Patterned response to odor in single neurones of goldfish olfactory bulb: influence of odor quality and other stimulus parameters.

Abstract

Responses of 75 single units in the goldfish [Carassius auratus] olfactory bulb were analyzed in detail for their relationship to the time-course of the change in odor concentration during each odor stimulus. Odor stimuli were controlled for rise time, duration and peak concentration by an apparatus developed for the purpose. This apparatus enabled aqueous odor stimuli to be interposed into a constant water stream without changes in flow rate. The time-course of the concentration change within the olfactory sac was inferred from conductivity measurements at the incurrent and excurrent nostrils. Temporal patterns of firing rate elicited by stimuli with relatively slow rising and falling phases could be quite complex combinations of excitation and suppression. Different temporal patterns were produced by different substances at a single concentration in most units. Statistical measures of the temporal response pattern for a small number of cells at a given concentration were more characteristic of the stimulus substance than any of 3 measures of magnitude of response. The temporal patterns changed when the peak concentration, duration and rise time of the stimuli were varied. The nature of these changes suggested that the different patterns are due primarily to the combined influence of 2 factors: a stimulus whose concentration varies over time and a relationship between concentration and impulse frequency which varies from unit to unit. Some units produced patterns suggestive of influence by neural events of long time constant. The importance of temporal patterns in odor quality and odor intensity coding was discussed.