Conectividad funcional asociada con procesamiento contextual en distintas poblacionesdesde trastornos motores a atletas profesionales

Abstract

Contextual processing is a cognitive ability associated with the management of relevant information in order to guide the execution of a certain task. In order to study contextual processing an experimental paradigm was used, in which subjects were presented with a series of visual stimuli and responded to target stimuli was used. A specific order of stimuli predicted the occurrence of the target stimulus, while other targets appeared in a random way. This paradigm was used to investigate how different groups of subjects recognize the predictive sequence and how they use it to facilitate target detection. During the test, apart from evaluating behavioral parameters such as reaction times and accuracy, electroencephalogram (EEG) was recorded using 64 electrodes to study the cognitive processes related to processing context. In both studies, functional connectivity between each pair of electrodes has been analyzed using the “synchronization likelihood” algorithm. Graph theory was used to characterize connectivity parameters and these were compared between the groups. The first study has examined a group of patients with Parkinson disease (PD), having taken their usual medication and a control group of healthy subjects. Both groups performed two experimental sessions, the first an implicit session where subjects were not made aware of the predictive sequence; while in the second session subjects were explicitly shown and instructed to detect the predictive sequence. Functional connectivity was compared across the two sessions (implicit and explicit) across PD patients and controls. In both sessions, a series of abstract stimuli consisting of 4 equilateral triangles with different orientation was used. A triangle with a horizontal edge and a vertex facing downwards was used as the target. The predictive sequence consisted of three triangles facing left, up and right. Both (PD and control subjects) showed faster reaction times for the predicted targets compared with random targets, in both the implicit and explicit sessions, although the difference between predicted and random targets was greater in the explicit session in both groups. Functional connectivity analysis revealed that during the visualization of the last, most informative, stimulus of the predictive sequence, PD patients showed a functional network with greater clustering, compared with controls, in the theta band. This finding was associated with weaker long – range connections between frontal, central and parietal regions in both sessions. These results suggest functional connectivity alterations during both implicit and explicit contextual processing in PD patients, within frontal top-down networks. The second study examined three groups: a professional basketball players group, a video game players group and another group of professional athletes who practice individual spoRT, in order to investigate the effects of physical exercise and dynamic decision making. Basketball players characterize the effects of the combined practice of physical exercise and constant fast decision making, while the two remaining groups exhibit these characteristics in isolation. In this experiment subjects performed two sessions of the paradigm previously described explicitly: one using abstract triangles and the other with stimuli of 4 real life images of a basketball player performing a basket shot. The three groups showed faster reaction times for predicted compared with random targets in both sessions. The functional connectivity analysis showed greater network clustering in basketball players compared with video-gamers, during the detection of random targets in the abstract session. Basketball players also showed greater clustering coefficients compared to individual athletes during the processing of the second stimulus of the predictive sequence, when basketball images were displayed. These findings were associated with stronger fronto – parietal connections in asketball players, suggesting increased allocation of attention towards task – relevant stimuli.