Biology subjects

Musa, L.

Publications and source records attributed to Musa, L..

3 recordsLinked to original sources

bioRxiv2026

Modular Integration of Auditory Instructions and Visual Cues into the Cortical Reach Network

Humans often need to integrate bottom-up stimulus attributes (e.g., object shape) with top-down instructions (e.g., how to pick it up) for adaptive behavior. To investigate how such cues are integrated into the cortical reach network, we employed an fMRI paradigm where participants viewed a cube to their left or right (visual cue) and were verbally instructed to use a horizontal or vertical grip (auditory cue), in varying order. Univariate voxel-wise and region-of-interest analysis confirmed the expected order-dependent activation of sensory regions, followed by robust parietofrontal activation. Graph-theory analysis revealed two significant subnetworks (modules): an Occipital-Parietal module (likely integrating the visual cue into the reach plan) and a Temporal-Frontal module (likely integrating the auditory cue into the grasp plan), both converging in somatomotor cortex. Cue-order influenced modularity, i.e., the module corresponding to the first cue tended to dominate contralateral motor cortex, and conversely a classification model decoded cue-order based on modularity. Local network hubs were order-independent and occupied traditional reach areas, whereas global (between module) hubs were order-dependent and more distributed. Overall, these results suggest that multisensory integration of top-down and bottom-up cues for action is a network phenomenon that relies on both lateral and serial communication between parallel sensorimotor modules.

neuroscience↗

bioRxiv2025

Spatial task instructions and global activation trends influence functional modularity in the cortical reach network

Humans can be instructed to ignore visual cues or use them as landmarks for aiming movements (Musa et al. 2024), but it is not known how such allocentric cues interact with egocentric target codes and general planning activity to influence cortical network properties. To answer these questions, we applied graph theory analysis (GTA) to a previously described fMRI dataset (Chen et al. 2014). Participants were instructed to reach toward targets defined in egocentric or landmark-centered (allocentric) coordinates. During Egocentric pointing, cortical nodes clustered into four bilateral modules with correlated BOLD signals: a superior occipital-parietal / somatomotor module, an inferior parietal / lateral frontal module, a superior temporal / inferior frontal module, and an inferior occipital-temporal / prefrontal module. The Allocentric task showed only three modules, in part because inferior occipital nodes were incorporated into the superior occipital-parietal / somatomotor module. Both tasks engaged local (within module) and global (between module) cortical hubs, but the Allocentric task recruited additional hubs associated with allocentric visual codes and ego-allocentric integration. Removing reach-related activation trends reduced global synchrony and increased clustering, specifically diminishing dorsoventral coupling in the allocentric task. Cross-validated decoding confirmed that modularity provided the best predicter of task type and suggest that temporal / parietal modules spanning prefrontal cortex play an important role in task instruction. These results demonstrate that activation trends related to motor plans influence global network integration, whereas task instructions influence intermediate / local network properties, such as the modular integration and hub recruitment observed in our Allocentric task. HighlightsO_LIThe study explores how egocentric and allocentric cues affect cortical networks. C_LIO_LIGraph theory analysis (GTA) was applied to fMRI data from pointing tasks. C_LIO_LIEgocentric pointing formed four cortical modules; allocentric formed three. C_LIO_LIAllocentric tasks recruited additional hubs for dorsal-ventral integration. C_LIO_LIRemoving reach-related activation trends reduced global synchrony in the allocentric task. C_LI

neuroscience↗

bioRxiv2024

Instruction Alters The Influence Of Allocentric Landmarks In A Reach Task

Allocentric landmarks have an implicit influence on aiming movements, but it is not clear how an explicit instruction (to aim relative to a landmark) influences reach accuracy and precision. Here, 12 participants performed a task with two instruction conditions (egocentric vs. allocentric), but with similar sensory and motor conditions. Participants fixated gaze near the centre of a display aligned with their right shoulder while a target stimulus briefly appeared alongside a visual landmark in one visual field. After a brief mask/memory delay the landmark then re-appeared at a different location (same or opposite visual field), creating an ego/allocentric conflict. In the egocentric condition, participants were instructed to ignore the landmark and point towards the remembered location of the target. In the allocentric condition, participants were instructed to remember the initial target location relative to the landmark and then reach relative to the shifted landmark (same/opposite visual field). To equalize motor execution between tasks, participants were instructed to anti-point (point to the visual field opposite to the remembered target) on 50 % of the egocentric trials. Participants were more accurate, precise, and quicker to react in the allocentric condition, especially when pointing to the opposite field. We also observed a visual field effect, where performance was worse overall in the right visual field. These results suggest that when egocentric and allocentric cues conflict, explicit use of the visual landmark provides better reach performance than reliance on noisy egocentric signals. Such instructions might aid rehabilitation when the egocentric system is compromised by disease or injury. HighlightsO_LI12 participants reached to remembered targets in the presence of a visual landmark C_LIO_LIParticipants were instructed to ignore, or point relative to, the landmark C_LIO_LIThe landmark instruction improved reaction time, precision, and accuracy C_LIO_LIThese effects were stronger when pointing was cued toward the opposite visual field C_LIO_LIKnowledge of these rules might be used to enhance performance or in rehabilitation C_LI

neuroscience↗