Identification of Functioning Cortex Using Cortical Optical Imaging

Abstract

COI is able to rapidly identify areas of cortex containing elicited neuronal activity. The technique allows cortical activation maps to be made rapidly with a very high degree of spatial resolution. COI is reliable and consistent over time. COI, if used carefully, holds promise as an intraoperative technique to study both human and experimental animal cortical function.

Intraoperative Human Functional Brain Mapping Using Optical Intrinsic Signal Imaging

“…These studies have repeatedly demonstrated the versatility of this modality and its numerous potential applications. The specificity of optical maps generated through OISI has been consistently confirmed in these various studies when compared to other established invasive methodologies, including single unit activity measurement [87,95], maximum field potential measurement [96][97], and cytochrome oxidase-staining [68,95]. OISI has also been used for mapping seizure propagation in the cortex [78] and for identifying epileptogenic foci [79].…”

“…Each of these different phenomena is observed and best quantified at different imaging wavelengths [30,87]. For example, imaging at 610 nm best detects deoxyhemoglobin concentration changes because the absorbance of oxyhemoglobin is much less than that of deoxyhemoglobin at 610 nm [30].…”

“…Vascular artifacts from blood vessels are another major source of noise. Focusing 1-2 mm below the cortical surface [87] and imaging only immediately after stimulus onset [92] can minimize this artifact when the area being imaged is close to large vessels [13, 71,93].…”

Intraoperative optical intrinsic signal imaging: a clinical tool for functional brain mapping

“…1 and 2). 26,42 For example, imaging at 610 nm emphasizes deoxyhemoglobin concentration changes; the absorbance of oxyhemoglobin is negligible compared with that of deoxyhemoglobin at 610 nm ( Fig. 1).…”

“…5,39,44 Imaging at wavelengths sensitive to oxygen extraction (600-630 nm) is thought to produce maps that are more highly spatially correlated with underlying neuronal activity than those that emphasize blood volume changes (850 nm). 16,20,26,57 This may be because fast changes in oxidative metabolism are more tightly coupled to electrical activity than the more delayed perfusion-related responses. 57 The 610-nm signals have also been shown to offer the greatest SNR 26 and, when focused 2 mm beneath the cortical surface, least emphasize blood vessel artifacts.…”