Regional cerebral blood flow response to visual stimulation measured quantitatively with PET

Abstract

Objectives: Regional cerebral blood flow (rCBF) was measured by positron emission tomography with bolus injections of 15 O-labeled water in order to learn the normal pattern of response of the occipital rCBF to flicker and video stimulation. Materials and methods: Six normal volunteers and a patient with partial cortical blindness were studied. They underwent quantitative rCBF measurement in the eye closed resting condition, under full-field stimulation with flickering light, and during video movie viewing, which contains form, color, and movement visual information. Stimulation-minus-rest subtraction PET images were overlaid onto the MRI images resliced parallel to the midline. Results: In normal subjects, the rCBF response to flickering stimuli and to the video in the posterior part of primary visual cortex was +30.5 and +34.5% of whole brain mean value, respectively. The rCBF increase in the association visual cortex was more pronounced by the video movie viewing (+27.5% of whole brain mean value) than by the flickering light stimulation (+6.5% of whole brain mean value). Activated areas in the primary visual cortex corresponded well to the stimulated visual field according to retinotopic organization. Poor activation in primary and in association visual cortex were seen in the patient with cortical blindness. Conclusion: Flickering light and video movie induced different activation patterns. More complicated visual stimuli, which require more extensive neuronal integration, caused greater activation of the higher visual cortex.