뇌과학연구센터 세미나 개최
주제 : Intrinsic and Extrinsic Optical Imaging for Functional Brain Mapping Research
발표자 : Vassiliy Tsytsarev (Human Brain Research Center, Kyoto University, Japan)
일자 : 2004년 11월 9일(화) 오후 1:00-2:30
장소 : KAIST 정문술빌딩 220호
A number of new imaging techniques have enabled to visualize the functioning brain directly. These imaging techniques have provided a new level of understanding of the principles underlying cortical development, organization and function. Actually for imaging in the living mammalian brain we can distinguish two complementary imaging techniques. The first technique is based on intrinsic signals. The second technique is based on voltage-sensitive dyes. Currently, these two optical imaging techniques offer the best spatial and temporal resolution, but also have inherent limitations.
At present, the easiest and most effective strategy of imaging functional architecture is based on the slow intrinsic changes in the optical properties of active brain tissue, permitting visualization of active cortical regions at a spatial resolution greater than 50 mcm. It is only recently that it has become possible to use optical detection of intrinsic signals for the imaging of the functional architecture of the cortex. Although to date most optical imaging studies have been done in the visual cortex, this is by no means the only sensory system which can be studied using this method. Indeed, this methodology has also proven useful for investigating functional architecture in the somatosensory cortex of the rat, monkey, guinea pig, gerbil and the chinchilla.
In our own project, using the intrinsic signal optical recording technique, we reconstructed the two-dimensional pattern of stimulus-evoked neuronal activities in the auditory cortex the cats. The average magnitude of intrinsic signal in response to a pure tone stimulus increased steadily as the sound pressure level increased. A detailed analysis demonstrated that the evoked signals at early frames were scaled by the sound pressure level, which in turn indicated the presence of a minimum level of sound pressure beyond which stimulus-related intrinsic signal can be generated. Intrinsic signals evoked significantly by pure tone stimuli of different frequencies were localized and arranged in an orderly manner in the middle ectosylvian gyrus, which indicates that the primary auditory field (AI) is tonotopically organized. The arrangement of optimal frequencies obtained from optical recordings of the same auditory cortex, which were conducted on different days, was highly reproducible. Furthermore, other auditory fields surrounding AI in the recorded area were allocated based on the observed tonotopicity. We also conducted unit recordings on the cats used for optical recording with the same set of acoustic stimuli.
Since most of the intrinsic signals are slow, the alternative is to utilize fast extrinsic probes. In such experiments the preparation under study is first stained with a suitable voltage-sensitive dye. The dye molecules bind to the external surface of excitable membranes and act as molecular transducers that transform changes in membrane potential into optical signals. The resulting changes in the absorption or the emitted fluorescence occur in microseconds and are linearly correlated with the membrane potential changes of the stained cells. These changes are then monitored with light measuring devices.
Perhaps a multipurpose imaging system for either slow intrinsic imaging or fast voltage sensitive dye imaging would become available in the near future and allow each laboratory to use each one of these imaging techniques alone, or in combination with another neuroscience methods.
뇌과학연구센터 세미나 개최
주제 : 얼굴 표정의 자동 인식 기술
발표자 : 이성환 교수(고려대학교 컴퓨터과학과)
일자 : 2004년 11월 3일(수) 오후 5:00-6:00
장소 : KAIST 정문술빌딩 220호
본 강연에서는, 얼굴 표정 인식에 필요한, 표정의 기술 방법, 특징 추적, 분류기 등의 핵심 기술 들을 사례를 통해 소개하고, 이러한 핵심 기술들을 바탕으로 표정 인식 시스템의 원리를 설명한다. 또한, 현재 연구의 문제점을 도출하기 위해 세계적 수준의 연구 현황을 파악하고, 표정 인식 기술의 과거와 현재의 비교를 통한 표정 연구의 미래를 추측하며, 이와 함께 표정 연구에 필수적인 얼굴 표정 데이터베이스와 표정 인식 기술에 대한 다양한 응용 분야를 제시하고자 한다.
- 개요 : 연구의 필요성 및 중요성, 표정 분류
- 핵심 기술 : 표정의 기술 방법, 특징 추적, 분류기
- 기술 동향 : 관련 연구, 표정 인식 데이터베이스, 연구 내용
- 응용 분야
(37KB, DN: 2108)
뇌신경정보학 Workshop 개최
일시 : 2004년 9월 11일(토), 09:30-18:00
장소 ; KAIST 정문술빌딩 219호
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