Biology subjects

Zaveri, H. P.

Publications and source records attributed to Zaveri, H. P..

3 recordsLinked to original sources

bioRxiv2024

Widespread brain activity increases in frontal lobe seizures with impaired consciousness

Impaired consciousness is a serious clinical manifestation of epilepsy with negative consequences on quality of life. Little work has investigated impaired consciousness in frontal lobe seizures, a common form of focal epilepsy. In temporal lobe seizures, previous studies showed widespread cortical slow waves associated with depressed subcortical arousal and impaired consciousness. However, in frontal lobe epilepsy, it is not known whether cortical slow waves are present, or whether a very different cortical activity pattern may be related to impaired consciousness. We used intracranial EEG recordings of 65 frontal lobe seizures in 30 patients for quantitative analysis of ictal cortical activity and its relationship to impaired consciousness. Behavioral changes based on blinded review of seizure videos were used to classify focal aware, focal impaired awareness, and focal to bilateral tonic-clonic seizures. Changes in intracranial EEG power from preictal baseline were analyzed in different cortical regions and across frequency ranges in these three categories. We found that frontal lobe focal aware seizures showed approximately 40% increases in intracranial EEG power localized to the frontal lobe of seizure onset across frequency ranges, with relatively smaller changes in other cortical regions. Frontal lobe focal impaired awareness seizures showed approximately 50% increases in intracranial EEG power, not significantly different from focal aware seizures in the frontal lobe of seizure onset (P = 1.038), but significantly greater than focal aware seizures in other broad cortical regions (P < 0.001). Importantly, the widespread cortical increases in EEG power observed in focal impaired awareness versus focal aware seizures were seen not just in the frequency range of slow waves, but were also observed across other frequencies including fast activity. However, the widespread cortical increases in focal impaired awareness seizures differed from focal to bilateral tonic-clonic seizures where intracranial EEG power increased to a much higher level by approximately 600%. The large power increases in focal to bilateral tonic-clonic were significantly greater than in focal impaired awareness seizures both in the frontal lobe of seizure onset and in other cortical regions (P < 0.001). Our findings contrast with focal temporal lobe epilepsy, where impaired consciousness is associated with cortical slow waves. We can speculate that different focal seizure types produce impaired consciousness by impacting widespread cortical regions but through different physiological mechanisms. Insights gained by studying mechanisms of impaired consciousness may be the first step towards developing novel treatments to prevent this important negative consequence of epilepsy.

neuroscience↗

bioRxiv2020

SOX7 deficiency causes ventricular sepal defects through its effects on endocardial-to-mesenchymal transition and the expression of Wnt4 and Bmp2

SOX7 is located in a region on chromosome 8p23.1 that is recurrently deleted in individuals with septal defects. Sox7-/- embryos die of heart failure around E11.5 due to defects in vascular remodeling. These embryos have hypocellular endocardial cushions with severely reduced numbers of mesenchymal cells. We also observed a ventricular septal defect in a rare Sox7flox/-;Tie2-Cre embryo that escaped early lethality. This led us to hypothesize that SOX7 plays a critical developmental role in the endocardium of the atrioventricular (AV) canal. We subsequently used AV explant studies to show that SOX7 deficiency leads to a severe reduction in endocardial-to-mesenchymal transition (EndMT). Since SOX7 is a transcription factor, we hypothesized that it functions in the endocardium by regulating the expression of EndMT-related genes. To identify these genes in an unbiased manner, we performed RNA-seq on pooled E9.5 hearts tubes harvested from Sox7-/- embryos and their wild-type littermates. We found that Wnt4 transcript levels were severely reduced, which we confirmed by RNA in situ hybridization. Previous studies have shown that WNT4 is expressed in the endocardium and promotes EndMT by acting in a paracrine manner to increase the expression of BMP2 in the myocardium. Consistent with these findings, we found that Bmp2 transcript levels were diminished in Sox7-/- embryonic hearts. We conclude that SOX7 promotes EndMT in the developing AV canal by modulating the expression of Wnt4 and Bmp2. These data also provide additional evidence that haploinsufficiency of SOX7 contributes to the congenital heart defects seen in individuals with recurrent 8p23.1 microdeletions. SUMMARY STATEMENTIn the developing atrioventricular canal, SOX7 promotes endocardial-to-mesenchymal transition (EndMT) by positively regulating Wnt4 and Bmp2 expression. SOX7 deficiency leads to the development of hypocellular endothelial cushions and ventricular septal defects.

developmental biology↗

bioRxiv2019

The Connectivity Index: An Effective Metric for Grading Epileptogenicity

ObjectiveTo investigate the performance of a metric of functional connectivity to classify and grade the excitability of brain regions based on evoked potentials to single pulse electrical stimulation (SPES).\n\nMethodsPatients who received 1-Hz frequency stimulation between 2003 and 2014 at Yale at prospectively selected contacts were included. The stimulated contacts were classified as seizure onset zone (SOZ), highly irritative zone (IZp) or control. Response contacts were classified as seizure onset zone (SOZ), active interictal (IZp), quiet or other. The normalized number of responses was defined as the number of contacts with any evoked responses divided by the total number of recorded contacts, and the normalized distance is the ratio of the average distance between the site of stimulation and sites of evoked responses to the average distances between the site of stimulation and all other recording contacts. A new metric we labeled the connectivity index (CI) is defined as the product of the two values.\n\nResults57 stimulation-sessions in 22-patients were analyzed. The connectivity index (CI) of the SOZ was higher than control (median CI of 0.74 vs. 0.16, p = 0.0002). The evoked responses after stimulation of SOZ were seen at further distance compared to control (median normalized distance 0.96 vs. 0.62, p = 0.0005). It was 1.8 times more likely to record a response at SOZ than in non-epileptic contacts after stimulation of a control site. Habitual seizures were triggered in 27% of patients and 35 % of SOZ contacts (median stimulation intensity 4 mA) but in none of the control or IZp contacts. Non-SOZ contacts in multifocal or poor surgical outcome cases had a higher CI than non-SOZ contacts in those with localizable onsets (medians CI of 0.5 vs. 0.12, p = 0.04). There was a correlation between the stimulation current intensity and the normalized number of evoked responses (r = + 0.49, p 0.01) but not with distance (r = + 0.1, p 0.64)\n\nConclusionsWe found enhanced connectivity when stimulating the SOZ compared to stimulating control contacts; responses were more distant as well. Habitual auras and seizures provoked by SPES were highly predictive of brain sites involved in seizure generation.

neuroscience↗