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Proceedings Paper

Multi-timescale measurements of brain responses in visual cortex during functional stimulation using time-resolved spectroscopy
Author(s): Solomiya Lebid; Raymond O'Neill; Charles Markham; Tomás Ward; Shirley Coyle
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Paper Abstract

Studies of neurovascular coupling (hemodynamic changes and neuronal activation) in the visual cortex using a time-domain single photon counting system have been undertaken. The system operates in near infrared (NIR) range of spectrum and allows functional brain monitoring to be done non-invasively. The detection system employs a photomultiplier and multi-channel scaler to detect and record emerging photons with sub-microsecond resolution (the effective collection time per curve point is ~ 200 ns). Localisation of the visual evoked potentials in the brain was done using knowledge obtained from electroencephalographic (EEG) studies and previous frequency-domain optical NIR spectroscopic systems. The well-known approach of visual stimulation of the human brain, which consists of an alternating black and white checkerboard pattern used previously for the EEG study of neural responses, is applied here. The checkerboard pattern is synchronized with the multi-channel scaler system and allows the analysis of time variation in back-scattered light, at different stimulation frequencies. Slow hemodynamic changes in the human brain due to Hb-HbO2 changes in the blood flow were observed, which is evidence of the system's capability to monitor these changes. Monocular visual tests were undertaken and compared with those done with an EEG system. In some subjects a fast optical response on a time scale commensurate with the neural activity associated with the visual cortex was detected. Future work will concentrate on improved experimental protocols and apparatus to confirm the existence of this important physiological signal.

Paper Details

Date Published: 3 June 2005
PDF: 12 pages
Proc. SPIE 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy, (3 June 2005); doi: 10.1117/12.604821
Show Author Affiliations
Solomiya Lebid, National Univ. of Ireland/Maynooth (Ireland)
Raymond O'Neill, National Univ. of Ireland/Maynooth (Ireland)
Charles Markham, National Univ. of Ireland/Maynooth (Ireland)
Tomás Ward, National Univ. of Ireland/Maynooth (Ireland)
Shirley Coyle, National Univ. of Ireland/Maynooth (Ireland)


Published in SPIE Proceedings Vol. 5826:
Opto-Ireland 2005: Optical Sensing and Spectroscopy
Gerard D. O'Sullivan; Brian D. MacCraith; Hugh James Byrne; Enda McGlynn; Alan G. Ryder, Editor(s)

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