Faculty Bibliography

A body of research demonstrates convincingly a role for synchronization of auditory cortex to rhythmic structure in sounds including speech and music. Some studies hypothesize that an oscillator in auditory cortex could underlie important temporal processes such as segmentation and prediction. An important critique of these findings raises the plausible concern that what is measured is perhaps not an oscillator but is instead a sequence of evoked responses. The two distinct mechanisms could look very similar in the case of rhythmic input, but an oscillator might better provide the computational roles mentioned above (i.e., segmentation and prediction). We advance an approach to adjudicate between the two models: analyzing the phase lag between stimulus and neural signal across different stimulation rates. We ran numerical simulations of evoked and oscillatory computational models, showing that in the evoked case,phase lag is heavily rate-dependent, while the oscillatory model displays marked phase concentration across stimulation rates. Next, we compared these model predictions with magnetoencephalography data recorded while participants listened to music of varying note rates. Our results show that the phase concentration of the experimental data is more in line with the oscillatory model than with the evoked model. This finding supports an auditory cortical signal that (i) contains components of both bottom-up evoked responses and internal oscillatory synchronization whose strengths are weighted by their appropriateness for particular stimulus types and (ii) cannot be explained by evoked responses alone.

OBJECTIVE/UNASSIGNED:The aim of this study was to determine whether a vitamin D genetic risk score (vitDGRS) is associated with 25-hydroxyvitamin D (25(OH)D) level and multiple sclerosis (MS) relapses in children. METHODS/UNASSIGNED:DNA samples were typed for single nucleotide polymorphisms (SNPs) from four genes previously identified to be associated with 25(OH)D levels. SNPs with strong associations with 25(OH)D after multiple comparison correction were used to create a genetic risk score (vitDGRS). Cox regression models tested associations of vitDGRS with relapse hazard. RESULTS/UNASSIGNED:Two independent SNPs within or near GC and NADSYN1/DHCR7 genes were strongly associated with 25(OH)D levels in the discovery cohort ( n = 182) after Bonferroni correction. The vitDGRS of these SNPs explained 4.5% of the variance of 25(OH)D level after adjustment for genetic ancestry. Having the highest versus lowest vitDGRS was associated with 11 ng/mL lower 25(OH)D level (95% confidence interval (CI) = -17.5, -4.5, p = 0.001) in the discovery cohort. Adjusting for ancestry, sex, disease-modifying therapy (DMT), and HLA-DRB1*15 carrier status, the highest versus lowest vitDGRS was associated with 2.6-fold (95% CI = 1.37, 5.03, p = 0.004) and 2.0-fold (95% CI = 0.75, 5.20, p = 0.16) higher relapse hazard in the discovery and replication cohorts, respectively. CONCLUSION/UNASSIGNED:The vitDGRS identifies children at greater risk of relapse. These findings support a causal role for vitamin D in MS course.

Snake venom L-amino acid oxidases (svLAAOs) are an interesting class of enzymes with important biological activities. Their participation in key metabolic processes, including pathological disorders, suggest that svLAAOs are potential lead compounds in drug discovery. However, their short-term stability defies their applications. This paper describes the stability studies together with functional and structural characterization of the LAAO bordonein-L. It has 498 amino acid residues, one N-glycosylation site and two disulfide bonds, revealed by high-resolution MS/MS. Molecular modeling approach showed its monomer folds into three conserved domains: FAD, substrate and helical domains. Differential scanning fluorimetry showed the enzyme tends to destabilize from neutral to basic pHs and in presence of mono/bivalent ions and it is highly stabilized by acid pHs and its substrates. However, high concentrations of L-amino acids decrease bordonein-L enzyme activity. Dynamic light scattering revealed bordonein-L remains in the dimeric and monodisperse form, so aggregation does not cause the rapidly decrease of enzyme activity. In vitro, the enzyme exhibited cytotoxicity against fibroblast cell line and killed Leishmania amazonensis promastigotes, intensified by substrate addition. Concluding, our results provide biochemistry and biophysical insights to improve LAAOs stability and better approaches to long-term storage. Moreover, our study emphasizes the importance of proper buffers choice mainly in cell-based assays.

Spinal dural fistulas (SDAVFs) occasionally arise from the same segmental artery as the radiculomedullary branch to the anterior spinal artery. In such cases, selective fistula embolization that does not endanger the anterior spinal artery is not possible, and surgical fistula disconnection is recommended. We present an exceptional case in which rational embolization strategy of SDAVF was feasible because of separate origins from a common segmental artery pedicle of the ventral radiculomedullary artery and the dorsal radicular artery branch supplying the fistula.

Little is known about the neural mechanisms that allow humans and animals to plan actions using knowledge of task contingencies. Emerging theories hypothesize that it involves the same hippocampal mechanisms that support self-localization and memory for locations. Yet limited direct evidence supports the link between planning and the hippocampal place map. We addressed this by investigating model-based planning and place memory in healthy controls and epilepsy patients treated using unilateral anterior temporal lobectomy with hippocampal resection. Both functions were impaired in the patient group. Specifically, the planning impairment was related to right hippocampal lesion size, controlling for overall lesion size. Furthermore, although planning and boundary-driven place memory covaried in the control group, this relationship was attenuated in patients, consistent with both functions relying on the same structure in the healthy brain. These findings clarify both the neural mechanism of model-based planning and the scope of hippocampal contributions to behavior.

Background It is uncertain whether there is an association between left ventricular (LV) ejection fraction ( LVEF ) or LV wall motion abnormality and embolic stroke of undetermined source ( ESUS ). Methods and Results We performed a retrospective, cross-sectional study of patients with acute ischemic stroke enrolled in the CAESAR (Cornell Acute Stroke Academic Registry) from 2011 to 2016. We restricted this study to patients with ESUS and, as controls, those with small- and large-artery ischemic strokes. LVEF had to be above 35% to be considered ESUS . In a secondary analysis, we excluded patients with ESUS who had any evidence of ipsilateral carotid atherosclerosis. Multiple logistic regression was used to evaluate whether LVEF or LV wall motion abnormality was associated with ESUS . We performed a confirmatory study at another tertiary-care center. We identified 885 patients with ESUS (n=503) or small- or large-artery strokes (n=382). Among the entire cohort, LVEF was not associated with ESUS (odds ratio per 5% decrement in LVEF , 1.0; 95% CI, 1.0-1.1) and LV wall motion abnormality was not associated with ESUS (odds ratio, 0.9; 95% CI, 0.5-1.6). The results were identical in our confirmatory study. In our secondary analysis excluding ESUS patients with any evidence of ipsilateral carotid atherosclerosis, there was an association between LVEF and ESUS (odds ratio per 5% decrement in LVEF , 1.2; 95% CI, 1.0-1.5; P=0.04). Conclusions Among the entire cohort, no association existed between LVEF or LV wall motion abnormality and ESUS ; however, after excluding ESUS patients with any evidence of ipsilateral carotid atherosclerosis, lower LVEF appeared to be associated with ESUS .