early visual areas, as reflected in the concentration of glutamate, was lower during suprathreshold than near threshold exposure. The lower the level of excitatory processing in the first exposure session, the more deteriorated the discrimination sensitivity for the coherent motion direction after suprathreshold exposure. When the coherent motion direction was rendered task-relevant, levels of glutamate in early visual areas reversed such that excitatory processing was greater when the coherent motion direction was presented suprathreshold than near threshold. This suggests that the level of excitatory processing in early visual areas changes with the task relevance and perceptual salience of a visual signal, which may modulate the extent of VPL for this signal when it is repeatedly exposed. Significance StatementVisual perceptual learning (VPL) enhances the efficiency in processing visual signals and is fundamental to the brains ability to adapt to changing environmental conditions. However, little is known about neural mechanisms that reduce VPL, although such mechanisms are crucial for adaptive VPL, which occurs primarily for visual signals relevant to an observers task but not for task-irrelevant signals. Here we find that early visual areas decrease excitatory processing for a salient task-irrelevant visual signal, which is associated with reduced VPL for this signal. This suggests, first, that a decrease of excitatory activity may be a mechanism that reduces VPL for salient task-irrelevant signals and, second, that this mechanism exerts its effect already at an early stage of cortical visual processing.

neuroscience↗

bioRxiv2025

Goal-directed visual information processing with GABAergic inhibition in parietal cortex

Goal-directed visual information processing involves tracking relevant visual signals (targets) over space and time. However, goal-irrelevant visual signals (distractors) can interfere with the tracking of targets. The neural mechanisms, which promote the tracking of targets in the challenge of interference from distractors remain elusive. Here, we used time-resolved functional magnetic resonance spectroscopy (fMRS) to measure concentrations of {gamma}-aminobutyric acid (GABA), a chief inhibitory neurotransmitter, and glutamate, a chief excitatory neurotransmitter, in parietal and visual cortex while participants performed a visual tracking task for targets among distractors. We found that the more targets had to be tracked, the greater the concentrations of GABA and glutamate in parietal cortex. In visual cortex only the concentration of glutamate increased with the number of targets. Concentration changes of GABA and glutamate only in parietal cortex were differentially associated with tracking performance: Better target tracking was associated with greater increase in GABA concentration and smaller increase in glutamate concentration. The results of control experiments showed that this differential association between tracking performance and metabolite changes in parietal cortex reflected individual differences in distractor suppression: participants with better distractor suppression during tracking tended to have greater increase in GABA concentration and smaller increase in glutamate concentration. This suggests that target-distractor interference during tracking is minimized by GABAergic suppression of goal-irrelevant distractors in parietal cortex, thereby promoting goal-directed visual information processing.

neuroscience↗

bioRxiv2023

Learning of the same task subserved by substantially different mechanisms between patients with Body Dysmorphic Disorder and healthy individuals

It is generally believed that learning of a perceptual task involving low-level neuronal mechanisms is similar between individuals. However, it is unclear whether this assumption also applies to individuals with psychiatric disorders that are known to have altered brain activation during visual processing. We investigated this question in patients with body dysmorphic disorder (BDD), a psychiatric disorder characterized by distressing or impairing preoccupation with nonexistent or slight defects in ones physical appearance, and in healthy controls. Participants completed six training sessions on separate days on a visual detection task for human faces with low spatial frequency (LSF) components. Brain activation during task performance was measured with functional magnetic resonance imaging (fMRI) on separate days prior to and after training. The behavioral results showed that both groups of participants improved on the visual detection task to a similar extent through training. Despite this similarity in behavioral improvement, neuronal changes in the Fusiform Face Area (FFA), a core cortical region involved in face processing, with training were substantially different between groups. First, activation in the right FFA for LSF faces relative to High Spatial Frequency (HSF) faces that were used as an untrained control increased after training in BDD patients but decreased in controls. Second, resting state functional connectivity between left and right FFAs decreased after training in BDD patients but increased in controls. Contrary to the assumption that learning of a perceptual task is subserved by the same neuronal mechanisms across individuals, our results indicate that the neuronal mechanisms involved in learning of a face detection task differ fundamentally between patients with BDD and healthy individuals. The involvement of different neuronal mechanisms for learning of even simple perceptual tasks in patients with BDD might reflect the brains adaptations to altered functions imposed by the psychiatric disorder.

neuroscience↗

bioRxiv2022

Efficient learning in children with rapid GABA boosting after training

It is unclear why and how children learn more efficiently than adults, although inhibitory systems, which play an important role in stabilizing learning, are immature in children. Here, we found that despite a lower baseline concentration of {gamma}-aminobutyric acid (GABA) in early visual cortical areas in children (8 to 11 years old) than adults (18 to 35 years old), children exhibited a rapid boost of GABA immediately after visual training, whereas the concentration of GABA in adults remained unchanged after training. Moreover, behavioral experiments showed that children stabilized visual learning much faster than adults, showing rapid development of resilience to retrograde interference. These results together suggest that inhibitory systems in childrens brains are more dynamic and adapt more quickly to stabilize learning than in adults. One Sentence SummaryChildren learn more efficiently than adults due to faster stabilization of learning with rapid GABA boosting after training.

neuroscience↗

bioRxiv2019

Perceptual learning of lesions in mammograms induced by response feedback during training

Detecting subtle lesions in mammograms indicative of early breast cancer usually requires years of experience. Well-designed training paradigms could be a strong tool for promoting perceptual learning (PL) with rapid and long-lasting improvement in detectability of these subtle mammographic lesions. Given that PL occurs without feedback about the accuracy of subjects responses, the role of feedback has been completely ignored in clinical applications of PL. However, in this study, we found that the contents of the feedback profoundly and differentially influence the formation and retention of PL to detect calcification and architectural distortion lesions, two types of mammographic lesions that are frequently missed in mammographic screenings. We trained subjects to detect one type of lesion in a mammogram and manipulated the content of the response feedback during training for 3 groups (no feedback, correctness only, and both correctness and location of the lesion). We found that PL occurred for both lesions when both correctness and location feedback were provided. PL also occurred for calcifications but not for distortions when only correctness was provided. No learning occurred without feedback for either lesion. A retest conducted six months later showed that PL was retained only in the group with both correctness and location feedback for both types of lesions. In contrast to the general consensus of basic PL studies, our results demonstrate that the content of the response feedback is a determining factor in forming and retaining PL to detect mammographic lesions.

neuroscience↗