Statistical Properties of Neuronal Firing in the Midbrain Auditory Center of the Frog in Response to Tones Modulated by Low-Frequency Noise
The temporal patterns of firing in single neurons located in brainstem auditory nuclei are the basic source of information about the characteristics of the perceived sound for upper brain centers. We estimated hypothetical firing in the small population inwardly independent midbrain neural elements those have identical responses to the external signal. For these purposes the firing evoked by continuous tones amplitude-modulated by repetitive low-frequency noise segments was recorded in torus semicircular neurons of grass frog (Rana t. temporaria). Shuffled autocorrelation functions including correlation of firing across all segments, excluding from within the same segment, were calculated. With such approach, the impact of refractory properties of investigated neuron on the response is virtually eliminated. As a result it is possible to estimate the output activity in a group of neurons having identical properties but independent moments of spike generation. The studied population of neurons revealed a significant diversity of the statistical characteristics of the output spike firing. Several units demonstrated high specificity of the reaction to particular features of the signal and very high values of correlation indexes.