Neurometabolic coupling varies with cortical lamina

The blood-oxygen-level-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI) is a hemodynamic measurement, which is used to make implications about neural processing. In cerebral cortex, BOLD responses to sensory stimuli are generally averaged across layers. There are clear anatomical and functional differences in laminar cortical organization which imply corresponding variation of BOLD responses. This has been reported in previous visual and somatosensory investigations, but without concurrent measurements of co-localized neural activity. We have modified a multichannel electrode to provide simultaneous measurements of tissue oxygenation and neural activity in different layers of primary visual cortex. We find laminar differences in tissue oxygen response amplitude. In the middle cortical layers, these differences are independent of local variations in neural activation. Our results suggest that neurometabolic coupling differs across cortical lamina