Transcranial Magnetic Stimulation in Smokers: an Examination of Mediating Neural Pathways.

Overview

The primary objective of this study is to examine the effects of repetitive transcranial magnetic stimulation (rTMS) on a regulation of craving task (ROC task) and evaluate the feasibility of targeting rTMS via fMRI based neuronavigation. Specifically, we will examine BOLD activation within the DLPFC when control over craving is exerted in order to identify if 1) the task produces reliable activations in an area capable of being targeted by a standard figure-8 coil and 2) examine if the coordinates of the area are distinct from the area targeted via anatomical neuronavigation alone. Last, we will examine if rTMS, compared to sham, is capable of improving cognitive control over craving measured at outcome. The current pilot study will examine these aims in a sample of tobacco dependent adults (N=16) (with final sample size dependent on availability of funds).

The study will include functional magnetic resonance imaging at baseline as well as demographic, psychological, and tobacco use assessments. Following initial assessment, participants will undergo one active rTMS session (20 Hz rTMS, 900 pulses per session, applied to left DLPFC). The outcome session will include assessments repeated from baseline. The current proposal will examine the following aims. Aim 1: To test the potential for active rTMS to improve cognitive control of craving. Hypothesis: Active rTMS (compared to sham rTMS) will result in significant improvement in control over craving assessed by self-reported craving during the ROC task as well as in terms of activity in prefrontal regions associated with cognitive control during the ROC task. Aim 2 (feasibility): To examine the feasibility of using fMRI BOLD activation in the DLPFC during the ROC task to target rTMS. BOLD activations during successful control over craving trials will be examined in terms of their reliability within participant and their feasibility as a target for rTMS delivered via standard figure 8 coil (capable of inducing synaptic firing 1.5-3.0 cm beneath the scalp). Additionally, the coordinates for the target identified via BOLD activation during the ROC task will be compared to the coordinates for the target identified by using standard neuronavigation to the DLPFC via anatomical fMRI, in order to determine if these areas are distinct in terms of the direct effect of the stimulation field (approximately 5 cm2).