The effects of mesial temporal and cerebellar hypometabolism on learning and memory

The effects of mesial temporal (MT) and cerebellar hypometabolism were studied using measures of verbal, visual and motor skill learning. Twelve patients with refractory temporal lobe epilepsy who showed asymmetrical mesial temporal lobe hypometabolism on [¹⁸F] fluoro-2-deoxy-glucose positron emission tomography (FDG-PET) were given tests involving 4 consecutive learning trials and a 30-min delayed recall trial. Delayed recognition was also assessed for the words and designs, and skill transfer was evaluated for mirror drawing. Compared to 9 normal control participants, patients with more marked MT hypometabolism on the left had impaired delayed recall of words and patients with more marked MT hypometabolism on the right showed impaired learning of novel designs, but normal retention over delay. Patients were not impaired in their mirror-drawing performance. The findings for MT hypometabolism correspond well to those obtained in other studies where patients have been classified on the basis of side of hippocampal atrophy or temporal lobe excision.