The effects of nicotine replacement on cognitive brain activity during smoking withdrawal studied with simultaneous fMRI/EEG.

Impaired attention ('difficulty concentrating') is a cognitive symptom of nicotine withdrawal that may be an important contributor to smoking relapse. However, the neurobiological basis of this effect and the potentially beneficial effects of nicotine replacement therapy both remain unclear. We used functional MRI with simultaneous electroencephalogram (EEG) recording to define brain activity correlates of cognitive impairment with short-term smoking cessation in habitual smokers and the effects of nicotine replacement. We found that irrespective of treatment (ie nicotine or placebo) EEG α power was negatively correlated with increased activation during performance of a rapid visual information processing (RVIP) task in dorsolateral prefrontal, dorsal anterior cingulate, parietal, and insular cortices, as well as, caudate, and thalamus. Relative to placebo, nicotine replacement further increased the α-correlated activation across these regions. We also found that EEG α power was negatively correlated with RVIP-induced deactivation in regions comprising the 'default mode' network (ie angular gyrus, cuneus, precuneus, posterior cingulate, and ventromedial prefrontal cortex). These α-correlated deactivations were further reduced by nicotine. These findings confirm that effects of nicotine on cognition during short-term smoking cessation occur with modulation of neuronal sources common to the generation of both the blood oxygen-level-dependent and α EEG signals. Our observations thus demonstrate that nicotine replacement in smokers has direct pharmacological effects on brain neuronal activity modulating cognitive networks.

A comparative clinical study investigating the efficacy of a dentifrice containing 8% strontium acetate and 1040 ppm fluoride in a silica base and a control dentifrice containing 1450 ppm fluoride in a silica base to provide immediate relief of dentin hypersensitivity.

OBJECTIVE: The objective of this clinical study was to evaluate and compare the efficacy of a dentifrice containing 8% strontium acetate and 1040 ppm fluoride (from sodium fluoride) in a silica base (test dentifrice) to a control dentifrice containing 1450 ppm fluoride (from sodium fluoride) in a silica base, to reduce dentin hypersensitivity immediately after a single dab-on self-application, and after subsequent twice-daily brushing for three days. METHODS: This was a randomized, examiner-blind, two-arm parallel group, three-day clinical study with seventy-nine subjects, stratified based on baseline tooth sensitivity. Tooth sensitivity was determined through subject responses to both evaporative (Schiff and Visual Analogue Scale [VAS]) and tactile stimuli (Yeaple probe), prior to and immediately after subjects self-applied a single pea-sized amount of either the test or control dentifrice to qualifying sensitive teeth, massaging the toothpaste onto the sensitive area for one minute. Tooth sensitivity was further assessed in response to the same stimuli after subjects brushed twice daily for an additional three days. Subject assessments were performed by the same examiner throughout the study. RESULTS: Seventy-nine subjects completed this clinical study. Both subject groups exhibited reductions in dentin hypersensitivity directly after a single dab-on application. These reductions were significant across all measures for the test dentifrice. Between-treatment analyses showed the test dentifrice to be significantly better at relieving subjects' sensitivity across all measures (Schiff p = 0.0003, tactile p = 0.0003, and VAS p = 0.0077) compared to the control. After the additional three days of twice-daily brushing, between-treatment analyses showed the test dentifrice to be significantly better at relieving subjects' sensitivity across all measures (Schiff p = 0.0102, tactile p = 0.0493, and VAS p = 0.0067) than the control dentifrice. CONCLUSION: The 8% strontium acetate, 1040 ppm fluoride dentifrice provided significant within-treatment reductions in dentin hypersensitivity for all measures at both time points (immediate and three-day brushing). Compared to the control dentifrice, significant between-treatment reductions in sensitivity were observed after a single dab-on application for all measures, and following the additional twice-daily brushing for three days in favor of the 8% strontium acetate, 1040 ppm fluoride dentifrice.