White matter microstructural changes in short-term learning of a continuous visuomotor sequence

Efficient neural transmission is crucial for optimal brain function, yet the plastic potential of white matter (WM) has long been overlooked. Growing evidence now shows that modifications to axons and myelin occur not only as a result of long-term learning, but also after short training periods. Motor sequence learning (MSL), a common paradigm used to study neuroplasticity, occurs in overlapping learning stages and different neural circuits are involved in each stage. However, most studies investigating short-term WM plasticity have used a pre-post design, in which the temporal dynamics of changes across learning stages cannot be assessed. In this study, we used multiple magnetic resonance imaging (MRI) scans at 7 T to investigate changes in WM in a group learning a complex visuomotor sequence (LRN) and in a control group (SMP) performing a simple sequence, for five consecutive days. Consistent with behavioral results, where most improvements occurred between the two first days, structural changes in WM were observed only in the early phase of learning (d1-d2), and in overall learning (d1-d5). In LRNs, WM microstructure was altered in the tracts underlying the primary motor and sensorimotor cortices. Moreover, our structural findings in WM were related to changes in functional connectivity, assessed with resting-state functional MRI data in the same cohort, through analyses in regions of interest (ROIs). Significant changes in WM microstructure were found in a ROI underlying the right supplementary motor area. Together, our findings provide evidence for highly dynamic WM plasticity in the sensorimotor network during short-term MSL.

The descending motor tracts are different in dancers and musicians

Long-term motor training, such as dance or gymnastics, has been associated with increased diffusivity and reduced fiber coherence in regions including the corticospinal tract. Comparisons between different types of motor experts suggest that experience might result in specific structural changes related to the trained effectors (e.g., hands or feet). However, previous studies have not segregated the descending motor pathways from different body-part representations in motor cortex (M1). Further, most previous diffusion tensor imaging studies used whole-brain analyses based on a single tensor, which provide poor information about regions where multiple white matter (WM) tracts cross. Here, we used multi-tensor probabilistic tractography to investigate the specific components of the descending motor pathways in well-matched groups of dancers, musicians and controls. To this aim, we developed a procedure to identify the WM regions below the motor representations of the head, hand, trunk and leg that served as seeds for tractography. Dancers showed increased radial diffusivity (RD) in comparison with musicians, in descending motor pathways from all the regions, particularly in the right hemisphere, whereas musicians had increased fractional anisotropy (FA) in the hand and the trunk/arm motor tracts. Further, dancers showed larger volumes compared to both other groups. Finally, we found negative correlations between RD and FA with the age of start of dance or music training, respectively, and between RD and performance on a melody task, and positive correlations between RD and volume with performance on a whole-body dance task. These findings suggest that different types of training might have different effects on brain structure, likely because dancers must coordinate movements of the entire body, whereas musicians focus on fewer effectors.

Structural Covariance Analysis Reveals Differences Between Dancers and Untrained Controls

Dancers and musicians differ in brain structure from untrained individuals. Structural covariance (SC) analysis can provide further insight into training-associated brain plasticity by evaluating interregional relationships in gray matter (GM) structure. The objectives of the present study were to compare SC of cortical thickness (CT) between expert dancers, expert musicians and untrained controls, as well as to examine the relationship between SC and performance on dance- and music-related tasks. A reduced correlation between CT in the left dorsolateral prefrontal cortex (DLPFC) and mean CT across the whole brain was found in the dancers compared to the controls, and a reduced correlation between these two CT measures was associated with higher performance on a dance video game task. This suggests that the left DLPFC is structurally decoupled in dancers and may be more strongly affected by local training-related factors than global factors in this group. This work provides a better understanding of structural brain connectivity and training-induced brain plasticity, as well as their interaction with behavior in dance and music.

Adverse childhood experiences and gender influence treatment seeking behaviors in obsessive-compulsive disorder

BACKGROUND

Exposure to adverse childhood experiences (ACE) increases the risk of adult physical and mental health disorders, including obsessive-compulsive disorder (OCD), and influences adult brain structure and function. ACE could influence the use of psychotropic drugs in adulthood, and treatment seeking behaviors.

