How inherently noisy is human sensory processing?

Noise in Brain Activity Engenders Perception and Influences Discrimination Sensitivity

“…The significant positive correlation between the magnitude of the mean activity of the brain region showing a differential response as a function of perceived pitch and discrimination sensitivity corroborate computational models linking perceptual discrimination proficiency with the magnitude of trial-to-trial variability in brain responses to identical stimuli (Neri, 2010), notably including signal detection theory (Macmillan and Creelman, 2005).…”

“…In other words, if the percepts can be predicted at above-chance levels from the scalp-recorded electrophysiological responses, it indicates that the fluctuations in the brain responses to the identical sounds are indeed related to the variations in the subjective percepts of the stimuli's dimensions attended to by the participants. We based our single-trial classification scheme on voltage topographies (De Lucia et al, 2007, 2010Murray et al, 2009;Tzovara et al, 2011a) because of their neurophysiological interpretability: a change in electric field topography necessarily follows from a change in the configuration of the underlying generators (Lehmann, 1987). The classification was conducted for each participant separately to obtain a distinct (although possibly overlapping) model of topographies for each participant.…”

“…Here, we hypothesize that differential brain responses to identical sensory stimulation also occur in the absence of any variation in the experimental context or in attention, due to random fluctuations in brain activity ("brain noise"; Faisal et al, 2008;Neri, 2010) that may exceed additional sources of external noise. Computational models suggest that due to noise, the trial-to-trial variations in brain responses to identical stimuli could be large enough to themselves cause perceptual differences (Micheyl et al, 2009;Neri, 2010).…”

“…Computational models suggest that due to noise, the trial-to-trial variations in brain responses to identical stimuli could be large enough to themselves cause perceptual differences (Micheyl et al, 2009;Neri, 2010). Signal detection theory (SDT) posits that the magnitude of noise along sensory processing pathways corresponds to the ratio between an observer's sensitivity to differences along a given stimulus dimension and the minimal physical distance between two different stimuli required to perceive them as different at an above-chance level (i.e., the discrimination threshold; Macmillan and Creelman, 2005).…”

Uncovering mental representations of smiled speech using reverse correlation

“…All but two participants (who had percentages of agreement of 49% and 51%) performed well above chance level over these repeated blocks: when these two participants were removed, the average percentage of the same responses over these two blocks was 68.1% (SD ¼ 5.8). We then estimated the amount of internal noise for each of these remaining eight subjects using a simple signal detection theory model with late additive noise 1 (Burgess and Colborne, 1988;Neri, 2010). We found an average internal noise level of 1.2 (SD ¼ 0.9), as expressed in units of external noise SD.…”