In Vivo Neural Tract Tracing Procedures: Unravelling Neural Hodology Using Fluorescent and Non-fluorescent Neural Tract Tracers, Optogenetic Approach, and Diffusion Tensor Neurotractography Protocols.

Fluorescent and non-fluorescent neural tract tracers enable the investigation of neural pathways in both peripheral and central nervous systems in laboratory animals demonstrating images with high resolution and great anatomic precision. Anterograde and retrograde viral tracers are important cutting-edge tools for neuroanatomical mapping. The optogenetic consists of an advanced alternative for in vivo neural tract tracing procedures, fundamentally considering the possibility to dissect and modulate pathways either exciting or inhibiting neural circuits in laboratory animals. The neurotractography by diffusion tensor imaging in vivo procedures enables the study of neural pathways in humans with reasonable accuracy. Here we describe the procedure of classical anatomic neural tract tracing and modern optogenetic technique performed in anima vili in addition to different diffusion tensor neurotractography performed in anima nobili.

Brain Tumor Anatomy with Tractography Fluorescence and Confocal Endoscopy.

Tractography fluorescence and confocal endomicroscopy are complementary technologies to targeted tumor resection, and it is certain that as our technology for fluorescent probes continues to evolve, the confocal microscope will continue to be refined. Recent work suggests that intraoperative high-resolution augmented reality endomicroscopy, a real-time alternative to invasive biopsy and histopathology, has the potential to better quantify tumor burden at the final stages of surgery and ultimately to improve patient outcomes when combined with wide-field imaging approaches. Additional studies are needed to further elucidate the clinical benefits of these new technologies for brain tumor patients.

[Frontal aslant tract: Anatomy and implications in brain glioma neurosurgery]. / Tracto oblicuo frontal: anatomía e implicancia en neurocirugía de gliomas cerebrales.

The frontal aslant tract (FAT) connects the supplementary motor area (SMA) with the pars opercularis. Its role in language and its implications in glioma surgery remain under discussion. We present an anatomosurgical study of three cases with surgical resolution. Three patients with gliomas in the left frontal lobe were operated on using an awake patient protocol with cortical and subcortical mapping techniques, conducting motor and language evaluations. Tractography was performed using DSI Studio software. All three patients showed intraoperative language inhibition through subcortical stimulation of the FAT. Resection involving the FAT correlated with language deficits in all cases and movement initiation deficits in two cases. All patients recovered from their deficits at six months postoperatively. In conclusion, the tract has been successfully reconstructed, showing both anatomical and functional complexity, supporting the idea of its mapping and preservation in glioma surgery. Future interdisciplinary studies are necessary to determine the transient or permanent nature of the deficits.

El tracto oblicuo frontal (TOF) conecta el área motora suplementaria (AMS) con la pars opercularis. Su rol en el lenguaje y su implicancia en la cirugía de gliomas siguen en discusión. Presentamos un estudio anatomoquirúrgico de tres casos con resolución quirúrgica. Se operaron tres pacientes con gliomas en el lóbulo frontal izquierdo utilizando protocolo de paciente despierto con técnicas de mapeo cortical y subcortical realizando evaluación motora y del lenguaje. Las tractografías fueron realizadas con el software DSI Studio. Los tres pacientes presentaron inhibición intraoperatoria del lenguaje mediante la estimulación subcortical de TOF. La resección en contacto con el TOF se correlacionó con déficits del lenguaje en todos los casos y en dos casos déficits en la iniciación del movimiento. Todos los pacientes recuperaron su déficit a los seis meses postoperatorios. En conclusión, se ha logrado reconstruir al tracto. Éste presenta una complejidad anatómica y funcional, que apoya la idea de su mapeo y preservación en la cirugía de gliomas. Futuros estudios interdisciplinarios son necesarios para determinar el carácter transitorio o permanente de los déficits.

Assessment of U-Net in the segmentation of short tracts: Transferring to clinical MRI routine.

