Hemispheric Differences in Relation to Smoking
The present investigations were designed to uncover differences in hemispheric interactions between tobacco smokers, smoking cigarettes with different nicotine concentrations, and non-smokers. In the first experiment, sensorimotor tasks, associated with hemisphere-specific processing, were presented either to the right hand (then stimuli had to be counted) or to the left hand (matching of stimulus patterns). A lever switch with the thumb of the stimulated hand was used to indicate the correct solution of the task. A warning stimulus presented to the same hand (6 sec prior to the task) primed these choice reaction time tasks. Non-smoking subjects, all right banders, performed faster in the right hand task. This difference, though more pronounced in sham-smoking subjects (smoking cigarettes with zero nicotine content) than in non-smokers vanished with increasing nicotine intake so that smokers responded faster in the left-hand task. Similarly, a difference in error rate between the two types of task was observed only in non-smokers or in smokers without recent nicotine intake. After nicotine intake, heart rate in smokers was higher for the left than for the right hand task and the task-dependent asymmetry of the slow brain potentials also interacted with smoking intake. Results may provide new evidence that nicotine in lower doses improves inter-hemispheric coordination or activates the right hemisphere of the brain.
The second experiment tested the self-regulation of the hemispheric asymmetry in slow brain potentials. Operant control was achieved by means of a biofeedback paradigm in non-smokers and smokers as well. Though only asymmetry over the central regions was required, smokers, unlike non-smokers, demonstrated an extended change in SP-distribution. Sham-smokers were less able to shift their slow negative brain potential to the left hemisphere. The results indicate that transmission of information between brain hemispheres might be impaired in deprived smokers and that nicotine helps to compensate for this regulation deficit. However, the finer tuning within limited brain regions is achieved by non-smokers only.
KeywordsNicotine Concentration Choice Reaction Time Task Nicotine Intake Nicotine Content Warning Stimulus
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