뇌-컴퓨터 인터페이스 (brain computer interface)

Electrophysiological vs hemodynamic methods

(1) 뇌 전기신호

Electroencephalography (EEG) - 뇌파

두뇌를 구성하는 신경세포들의 전기적 활동을 두피에서 전극을 통해 간접적으로 측정할 수 있는 전기신호

Electrocorticography (ECoG) - 뇌피질전도

전극을 대뇌 피질 바로 위에 두어 뇌의 전기신호를 측정하는 전기생리학적 측정방법

(2) 혈 역학 - 헤모글로빈의 산소 포함 여부

Functional magnetic resonance imaging (fMRI)

혈류와 관련된 변화를 감지하여 뇌 활동을 측정하는 기술

Functional near-infrared spectroscopy (fNIRS)

생체조직에 대해 투과성이 높은 근적외광(파장 680㎚~1000㎚) 을 두피로부터 조사하여 조직을 투과해 온 빛을 분석함으로써 조직을 흐르고 있는 혈액 속의 헤모글로빈(Hemoglobin) 산소화 상태를 비침습 적으로 계측하는 방법

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Brain-computer Interface는 EEG를 사용한다

Most of BCI is based on the EEG
- EEG provides high temporal resolution, it is comparably easy to use, and not too expansive

- IN the last century, numerous studies were conducted that were based on analyses of EEG features corresponding to cognitive processes

뇌파 (Brainwaves)

주파수가 높을수록 깨어있는 상태(활성화)이다.

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An electrophysiological monitoring method to record electrical activity of the brain

• Non-invasive

Electrode types and position

• EEG : surface of the skull
• ECoG : surface of the brain
• Penetrating electrodes : Inside the brain

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The international standard of electrode placement

• pre-frontal (Fp), Frontal (F), Temporal (T), Parietal (P), Occipital (O), and Central (C), lobes
• There ar also (Z) sites : A "Z" (zero)

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Instrumentation

• Cap
• Ammplifier
• GEL (wet electrode)

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BCI Research

What people want to do with BCI?

• people with disabilities may have no other option for HCI than BCI
• for general people, combining EEG to improve the HCI-Hybrid HCI
  • recognizing the mental states of a person

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Event-Related potential (ERP)

The measured brain respones that is the direct result of a specific sensory, cognitive, or motor event

• Very small voltage fluctuations in response to specific events or stimuli

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Oddball Paradigm

A train of stimuli is persented in which some stimuli are persented often and others rarely

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BCI Speller

 P300 speller (1988)

• a matrix of 6-by-6 displaying all 26 Ietters of the alphabet and 10 numerals
• Rows and columns are randomly highlighted several times
• When a column or row contains the character a subject desires to communicate, the P300 response is elicited

Hex-O-spell

Steady-state Visualy Evoked Potential (SSVEP)

Brain responses at the same (or multiples of) frequency of the visual stimuli

Motor Imagery

motor imagery (MI) is relying on the same brain systems that would be used for actual performance

• can be used as primary input