Accurately studying structural connectivity requires precise tract segmentation strategies. The U-Net network has been widely recognized for its exceptional capacity in image segmentation tasks and provides remarkable results in large tract segmentation when high-quality diffusion-weighted imaging (DWI) data are used. However, short tracts, which are associated with various neurological diseases, pose specific challenges, particularly when high-quality DWI data acquisition within clinical settings is concerned. Here, we aimed to evaluate the U-Net network ability to segment short tracts by using DWI data acquired in different experimental conditions. To this end, we conducted three types of training experiments involving 350 healthy subjects and 11 white matter tracts, including the anterior, posterior, and hippocampal commissure, fornix, and uncinated fasciculus. In the first experiment, the model was exclusively trained with high-quality data of the Human Connectome Project (HCP) dataset. The second experiment focused on images of healthy subjects acquired from a local hospital dataset, representing a typical clinical routine acquisition. In the third experiment, a hybrid training approach was employed, combining data of the HCP and local hospital datasets. Then, the best model was also tested in unseen DWIs of 10 epilepsy patients of the local hospital and 10 healthy subjects acquired on a scanner from another company. The outcomes of the third experiment demonstrated a notable enhancement in performance when contrasted with the preceding trials. Specifically, the short tracts within the local hospital dataset achieved Dice scores ranging between 0.60 and 0.65. Similar intervals were obtained with HCP data in the first experiment, and a substantial improvement compared to the scores between 0.37 and 0.50 obtained with the local hospital dataset at the same experiment. This improvement persisted when the method was applied to diverse scenarios, including different scanner acquisitions and epilepsy patients. These results indicate that combining datasets from different sources, coupled with resolution standardization strengthens the neural network ability to generalize predictions across a spectrum of datasets. Nevertheless, short tract segmentation performance is intricately linked to the training composition, to validation, and to testing data. Moreover, curved tracts have intricate structural nature, which adds complexities to their segmenting. Although the network training approach tested herein has provided promising results, caution must be taken when extrapolating its application to datasets acquired under distinct experimental conditions, even in the case of higher-quality data or analysis of long or short tracts.

Selective Medial Septum Lesions in Healthy Rats Induce Longitudinal Changes in Microstructure of Limbic Regions, Behavioral Alterations, and Increased Susceptibility to Status Epilepticus.

Septo-hippocampal pathway, crucial for physiological functions and involved in epilepsy. Clinical monitoring during epileptogenesis is complicated. We aim to evaluate tissue changes after lesioning the medial septum (MS) of normal rats and assess how the depletion of specific neuronal populations alters the animals' behavior and susceptibility to establishing a pilocarpine-induced status epilepticus. Male Sprague-Dawley rats were injected into the MS with vehicle or saporins (to deplete GABAergic or cholinergic neurons; n = 16 per group). Thirty-two animals were used for diffusion tensor imaging (DTI); scanned before surgery and 14 and 49 days post-injection. Fractional anisotropy and apparent diffusion coefficient were evaluated in the fimbria, dorsal hippocampus, ventral hippocampus, dorso-medial thalamus, and amygdala. Between scans 2 and 3, animals were submitted to diverse behavioral tasks. Stainings were used to analyze tissue alterations. Twenty-four different animals received pilocarpine to evaluate the latency and severity of the status epilepticus 2 weeks after surgery. Additionally, eight different animals were only used to evaluate the neuronal damage inflicted on the MS 1 week after the molecular surgery. Progressive changes in DTI parameters in both white and gray matter structures of the four evaluated groups were observed. Behaviorally, the GAT1-saporin injection impacted spatial memory formation, while 192-IgG-saporin triggered anxiety-like behaviors. Histologically, the GABAergic toxin also induced aberrant mossy fiber sprouting, tissue damage, and neuronal death. Regarding the pilocarpine-induced status epilepticus, this agent provoked an increased mortality rate. Selective septo-hippocampal modulation impacts the integrity of limbic regions crucial for certain behavioral skills and could represent a precursor for epilepsy development.

Paternal Prenatal and Lactation Exposure to a High-Calorie Diet Shapes Transgenerational Brain Macro- and Microstructure Defects, Impacting Anxiety-Like Behavior in Male Offspring Rats.

