Browsing by Subject "synkronia"

Rhythmic fluctuations in the temporal activity of neuronal populations (neuronal oscillations) have been long since identified in electrophysiological recordings. Studies have also found correlations between oscillations across different brain areas during various cognitive tasks. These correlations between oscillations are called synchrony. Neuronal oscillations and synchrony are thought to be linked to behavior in at least three following ways: as a mechanism for sensory representations; gating and regulation of information flow across brain areas; and as a mechanism for storage and retrieval of information. Sensory systems continuously receive enormous amounts of information. Attention is a limited and selective process that directs an individual’s information processing resources to a subset of all the received sensory information. Stimuli can automatically capture our attention (exogenous attention) or we can willingly focus on specific stimuli (endogenous attention). Attention controls the selection of stimuli and enhances the processing of selected stimuli. Different brain networks have been found to underlie exogenous and endogenous attention. This thesis focuses on endogenous visual attention, which is a form of attention that concentrates on the attentional processing of visual information. Neuronal oscillations and synchrony appear to play a critical role in attention. Endogenous visual attention is based on fluent communication between different brain areas, especially between frontal, parietal and occipital lobes. Oscillations and synchrony gate information between areas responsible for stimulus selection and enhance stimulus processing in areas that represent the selected stimuli. Several different frequency bands have been linked to attentional processing, most notably alpha (8-14 Hz), beta (15-30 Hz) and gamma (>30 Hz) frequencies. However, aforementioned frequency bands have also been linked to other cognitive functions, e.g. to working memory. Abnormal oscillations and synchrony have also been found in certain pathophysiological states, e.g. schizophrenia and attention-deficit/hyperactivity disorder (ADHD). Future studies require more specific models and methods to achieve a unified view of oscillations and synchrony in their relation to cognitive functions and disorders.