Abstract-Growing interest is devoted to understand how brain signals recorded from scalp electroencephalography (EEG) may represent unique fingerprints of individual neural activity. In this context, the present paper aims to investigate the impact of some of the most commonly used techniques to estimate functional connectivity on the ability to unveil personal distinctive patterns of inter-regional interactions. Experimental results on two publicly available datasets suggest that different functional connectivity metrics have different mechanism to detect subject specific patterns of inter-channel interactions, that it is important to consider the effect of the frequency content and that spurious connectivity values may play an important role in this context.
Index Terms-EEG, functional connectivity, biometric.
I. INTRODUCTIONHE interest towards the investigation of subject specific human characteristics that can be used to develop robust biometric systems still represents a big challenge. In this context, growing interest is devoted to understanding how brain signals recorded from scalp electroencephalography (EEG) may represent a unique fingerprint of individual neural activity. In the last few years a huge number of works have investigated the potential role of EEG signal characteristics as biometric system (about 300 new papers in the last 10 years). A detailed literature overview of the proposed methods is therefore quite challenging and in any case out of the scope of the present paper. Nevertheless, some attempts to summarize the state of the art was previously proposed in [1]-[3]. In brief, it is possible to consider the approaches proposed so far mainly organized into two fundamental categories: (i) task based and (ii) resting-state based EEG analysis. The first category is oriented on experimental setups that allow to investigate properties of the EEG signal that are strictly related to the onset of a specific stimulus. Motor (real and imagery) tasks [4], visual evoked potentials [5]- [7], auditory stimuli [8], imagined speech [9], eye blinking [10] and multiple functional brain systems [11] have been proposed so far in order to elicit individual unique responses. In contrast, the second category is mainly oriented to detect characteristic patterns of induced [18] as EEG-based biometric traits. However, it seems still evident that there exists a gap between current investigations of EEG signal as neurophysiological marker and its application in personal verification systems. In particular, it is widely accepted that each metric used to assess functional connectivity carry specific information in respect to the underlying interactions network [19].Nevertheless, the reason why these metrics convey different subject specific information has not been investigated yet.Following what reported in [16], [18], the present paper aims to investigate and compare the impact of some of the most commonly used techniques to estimate functional connectivity on the ability to detect personal unique discriminative feat...