Prenatal exposure to high-energy diets (HED) increases the susceptibility to behavioral alterations in the male offspring. We addressed whether prenatal HED primes the transgenerational inheritance of structural brain changes impacting anxiety/depression-like behavior in the offspring. For this, we used female Wistar rats exposed to a HED [cafeteria (CAF) diet, n = 6] or chow [control (CON) n = 6] during development. Anxiety and depression-like behavior were evaluated in filial 1 (F1), filial 2 (F2), and filial 3 (F3) male offspring using the open field (OFT), elevated plus maze, novelty suppressed feeding (NSFT), tail suspension (TST), and forced swimming tests. Structural brain changes were identified by deformation-based morphometry (DBM) and diffusion tensor imaging using ex vivo MRI. We found that the F1, F2, and F3 offspring exposed to CAF diet displayed higher anxious scores including longer feeding latency during the NSFT, and in the closed arms, only F1 offspring showed longer stay on edges during the OFT versus control offspring. DBM analysis revealed that CAF offspring exhibited altered volume in the cerebellum, hypothalamus, amygdala, and hippocampus preserved up to the F3 generation of anxious individuals. Also, F3 CAF anxious exhibited greater fractional anisotropy and axial diffusivity (AD) in the amygdala, greater apparent diffusion coefficient in the corpus callosum, and greater AD in the hippocampus with respect to the control. Our results suggest that prenatal and lactation exposure to HED programs the transgenerational inheritance of structural brain changes related to anxiety-like behavior in the male offspring.

Microstructural brain abnormalities, fatigue, and cognitive dysfunction after mild COVID-19.

Although some studies have shown neuroimaging and neuropsychological alterations in post-COVID-19 patients, fewer combined neuroimaging and neuropsychology evaluations of individuals who presented a mild acute infection. Here we investigated cognitive dysfunction and brain changes in a group of mildly infected individuals. We conducted a cross-sectional study of 97 consecutive subjects (median age of 41 years) without current or history of psychiatric symptoms (including anxiety and depression) after a mild infection, with a median of 79 days (and mean of 97 days) after diagnosis of COVID-19. We performed semi-structured interviews, neurological examinations, 3T-MRI scans, and neuropsychological assessments. For MRI analyses, we included a group of non-infected 77 controls. The MRI study included white matter (WM) investigation with diffusion tensor images (DTI) and functional connectivity with resting-state functional MRI (RS-fMRI). The patients reported memory loss (36%), fatigue (31%) and headache (29%). The quantitative analyses confirmed symptoms of fatigue (83% of participants), excessive somnolence (35%), impaired phonemic verbal fluency (21%), impaired verbal categorical fluency (13%) and impaired logical memory immediate recall (16%). The WM analyses with DTI revealed higher axial diffusivity values in post-infected patients compared to controls. Compared to controls, there were no significant differences in the functional connectivity of the posterior cingulum cortex. There were no significant correlations between neuropsychological scores and neuroimaging features (including DTI and RS-fMRI). Our results suggest persistent cognitive impairment and subtle white matter abnormalities in individuals mildly infected without anxiety or depression symptoms. The longitudinal analyses will clarify whether these alterations are temporary or permanent.

Severity of white matter microstructural damage in a Brazilian relapsing-remitting multiple sclerosis cohort: A possible window to optimize treatment.

BACKGROUND: Multiple sclerosis (MS) is an important cause of acquired neurological disability in young adults, characterized by multicentric inflammation, demyelination, and axonal damage. OBJECTIVE: The objective is to investigate white matter (WM) damage progression in a Brazilian MS patient cohort, using diffusion tensor imaging (DTI) post-processed by tract-based spatial statistics (TBSS). METHODS: DTI scans were acquired from 76 MS patients and 37 sex-and-age matched controls. Patients were divided into three groups based on disease duration. DTI was performed along 30 non-collinear directions by using a 1.5T imager. For TBSS analysis, the WM skeleton was created, and a 5000 permutation-based inference with a threshold of p < .05 was used, to enable the identification of abnormalities in fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD). RESULTS: Decreased FA and increased RD, MD, and AD were seen in patients compared to controls and a decreased FA and increased MD and RD were seen, predominantly after the first 5 years of disease, when compared between groups. CONCLUSION: Progressive WM deterioration is seen over time with a more prominent pattern after 5 years of disease onset, providing evidence that the early years might be a window to optimize treatment and prevent disability.

