Abstract
Norepinephrine and dopamine are both believed to affect signal-to-noise in the cerebral cortex. Dopaminergic agents appear to modulate semantic networks during indirect semantic priming, but do not appear to affect problem solving dependent on access to semantic networks. Noradrenergic agents, though, do affect semantic network dependent problem solving. We wished to examine whether noradrenergic agents affect indirect semantic priming. Subjects attended three sessions: one each after propranolol (40 mg) (noradrenergic antagonist), ephedrine (25 mg) (noradrenergic agonist), and placebo. During each session, closely related, distantly related, and unrelated pairs were presented. Reaction times for a lexical decision task on the target words (second word in the pair) were recorded. No decrease in indirect semantic priming occurred with ephedrine. Furthermore, across all three drugs, a main effect of semantic relatedness was found, but no main effect of drug, and no drug/semantic relatedness interaction effect. These findings suggest that noradrenergic agents, with these drugs and at these doses, do not affect indirect semantic priming with the potency of dopaminergic drugs at the doses previously studied. In the context of this previous work, this suggests that more automatic processes such as priming and more controlled searches of the lexical and semantic networks such as problem solving may be mediated, at least in part, by distinct mechanisms with differing effects of pharmacological modulation.
Highlights
Groups of representations of words related in meaning are believed to be neurally linked in the semantic network [16,34]
Beversdorf et al showed that performance on anagram- solving tasks, involving access to the lexical/semantic network, is modulated by administration of noradrenergic agents [7,8]. These findings reveal an effect of the noradrenergic system on semantic problem solving tasks, while the dopaminergic system affects the semantic network in priming
Previous research had shown an effect of dopamine inhibiting the indirect semantic priming effect on word recognition tasks by restricting the semantic network [2,25]
Summary
Groups of representations of words related in meaning are believed to be neurally linked in the semantic network [16,34]. One mechanism of investigating semantic networks is the effect of word association on priming. Priming experiments involve giving subjects a lexical decision task requiring recognition of words (target) after they have been previously exposed to another word (prime). The degree of relation between the prime and target words, or semantic distance, has a relationship to the speed of word recognition. Whereas subjects exposed to prime words, such as “summer,” react more quickly to closely related words, such as “winter” (direct priming), this effect has been observed to a lesser degree in more distantly related word pairs, such as “summer” and “snow”
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