TEMPORAL RESOLUTION OF GENERAL ODOR PULSES BY OLFACTORY SENSORY NEURONS IN AMERICAN COCKROACHES

Behavioral and physiological evidence indicates that insect pheromone sensory neurons are able to resolve pulses of pheromone concentration as they occur downwind from a point source, but the abilities of insec t sensory neurons that are sensitive to general odors to respond to pu lsatile stimuli are unknown, The temporal response characteristics of olfactory sensory neurons of female American cockroaches Periplaneta a mericana in response to general odors were measured using a series of short odor pulses (20-400 ms), Odor pulses mere delivered to olfactory sensilla in a moving airstream controlled by electromagnetic valves. The responses of sensory neurons were recorded using a tungsten electr ode placed at the base of the sensillum, The temporal sensory neurons followed the temporal changes stimulus concentration, which were estim ated by replacing the odorant with oil smoke and measuring the concent ration of smoke passing through a light beam, Spike frequency varied w ith odorant concentration with surprisingly fine temporal resolution, Cockroach olfactory sensory neurons were able reliably to follow 25 ms pulses of the pure odorant 1-hexanol and 50 ms pulses of the complex odor blend coconut oil, Lower concentrations of odorants elicited resp onses with lower peak spike frequencies that still retained the tempor al resolution of the stimulus pulses. Thus, responses of olfactory sen sory neurons can reflect the fine structures of non-uniform distributi ons of general odorants in a turbulent odor plume as well as the avera ge odorant concentration.