Social isolation leads to mild social recognition impairment and losses in brain cellularity.

Chronic social stress is a significant risk factor for several neuropsychiatric disorders, mainly major depressive disorder (MDD). In this way, patients with clinical depression may display many symptoms, including disrupted social behavior and anxiety. However, like many other psychiatric diseases, MDD has a very complex etiology and pathophysiology. Because social isolation is one of the multiple depression-inducing factors in humans, this study aims to understand better the link between social stress and MDD using an animal model based on social isolation after weaning, which is known to produce social stress in mice. We focused on cellular composition and white matter integrity to establish possible links with the abnormal social behavior that rodents isolated after weaning displayed in the three-chamber social approach and recognition tests. We used the isotropic fractionator method to assess brain cellularity, which allows us to robustly estimate the number of oligodendrocytes and neurons in dissected brain regions. In addition, diffusion tensor imaging (DTI) was employed to analyze white matter microstructure. Results have shown that post-weaning social isolation impairs social recognition and reduces the number of neurons and oligodendrocytes in important brain regions involved in social behavior, such as the anterior neocortex and the olfactory bulb. Despite the limitations of animal models of psychological traits, evidence suggests that behavioral impairments observed in patients might have similar biological underpinnings.

Altered structural connectivity in olfactory disfunction after mild COVID-19 using probabilistic tractography.

We aimed to investigate changes in olfactory bulb volume and brain network in the white matter (WM) in patients with persistent olfactory disfunction (OD) following COVID-19. A cross-sectional study evaluated 38 participants with OD after mild COVID-19 and 24 controls, including Sniffin' Sticks identification test (SS-16), MoCA, and brain magnetic resonance imaging. Network-Based Statistics (NBS) and graph theoretical analysis were used to explore the WM. The COVID-19 group had reduced olfactory bulb volume compared to controls. In NBS, COVID-19 patients showed increased structural connectivity in a subnetwork comprising parietal brain regions. Regarding global network topological properties, patients exhibited lower global and local efficiency and higher assortativity than controls. Concerning local network topological properties, patients had reduced local efficiency (left lateral orbital gyrus and pallidum), increased clustering (left lateral orbital gyrus), increased nodal strength (right anterior orbital gyrus), and reduced nodal strength (left amygdala). SS-16 test score was negatively correlated with clustering of whole-brain WM in the COVID-19 group. Thus, patients with OD after COVID-19 had relevant WM network dysfunction with increased connectivity in the parietal sensory cortex. Reduced integration and increased segregation are observed within olfactory-related brain areas might be due to compensatory plasticity mechanisms devoted to recovering olfactory function.

Is structural connectivity different in child and adolescent relatives of patients with bipolar disorder? A narrative review according to studies with DTI.

INTRODUCTION: Bipolar disorder (BD) has been associated with a decrease in white matter integrity. Diffusion tensor imaging (DTI) studies have enabled these changes to be elucidated with higher quality. Due to BD's high heritability, some studies have been conducted in relatives of BD patients looking at white matter integrity, and have found that structural connectivity may also be affected. This alteration has been proposed as a potential BD biomarker of vulnerability. However, there are few studies in children and adolescents. OBJECTIVE: To conduct a review of the literature on changes in white matter integrity determined by DTI in high-risk children and adolescents. RESULTS: Brain structural connectivity in the paediatric population is described in studies using DTI. Changes in the myelination process from its evolution within normal neurodevelopment to the findings in fractional anisotropy (FA) in BD patients and their high-risk relatives are also described. CONCLUSIONS: Studies show that both BD patients and their at-risk relatives present a decrease in FA in specific brain regions. Studies in children and adolescents with a high risk of BD, indicate a reduced FA in axonal tracts involved in emotional and cognitive functions. Decreased FA can be considered as a vulnerability biomarker for BD.

