Biology subjects

Mooshagian, E.

Publications and source records attributed to Mooshagian, E..

3 recordsLinked to original sources

bioRxiv2026

Reaction-time asymmetry covaries with shifts in hand choice in macaques

How primates choose which hand to reach with remains poorly understood. Humans prefer the hand on the target's side of the body midline, and that preference shifts with biomechanical cost and with head and gaze direction. Earlier monkey studies used only two targets, one per side, too few to fit a psychometric function. Reaction time may also reflect the choice; in humans it is longest at the point of subjective equality (PSE), the target position at which either hand is equally likely to be chosen. We measured hand choice at ten horizontal target positions in two male rhesus macaques (Macaca mulatta) that chose freely on each trial. For peripheral targets, both animals used the hand on the same side of the body midline, with a well-defined transition in between. Displacing the hands, rotating the head, or displacing gaze to one side each moved the PSE toward that side. Reaction time was longest near the PSE. Hand displacement slowed the hand on the displaced side, and gaze displacement slowed the hand opposite the gaze. In every condition, the farther the PSE lay toward one side, the slower that side's hand was relative to the other. Macaque hand choice thus resembles human hand choice, making the macaque a tractable model for studying how the brain chooses a hand.

neuroscience↗

bioRxiv2025

A causal role for the posterior corpus callosum in bimanual coordination

Inter-areal communication is crucial for brain function. Given the largely contralateral organization of the brain, bimanual coordination likely involves interactions across the two cerebral hemispheres for motor planning and execution. The parietal reach region (PRR) is an early node in the sensorimotor transformation stream. Here we examine the contributions of direct callosal connections between left and right PRR to bimanual coordination. Using manganese-enhanced magnetic resonance imaging, we traced callosal pathways crossing the midline and found that PRR-PRR connections are restricted to the splenium. We then temporarily blocked these fibers with lidocaine while measuring behavioral performance and interhemispheric coherence. Blockade reduced task-specific PRR-PRR coherence during bimanual movements. Behaviorally, blockade sped movement initiation across tasks, consistent with an inhibitory role of interhemispheric communication, reduced the temporal synchrony of bimanual movements to a common target and reduced errors for bimanual movements to separate targets. These findings provide causal evidence that posterior callosal communication supports spatial coordination of bimanual actions but may also constrain independent limb control. Significance StatementClassic split-brain studies revealed that severing the corpus callosum impairs bimanual coordination, but the specific pathways and mechanisms remain unclear. In macaques, we transiently disrupted the posterior corpus callosum connecting left and right parietal reach regions (PRR), which encode planned contralateral arm movements. This targeted blockade reduced task-specific neural synchrony between PRRs and selectively impaired coordination when both arms reached to a common target, while improving performance when the arms moved to separate targets. Movement initiation was also sped up across tasks, consistent with an inhibitory role of interhemispheric communication. These findings provide causal evidence that posterior callosal communication enables spatially coordinated bimanual movements, extending foundational split-brain insights to defined cortical circuits in a non-human primate model.

neuroscience↗

bioRxiv2023

Inferring functional organization of posterior parietal cortex circuitry based on information flow

Many studies infer the role of neurons by asking what information can be decoded from their activity or by observing the consequences of perturbing their activity. An alternative approach is to consider information flow between neurons. We applied this approach to the Parietal Reach Region (PRR) and the Lateral Intraparietal area (LIP) in posterior parietal cortex. Two complementary methods show that, across a range of reaching tasks, information flows primarily from PRR to LIP but not vice versa. This suggests that PRR determines the spatial goals of coordinated eye and arm movements and instructs LIP of those goals. Based on these findings, we conclude that PRR and LIP operate in a parallel rather than hierarchical manner to plan arm and eye movements, respectively. Similar methodology can be applied to other areas to infer their relative relationships.

neuroscience↗