The human brain shows great flexibility to adjust itself to dynamically ever-changing environment. Despite more than 100 years of cognitive brain research, the dynamical aspect of cognitive process has remained poorly understood compared to the static aspect of that. This dissertation concerns the dynamic character and functional significance of periodically forced synchronization in visual attention and binocular rivalry. The hypotheses, experimental paradigms, data analyses, and interpretation of the results were inspired by recent insights from physics and neuroscience - most notable the theory of synchronization and the phenomenon of stochastic resonance whose applicability to cognitive processes is explained. In the first and the second electroencephalography (EEG) experiment, we show that voluntary sustained visual attention multiplicatively increases the stimulus-location selective population electrophysiological activity by monitoring frequency-tagged steady-state visual evoked potentials (SSVEP) in human brain. Furthermore, analyses of inter-trial phase coherence show that this attentional response gain is at least partially due to increased synchronization of SSVEPs to stimulus flicker. Finally, it is revealed that the harmonic-based topographic difference exists in that the scalp distribution of the fundamental harmonic is central/bilateral and that of the second harmonic is contralateral. In the third behavioral experiment, we demonstrate quantitative evidence of stochastic resonance in binocular rivalry by subjecting binocular rivalry to weak periodic contrast modulations spanning a range of frequencies. We propose that the experimental findings in the frequency-locked SSVEP activities - the multiplicative response gain in SSVEPs by sustained visual attention, the harmonic-dependent topographic differences - and the stochastic resonance in binocular rivalry may find a unifying explanation within the theory of synchronization. This theory offers a general mechanism for the emergence of collective dynamics in large networks with many units adjusting a given property of their motion due to a suitable coupling configuration, or to an external forcing. Based on the above results, we conjecture that a mechanism of synchronization in nonlinear dynamical systems may be a general organizing principle of great importance for cognitive processes and account for how we perceive and react to the outside world.

Last modified

• 09/07/2018

Creator

• Yee Joon Kim

DOI

• https://doi.org/10.21985/N2MM9Q

Subject

• Psychology

Keyword

• Psychology

Date created

• 2008-05-07

Resource type

• Dissertation

Rights statement

• In Copyright