METHODS

We assessed the severity of ACE in a sample of 31 healthy controls and 66 patients with OCD who were consecutively referred for hospitalization and were either drug-naïve or drug-treated. In addition, we explored the possible clinical relevance of ACE with two additional analyses: (a) a discriminant function analysis with sex and ACE as factors, and (b) a logistic regression with use of medication as dependent variable and ACE as factor.

RESULTS

Despite comparable age, years at school, age at onset of illness, duration of illness, and severity of illness (Y-BOCS), adult drug-naïve patients reported lower exposure to ACE and later contacts with mental health professionals than drug-treated. This effect was particularly evident in female patients compared to males.

CONCLUSIONS

The interaction of gender with factors linked with the early familial environment biased access to psychiatric care and use of medication, independent of OCD-associated factors such as severity of symptoms or duration of illness. The need for medications of patients could be higher in families where OCD symptomatology is associated with ACE.

Widespread changes of white matter microstructure in obsessive-compulsive disorder: effect of drug status

Diffusion tensor imaging (DTI) allows the study of white matter (WM) structure. Literature suggests that WM structure could be altered in obsessive-compulsive disorder (OCD) proportional to the severity of the disease. Heterogeneity of brain imaging methods, of the studied samples, and of drug treatments make localization, nature, and severity of the WM abnormalities unclear. We applied Tract-Based Spatial Statistics (TBSS) of DTI measures to compare fractional anisotropy (FA), mean, axial, and radial diffusivity of the WM skeleton in a group of 40 consecutively admitted inpatients affected by severe OCD (18 drug-naive, and 22 with an ongoing drug treatment) and 41 unrelated healthy volunteers from the general population. Data were analyzed accounting for the effects of multiple comparisons, and of age, sex, and education as nuisance covariates. Compared to controls, OCD patients showed a widespread reduction of FA with a concurrent increase of mean and radial diffusivity. In no brain areas patients had higher FA or lower diffusivity values than controls. These differences were observed in drug-treated patients compared to drug-naive patients and healthy controls, which in turn did not differ among themselves in any DTI measure. Reduced FA with increased mean and radial diffusivity suggests significant changes in myelination of WM tracts, without axonal loss. Drug treatments could modify the structure of cell membranes and myelin sheaths by influencing cellular lipogenesis, cholesterol homeostasis, autophagy, oligodendrocyte differentiation and remyelination. Changes of DTI measures in drug-treated OCD patients could reflect pathophysiological underpinnings of OCD, or a yet unexplored part of the mechanism of action of drugs.

Renal transplantation from cadaveric donor after myocardial revascularization: still a matter of concern?

Renal transplantation in patients who have undergone coronary revascularization remains a matter of concern, few experiences have been reported in literature. From January 1997 to March 2003, 23 previously revascularized patients underwent renal transplants from cadaveric donors. We analyzed patient survival and cardiac events in this group of patients (group A) versus a similar population of 38 revascularized patients who were still on dialysis (group B) on the active waiting list (awl). After a similar follow-up (29.30 +/- 21.34 months versus 32.98 +/- 31.33 months; P = .56), survival was 100% for renal transplant patients and 94.74% for dialysis patients, two of whom (5.26%) died from acute myocardial infarction and four (10.52%) were excluded from the waiting list because of cardiac problems. The event-person ratio was 0.51 for group A patients (75% of events clustered within the first 6 months) and 0.71 for group B. The need for therapy with nitrates decreased from 11/23 (47.8%) to 6/23 (26%) after transplant. The ejection fraction remained stable (53.82% +/- 10.4% vs pre-Tx value of 54.8% +/- 9.4%). Renal survival was 100% (sCr = 1.4 +/- 0.4 mg/dL). Although no statistical significance has emerged, there was a general trend in favor of transplanted patients. On the basis of this experience we believe that coronary revascularization per se should no longer be a matter of concern for renal transplantation, which could be superior to dialysis for this type of patient.