Mapping of neural activity patterns using intrinsic optical signals: from isolated brain preparations to the intact human brain.

Abstract

It has long been known, since the work of Hill and Keynes (1949), that the intrinsic optical properties of nerve tissue change with neuronal activity (reviewed in Cohen, 1973). There are several possible cellular mechanisms which could underlie activity-dependent changes in the optical properties of neuronal tissue. These include neuronal and glial swelling (MacVicar and Hochman, 1991), neurosecretion (Salzberg et al., 1985) and the rapid reorientation of membrane dipoles induced by membrane depolarization (Stepnoski et al., 1991). Neuronal activity can also alter the optical properties of tissue by inducing changes in the characteristics of intrinsic chromophores such as hemoglobin or cytochromes (Chance and Williams, 1955; La Manna et al., 1987; Federico et al., 1991; Frostig et al., 1990; Grinvald et al., 1986), or by changing local blood flow and tissue hemoglobin content (Frostig et al., 1990).