Conduction Pathway of With Velocity in a Brain Nerve Normal Adults Correlates Intelligence Level

This is a detailed report of the first demonstration in normal individuals of a correlation between intelligence level ("IQ") and nerve conduction velocity (NCV) in a brain nerve pathway. A total of 147 postsecondary students were tested for nonverbal 1Q and latency of the PI00 (a visually evoked potential recorded over the primary visual cortex); this latency was used to estimate an approximate NCV in the visual pathway (retina to visual cortex). The correlation between this NCV and IQ is + .26 (p = .002); after correction for the restricted IQ range (but not for test ceiling or attenuation), it is + .37. Three recent studies of mentally retarded patients, using similar stimulation and recording, also showed increased PI00 latencies relative to controls. These results, plus those of other IQ studies using choice reaction time or long-latency evoked potentials, are all explainable by positive correlations between brain NCV and speed of information processing and between this speed and intelligence level.