Brain volumes and white matter diffusion across the adult lifespan in temporal lobe epilepsy.

OBJECTIVE: Typical aging is associated with gradual cognitive decline and changes in brain structure. The observation that cognitive performance in mesial temporal lobe epilepsy (TLE) patients diverges from controls early in life with subsequent decline running in parallel would suggest an initial insult but does not support accelerated decline secondary to seizures. Whether TLE patients demonstrate similar trajectories of age-related gray (GM) and white matter (WM) changes as compared to healthy controls remains uncertain. METHODS: 3D T1-weighted and diffusion tensor images were acquired at a single site in 170 TLE patients (aged 23-74 years) with MRI signs of unilateral hippocampal sclerosis (HS, 77 right) and 111 healthy controls (aged 26-80 years). Global brain (GM, WM, total brain, and cerebrospinal fluid) and regional volumes (ipsi- and contralateral hippocampi), and fractional anisotropy (FA) of 10 tracts (three portions of corpus callosum, inferior longitudinal, inferior fronto-occipital and uncinate fasciculi, body of fornix, dorsal and parahippocampal-cingulum, and corticospinal tract) were compared between groups as a function of age. RESULTS: There were significant reductions of global brain and hippocampi volumes (greatest ipsilateral to HS), and FA of all 10 tracts in TLE versus controls. For TLE patients, regression lines run in parallel to those from controls for brain volumes and FA (for all tracts except the parahippocampal-cingulum and corticospinal tract) versus age across the adult lifespan. INTERPRETATION: These results imply a developmental hindrance occurring earlier in life (likely in childhood/neurodevelopmental stages) rather than accelerated atrophy/degeneration of most brain structures herein analyzed in patients with TLE.

Can Apparent Diffusion Coefficient (ADC) maps replace Diffusion Tensor Imaging (DTI) maps to predict the volumetric response of meningiomas to Gamma Knife Radiosurgery?

PURPOSE: Noninvasive methods are desired to predict the treatment response to Stereotactic Radiosurgery (SRS) to improve individual tumor management. In a previous study, we demonstrated that Diffusion Tensor Imaging (DTI)-derived parameter maps significantly correlate to SRS response. This study aimed to analyze and compare the predictive value of intratumoral ADC and DTI parameters in patients with meningiomas undergoing radiosurgery. METHODS: MR images of 70 patients treated with Gamma Knife SRS for WHO grade I meningiomas were retrospectively reviewed. MR acquisition included pre- and post-treatment DWI and DTI sequences, and subtractions were calculated to assess for radiation-induced changes in the parameter values. RESULTS: After a mean follow-up period (FUP) of 52.7 months, 69 of 70 meningiomas were controlled, with a mean volume reduction of 34.9%. Whereas fractional anisotropy (FA) values of the initial exam showed the highest correlation to tumor volume change at the last FU (CC = - 0.607), followed by the differences between first and second FU values of FA (CC = - 0.404) and the first longitudinal diffusivity (LD) value (CC = - 0.375), the correlation coefficients of all ADC values were comparably low. Nevertheless, all these correlations, except for ADC measured at the first follow-up, reached significance. CONCLUSION: For the first time, the prognostic value of ADC maps measured in meningiomas before and at first follow-up after Gamma Knife SRS, was compared to simultaneously acquired DTI parameter maps. Quantities assessed from ADC maps present significant correlations to the volumetric meningioma response but are less effective than correlations with DTI parameters.

Prenatal Cafeteria Diet Primes Anxiety-like Behavior Associated to Defects in Volume and Diffusion in the Fimbria-fornix of Mice Offspring.

