Allen M. Granda

EEG frequency and finger pulse volume as predictors of reaction time during sleep loss

Abstract The validity of EEG frequency and finger pulse volume for predicting reaction time increased as sleep loss increased. In general, the EEG showed the highest correlation with reaction time, especially in the 1 sec interval just before and just after the signal. As sleep loss increased, the “lead time” for the EEG increased so that by 50 h of sleep loss, valid predictions of reaction time could be made at least 2–3 sec before the signal. Five out of seven subjects showed a bimodal EEG frequency distribution during sleep loss. For these five subjects, perceptual-motor lapses occurred during periods in which the EEG frequency was in the theta rhythm (4–7 c/sec) range. For two of the subjects whose modal EEG frequency slowed somewhat, but did not have a secondary mode at 4–7 c/sec, neither the EEG nor finger pulse volume could be used to predict reaction time. Finger vasodilation was significantly related to long reaction times during sleep loss, but its contribution to the prediction of reaction time was small.

The spectral sensitivity of the turtle's eye to very dim lights

Abstract Spectral sensitivity curves derived from electroretinograms in the turtles eye have shown characteristic peaks near 640 nm and 575 nm, with a very sharp fall-off in sensitivity toward the shorter wavelengths. During simultaneous recording from the optic tectum, however, a blue-green process near 530 nm is present at low levels of light which is not evident in the peripheral record from the eye. In an attempt to assess the spectral sensitivity of this eye to very dim light levels, a high-speed digital computer was used to detect the very small responses hidden in noise. The method averaged synchronized responses over a given number of times to repetitive light flashes. The wave-forms so derived show the same kind of ripples characteristic of responses obtained at more intense levels of light. A plot of wave-form peak-to-peak amplitude versus log stimulus intensity shows essentially a linear relationship over a one and a half log unit range. Spectral curves based on low constant criteria of response show rather wide differences between subjects, but in general, indicate a broad, blue-green process as well as yellow and deep-red processes.

Electrical responses of the light- and dark-adapted turtle eye

Abstract Electroretinograms were obtained from intact turtle eyes under conditions of light and dark-adaptation. Dark-adapted responses showed several ripples when stimulated by red or white light. Responses obtained under light-adaptation were characterized by shorter implicit times and faster rise times. Spectral curves plotted for both conditions peak at around 640–650 mμ, although the dark-adapted curve shows an additional shoulder at about 575 mμ. The results are discussed in relation to Duality Theory.

A method for producing avoidance behavior in the turtle

A method for determining sensory thresholds in turtles is described using an aversive behavioral paradigm. Relatively large stimulus intensity effects on both latency and amplitude of the response are demonstrated.

Effects of stimulus duration upon spectral sensitivity of the human electroretinogram.

The effects of three stimulus durations on spectral sensitivity of the electroretinogram were examined under moderate light adaptation. The durations were 11, 42, and 109 msec. At a low criterion amplitude of response, the 11-msec duration showed lower sensitivity in the green and blue regions of the spectrum than the two longer durations. At the red end of the spectrum all curves showed elevated sensitivity of approximately equal amounts. For a moderate criterion amplitude, the curves for the various durations retained their relative positions at the shorter wavelengths. At the red end of the spectrum, sensitivity decreased for all durations, but to a greater amount for the two longer durations. For a high criterion response, the 11-msec duration became more sensitive throughout the spectrum; however, it retained a form similar to that for the two longer durations. The curves were presumed to include at least two components: a scotopic process and a red-sensitive process. Possible interpretations of the duration effects on the spectral curves included the Bunsen–Roscoe law and the summation of on- and off-responses.

Electrical responses of the human eye following intense chromatic pre-exposures

Abstract The spectral sensitivity of the human electroretinogram was investigated in early dark-adaptation following high-luminance pre-exposures of yellow, blue and green light. The scotopic contribution to the spectral curves was greatly reduced, with maximum sensitivity occurring at longer wavelengths. For low-criterion a -waves the peak sensitivity was near 555 mμ, while low-criterion b -waves tended to have higher sensitivity in the red region of the spectrum. Selective effects from the chromatic pre-exposures were small for the b -wave and not apparent for the a -wave. Comparison of the a - and b -wave sensitivities showed that the b -wave retained more responsiveness at short wavelengths.

The spectral sensitivity of the human electroretinogram during the temporal course of dark-adaptation

Abstract Threshold curves derived from the b-wave of the ERG show similarities to analogous psychophysical data. There is an immediate decrease in threshold for the first minute and then a leveling off at about 8–12 min depending on the color of the stimulus light. For shorter wavelengths there is a clear break in the curve, the threshold decreasing again and becoming asymptotic between 22 and 30 min. This total change of threshold covers a range of over 3 log units. With longer wavelengths, the break in the curve is scarcely evident. Peak latency curves of threshold responses show pronounced breaks for all tested wavelengths. The a-waves show little evidence of breaks. Spectral curves derived early in dark-adaptation show a characteristic scotopic function plus a long wavelength process for the b-wave. The a-wave at this time shows scotopic plus elevated middle and long wavelength activity. For both waves, with more time in the dark, the longer wavelength processes tend to diminish in sensitivity The spectral curves here tend to conform more closely to the scotopic function.