Power spectrum scale invariance as a neural marker of cocaine misuse and altered cognitive control

Abstract

Background: Magnetic resonance imaging (MRI) has highlighted the effects of chronic cocaine exposure on cerebral structures and functions, and implicated the prefrontal cortices in deficits of cognitive control. Recent investigations suggest power spectrum scale invariance (PSSI) of cerebral blood oxygenation level dependent (BOLD) signals as a neural marker of cerebral activity. We examined here how PSSI is altered in association with cocaine misuse and impaired cognitive control.

Methods: Eighty-eight healthy (HC) and seventy-five age and gender matched cocaine dependent (CD) adults participated in functional MRI of a stop signal task (SST). BOLD images were preprocessed using standard procedures in SPM, including detrending, band-pass filtering (0.01-0.25 Hz), and correction for head motions. Voxel-wise PSSI measures were estimated by a linear fit of the power spectrum with a log-log scale. In group analyses, we examined differences in PSSI between HC and CD, and its association with clinical and behavioral variables using a multiple regression. A critical component of cognitive control is post-signal behavioral adjustment, which is compromised in cocaine dependence. Therefore, we examined the PSSI changes in association with post-signal slowing (PSS) in the SST.

Results: Compared to HC, CD showed decreased PSS and PSSI in multiple frontoparietal regions. PSSI was positively correlated with PSS in HC in multiple regions, including the left inferior frontal gyrus (IFG) and right supramarginal gyrus (SMG), which showed reduced PSSI in CD.

Conclusions: These findings suggest disrupted connectivity dynamics in the fronto-parietal areas in association with post-signal behavioral adjustment in cocaine addicts. These new findings support PSSI as a neural marker of impaired cognitive control in cocaine addiction.

Keywords: Cocaine addiction; Cognitive control; Conflict monitoring; PSSI; Post-signal slowing; post-error slowing; stimulant.

Fig. 1

(a) Regions showing reduced PSSI in CD as compared to HC; two sample t-test with age as covariate. No brain regions showed increased PSSI in CD as compared to HC at the same threshold. Clusters that survived the corrected extent threshold are shown in Table 3. (b) Regions with PSSI in linear correlation with post-signal slowing (PSS) in the HC; multiple regression with PSS and age as covariates. p < 0.05, corrected AlphaSim threshold. Clusters that survived the corrected extent threshold are shown in Table 4. The inset each highlights the overlap in the left inferior frontal gyrus (IFG), left angular gyrus (AG) and right supramarginal gyrus (SMG) between these two group analyses.

Fig. 2

(a) Compared to HC, CD showed decreased PSSI in the left inferior frontal gyrus (IFG) and right supramarginal gyrus (SMG) (two sample t-test); (b) PSSI increased in association with post-signal slowing in the IFG (r = 0.31, p = 0.003) and SMG (r = 0.35, p = 0.001) in HC but not CD. A direct test shows a significant difference in slope of the linear regression in both cases (Zar, 1999).