Numerical exploration of the influence of neural noise on the psychometric function at low stimulation intensity levels

Abstract

The relationship between stimulus intensity and the probability of detecting the presence of the stimulus is described by the psychometrical function.The probabilistic nature of this relationship is based on the stochastic behaviour of sensory neural channels and sensory networks involved in perceptual processing (Kiang 1968). This study tries to establish a continuum of variability across different levels of integration in the central nervous system. Once the opening and closing times of ionic channels was simulated, a threshold to the collective behaviour of voltage-gated ionic channels was imposed in order to generate the spike train of a single neuron. Afterwards,the trains of spikes of different neurons were added up,simulating the activity of a sensory nerve. By adding the activity due to the stimulus to the spontaneous neural behaviour,the psychometric function was simulated using a thresholding approach.The results can replicate the stochastic resonance phenomenon, but also open up the possibility that attentional phenomena can be mediated not only by increasing neural activity (bursting or oscillatory),but also by increasing noise at the neural level.

Unavoidability and Functionality of Nervous System and Behavioral Randomness

“…The whole model can be validated at the different levels of description from ionic channels to the psychometric function; I would concentrate here on the psychometric function. The validation of more basic levels can be found in the original publication [13]. The obtained shape in the simulation is similar to the sigmoid psychometric function obtained experimentally [31,32].…”

“…qualitatively, there were no time dependencies in the successive events. The obtained psychometric function was based on a simulation in which the organismic response (the psychometric or psychophysics function) was constructed from its more basic underpinnings [13], in the interaction between the stimulus intensity and the random closing and opening of ionic channels. We will comment first on the psychometric function study given its more detailed description extending from the molecular to the organismic level.…”

“…In fact, the influence of neural noise on the discharge of neurons [8], as well as the influence of noisy spike trains on perception [30] has already been addressed. The simulation, best defined as numerical exploration, brought from the random opening of ionic channels to the psychometric function is described in Figures 6-8 (details in Gómez, [13]).…”

“…The lever press response of rats during variable interval schedules of reinforcement (VI) [10,11]; the fluctuations of the macroscopic activity of the abducens nerve [6], giving place to the ocular tremor; the perceptual changes during the observation of images in eye rivalry and ambiguous images [12]; and the psychometric (also called psychophysics) function [13]. The integration of unavoidable levels of neural randomness at the organismic level would facilitate flexibility in behavior [14].…”

Necessity of noise in physiology and medicine

“…For example, thermal agitation causes voltage-gated ion channels in neuronal membranes to fluctuate randomly between conducting and nonconducting states inducing noisy membrane currents and subthreshold voltage fluctuations [40], [41]. It is now understood that channel noise affects spike-timing reliability, action potential dynamics, signal detection, the tuning properties of the cell and overall has important effects on neuronal information processing capabilities [36], [40], [41]. Lastly, while noise often leads to increased responsiveness in the nervous system, empirical data and neuronal models demonstrate that noise can also subdue or turn off repetitive neuronal activity [8], [42].…”