Electroencephalography (EEG)-derived markers to Measure Components of Attention Processing

Although extensively studied for decades, attention system remains an interesting challenge in neuroscience field. The Attention Network Task (ANT) has been developed to provide a measure of the efficiency for the three attention components identified in the Posner’s theoretical model: alerting, orienting and executive control. Here we propose a study on 15 healthy subjects who performed the ANT. We combined advanced methods for connectivity estimation on electroencephalographic (EEG) signals and graph theory with the aim to identify neuro-physiological indices describing the most important features of the three networks correlated with behavioral performances. Our results provided a set of band-specific connectivity indices able to follow the behavioral task performances among subjects for each attention component as defined in the ANT paradigm. Extracted EEG-based indices could be employed in future clinical applications to support the behavioral assessment or to evaluate the influence of specific attention deficits on Brain Computer Interface (BCI) performance and/or the effects of BCI training in cognitive rehabilitation applications. INTRODUCTION Attention is fundamental for human cognitive processing. As such, it includes a wide class of processes related with the ability of a subject to interact with the external environment. According to Posner’s theoretical model [1], this is possible through a sustained state of alertness (alerting), the selection of the important information in a noisy context (orienting) and the ability to control a situation and solve conflicts (executive control). When the complex mechanism at the basis of attention is altered, e.g. following a stroke event, consequences may affect a wide range of behavioural and social aspects. Several neuroimaging and neurophysiological studies have employed the so-called Attention Network Task (ANT), a behavioural task which allows to disentangle the three components (alerting, orienting and executive control) as described by Fan et al. in [2]. The available evidences indicate that the three attention components are independent [3], involve different anatomical areas (functional magnetic resonance imaging, fMRI, studies) [4] and each of them has a distinct oscillatory activity and time course (EEG study) [5]. In this study, we applied modern methodologies for effective connectivity estimation and graph theory approaches with the aim to define stable and reliable descriptors of the dynamic brain circuits underpinning the attentional components in terms of directed relationships between the brain areas and their frequency content. Currently available brain connectivity studies on attention are based on structural networks (anatomical connectivity) [6] or functional networks extracted from fMRI data [7]. We were interested in extracting markers of the brain circuits elicited by the ANT performed by healthy volunteers while recording high density EEG (hdEEG) and thus, exploiting its high temporal resolution, low invasiveness and cost-effective. To this purpose we explore whether connectivity-based indices would correlate with behavioural data in order to strengthen their relevance as measure of attention processing for future applications. [8], [9]. MATERIALS AND METHODS Experimental Design: Data (60 EEG channels + 4 EOG channels, reference at linked mastoids and ground at Fpz, Brain Products) were recorded from 15 healthy volunteers (10 female, age 27.2 ± 2.5) during the execution of the ANT [5] (Fig.1). They had no history of neurological or psychiatric disorders. The experimental protocol was approved by the local Ethical Committee. Participants were seated in front of a computer screen; a row of 5 black arrows pointing left or right was presented in the middle part of the screen. Subjects were asked to indicate the direction of the central arrow (target stimulus) as quickly and accurately as possible with the left arrow keyboard or the right arrow keyboard button according to the direction of the target, using their right hand. Trials were defined as Congruent if the 4 lateral flankers and the central arrow had the same direction, Incongruent if the flankers pointed at the opposite direction. In addition there were three cue (an asterisk sign) conditions: No cue, Center cue (in the center of the screen for alerting), and Spatial cue (at the target location, above or below a fixation cross, for alerting plus orienting) [3]. The timeline of the paradigm is showed in Fig.1. The contrast between the different experimental conditions (72 trials each condition) allowed to extract the three attention components: i) Center cue and No cue conditions define the alerting, ii) Spatial cue and Center Proceedings of the 7th Graz Brain-Computer Interface Conference 2017 DOI: 10.3217/978-3-85125-533-1-04