Similar Neural Correlates of Planning and Execution to Inhibit Continuing Actions

Correlations Between Morpho-structural Properties of the Brain and Cognitive and Motor Deficits in Individuals with Traumatic Brain Injury

Traumatic brain injury (TBI) results in changes in brain networks followed by long-lasting behavioral and social impairments. This study explores the relationship between neurobehavioral as well as physical function deficits and structural changes in brain white matter (WM) and gray matter (GM) in individuals with TBI by evaluating morphometric magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) data. The structural MRI-based fractal analysis has emerged as a promising new approach to measure the morphology of the WM and GM. While DTI metrics reflect the microstructural properties of WM, the fractal dimension (FD) is regarded as a measure of morphometric complexity of the system, thus providing complementary information on the brain structure. This study included 10 individuals having moderate-to-severe TBI with balance/postural control deficits and 8 healthy controls. The network-based GM and WM morphologies were measured using FD and structural connectivity metrics, and fractional anisotropy (FA) was assessed using DTI in major WM tracts. The associations between brain structural (FA and FD) measures and a number of neuropsychological assessment and sensorimotor function outcomes were evaluated using partial least square correlation analysis. Our findings showed that the complexity in GM of default mode network, salience network, sensorimotor network, and frontoparietal network is positively correlated with the performance in cognitive and balance outcomes in patients with TBI. On the contrary, in DTI connectivity measures, only few regions including corona radiata, inferior longitudinal fasciculus, and middle cerebellar peduncle were strongly correlated with the behavioral outcomes in the TBI group. Our study suggests that the brain structure complexity measured by FD is a promising and complementary approach to DTI for potentially serving as a biomarker of cognitive and sensorimotor functions in TBI population.

Structural and functional correlates of disability, motor and cognitive performances in multiple sclerosis: Focus on the globus pallidus

OBJECTIVES

To explore structural and functional alterations of external (GPe) and internal (GPi) globus pallidus in people with multiple sclerosis (pwMS) compared to healthy controls (HC) and analyze their relationship with measures of clinical disability, motor and cognitive impairment.

METHODS

Sixty pwMS and 30 HC comparable for age and sex underwent 3.0T MRI, including conventional, diffusion tensor MRI and resting state (RS) functional MRI. Expanded Disability Status Scale (EDSS) scores were rated and timed 25-foot walk (T25FW) test, nine-hole peg test (9HPT), and paced auditory serial addition test (PASAT) were administered. Two operators segmented the GP into GPe and GPi. Volumes, T1/T2 ratio, diffusivity indices and seed-based RS functional connectivity (FC) of the GP and its components were assessed.

RESULTS

PwMS had no atrophy or altered diffusivity measures of the GP. Compared to HC, pwMS had higher T1/T2 ratio in both GP regions, which correlated with EDSS score (r = 0.26-0.39, p = 0.01-0.05). RS FC analysis highlighted component-specific functional alterations in pwMS: the GPe had decreased RS FC with fronto-parietal cortices, whereas the GPi had decreased intra-GP RS FC and increased RS FC with the thalamus. Worse EDSS, 9HPT, T25FW and PASAT scores were associated with GP RS FC modifications (r=-0.51‒0.51, p < 0.001).

CONCLUSIONS

Structural GP involvement in MS was homogeneous across its portions. Increased T1/T2 ratio values, possibly representing iron accumulation, were related to more severe disability. RS FC alterations of the GPe and GPi were consistent with their roles within the basal ganglia network and correlated with worse functional status, suggesting less efficient communication between structures.

Libet's legacy: A primer to the neuroscience of volition

The neuroscience of volition is an emerging subfield of the brain sciences, with hundreds of papers on the role of consciousness in action formation published each year. This makes the state-of-the-art in the discipline poorly accessible to newcomers and difficult to follow even for experts in the field. Here we provide a comprehensive summary of research in this field since its inception that will be useful to both groups. We also discuss important ideas that have received little coverage in the literature so far. We systematically reviewed a set of 2220 publications, with detailed consideration of almost 500 of the most relevant papers. We provide a thorough introduction to the seminal work of Benjamin Libet from the 1960s to 1980s. We also discuss common criticisms of Libet's method, including temporal introspection, the interpretation of the assumed physiological correlates of volition, and various conceptual issues. We conclude with recent advances and potential future directions in the field, highlighting modern methodological approaches to volition, as well as important recent findings.

