Opis: Working memory is important for a number of higher cognitive functions such as problem solving, reasoning, reading and language comprehension. Moreover, working memory measures are significantly correlated with measures of intellectual abilities. Investigating the neural basis of working memory provides the opportunity to gain a deeper understanding of individual differences in general cognitive ability. This thesis aimed to elucidate the roles of brain oscillations in working memory, with a particular focus on theta and gamma frequency bands. Two techniques were employed that are best suited for the non-invasive study of brain oscillations: scalp recorded EEG and transcranial alternating current stimulation (tACS). In the first step, correlational studies were conducted followed by neuromodulatory studies in the next step. The results showed that individuals with high working memory capacity, contrasted against individuals with low working memory capacity, display stronger alpha and gamma band desynchronisation and increased coherence in the theta frequency band between fronto- parietal areas during maintenance and between frontal brain areas during retrieval. The results further demonstrated that interactions between theta and gamma frequency bands are related to individual differences in working memory capacity. The neuromodulatory studies showed that theta tACS applied over parietal brain areas can be used to enhance performance on working memory tasks, thereby providing support for the causal role of theta band oscillations in working memory. Ključne besede:working memory, brain oscillations, capacity, electroencephalograpy, tACS, theta, gamma Objavljeno: 28.07.2017; Ogledov: 360; Prenosov: 37 Celotno besedilo (3,46 MB)

Opis: Omega polynomial was proposed by Diudea (Omega Polynomial, Carpath. J. Math., 2006, 22, 43-47) to count the opposite topologically parallel edges in graphs, particularly to describe the polyhedral nanostructures. In this paper, the main definitions are re-analyzed and clear relations with other three related polynomials are established. These relations are supported by close formulas and appropriate examples. Ključne besede:mathematics, chemical graph theory, counting polynomials, Ommega polynomial, Theta polynomial, Pi polynomial, PI index, Sadhana polynomial, Cluj-Ilmenau index, CI index Objavljeno: 24.08.2017; Ogledov: 155; Prenosov: 21 Celotno besedilo (263,85 KB)