Protocerebral Olfactory Processing

Abstract

Behavioural plasticity has not always been considered a property of insects (Heisenberg 1989; Menzel and Müller 1996; Tully 1996). While many examples of innate behaviour and fixed action patterns have been described, such as the sequential components of courtship in Drosophila flies (reviews: Hall 1994; Yamamoto et al. 1997), insects in both field and laboratory settings demonstrate an astonishing degree of experience-dependent modification of their behaviour (reviews: McGuire 1984; Menzel 1985; Heisenberg 1989; Farbach and Robinson 1995; Hammer and Menzel 1995; Davis 1996; Menzel and Müller 1996; Tully 1996; Tully et al. 1996; Hammer 1997). For example, honeybees improve their foraging efficiency with practice (Dukas and Visscher 1994). Even the elements of courtship in flies can be modified by a variety of different experiences (e.g., Siegal and Hall 1979; Gailey et al. 1986; Griffiths et al. 1993). This behavioural plasticity is well reflected in brain design. The protocerebrum (PC), which is by far the largest of the three supraesophageal ganglia (Power 1943; Strausfeld 1976; Mobbs 1985; Reichert and Boyan 1997), is built of neuronal assemblies that function in the integration of input from peripheral sensory centres, and in the co-ordination of appropriate output to peripheral motor centres (Howse 1974; Schürmann 1974; Erber et al. 1987; Homberg 1987; Heisenberg 1994; Menzel et al. 1994; de Belle 1995; Kanzaki 1996).