نوع مقاله: مقاله کامل پژوهشی

نویسندگان

1 کارشناسی مهندسی پزشکی، گروه مهندسی پزشکی، دانشکده فنی و مهندسی، دانشگاه اصفهان، اصفهان

2 استادیار، گروه مهندسی پزشکی، دانشکده فنی و مهندسی، دانشگاه اصفهان، اصفهان

10.22041/ijbme.2017.65746.1226

چکیده

پتانسیل برانگیختة بینایی حالت دائمی (SSVEP)، به­صورت گسترده در پیاده­سازی واسط­های مغز-رایانه استفاده شده است، با این‌حال، دستیابی به محرک­های بینایی که پاسخ SSVEP مناسبی را ایجاد کنند و درعین‌حال به کمترین خستگی چشم منجر شوند، یک چالش تحقیقاتی به­روز است. در این مطالعه، شکل موج­های سینوسی، مربعی، دندان‌اره‌ای، جمع دو سینوسی، و مدولاسیون فرکانس، با استفاده از یک سخت‌افزار اختصاصی توسط LED و شکل­های دایره، حلقه و دو مستطیل چشمک­زن با فاز مخالف، با استفاده از نرم‌افزار Cogent روی صفحه LCD تولید شدند. با آزمایش روی 12 نفر، قدرت پاسخ و هم­چنین سطح خستگی چشم در نگاه کردن به محرک­ها، مقایسه شدند. نتایج آزمایش­ها با محرک­های تولیدشده توسط LED، نشان داد که قدرت پاسخ برای محرک به‌صورت جمع دو سینوسی، به‌طور معناداری کمتر از سایر محرک­ها بود و پاسخ سایر محرک‌ها، تفاوت معناداری نداشتند. دراین ‌بین، تحریک با مدولاسیون فرکانس، کمترین سطح خستگی چشم را به دنبال داشت؛ بنابراین، اگر هر دو معیار سطح خستگی و قدرت پاسخ برای مقایسه در‌نظر‌گرفته شوند، تحریک با استفاده از مدولاسیون فرکانس با قدرت پاسخ (2 pV)4/17 و میانگین امتیاز سطح خستگی 58/1، بهترین نتیجه را به دنبال داشت. نتایج آزمایش­ها با محرک­های تولیدشده روی LCD، نشان داد تحریک به شکل دایره، حلقه و مستطیل، به‌ترتیب بیشترین قدرت پاسخ را داشته­اند؛ اما هر سه تحریک، در سطح خستگی آزاردهنده برای چشم بودند. اگرچه محرک دایره­ای شکل (با قدرت پاسخ 2 pV7/26 و میانگین امتیاز سطح خستگی 8/3)، دامنة پاسخ بالایی داشته است؛ اما پیشنهاد نمی­شود که از محرک­های گرافیکی و دایره­ای‌شکل برای توسعة واسط­های مغز-رایانه استفاده شود؛ چون مؤلفة سطح خستگی پایین را تأمین نمی­کند. در‌مجموع، پیشنهاد می­شود در توسعة واسط­های مغز-رایانه مبتنی‌بر SSVEP، از شکل موج­های مدوله­شده توسط مدولاسیون فرکانس استفاده شود، تا ضمن بهره بردن از دامنة پاسخ مناسب، خستگی چشم کاربر در سطح پایینی نگه داشته شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Comparison of Several Visual Stimuli for Development of a Brain Computer Interface Based on Steady-State Visual Evoked Potentials

نویسندگان [English]

  • Mohsen Keshtkar 1
  • Amin Mahnam 2
  • Pegah Poladian 1

1 BSc, Department of Biomedical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran

2 2Assistant Professor, Department of Biomedical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran

چکیده [English]

Steady State Visual Evoked Potentials (SSVEP) have been widely used in development of Brain Computer Interfaces (BCI). However, it is still a research challenge to have visual stimuli which provide strong SSVEP response while produce little eye fatigue. In this study, rectangular, sinosoidal, sawtooth waveforms applied to a LED were compared with sum of two sinusoidals and a frequency modulated waveform to determine the most appropriate visual stimulus for realization of a BCI system. Moreover, circular, ring and anti-phase two rectangular flickers were generated by Cogent toolbox on a laptop screen and compared. Experiments were performed on 12 participants to determine the SSVEP response and eye fatigue corresponding to each of these visual stimuli. Experiments with the waveforms demonstrate that sum of two sine waves generated significantly lower SSVEP amplitude, but the responses for other four waveforms were not significantly different. On the other hand, the frequency modulated waveform resulted in the least eye fatigue significantly lower from other waveforms. Therefore, considering both criteria, frequency modulated waveform can provide superor performance in a BCI system with an average response of 17.3 pV2 and 1.58 fatigue level in a 1-4 fatigue scale.
Experiments with visual stimuli on LCD showed that circular stimuli provided highest and anti-phase rectangular the lowest response. But all of them produced high levels of eye fatigue. Although, Circular stimuli had the highest power (26.7pV2) but due to its related high eye fatigue (3.8) it is not recommended for practical applications. In conclusion it is recommended to use frequency modulated visual stimuli for development of practical BCI systems to satisfy both strong response and low eye fatigue criteria.

کلیدواژه‌ها [English]

  • Steady-State Visual Evoked Potentials
  • Eye Fatigue
  • Repetitive Visual Stimulus
  • Waveform
  • Frequency Modulation

 

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