Biology subjects

Papageorgiou, G. K.

Publications and source records attributed to Papageorgiou, G. K..

4 recordsLinked to original sources

bioRxiv2024

Functional Dichotomy of Orbitofrontal Cortex and Anterior Cingulate Cortex Subregions in Decision-Making and Brain-Body Regulation

Mood disorders are associated with complex disruptions in brain networks, including those associated with the orbitofrontal cortex (OFC) and pregenual anterior cingulate cortex (pACC). The functional contribution of the caudal OFC (cOFC) has remained largely unexplored. We investigated the functions of the cOFC and pACC in macaques performing an approach-avoidance task by the combination of multimodal recordings and electrical microstimulation (EMS) of the cOFC. We assessed neural, autonomic and behavioral responses. We found the cOFC to be sensitive to both positive and negative stimuli, whereas the pACC was singificantly more active during aversive outcomes. EMS of the cOFC increased avoidance behavior, suggesting a causal role for the OFC subdivision in cost-benefit decision-making. Physiological measurements were positively correlated with behavioral patterns, emphasizing body-brain synchronization during emotionally significant decision-making. We suggest that the cOFC contributes to inducing pessimistic states, thereby making its dysfunction a potential contributor to the etiology of mood disorders.

neuroscience↗

bioRxiv2019

Microstimulation of primate neocortex targeting striosomes induces negative decision-making

Affective judgment and decision-making are strongly modulated by the pregenual anterior cingulate (pACC) and caudal orbitofrontal (cOFC) cortical regions. By combining MRI-guided electrical microstimulation with viral tracing methods in non-human primates, we demonstrate that circumscribed pACC and cOFC microstimulation sites that induce negative decision-making preferentially project to striosomes in the anterior striatum. These results outline a behaviorally important circuit from pACC/cOFC to striosomes causally modulating decision-making under emotional conflict.

neuroscience↗

bioRxiv2019

Behavioral flexibility is associated with changes in structure and function distributed across a frontal cortical network in macaques

One of the most influential accounts of central orbitofrontal cortex- that it mediates behavioral flexibility - has been challenged by the finding that discrimination reversal in macaques -the classic test of behavioral flexibility -is unaffected when lesions are made by excitotoxin injection rather than aspiration. This suggests the critical brain circuit mediating behavioral flexibility in reversal tasks lies beyond the central orbitofrontal cortex. To determine its identity a group of nine macaques were taught discrimination reversal learning tasks and its impact on grey matter was measured. Magnetic resonance imaging scans were taken before and after learning and compared with scans from two control groups each comprising ten animals. One control group learned similar discrimination tasks but which lacked any reversal component and the other control group engaged in no learning. Grey matter changes were prominent in posterior orbitofrontal cortex/anterior insula but also were found in three other frontal cortical regions: lateral orbitofrontal cortex (12o), cingulate cortex, and lateral prefrontal cortex. In a second analysis, neural activity in posterior orbitofrontal cortex/anterior insula was measured at rest and its pattern of coupling with the other frontal cortical regions was assessed. Activity coupling increased significantly in the reversal learning group in comparison to controls. In a final set of experiments we used similar structural imaging procedures and analyses to demonstrate that aspiration lesion of central orbitofrontal cortex, of the type known to affect discrimination learning, affected structure and activity in the same frontal cortical circuit. The results identify a distributed frontal cortical circuit associated with behavioral flexibility.

neuroscience↗

bioRxiv2018

The macaque anterior cingulate cortex translates counterfactual choice value into actual behavioral change

The neural mechanisms mediating sensory-guided decision making have received considerable attention but animals often pursue behaviors for which there is currently no sensory evidence. Such behaviors are guided by internal representations of choice values that have to be maintained even when these choices are unavailable. We investigated how four macaque monkeys maintained representations of the value of counterfactual choices - choices that could not be taken at the current moment but which could be taken in the future. Using functional magnetic resonance imaging, we found two different patterns of activity co-varying with values of counterfactual choices in a circuit spanning hippocampus, anterior lateral prefrontal cortex, and anterior cingulate cortex (ACC). ACC activity also reflected whether the internal value representations would be translated into actual behavioral change. To establish the causal importance of ACC for this translation process, we used a novel technique, Transcranial Focused Ultrasound Stimulation, to reversibly disrupt ACC activity.

neuroscience↗