Studying Cognitive Cerebral Activity - Chapter 3: Event Related Cortical Activity

Abstract

Averaging (v_e (s)) the electrical activity v^k_e(s) recorded by each electrode while a volunteer (k) is performing a cognitive activity is a very common technique used by neuroscientist to study cortical computing. The averaging (v(s)) of (v(s)) is called Event Related activity and have provided very useful information about the brain activity supporting human cognition. In this chapter, ERA is calculated for many different cognitive tasks, ranging from language and video understanding to expert and financial decisions. The minimum duration of the EEG epoch for ERA calculation is 2 seconds and the maximum is 6 seconds. ERA was calculated for the EEG recorded after the beginning (as, for example, in language and visual understanding) or preceding the end (as, for example, in expert and financial decisions) the cognitive tasks. Polynomial regression analysis (PR) is used to disclose the patterns of activity of the studied ERAs. It is shown that large ERAs (longer than 2 seconds) may be segmented into a corresponding number of sequential ERA_i of 2 seconds of duration. PR analysis reveals that these ERA_i are, in turn composed by 4 different waves W_j having a duration around 500 Ms, each. Entrainment of the cortical oscillatory activity (see chapter 2) explains this ERA_i segmentation and their components. ERA_i and their different components are sequentially nested due to the oscillatory properties of the electrical activity of the neuronal and glial membranes (see chapter 2). It is proposed that cognitive cortical computation (COMP) is based on a sequential set of periodic processing modules (ERA_i) of nested oscillatory activity associated to these W_j waves.

Keywords: ERA. Event Related Activity, Evoked Potential, Brain Processing, Cognition, Language, Vision, Decision making