Title: Nonlinear Feature Analysis for EEG-Based Biometric Authentication via Machine-Learning

Abstract: Among biometric recognition systems, a system using brain waves via EEG will hold a special place. The EEG signal, with its nonlinear structure, is unique to the individual and nearly impossible to replicate. In designing such a system, various signal processing and classification methods are considered. In this study, nonlinear features such as Fractal Dimension, Second Order Sample Entropy, Quantities Graph, and Visibility Graph were used, allowing the examination of the EEG signal independently of the amplitude scale. To reduce computational load, the resting state alpha waves, which are prominent features of the EEG, were focused on, and a low number (8) of electrodes were used. The obtained features were analyzed separately for each electrode, aiming to identify the most distinctive feature and electrode. The classification was performed using five different machine-learning methods. The highest accuracy was achieved by the Random Forest algorithm. The most distinctive electrode and features were identified as the Fractal Dimension of the F5 electrode and the Fractal Dimension of the Oz electrode.

Keywords: EEG, biometric, fractal dimension, quadratic sample entropy, quantiles graph, visibility graph

Başlık: Makine Öğrenmesi Yoluyla EEG Tabanlı Biyometrik Kimlik Doğrulama için Doğrusal Olmayan Özellik Analizi

Özet: Biyometrik tanıma sistemleri arasında EEG ile beyin dalgalarının kullanıldığı bir sistem özel bir yer teşkil edecektir. EEG sinyali nonlinear yapısıyla kişiye özgüdür ve taklit edilmesi neredeyse imkansızdır. Böyle bir sistemin tasarlanması aşamasında farklı sinyal işleme ve sınıflama yöntemleri ele alınmaktadır. Bu çalışmada EEG sinyalini genlik skalasından bağımsız bir şekilde incelemeye fırsat verecek doğrusal olmayan Fraktal Boyut, İkinci Dereceden Örnek Entropisi, Nicelikler Grafiği, Görünürlük Grafiği özellikleri kullanılmıştır. Hesaplama yükünü azaltmak için EEG'nin belirgin özelliklerinden olan resting state alfa dalgaları odağa alınmış ve düşük sayıda elektrot (8) kullanılmıştır. Elde edilen özellikler her bir elektrot için ayrı ayrı ele alınmış, sonuçta en büyük ayırt ediciliği gösteren özellik ve elektrotun saptanması amaçlanmıştır. 5 farklı makine öğrenmesi metoduyla sınıflama gerçekleştirilmiştir. En yüksek doğruluk Rastgele Orman algoritmasına aittir. En ayırt edici elektrot ve özellikler F5 elektrotu Fraktal Boyutu ve Oz elektrotu Fractal Boyutu özelliği olarak bulunmuştur.

Anahtar kelimeler: EEG, biometrik, fraktal boyut, ikinci dereceden örnek entropisi, nicelikler grafiği, görünürlük grafiği

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