International Journal of Physiology

Visual evoked potentials (VEPs) are electrical potentials evoked from visual stimuli and recorded from the human scalp. VEP latencies and amplitudes are affected by many variables like age, gender, core body temperature, hormones and head size. It was hypothesized that head size would indirectly reflects brain size and the length of the visual pathway and hence the conduction time. In this study P100 latency (P100L) of VEP was compared with head size for males and females to analyze the impact of length of the visual pathway on P100L of VEP.

34 subjects, 17 males and 17 females of age group 17–25 were participated. Head measurements like head circumference (HC), nasion to inion (AP-anteroposterior-measured across the top of the head), and right external auditory meatus to left (RL-also measured across the top of the head) were measured. Total head size was formed by adding all three measures. VEP was performed by checker board reversal stimuli system.

Statistical analysis showed significant differences between males and females in head size (HC, AP, RL and total head size) with a P value of < 0.01.P100 L was prolonged in males than females with a significance of P value < 0.01. Pearson's correlation of head size with P100L showed that head size has a moderate positive influence on latencies.

In the present study significant positive correlation have been found between external measurements of head and VEP latency. This study support the theory that length of the visual pathway and hence the conduction time can be correlated to the size of the head. Thus head size should be considered for normal VEP recording. Further studies can also be carried out in different age groups.