Analyses of response patterns clarify lead effects in olfactory reversal and extradimensional shift tasks: assessment of inhibitory control, associative ability, and memory.
Rats exposed to lead (Pb) chronically from conception were tested on (a) an olfactory serial reversal task and (b) an extradimensional shift (EDS) task. Pb exposure did not impair learning of the original olfactory discrimination but did impair learning of the 5 reversals and the EDS task. In the reversals, Pb exposure tended to shorten the initial period of persistent responding to the previously correct cue, but significantly prolonged the postperseverative learning phase (both the "chance" and "greater-than-chance" components). These effects are similar to those produced by lesions of the amygdala, a structure implicated in the process by which stimuli acquire incentive value. This similarity, coupled with the pattern of findings, suggests that Pb-induced impairment of reversal learning is due to a deficiency in learning the new contingencies of the task (an associative deficit), not inflexibility or deficient inhibitory control. These findings also illustrate the importance of analyzing the types of errors committed, rather than focusing solely on learning rate.
Hilson
J A
JA
Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA.
Strupp
B J
BJ
D000679:Amygdala / Q000187:drug effects / Q000503:physiopathology; D000818:Animals; D001245:Association Learning / Q000187:drug effects* / Q000502:physiology; D001288:Attention / Q000187:drug effects* / Q000502:physiology; D005260:Female; D007854:Lead / Q000493:pharmacokinetics; D007855:Lead Poisoning / Q000503:physiopathology*; D008297:Male; D011939:Mental Recall / Q000187:drug effects* / Q000502:physiology; D009042:Motivation; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009949:Orientation / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011340:Problem Solving / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012055:Reinforcement Schedule; D012193:Reversal Learning / Q000187:drug effects* / Q000502:physiology; D012903:Smell / Q000187:drug effects* / Q000502:physiology
D007854:Lead