Real World Applications of Source Separation Techniques

Abstract

During the last couple of years, optical imaging of neuronal population activity using Ca2+-sensitive dyes (Tsien, 1980; Poenie, 1992; Galizia et al., 1997) has become an important experimental tool for die investigation of neuronal response properties and coding strategies. As mentioned in chapter 4, section 1.2, Ca2+ imaging uses the fact that postsynaptic intracellular Ca2+ concenttation often increases when die cells are activated, and that a presynaptic calcium-influx is necessary for transmitter release. Neural population activity is recorded by introducing a Ca2+-sensitive fluorescent dye to the infra-cellular neuronal space of the considered tissue, illuminating it, and recording the amount of fluorescent light over space and time during neuronal stimulation. The resulting change in the two-dimensional pattern of fluorescent light intensity is taken as a measure of the pattern of neuronal population activity. Recently, this technique has been successfully applied to characterize important aspects of neuronal olfactory coding in the antennal lobe of honeybees (Joerges et al., 1997; Galizia et al., 1998; Galizia et al, 1999; Sachse et al., 1999).