Prenatal exposure to high-energy diets primes brain alterations that increase the risk of developing behavioral and cognitive failures. Alterations in the structure and connectivity of brain involved in learning and memory performance are found in adult obese murine models and in humans. However, the role of prenatal exposure to high-energy diets in the modulation of the brain's structure and function during cognitive decline remains unknown. We used female C57BL6 mice (n = 10) exposed to a high-energy diets (Cafeteria diet (CAF)) or Chow diet for 9 weeks (before, during and after pregnancy) to characterize their effect on brain structural organization and learning and memory performance in the offspring at two-month-old (n = 17). Memory and learning performance were evaluated using the Y-maze test including forced and spontaneous alternation, novel object recognition (NORT), open field and Barnes maze tests. We found no alterations in the short- or long-time spatial memory performance in male offspring prenatally exposed to CAF diet when compared to the control, but they increased time spent in the edges resembling anxiety-like behavior. By using deformation-based morphometry and diffusion tensor imaging analysis we found that male offspring exposed to CAF diet showed increased volume in primary somatosensory cortex and a reduced volume of fimbria-fornix, which correlate with alterations in its white matter integrity. Biological modeling revealed that prenatal exposure to CAF diet predicts low volume in the fimbria-fornix, which was associated with anxiety in the offspring. The findings suggest that prenatal exposure to high-energy diets prime brain structural alterations related to anxiety in the offspring.

Whole-brain DTI parameters associated with tau protein and hippocampal volume in Alzheimer's disease.

The causes of the neurodegenerative processes in Alzheimer's disease (AD) are not completely known. Recent studies have shown that white matter (WM) damage could be more severe and widespread than whole-brain cortical atrophy and that such damage may appear even before the damage to the gray matter (GM). In AD, Amyloid-beta (Aß42 ) and tau proteins could directly affect WM, spreading across brain networks. Since hippocampal atrophy is common in the early phase of disease, it is reasonable to expect that hippocampal volume (HV) might be also related to WM integrity. Our study aimed to evaluate the integrity of the whole-brain WM, through diffusion tensor imaging (DTI) parameters, in mild AD and amnestic mild cognitive impairment (aMCI) due to AD (with Aß42 alteration in cerebrospinal fluid [CSF]) in relation to controls; and possible correlations between those measures and the CSF levels of Aß42 , phosphorylated tau protein (p-Tau) and total tau (t-Tau). We found a widespread WM alteration in the groups, and we also observed correlations between p-Tau and t-Tau with tracts directly linked to mesial temporal lobe (MTL) structures (fornix and hippocampal cingulum). However, linear regressions showed that the HV better explained the variation found in the DTI measures (with weak to moderate effect sizes, explaining from 9% to 31%) than did CSF proteins. In conclusion, we found widespread alterations in WM integrity, particularly in regions commonly affected by the disease in our group of early-stage disease and patients with Alzheimer's disease. Nonetheless, in the statistical models, the HV better predicted the integrity of the MTL tracts than the biomarkers in CSF.

Use of diffusion tensor imaging as a prognostic biomarker after decompression surgery for carpal tunnel syndrome.

BACKGROUND: Magnetic resonance diffusion tensor imaging (MR-DTI) has been increasingly applied for carpal tunnel syndrome (CTS) diagnosis, but relatively little is known about the effect of CTS treatment on median nerve (MN) integrity and functional outcome prediction. PURPOSE: To assess how structural changes in MR-DTI of the MN correlates with symptom severity, functional status, and electrophysiological parameters in patients suffering from CTS before and after decompression surgery. MATERIAL AND METHODS: Nine wrists were prospectively enrolled to perform MR-DTI pre- and postoperatively. The apparent diffusion coefficients (ADC) and fractional anisotropy (FA) of the MN were examined in three different regions-distal radioulnar joint, pisiform bone, and hamate bone-and correlated with clinical and electrophysiological parameters. RESULTS: Postoperatively, mean Boston Carpal Tunnel Questionnaire scores decreased 1.55 points (range = 0.08-3; P = 0.0172) and 1.01 points (-0.13 to 1.88; P = 0.0381) in the symptomatic and functional domains, respectively. Postoperative clinical improvement was reflected in proximal FA elevation (P = 0.0078), but not in diffusivity in comparison to baseline examination. Preoperative electrophysiological parameters were correlated with a reduction in the pre- (sensory latencies [rho = -0.6826; P = 0.0312]) and postoperative (motor latencies [rho = -0.7488; P = 0.0325]) distal FA values. Higher sensory amplitudes indicated higher postoperative proximal FA values (rho = 0.7618; P = 0.0280) ​​and lower postoperative proximal ADC values (rho = -0.9047; P = 0.0020). CONCLUSION: Our study demonstrated that pre- and postoperative proximal FA values are useful biomarkers for the structural evaluation of the MN in patients with CTS. Symptomatic improvement can be better predicted by analyzing FA changes.

