Abstract
Visual exploration is related to activity in the hippocampus (HC) and/or extended medial temporal lobe system (MTL), is influenced by stored memories, and is altered in amnesic cases. An extensive set of polysynaptic connections exists both within and between the HC and oculomotor systems such that investigating how HC responses ultimately influence neural activity in the oculomotor system, and the timing by which such neural modulation could occur, is not trivial. We leveraged TheVirtualBrain, a software platform for large-scale network simulations, to model the functional dynamics that govern the interactions between the two systems in the macaque cortex. Evoked responses following the stimulation of the MTL and some, but not all, subfields of the HC resulted in observable responses in oculomotor regions, including the frontal eye fields, within the time of a gaze fixation. Modeled lesions to some MTL regions slowed the dissipation of HC signal to oculomotor regions, whereas HC lesions generally did not affect the rapid MTL activity propagation to oculomotor regions. These findings provide a framework for investigating how information represented by the HC/MTL may influence the oculomotor system during a fixation and predict how HC lesions may affect visual exploration.
Highlights
Memory influences ongoing active exploration of the visual environment (Hannula et al, 2010)
We modeled the influence of HC/medial temporal lobe system (MTL) activity on the oculomotor system using a connectomebased approach using TheVirtualBrain
A preponderance of evidence has demonstrated a correlation between HC/MTL neural activity and oculomotor behavior (Hannula et al, 2010; Killian, Potter, & Buffalo, 2015; Liu et al, 2017), but research had not shown whether HC/MTL activity can reach the oculomotor system in time to influence the preparation of a saccade
Summary
Memory influences ongoing active exploration of the visual environment (Hannula et al, 2010). A. Simulated dynamics of hippocampal responses in oculomotor regions. Hippocampus: A region within the medial temporal lobe of the brain that has a critical role in the formation of memory representations that consist of the relations among distinct elements. Medial temporal lobe: A collection of neural regions that includes the hippocampus, subicular complex, and surrounding entorhinal cortex, parahippocampal cortex, and perirhinal cortex, which collectively support cognitive functions such as perception, navigation, and memory. Entails the active process of alternating ballistic movements of the eyes (saccades)and pauses by the eyes in order to inspect regions in space (gaze fixations)
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