OLFACTORY IDENTIFICATION DEFICITS IN DOWNS-SYNDROME AND IDIOPATHIC MENTAL-RETARDATION

We investigated olfactory identification in children and adults with D own's syndrome (DS) and idiopathic mental retardation (IMR) and in age -matched normal controls (NC). Identification was assessed with a four alternative-forced-choice task modified from the University of Pennsy lvania Smell Identification Test (M-UPSIT) and a yes/no task yielding measures of discrimination and response bias for the same stimulus mat erial. Control tactile identification tasks were also administered. Re sults were that odor identification performance on both tasks was spec ifically impaired in DS compared to IMR and NC. Accuracy of identifica tion on the M-UPSIT correlated inversely with age in DS only. When unc ertain, DS and IMR subjects guessed ''yes'' more often than ''no'' on the Yes/No task (liberal decision bias) and guessed the last response alternative on the M-UPSIT (recent position bias), whereas the normal subjects had neutral decision bias on the Yes/No task and matched the objective position presentation probabilities on the M-UPSIT. Decision bias correlated with accuracy of identification in both tasks for the DS subjects only.