Abstract:
Positron computed tomography was used to investigate changes in
the local cerebral metabolic rate for glucose (LCMRGlc) of the visual
cortex. Progressive increases in LCMRGlc were found from eyes-closed
control to stimulation with white light, alternating black/white
checkerboard pattern, and a complex visual scene of a park, with the
associative visual cortex increasing at a faster rate than the primary
visual cortex as the visual scene complexity increased. A graded
decrease in LCMRGlc of the visual cortex was found with a stepwise
deletion of spontaneous cell firing at the retinal, geniculate and
cortical level due to lesions. Left/right metabolic symmetry of the
visual cortex during monocular stimulation confirms 50% crossing of the
human visual system. Neonatal blindness showed no apparent degeneration
of the visual cortex and was equivalent to eyes-closed controls. The
interictal state of a patient with visual seizures demonstrated a
hypometabolic visual cortex with a 2.5-fold increase in metabolism
during an ictal visual hallucination