Untitled

Abstract

Steady-state stimulation is a useful paradigm in many physiologic and clinical situations, for ERG, Pattern-ERG and VEP. One of the advantages is the easy evaluation of the response via Fourier analysis. However, the question whether a given response is statistically significant or not has received little attention so far, although it is especially relevant in high noise, low amplitude recordings, as often occur in pathologic conditions. A given response is statistically significant if it is unlikely that its value is due to noise fluctuations. Thus appropriate estimates of noise and response are required. We have analytically derived formulas for the statistical significance of a given signal-to-noise-ratio s, based on two different estimates of noise: (1) Noise estimate by a 'no stimulus' recording, or by a '+/-average'. The former needs an additional recording, the latter can simultaneously be calculated as the standard average. (2) Noise is estimated as the average of the two neighboring spectral lines (one below, and one above the response frequency). Analytical solutions were obtained for both noise estimates that can easily be evaluated in all appropriate recordings. Noise estimate (1) performs much poorer than noise estimate (2), as can be seen from the following landmark values: Typical significance levels of 5%, 1%, and 0.1% require s values of 4.36, 9.95, and 31.6 (1), and 2.82, 4.55, and 8.40 (2). The noise estimate based on the neighboring frequencies can be easily applied after recording, provided that the noise spectrum is reasonably smooth around the response and frequency-overspill was avoided. It allows a quantitative assessment of low responses in physiological threshold analyses and pathological conditions, e.g., 'submicrovolt flicker-ERG'.

Rod and cone contributions to the dark-adapted 15-Hz flicker electroretinogram

“…cd/m 2 , where the SNR was typically greater than the 2.82 criterion that corresponds to a p-value of 0.05 [26]. Specifically, SNRs for the ERG R+C (first column) and ERG C (third column) were greater than 2.82 for all subjects, with the exception of the three lowest luminance levels that were of borderline statistical significance (the SNR for these luminance levels ranged from 1.70 [p = 0.19] to 2.34 [p = 0.09]).…”

“…The phases are given in cosine phase and are “unwrapped” to extend beyond 360°, per convention. A subject’s response at a given stimulus luminance was considered statistically distinguishable from noise if the amplitude at 15 Hz was 2.82 times larger than the mean of the noise amplitudes measured at 14 Hz and 16 Hz, which corresponds to a significance value of 0.05, as discussed elsewhere [26]. …”

Parallels in Stimulus-Driven Oscillatory Brain Responses to Numerosity Changes in Adults and Seven-Month-Old Infants

“… 1 Rapidly flickering visual stimuli have been found to drive the neural response and provide an improvement in signal-to-noise ratio (Meigen & Bach, 2000). Traditional EEG studies with infants often struggle with low signal-to-noise ratio; thus, we sought to overcome this issue by employing a rapid steady-state visual-presentation.…”

Abnormal 8-Hz flicker electroretinograms in carriers of X-linked retinoschisis

“…A subject’s response at a given stimulus frequency was considered distinguishable from noise if the amplitude at the stimulus frequency (8 or 15 Hz) was at least 2.82-times larger than the mean of the noise amplitudes measured at neighboring frequencies (±1 Hz above and below the stimulus frequency). As discussed elsewhere [25], this signal-to-noise ratio (SNR) corresponds to a significance level of p = 0.05. Individual responses that did not achieve an SNR of at least 2.82 were excluded from the results presented below.…”