A comprehensive study of sensorimotor cortex excitability in chronic cocaine users: Integrating TMS and functional MRI data

Abstract

Background Disruptions in motor control are often overlooked features of chronic cocaine users. During a simple sensorimotor integration task, for example, cocaine users activate a larger area of cortex than controls but have lower functional connectivity between the cortex and dorsal striatum, which is further correlated with poor performance. The purpose of this study was to determine whether abnormal cortical excitability in cocaine users was related to disrupted inhibitory or excitatory mechanisms, as measured by transcranial magnetic stimulation (TMS). Methods A battery of TMS measures were acquired from 87 individuals (50 cocaine dependent, 37 controls). Functional MRI data were acquired from a subset of 28 individuals who performed a block-design finger tapping task. Results TMS measures revealed that cocaine users had significantly higher resting motor thresholds and higher intracortical cortical facilitation (ICF) than controls. There was no between-group difference in either measure of cortical inhibition. Task-evoked BOLD signal in the motor cortex was significantly correlated with ICF in the cocaine users. There was no significant difference in brain-skull distance between groups. Conclusion These data demonstrated that cocaine users have disrupted cortical facilitation (as measured with TMS), which is related to elevated BOLD signal. Cortical inhibition, however, is largely intact. Given the relationship between ICF and glutamatergic agents, this may be a potentially fruitful and treatable target in addiction. Finally, among controls the distance from the scalp to the cortex was correlated with the motor threshold which may be a useful parameter to integrate into therapeutic TMS protocols in the future.

Modulating Neural Circuits with Transcranial Magnetic Stimulation: Implications for Addiction Treatment Development

“…Causal relationship between TMS input and MEP output Hanlon et al (2015a) Brain Imaging and Stimulation Targets for Addiction that took the first approach-evaluating the effect of various drugs on TMS electrophysiology parameters. These parameters include resting motor threshold, cortical silent period (CSP), paired pulse inhibition, and paired pulse facilitation.…”

Contribution of transcranial magnetic stimulation to assessment of brain connectivity and networks

“…This method has also been applied to analyze the networks responsible for higher cerebral functions such as attention (Leitao et al, 2015), working memory (Lorenc et al, 2015), perception (Pitcher et al, 2014), learning (Steel et al, 2016), and decision making (Rahnev et al, 2016). Furthermore, recently, the application of these methods has been expanded to some patients with neurological and psychological disorders such as Parkinson’s disease (Cerasa et al, 2015), stroke (Cunningham et al, 2015), epilepsy (Makela et al, 2013), pain (Martin et al, 2013), addiction (Hanlon et al, 2015), brain injury (Guller et al, 2014), peripheral nerve injury (Li et al, 2015), depression (Li et al, 2004), and schizophrenia (Gromann et al, 2012, Guller et al, 2012). …”

Brain Stimulation in Addiction

“…Cocaine abuse is associated with a higher resting MTs and higher intracortical facilitation compared with controls (Bunse et al, 2014; Hanlon et al, 2015a). Given that cortical inhibition and excitability can serve as surrogates for GABA and glutamate signaling, these studies provide some insight into potential alteration in these neurotransmitters (Bunse et al, 2014;Hanlon et al, 2015a).…”