Introduction: The accurate intraoperative localization of epileptic foci and surrounding functional architecture is critical to a successful surgical outcome. Current techniques are limited either by their inability to simultaneously sample large areas of cortex with high spatial resolution or account for dynamic alterations in cortical morphology. Optical recording of intrinsic signals can map neuronal activity in a large area of cortex with a spatial resolution in the order of <100 mum. We explored methods of simultaneously representing localizing information, functional architecture and the border of an epileptic focus in vivo with intrinsic signal imaging.
Methods: The functional architecture of V1 was mapped using optical imaging of intrinsic signals in the ferret at 707 nm (n = 9). Interictal and ictal foci were then generated with focal iontophoresis of bicuculline methiodide and 4-aminopyridine into V1 and mapped optically. Blood vessel architecture was mapped using light acquired at 540 nm.
Results: Epilepsy maps could be superimposed on maps of the underlying functional architecture and surface blood vessel pattern to produce composite pathological-functional maps. Sufficient data for localization as well as identification of both pathological and functional architecture could be conveyed in a single image.
Conclusions: Cortical maps generated with intrinsic signal imaging can combine topographic and localizing information about normal functional architecture and interictal and ictal onset zones with extremely high spatial resolution. These maps may be useful in guiding surgical resections and multiple subpial transections to minimize unnecessary damage to functional brain surrounding neocortical pathology.