DEPENDENCE OF RESPONSE VARIABILITY IN AUDITORY NEURONS UPON SIGNAL’S PARAMETERS.
N. G. Bibikov.
Federal State Unitary Enterprise Acoustical institute. Moscow, Russia; firstname.lastname@example.org
For many decades it was accepted that sensory neurons code input signal’s parameters exclusively by density of the output impulsation or by number of spikes, evoked by a single signal. Later experimental evidence demonstrates important roles both the temporal spike distribution and cross correlation of spikes generated by different neurons. Quite often just these temporal parameters of the response, which determined by specific features of signal, define the subsequent reaction of whole organism. However the number of spikes evoked by sensory events still remains the main criterion of output activity, both for single neuron, and for population of units. Meanwhile in recent years more and more evidences testify that along with intensity of the reaction (determined by mean pulse number in response to a signal presentation) significant role plays also variability of these numbers for subsequent identical presentations. For an assessment of such variability the value resulted from division of dispersion of spike number upon mean value of this number (so called Fano factor) was usually used. We carried out the estimation of this parameter for many single auditory units of the immobilized grassy frog. Earlier [1-2] we investigated correlations of the variability (determined by Fano factor) with some other characteristics of the neuron’s response: mean spike number and a type of peristimulus histogram. Meanwhile some undoubted interest represents the investigation of interconnection between the response variability and some main parameters of input sensory signals. Now we present our preliminary experimental material dealt with the dependence of Fano factor of neuron’s reaction in frog’s auditory pathway upon the following parameters of input acoustical stimuli: signal level (dB over the threshold), the carrier frequency of a tonal signal, frequency and depth of sinusoidal amplitude modulation. The analysis of these experiments demonstrates that the variability (determined by Fano factor value) represents an independent response characteristic which can be correlated with the reaction intensity (determined by mean number of spikes upon a presentation) whether negatively or positively. The study was supported by a grant of the RFBR 12-04-13070.
1. Bibikov N.G. Variability of responses of auditory units to identical acoustical stimuli//Proceed. IX International interdisciplinary congress “Neuroscience for medicine and psychology” Sudak. 2010. Max-Press. P. 69-70.
2. Bibikov N.G. Statistics of pulse number variability of single unit responses to identical stimuli in torus semicircularis of the frog// Sensornye systemy 2011. V.25. №2. P. 131-142.