Projeto e construção de um estimulador optico alternador e reversor de padrões para potencial evocado

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

Visual evoked potential (VEP) is a cortical response elicited by optical stimulation of the retina recorded on the scalp in the occipital region. It- can.be( used as an objective index of visual experience in studies of human visual system, requirino little patient cooperation and without involvement of subjective judgement. Two kinds of stimuli have been used to elicit VEP: non-patterned stimuli, i.e.. ligth flashes and patterned stimuli. l.e.. optical patterns such as checkerboards or vertical bars. Patterned stimuli can be presented either alternating patterns with black frames (non-constant luminance) or reversing black elements to white and vlce-versa (constant luminance). A programmable optical-pattern stimulator for VEP was built with an 8-bit microprocessor (8085) . decoders, RAM (2114) . EPROM (2716). a video controller (8275), and a parallel interface (8255). The patterned stimuli generated are presented to patient on the screen of a 16-inch black-and-white TV set. Five switches on the front panel are available for selection of the stimulation parameters: - patterns: checkerboard. horizontal bars, and vertical bars; - number of elements: checkerboard - lx1, 2x2, 4x4, 8x8. 16x16, 30x30. 40x40 and 80x80; bars - 1, 2, 4, 8, 16, 30, 40 and 80; - stimulation mode: alternating or rever sal; - stimulation rate: 0.5, 1.0. 1.5. 2.0, 3.0 3.75, 5.0, 6.0, 7.5 and 15 stimuli/s; and - visual field: full. The bench tests and the experimental results have confirmed the Qood performance of the prototype. Further work will be done towards clinical assesment of the optical stimulator in conjunction with the inteQrated system for evoked potential (currently, beinQ developed) at the University Hospital of Campinas

ASSUNTO(S)

engenharia biomedica

ACESSO AO ARTIGO

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