Olfaction

Abstract

The relative significance assigned to olfactory function has, in the past, been largely a matter of disciplinary approach. Thus, in contrast to its fluctuating fortunes in the hands of neuroanatomists assessing components of forebrain function, olfaction has long been accorded a major role by animal behaviorists in sexual and social behavior, trail following, feeding behavior, and identification of territory. Or consider the view that olfaction can directly influence certain physiological functions. Until about the middle of this century this suggestion would have had little support. Then came evidence that, in mice, the odors of a strange male can block the pregnancy of females, while isolation of nonpregnant mice in a large group away from males induces anestrus in a proportion of them (Parkes and Bruce, 1961; Bruce, 1970; Whitten, 1959). Since then, numerous studies have pointed to close functional links between olfaction and endocrine activity. Other reports claimed that olfactory input can influence growth, water balance, and temperature regulation, and that bulbectomy causes marked changes in norepinephrine content of several brain regions (Digiesi et al., 1963; Novákova and Dlouhá, 1960; Edwards and Roberts, 1972; Pohorecky et al., 1969; Eichelman et al., 1972; King and Cairncross, 1974). Similarly, there was until recently limited evidence to support Herrick’s (1933) contention that the olfactory system serves as a nonspecific activator for all cortical functions. It is now known that bulbectomized animals show a tendency toward increased aggression and hyperactivity and are slower to habituate. Indeed, the olfactory system appears to be implicated in many functions attributed to limbic and hypothalamic structures (see Wenzel, 1974).