A new perspective for evaluating the efficacy of tACS and tDCS in improving executive functions: A combined tES and fNIRS study

BACKGROUND

Executive function enhancement is considered necessary for improving the quality of life of patients with neurological or psychiatric disorders, such as attention-deficit/hyperactivity disorder, obsessive-compulsive disorder and Alzheimer's disease. Transcranial electrical stimulation (tES) has been shown to have some beneficial effects on executive functioning, but the quantification of these improvements remains controversial. We aimed to explore the potential beneficial effects on executive functioning induced by the use of transcranial alternating current stimulation (tACS)/transcranial direct current stimulation (tDCS) on the right inferior frontal gyrus (IFG) and the accompanying brain function variations in the resting state.

METHODS

We recruited 229 healthy adults to participate in Experiments 1 (105 participants) and 2 (124 participants). The participants in each experiment were randomly divided into tACS, tDCS, and sham groups. The participants completed cognitive tasks to assess behavior related to three core components of executive functions. Functional near-infrared spectroscopy (fNIRS) was used to monitor the hemodynamic changes in crucial cortical regions in the resting state.

RESULTS

Inhibition and cognitive flexibility (excluding working memory) were significantly increased after tACS/tDCS, but there were no significant behavioral differences between the tACS and tDCS groups. fNIRS revealed that tDCS induced decreases in the functional connectivity (increased neural efficiency) of the relevant cortices.

CONCLUSIONS

Enhancement of executive function was observed after tES, and the beneficial effects of tACS/tDCS may need to be precisely evaluated via brain imaging indicators at rest. tDCS revealed better neural benefits than tACS during the stimulation phase. These findings might provide new insights for selecting intervention methods in future studies and for evaluating the clinical efficacy of tES.

Smoking status affects cognitive, emotional and neural-connectivity response to distress-inducing auditory feedback

BACKGROUND

An important motive for cigarette smoking and impediment to cessation success is the avoidance of affective distress. Low levels of distress tolerance have been linked to smoking behavior, cessation history, smoking characteristics, and risk of recurrence among people who smoke. A better understanding of the neural mechanisms underlying distress sensitivity could inform approaches to help reduce avoidance of affective distress during smoking cessation. Previously among healthy participants, low distress tolerance on an MRI version of the Paced Auditory Serial Addition Task (PASAT-M), which induces distress via negative auditory feedback, was associated with larger differences in task-based functional connectivity (TBFC) between the auditory seed region and the anterior insula.

METHODS

Here, we tested differences in task performance and TBFC during affective distress among people who smoke (Smoke; n = 31) and people who quit smoking (Ex-smoke; n = 31).

RESULTS

Smoke had poorer task accuracy and reported a steeper increase in negative mood from the easy to distress blocks. Smoke had a larger difference in connectivity (distress > easy condition) between the auditory seed region and the left inferior frontal gyrus and right anterior insula. Additionally, task accuracy positively correlated with the difference in connectivity (distress > easy condition) with the left inferior frontal gyrus and the right anterior insula among Smoke but not Ex-smoke.

CONCLUSIONS

These results are consistent with the idea that people who smoke are more sensitive to cognitive-affective distress and that the inferior frontal gyrus and anterior insula play important roles in the regulation of distress.

Association between Motor Planning and the Frontoparietal Network in Children: An Exploratory Multimodal Study

OBJECTIVE

Evidence from adult literature shows the involvement of cortical grey matter areas of the frontoparietal lobe and the white matter bundle, the superior longitudinal fasciculus (SLF) in motor planning. This is yet to be confirmed in children.

METHOD

A multimodal study was designed to probe the neurostructural basis of childhood motor planning. Behavioural (motor planning), magnetic resonance imaging (MRI) and diffusion weighted imaging (DWI) data were acquired from 19 boys aged 8-11 years. Motor planning was assessed using the one and two colour sequences of the octagon task. The MRI data were preprocessed and analysed using FreeSurfer 6.0. Cortical thickness and cortical surface area were extracted from the caudal middle frontal gyrus (MFG), superior frontal gyrus (SFG), precentral gyrus (PcG), supramarginal gyrus (SMG), superior parietal lobe (SPL) and the inferior parietal lobe (IPL) using the Desikan-Killiany atlas. The DWI data were preprocessed and analysed using ExploreDTI 4.8.6 and the white matter tract, the SLF was reconstructed.

RESULTS

Motor planning of the two colour sequence was associated with cortical thickness of the bilateral MFG and left SFG, PcG, IPL and SPL. The right SLF was related to motor planning for the two colour sequence as well as with the left cortical thickness of the SFG.

CONCLUSION

Altogether, morphology within frontodorsal circuity, and the white matter bundles that support communication between them, may be associated with individual differences in childhood motor planning.

