First- and second-order contrast sensitivity functions reveal disrupted visual processing following mild traumatic brain injury

- TBI patients have increased sensitivity for 1st order motion stimuli.
- TBI patients have decreased sensitivity to contrast-defined 2nd order stimuli.
- TBI patients have decreased sensitivity to orientation-defined 2nd order stimuli.
- CSFs are shifted towards higher spatial frequencies in TBI patients.

Vision is disrupted by traumatic brain injury (TBI), with vision-related complaints being amongst the most common in this population. Based on the neural responses of early visual cortical areas, injury to the visual cortex would be predicted to affect both 1st order and 2nd order contrast sensitivity functions (CSFs)-the height and/or the cut-off of the CSF are expected to be affected by TBI. Previous studies have reported disruptions only in 2nd order contrast sensitivity, but using a narrow range of parameters and divergent methodologies-no study has characterized the effect of TBI on the full CSF for both 1st and 2nd order stimuli. Such information is needed to properly understand the effect of TBI on contrast perception, which underlies all visual processing. Using a unified framework based on the quick contrast sensitivity function, we measured full CSFs for static and dynamic 1st and 2nd order stimuli. Our results provide a unique dataset showing alterations in sensitivity for both 1st and 2nd order visual stimuli. In particular, we show that TBI patients have increased sensitivity for 1st order motion stimuli and decreased sensitivity to orientation-defined and contrast-defined 2nd order stimuli. In addition, our data suggest that TBI patients' sensitivity for both 1st order stimuli and 2nd order contrast-defined stimuli is shifted towards higher spatial frequencies.