Browsing by Author "Medel Sierralta, Vicente"

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    Dynamics of cortical computations underlying attentive states
    (2021) Medel Sierralta, Vicente; Ossandón, Tomás; Pontificia Universidad Católica de Chile. Facultad de Medicina
    Spontaneous fluctuations occur at different spatial and temporal scales in the brain. Depending on its scale, these activities can show characteristic hallmarks. From a mesoscale perspective, in spontaneous conditions, cortical neurons fire action potentials in a seemingly stochastic manner, which extrapolated to an entire population shows a dynamical state coined as the asynchronous irregular state. Interestingly, when a local population of balanced excitation and inhibition is recurrently connected, the asynchronous population generates a baseline of stochastic perturbation over the neuron’s membrane potential of that local population. These perturbations have been proposed as optimal for information computation and are associated with different states of attention at the behavioral level. Specifically, Locus-Coeruleus Noradrenergic (LC-NE) neuromodulation -which regulates brain states- has been highly implicated in the modulation of desynchronized activity. In this dissertation, we will use a modeling-driven analysis of attentional modulation of local electrophysiological desynchronization, hypothesizing that LC-NE neuromodulation shapes desynchronized background state and the balance between excitation and inhibition. We will show how the complexity of the electrophysiological signals depends on the excitation-inhibition balance of cortical activity, how it tracks behavioral performance, and how it can be related to LC-NE activity and arousal-related neuromodulation. Finally, we show how this complexity fluctuates at different spatial scales with low-dimensionality in attention, and how it is tracked by pupil diameter fluctuations -a non-invasive proxy of LC-NE activity and arousal- in a visuospatial working memory task in humans.
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    Transitions between human functional brain networks reveal complex, cost-efficient and behaviorally-relevant temporal paths
    (2020) Ramírez Mahaluf, J. P.; Medel Sierralta, Vicente; Tepper, Angeles; Alliende, L. M.; Sato, J. R.; Ossandón, Tomás; Crossley, Nicolás