Pseudorandom binary sequence stimulation applied to the visual evoked response. Normative data and a comparative study with pattern and flash stimulation

Extraction of M and P components from the visual evoked potential using pseudorandom stimulation with swept parameter technique

To develop a method of extract magnocellular (M) and parvocellular (P) components from VEP, the nonlinear system identification method using pseudorandom binary sequence (PRBS) stimulation combined with swept parameter technique was examined. VEP elicited by achromatic sinusoidal grating reverse based on PRBS was recorded and their binary kernels were calculated as cross-correlation between PRBS and VEP. To manipulate the magnitudes of M and P visual pathways responses in VEP, the spatial frequency of gratings were swept during the PRBS stimulation. VEP to this stimulation was recorded from 4 healthy participants and their binary kernels changes during the stimulation were evaluated. PRBS stimulation of 40950 ms period was repeated twice, and the spatial frequency was swept from 0.5 to 9 [c/d] or 9 to 0.5 [c/d] within the period. Binary kernel of each epoch was calculated by cross-correlating VEP with PRBS of 40950 ms duration. Different waveforms of binary kernels obtained from the former and latter half of the PRBS stimulation were confirmed, and the waveforms were continuously changed during the stimulation. The changes may reflect the M and P pathway contribution changes during the stimulation and depend on the spatial frequency sweeping. The suggested technique would be effective for studying and screening several eye and neurocognitive disorders which have been reported to relate with selective damage in M/P pathways.

White noise analysis of a chromatic type horizontal cell in the Xenopus retina

The dynamics of color-coded signal transmission in the light-adapted Xenopus retina were studied by a combination of white noise (Wiener) analysis and simultaneous recordings from two types of horizontal cells: chromatic-type horizontal cells (C-HCs) are hyperpolarized by blue light and depolarized by red light, whereas luminosity-type horizontal cells (L-HCs) are hyperpolarized by all wave-lengths. The retina was stimulated by two superimposed fields of red and blue light modulated by two independent white noise signals, and the resulting intracellular responses were decomposed into red and blue components (first-order kernels). The first-order kernels predict the intracellular responses with a small degree of error (3.5-9.5% in terms of mean square error) under conditions where modulated responses exceeded 30 mV in amplitude peak-to-peak, thus demonstrating that both red and blue modulation responses are linear. Moreover, there is little or no interaction between the red- and blue-evoked responses; i.e., nearly identical first-order kernels were obtained for one color whether the other color was modulated or not. In C-HCs (but not L-HCs), there were consistent differences in the dynamics of the red and blue responses. In the C-HC, the cutoff frequency of the red response was higher than for the blue (approximately 12 vs 5 Hz), and the red kernel was more bandpass than the blue. In the L-HC, kernel waveform and cutoff frequencies were similar for both colors (approximately 12 Hz or greater), and the time-to-peak of the L-HC kernel was always shorter than either the red or blue C-HC kernel. These results have implications for the mechanisms underlying color coding in the distal retina, and they further suggest that nonlinear phenomena, such as voltage-dependent conductances in HCs, do not contribute to the generation of modulation responses under the experimental conditions used here.