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Abstract:
Simultaneous intracortical recordings of neural activity (NA) and BOLD responses in the anaesthetized monkey (Logothetis et al,2001)demonstrated various degrees of correlation between the fMRI data and LFP,MUA and SUA. The present work is a further step in the study of the relationship of BOLD to NA in the behaving monkey in a vertical-bore 7T/60cm scanner equipped with a 38-cm gradient insert (80mT/m,130us, Bruker Inc.). The upright positioning of the animal used in every alert monkey laboratory was also chosen for fMRI to minimize discomfort in the monkeys, expedite their training process, and ensure longer cooperation during psychophysical testing. Here, the monkeys were first trained to perform a fixation task (Wurtz, 1969) using juice as a reward. Stimuli were presented through a fiber-optic system (Silent Vision, FL), and eye movements were measured with the iView eye tracking system (SensorMotoric Inst.,GmbH). During data acquisition suction of juice and body movements were prevented by using a number of pressure and motion sensors and by training the animal to remain relaxed during the observation period. MR-compatible plastic chambers and electrodes made of platinum-iridium coated with glass were used for intracortical recordings. Gradient-induced interference was compensated with custom-made electronics (Patent 01116436.5). Brief pulse stimulation with full-field patterns and small stimuli placed within the receptive field of each recording site was used to elicit cortical responses followed by a BOLD response. The correlation of BOLD to different frequency bands with different spatio-temporal stimulation patterns will be discussed.
