In an early study, Maas et al. (1998) found significantly higher activation in the anterior cingulate cortex (ACC) and left dorsolateral PFC (DLPFC) in crack-cocaine abusers compared with HCs. This was the first study that used a robust design (including HCs, a block design, and analyses following selected regions of interest [ROI]) and showed that fMRI was able to visualize craving in cocaine-dependent individuals, however, including important limitations such as the small sample size, the inclusion of cocaine-dependent individuals who were allowed to have a history of other drug use, and
presenting Inhibitors,research,lifescience,medical of the visual analog scale (VAS) only twice (before and after the experiment), so that carry-over effects of craving across blocks could not be ruled out. Fulvestrant supplier Subsequently, Childress et al. (1999) showed higher regional cerebral blood flow (rCBF) in limbic structures (amygdala and anterior cingulate) Inhibitors,research,lifescience,medical and lower
rCBF in basal ganglia (caudate) compared with HCs using [15O] PET. It should be noted that PET has lower spatial resolution than MRI, even when ROI are delineated on co-registered anatomical MRI scans, as in this study. Therefore, rCBF of the nucleus accumbens (NAcc) could not be assessed. A methodological problem was the small HC group (see Table 2), who were additionally significantly younger and higher educated than those in the cocaine-dependent group (Childress Inhibitors,research,lifescience,medical et al. 1999). Table 2 Overview of the selected reviewed studies using cue-reactivity paradigms in stimulant abusers versus healthy control subjects Whereas formal power calculations Inhibitors,research,lifescience,medical are problematic for [15O]-PET and fMRI, it has since been shown that in fMRI group sizes of at least 12 are required to reliably detect typical activations (Desmond and Glover 2002). Also, note that early imaging studies Inhibitors,research,lifescience,medical tend to report fixed-effects analyses, which limits generalizability
of findings. The first fMRI study on cue exposure using an adequate sample was conducted by Garavan et al. (2000). Watching a cocaine video was associated with greater activation (compared with the neutral video) in a number of ROIs, including various isothipendyl prefrontal and limbic areas in cocaine abusers but not in HCs. The authors thus replicated the limbic activation found by Childress et al. (1999), concluding that cue-induced cocaine craving was primarily reflected by higher activation of prefrontal and limbic regions, that craving was not associated with a specific neuroanatomical substrate, but that cocaine users have a unique ability for learned, drug-related cues to produce similar brain activation patterns as potent, nondrug evocative stimuli in HCs. Furthermore, lower prefrontal and limbic activations were found in cocaine abusers compared with HCs during sexually arousing stimuli (Garavan et al. 2000) and this may indicate a relatively low sensitivity to natural rewards in SAs, also referred to as reward deficiency (Blum et al. 2000). Strengths of the Garavan et al.