Search

The involvement of the frontal cortex and thalamic nucleus in odor discrimination in humans was assessed. Six patients with frontal lobe brain damage, seven patients with alcoholic Korsakoff’s syndrome and 16 healthy comparison subjects completed odor detection and odor discrimination tasks. Multivariate general linear modeling with age as a covariant revealed significantly decreased odor discrimination ability in frontal lobe damaged patients and marginally decreased odor discrimination ability in Korsakoff’s syndrome patients as compared to the healthy comparison subjects. No deficits were found in odor detection ability. The findings suggest that in human odor discrimination, there is more involvement of cortico-cortical pathways than of thalamo-cortical pathways.

Four tasks relying on short-term retention, i.e. digit span, missing scan, randomization span, and pointing span were presented to patients with frontal-lobe lesions and normal controls. Digit span was considered a measure of passive short-term memory, the other three tasks additionally reflect comparison processes, and two of these, the randomization and pointing spans, also measure active ordering by the subject. The results confirmed Petrides and Milner's (Neuropsychologia20, 249–262, 1982) hypothesis that frontal-lobe patients are typically deficient in subject-ordered tasks. It is also suggested that they are deficient in a spontaneous generation, rather than comparison, component of subjective ordering.