Abstract

NOISE, CENTRAL NORADRENALINE AND SELECTIVITY IN MEMORY AND ATTENTION

Andrew P. Smith*, PhD

ABSTRACT

Background: Initial noise exposure can increase arousal and lead to increased selectivity in memory and attention. Less is known about the effects of prolonged noise exposure and noradrenergic drugs on selectivity in attention and memory. Clonidine, an antihypertensive α2-adrenergic receptor agonist, reduces arousal, which leads to lower subjective alertness, impaired sustained attention, slower choice reaction time and saccadic eye movements. These Clonidine-induced impairments can be reversed by the selective antagonist, Idazoxan, and acute exposure to noise. The present analyses investigated the effects of Clonidine on selectivity in memory and attention and examined whether Idazoxan and noise blocked the effects of Clonidine. Method: A parallel-group double-blind design was used. Seventy-six healthy male volunteers were given either a placebo, 40mg Idazoxan, 200μg Clonidine, or a combination of 200μg Clonidine plus 40mg Idazoxan.  Half of each drug condition was exposed to 80dB white noise via headphones. At baseline and on three occasions post-drug administration, volunteers carried out a Stroop task, a category instances task, and a dual memory task. Results: Neither the noradrenergic drugs nor noise influenced selective attention and memory. The speed of reaction times in the category instances task was slower after Clonidine, and this effect was reduced by Idazoxan and noise. Conclusion: Neither noradrenergic drugs nor prolonged noise exposure changed selectivity in memory and attention. Clonidine led to psychomotor slowing, an effect which was reduced by Idazoxan and noise.

Keywords: Central Noradrenaline; Noise; Clonidine; Idazoxan; Selective Attention; Task Priority; Category Instances; Stroop Task.