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Steady State Visual Evoked Responses to sum-of-sine wave modulated light were measured for subjects as they performed a decision making task. Describing function phase values demonstrated a positive shift under task conditions. For those subjects classified as Alpha producers (peak response in the 8 to 12 Hz region) there was an attenuation of gain with increasing task difficulty. In the beta range (above 12 Hz) a resistance to gain attenuation with increasing task difficulty, even to the point of gain increase, was observed.

The objective of this research was to assess the feasability of using ElectroEncephaloGrams (EEG) to measure the extent of acceleration induced Peripheral Light Loss (PLL). Two pilot studies were conducted to determine if an EEG response to peripherally localized stimuli could be detected and to establish the stimulus parameters that would yield a strong response. Results revealed: (1) identifiable EEG responses to stimuli located as far as ± 60 degrees from the foveal line-of-sight; (2) higher stimulus intensity and, in particular, higher depth of modulation yielded stronger EEG responses; and (3) coherence was found to be a more sensitive measure than RMS Power or Gain. These findings were used to establish the experimental conditions that were used in a study whose objective was to estimate the minimum time necessary to detect the presence, or absence, of an EEG response to peripherally localized stimuli. Results revealed a reliabe determination for stimuli located at ± 45 degrees could be made in 20 seconds or less.