AN EVALUATION OF LINEAR-MODEL ANALYSIS TECHNIQUES FOR PROCESSING IMAGES OF MICROCIRCULATION ACTIVITY

Sequences of images of the cortical surface can be processed to reveal information about the cortical microcirculation, regional cerebral bl ood how (rCBF), and changes induced by neuronal activity. This study e xamined the use of different analysis methodologies on intrinsic optic al images taken from rat sensory motor cortex and testes. Generalized linear model (GLM) analysis was used and compared with standard signal processing methods including principal component analysis. The GLM me thod has been used by Friston et al. (1994, Hum. Brain Map., 1: 214-22 0) in the analysis of functional magnetic resonance imagery to identif y regions of focal activity. We investigated the use of this method to analyze video image data of the modulation of rCBF from rat cortex. T he results revealed spatiotemporal variations in rCBF in response to s timulation within local regions of cortex, The advantage of the GLM me thod is that it augments ordinary signal processing methods with an es timate of statistical reliability. The use of different wavelengths of illumination reveals spatial structures with different temporal relat ionships. In image time series data collected under green and red illu mination a phase difference was found in the low frequency similar to 0.1 Hz vasomotion oscillation. This phase difference occurred in data from both cortex and testes. A possible explanation of these differenc es is that the spectral absorption characteristics of the tissue refle ct changes in the volume proportions of the different hemoglobin deriv atives in interacting with the modulation of the volume of blood. It i s suggested that the combination of these effects produces the phase d ifferences we detect. (C) 1998 Academic Press.