The effect of moderately increased CO2 concentration on perception of coherent motion

Several studies have shown that some aspects of vision are impaired when exposed to higher than normal CO2 concentrations in air. The effect of moderately increased CO2 concentration on coherent motion perception, however, has not been studied.

Studies in neurophysiology and cell biology have provided evidence that higher than normal CO2 concentration in air affects cell activities from the retina to the cortex, including the V1 area in the visual cortex. We predicted that motion perception may be impaired by moderately increased CO2, since the V1 area is a gateway for visual motion information processing. The purpose of the present work was to investigate the effect of 2.5% CO2 concentration in air on coherent motion perception.

Random dot cinematograms were generated by a computer and served as visual stimuli. A whole-room indirect calorimeter was used for the accurate measurement and control of CO2 concentration in air, and served as the experimental environment. A two-interval-forced choice (2IFC) psychophysical procedure was employed to obtain psychometric functions.

For all three subjects, psychometric functions were shifted to the right when exposed to 2.5% CO2 in breathing air, compared to those using fresh air.

This finding implies that human ability in detecting coherent motion can be temporally impaired when CO2 concentration in air is raised to 2.5%.