Statistical Nonparametric fMRI Maps in the Analysis of Response Inhibition in Abstinent Individuals with History of Alcohol Use Disorder

Inhibitory impairments may persist after abstinence in individuals with alcohol use disorder (AUD). Using traditional statistical parametric mapping (SPM) fMRI analysis, which requires data to satisfy parametric assumptions often difficult to satisfy in biophysical system as brain, studies have reported equivocal findings on brain areas responsible for response inhibition, and activation abnormalities during inhibition found in AUD persist after abstinence. Research is warranted using newer analysis approaches. fMRI scans were acquired during a Go/NoGo task from 30 abstinent male AUD and 30 healthy control participants with the objectives being (1) to characterize neuronal substrates associated with response inhibition using a rigorous nonparametric permutation-based fMRI analysis and (2) to determine whether these regions were differentially activated between abstinent AUD and control participants. A blood oxygen level dependent contrast analysis showed significant activation in several right cortical regions and deactivation in some left cortical regions during successful inhibition. The largest source of variance in activation level was due to group differences. The findings provide evidence of cortical substrates employed during response inhibition. The largest variance was explained by lower activation in inhibition as well as ventral attentional cortical networks in abstinent individuals with AUD, which were not found to be associated with length of abstinence, age, or impulsiveness.

Electrocorticography to Investigate Age-Related Brain Lateralization on Pediatric Motor Inhibition

Response inhibition refers to the ability to suppress inappropriate actions that interfere with goal-driven behavior. The inferior frontal gyrus (IFG) is known to be associated with inhibition of a motor response by assuming executive control over motor cortex outputs. This study aimed to evaluate the pediatric development of response inhibition through subdural electrocorticography (ECoG) recording. Subdural ECoG recorded neural activities simultaneously during a Go/No-Go task, which was optimized for children. Different frequency power [theta: 4–8 Hz; beta: 12–40 Hz; high-gamma (HG): 70–200 Hz] was estimated within the IFG and motor cortex. Age-related analysis was computed by each bandpass power ratio between Go and No-Go conditions, and phase-amplitude coupling (PAC) over IFG by using the modulating index metric in two conditions. For all the eight pediatric patients, HG power was more activated in No-Go trials than in Go trials, in either right- or left-side IFG when available. In the IFG region, the power over theta and HG in No-Go conditions was higher than those in Go conditions, with significance over the right side (p < 0.05). The age-related lateralization from both sides to the right side was observed from the ratio of HG power and PAC value between the No-Go and Go trials. In the pediatric population, the role of motor inhibition was observed in both IFG, with age-related lateralization to the right side, which was proved in the previous functional magnetic resonance imaging studies. In this study, the evidence correlation of age and response inhibition was observed directly by the evidence of cortical recordings.

Brain activation changes following motor training in children with unilateral cerebral palsy: An fMRI study

BACKGROUND

Intensive motor-learning-based interventions have demonstrated efficacy for improving motor function in children with unilateral spastic cerebral palsy (USCP). Although this improvement has been associated mainly with neuroplastic changes in the primary sensori-motor cortices, this plasticity may also involve a wider fronto-parietal network for motor learning.

OBJECTIVE

To determine whether hand-arm bimanual intensive therapy including lower extremities (HABIT-ILE) induces brain activation changes in an extensive network for motor skill learning and whether these changes are related to functional changes observed after HABIT-ILE.

METHODS

In total, 25 children with USCP were behaviourally assessed in manual dexterity and everyday activities before and after HABIT-ILE. Functional imagery monitored brain activity while participants manipulated objects using their less-affected, more-affected or both hands. Two random-effects-group analyses performed at the whole-brain level assessed the brain activity network before and after therapy. Three other random-effects-group analyses assessed brain activity changes after therapy. Spearman's correlations were used to evaluate the correlation between behavioural and brain activity changes.

RESULTS

The same fronto-parietal network was identified before and after therapy. After the intervention, the more-affected hand manipulation elicited a decrease in activity on the motor cortex of the non-lesional hemisphere and an increase in activity on motor areas of the lesional hemisphere. The less-affected hand manipulation generated a decrease in activity of sensorimotor areas in the non-lesional hemisphere. Both-hands manipulation elicited an increase in activity of both hemispheres. Furthermore, we observed an association between brain activity changes and changes in everyday activity assessments.

CONCLUSION

Brain activation changes were observed in a fronto-parietal network underlying motor skill learning with HABIT-ILE in children with USCP. Two different patterns were observed, probably related to different phases of motor skill learning, representing an increased practice-dependent brain recruitment or a brain activation refinement by more efficient means. CLINICALTRIALS.GOV: NCT01700777 &NCT02667613.