Human olfactory memory : effect of temporal-lobe lesions on immediate and delayed recognition of odours

Odour recognition memory was studied in 49 patients with unilateral temporal lobe excision, and 20 control subjects. Odours were presented monorhinally to explore any asymmetry in performance between nostrils, and to test for hemispheric differences between patients with excision from the right versus the left temporal lobe. Testing was by a 2-alternative, forced-choice procedure, immediately after presentation and 24 hours later. A discrimination test was carried out at the conclusion of the memory test, and nondiscriminated odours were excluded from the final memory scores. The contribution of the hippocampus to odour memory was investigated by dividing patient groups according to the size of hippocampal excision. The memory test showed that only patients with excision from the left temporal lobe that included a large hippocampal removal were impaired after 24 hours. The discrimination test revealed deficits only for patients with right temporal lobectomy, and only in the right nostril