Sex-Related Differences in Visual-Orientation Discrimination Thresholds

Visually induced peak gamma frequency was associated with lower orientation discrimination (OD) thresholds and was higher for females than males. Accordingly, females would be expected to have lower OD thresholds than males. However, behavioural evidence suggests the opposite as males outperformed females in several visual perceptual tasks, such as visual acuity and orientation identification tasks. The current exploratory study aimed to investigate whether there would be differences in OD thresholds between neurotypical adult females and males using a visual-orientation discrimination task (ODT). The ODT is a low-level psychophysical task comprising vertical and oblique conditions and is suggested to indicate cortical Excitation Inhibition (E-I) balance in the visual cortex. The results showed that females and males had lower OD thresholds in the vertical condition than in the oblique condition, reflecting the well-known oblique effect. Unexpectedly, the results also showed that females had higher OD thresholds in the vertical and oblique conditions than males, indicating potential differences in cortical E-I balance between females and males. Possible explanations for the sex related differences in ODT performance are addressed.