White matter predicts tDCS antidepressant effects in a sham-controlled clinical trial study.

Transcranial direct current stimulation (tDCS) has been used as treatment for depression, but its effects are heterogeneous. We investigated, in a subsample of the clinical trial Escitalopram versus Electrical Direct Current Therapy for Depression Study (ELECTTDCS), whether white matter areas associated with depression disorder were associated with tDCS response. Baseline diffusion tensor imaging data were analyzed from 49 patients (34 females, mean age 41.9) randomized to escitalopram 20 mg/day, tDCS (2 mA, 30 min, 22 sessions), or placebo. Antidepressant outcomes were assessed by Hamilton Depression Rating Scale-17 (HDRS) after 10-week treatment. We used whole-brain tractography for extracting white matter measures for anterior corpus callosum, and bilaterally for cingulum bundle, striato-frontal, inferior occipito-frontal fasciculus and uncinate. For the rostral body, tDCS group showed higher MD associated with antidepressant effects (estimate = -5.13 ± 1.64, p = 0.002), and tDCS significantly differed from the placebo and the escitalopram group. The left striato-frontal tract showed higher FA associated with antidepressant effects (estimate = -2.14 ± 0.72, p = 0.003), and tDCS differed only from the placebo group. For the right uncinate, the tDCS group lower AD values were associated with higher HDRS decrease (estimate = -1.45 ± 0.67, p = 0.031). Abnormalities in white matter MDD-related areas are associated with tDCS antidepressant effects. Suggested better white matter microstructure of the left prefrontal cortex was associated with tDCS antidepressant effects. Future studies should investigate whether these findings are driven by electric field diffusion and density in these areas.

White matter brain structure predicts language performance and learning success.

Individual differences in the ability to process language have long been discussed. Much of the neural basis of these, however, is yet unknown. Here we investigated the relationship between long-range white matter connectivity of the brain, as revealed by diffusion tractography, and the ability to process syntactically complex sentences in the participants' native language as well as the improvement thereof by multiday training. We identified specific network motifs by singular value decomposition that indeed related white matter structural connectivity to individual language processing performance. First, for two such motifs, one in the left and one in the right hemisphere, their individual prevalence significantly predicted the individual language performance, suggesting an anatomical predisposition for the individual ability to process syntactically complex sentences. Both motifs comprise a number of cortical regions, but seem to be dominated by areas known for the involvement in working memory rather than the classical language network itself. Second, we identified another left hemispheric network motif, whose change of prevalence over the training period significantly correlated with the individual change in performance, thus reflecting training induced white matter plasticity. This motif comprises diverse cortical areas including regions known for their involvement in language processing, working memory and motor functions. The present findings suggest that individual differences in language processing and learning can be explained, in part, by individual differences in the brain's white matter structure. Brain structure may be a crucial factor to be considered when discussing variations in human cognitive performance, more generally.

White Matter Hyperintensities and Poststroke Apathy: A Fully Automated MRI Segmentation Study.

