TNAD individuals in Chao and colleagues’ (2003) study differed from control subjects on categories completed, non-perseverative errors on the WCST, and word reading for the Stroop, they did not differ on those measures which are most commonly associated with frontal lobe function (perseverative errors on the WCST, color-word interference on the Stroop, and Trails B). It should be noted that some studies (Drewe, 1974; Grafman et al., 1986) have found that the number of categories completed on the WCST was reduced in patients with frontal lobe damage, although others (Janowsky et al., 1989; Stuss et al., 1983) have found that frontal patients did not differ from control subjects on this measure. Chao and colleagues’ (2003) TNAD sample did exhibit reduced late contingent negative variation (CNV) ERPs (which are linked to response preparation) over midline and parietal electrode sites. Although there was no significant difference in frontal lobe volume between TNAD and controls, in TNAD reduced late CNV amplitudes were associated with decreased frontal lobe gray matter volume.
