A 2013 review comparing different structural and functional imaging studies showed morphological brain alterations in long-term cannabis users which were found to possibly correlate to cannabis exposure.[28] A 2010 review found resting blood flow to be lower globally and in prefrontal areas of the brain in cannabis users, when compared to non-users. It was also shown that giving THC or cannabis correlated with increased bloodflow in these areas, and facilitated activation of the anterior cingulate cortex and frontal cortex when participants were presented with assignments demanding use of cognitive capacity.[29] Both reviews noted that some of the studies that they examined had methodological limitations, for example small sample sizes or not distinguishing adequately between cannabis and alcohol consumption