INTRODUCTION: Poststroke apathy (PSA) is a common neuropsychiatric disorder that may affect up to 30% of stroke patients. Despite the difficulties of investigating this condition (overlapping with depression, heterogeneity of diagnostic criteria, a small number of studies), some recent diffusion tensor imaging studies have suggested that widespread microstructural white matter (WM) disruption plays a key role in the development of PSA. Therefore, we intended to investigate this hypothesis by evaluating the relationship between WM hyperintensities (WMH) and apathy in patients with cerebrovascular disease. METHODS: We studied patients with apathy (n = 7), depression (n = 13), comorbid apathy and depression (n = 13), and controls (n = 20), and we investigated the variables associated with the volume of WMH measured by an automated brain MRI segmentation software. RESULTS: The overall prevalence of PSA was 37.7% (pure and comorbid). Patients with apathy presented a higher volume of WMH in comparison to controls. Mini-Mental State Examination (MMSE), NPI-A, and the number of cerebral microbleeds were the only variables associated with WMH. Conversely, NPI-D did not correlate to WMH. DISCUSSION/CONCLUSION: This is an exploratory study that supports the view of PSA as a distinct syndrome from PSD mediated mainly by diffuse white matter hyperintensities, which suggests that WM disruption is an important pathway to the development of apathy in stroke patients.

Applying a unified model of fiber dissection, tractography, microscopic anatomy and plastination techniques for basic neuroanatomy education: Hacettepe University experience / Aplicación de un modelo unificado de disección de fibras, tractografía, anatomía microscópica y técnicas de plastinación para la educación básica en neuroanatomía: experiencia de la Universidad Hacettepe

SUMMARY: Anatomy education has gathered together a great many of many new modalities and was modified from classical lecture-based and laboratory practice system to the blended modules. In the scope of the present study, we develop a new, practical, cost- effective and efficient three dimensional (3D) educational model, which aimed to be helpful for the detection and better understanding of basic neuroanatomy education. Tractographic imaging, fiber dissection, microscopic anatomy and plastination techniques were applied to the white matter regions of the two brains. After the photographs that were taken were converted to 3D images, the specimens were plastinated. By way of establishing an educational model as a whole, we applied it to 202 second-year medical students. The students were separated into two groups when they attended to the theoretical lecture. Group 1 took the classical laboratory education; on the other hand, Group 2 received the newly designed educational model. Pre and post-tests were introduced to each group before and after laboratory sessions, respectively. The success scores were put to comparison. The average achievement scores of each group showed increase significantly (p<0.05) after the laboratory sessions, besides the increase in the post-test results of Group 2 was more statistically significant (p<0.05). Consequently, this new educational model enriched by newly designed unified methods could be regarded as useful for grasping and improving the basic neuroanatomy knowledge.

La educación en anatomía ha reunido una gran cantidad de nuevas modalidades, modificándose el sistema clásico de la práctica del laboratorio y de las clases basadas en conferencias, hacia los módulos combinados. En el ámbito del presente estudio, desarrollamos un modelo educativo tridimensional (3D) nuevo, práctico, rentable y eficiente, que pretendía ser útil para la detección y una mejor comprensión de la educación básica en neuroanatomía. Se tomaron imágenes tractográficas, disección de fibras, anatomía microscópica y técnicas de plastinación en los cerebros. Después de convertir las fotografías que se tomaron en imágenes 3D, se plastinaron los especímenes. A modo de establecer un modelo educativo en su conjunto, lo aplicamos a 202 estudiantes de segundo año de medicina. Los estudiantes fueron separados en dos grupos cuando asistieron a la clase teórica. El Grupo 1 tomó la educación clásica de laboratorio; por su parte, el Grupo 2 recibió el nuevo modelo educativo diseñado para el estudio. Se introdujeron pruebas previas y posteriores a cada grupo, antes y después de las sesiones de laboratorio. Se compararon las puntuaciones. Los puntajes promedio de rendimiento de cada grupo mostraron un aumento significativo (p<0,05) después de las sesiones de laboratorio. Además, se obtuvo un aumento en los resultados positivos, posteriores a la prueba del Grupo 2, siendo estadísticamente significativo (p<0,05). En consecuencia, este modelo educativo, enriquecido por métodos unificados de nuevo diseño, podría considerarse útil para captar y mejorar los conocimientos básicos de neuroanatomía.