Thalamic volume and functional connectivity are associated with nicotine dependence severity and craving.

Tobacco smoking is associated with deleterious health outcomes. Most smokers want to quit smoking, yet relapse rates are high. Understanding neural differences associated with tobacco use may help generate novel treatment options. Several animal studies have recently highlighted the central role of the thalamus in substance use disorders, but this research focus has been understudied in human smokers. Here, we investigated associations between structural and functional magnetic resonance imaging measures of the thalamus and its subnuclei to distinct smoking characteristics. We acquired anatomical scans of 32 smokers as well as functional resting-state scans before and after a cue-reactivity task. Thalamic functional connectivity was associated with craving and dependence severity, whereas the volume of the thalamus was associated with dependence severity only. Craving, which fluctuates rapidly, was best characterized by differences in brain function, whereas the rather persistent syndrome of dependence severity was associated with both brain structural differences and function. Our study supports the notion that functional versus structural measures tend to be associated with behavioural measures that evolve at faster versus slower temporal scales, respectively. It confirms the importance of the thalamus to understand mechanisms of addiction and highlights it as a potential target for brain-based interventions to support smoking cessation, such as brain stimulation and neurofeedback.

Cortical encoding of speech enhances task-relevant acoustic information.

Speech is the most important signal in our auditory environment, and the processing of speech is highly dependent on context. However, it is unknown how contextual demands influence the neural encoding of speech. Here, we examine the context dependence of auditory cortical mechanisms for speech encoding at the level of the representation of fundamental acoustic features (spectrotemporal modulations) using model-based functional magnetic resonance imaging. We found that the performance of different tasks on identical speech sounds leads to neural enhancement of the acoustic features in the stimuli that are critically relevant to task performance. These task effects were observed at the earliest stages of auditory cortical processing, in line with interactive accounts of speech processing. Our work provides important insights into the mechanisms that underlie the processing of contextually relevant acoustic information within our rich and dynamic auditory environment.

Connectivity changes underlying neurofeedback training of visual cortex activity.

Neurofeedback based on real-time functional magnetic resonance imaging (fMRI) is a new approach that allows training of voluntary control over regionally specific brain activity. However, the neural basis of successful neurofeedback learning remains poorly understood. Here, we assessed changes in effective brain connectivity associated with neurofeedback training of visual cortex activity. Using dynamic causal modeling (DCM), we found that training participants to increase visual cortex activity was associated with increased effective connectivity between the visual cortex and the superior parietal lobe. Specifically, participants who learned to control activity in their visual cortex showed increased top-down control of the superior parietal lobe over the visual cortex, and at the same time reduced bottom-up processing. These results are consistent with efficient employment of top-down visual attention and imagery, which were the cognitive strategies used by participants to increase their visual cortex activity.