Functional Magnetic Resonance Imaging
Functional magnetic resonance imaging (fMRI) is an in-vivo technique that reveals regions of the brain that become active during certain cognitive-behavioral-affective tasks relative to a specified baseline. Increased oxygen delivery to activated regions is revealed using the blood oxygen level dependent (BOLD) effect. The BOLD effect arises from changes in local 'magnetic susceptibility' (the extent to which an applied magnetic field is distorted as it interacts with a material) between oxygenated blood (diamagnetic) and deoxygenated blood (paramagnetic). The MRI signal is inversely proportional to the deoxygenated blood. The BOLD signal can be assessed for each voxel (volume element) of a brain slice.
For a more in depth explanation of the biophysics underlying fMRI,
we recommend: The Basics of MRI:
Our fMRI Studies in Cocaine Addiction
Monetary Reward Processing:
Inhibitory control and drug cue reactivity:
Results suggest a disruption in drug addiction of neural habituation to practice that possibly encompasses opponent anterior vs. posterior brain adaptation to the novelty of the experience: overly expeditious for the former but overly protracted for the latter.
Cocaine addicted individuals may therefore be predisposed to an increased challenge when required to maintain alertness as a task progresses, not able to optimally utilize a prematurely habituating PFC to compensate with an increased attribution of salience to a desired reward (Goldstein et al., 2007e).
Visuospatial Processing and working memory:
We also use other tasks of attention and cognitive
function (e.g., sustained visuospatial attention and verbal
working memory) in cocaine addicted individuals. Here, findings provide evidence of
a widespread neurofunctional disruption that may underlie
compromises in sensory processing, attention and vigilance, and
executive control in cocaine abusers
(Tomasi et al., 2007a; Tomasi et al., 2007b).