Spiking frequency versus odorant concentration in olfactory receptor neurons

The spiking response of receptor neurons to various odorants has been analy zed at different concentrations. The interspike intervals were measured ext racellularly before, during and after the stimulation from the olfactory ep ithelium of the frog Rana ridibunda. First, a quantitative method was devel oped to distinguish the spikes in the response from the spontaneous activit y. Then, the response intensity, characterized by its median instantaneous frequency, was determined. Finally, based on statistical analyses, this cha racteristic was related to the concentration and quality of the odorant sti mulus. It was found that the olfactory neuron is characterized by a low mod ulation in frequency and a short range of discriminated intensities. The si gnificance of the results is discussed from both a biological and a modelli ng point of view. (C) 2000 Elsevier Science Ireland Ltd. All. rights reserv ed.