Characterizing Spatiotemporal Population Receptive Fields in Human Visual Cortex with fMRI.

The use of fMRI and computational modeling has advanced understanding of spatial characteristics of population receptive fields (pRFs) in human visual cortex. However, we know relatively little about the spatiotemporal characteristics of pRFs because neurons' temporal properties are one to two orders of magnitude faster than fMRI BOLD responses. Here, we developed an image-computable framework to estimate spatiotemporal pRFs from fMRI data. First, we developed a simulation software that predicts fMRI responses to a time-varying visual input given a spatiotemporal pRF model and solves the model parameters. The simulator revealed that ground-truth spatiotemporal parameters can be accurately recovered at the millisecond resolution from synthesized fMRI responses. Then, using fMRI and a novel stimulus paradigm, we mapped spatiotemporal pRFs in individual voxels across human visual cortex in 10 participants (both females and males). We find that a compressive spatiotemporal (CST) pRF model better explains fMRI responses than a conventional spatial pRF model across visual areas spanning the dorsal, lateral, and ventral streams. Further, we find three organizational principles of spatiotemporal pRFs: (1) from early to later areas within a visual stream, spatial and temporal windows of pRFs progressively increase in size and show greater compressive nonlinearities, (2) later visual areas show diverging spatial and temporal windows across streams, and (3) within early visual areas (V1-V3), both spatial and temporal windows systematically increase with eccentricity. Together, this computational framework and empirical results open exciting new possibilities for modeling and measuring fine-grained spatiotemporal dynamics of neural responses using fMRI.

Neural representations of perceptual color experience in the human ventral visual pathway.

Color is a perceptual construct that arises from neural processing in hierarchically organized cortical visual areas. Previous research, however, often failed to distinguish between neural responses driven by stimulus chromaticity versus perceptual color experience. An unsolved question is whether the neural responses at each stage of cortical processing represent a physical stimulus or a color we see. The present study dissociated the perceptual domain of color experience from the physical domain of chromatic stimulation at each stage of cortical processing by using a switch rivalry paradigm that caused the color percept to vary over time without changing the retinal stimulation. Using functional MRI (fMRI) and a model-based encoding approach, we found that neural representations in higher visual areas, such as V4 and VO1, corresponded to the perceived color, whereas responses in early visual areas V1 and V2 were modulated by the chromatic light stimulus rather than color perception. Our findings support a transition in the ascending human ventral visual pathway, from a representation of the chromatic stimulus at the retina in early visual areas to responses that correspond to perceptually experienced colors in higher visual areas.

Can concomitant above-knee femoropopliteal bypass with artificial graft affect the outcome of femorofemoral bypass with artificial graft?

OBJECTIVES: Few have studied the effect of concomitant femoropopliteal (FEM-POP) bypass surgery on the outcome of femorofemoral (FEM-FEM) bypass in patients with peripheral arterial disease (PAD). This study was aimed to analyze the risk relationship of concomitant FEM-POP bypass on the patency of FEM-FEM bypass. METHODS: From March 2009 to April 2020, a total of 27 patients who underwent FEM-FEM bypass surgery using polytetrafluoroethylene grafts were retrospectively analyzed according to concomitant FEM-POP bypass surgery. The mean follow-up duration was 38.20 ± 34.56 months. RESULTS: The overall primary patency of the FEM-FEM bypass grafts in all 27 patients was 83.7, 78.5, and 72.0 at one, two, and 3 years, respectively. The overall limb salvage rate was 100, 94.1, and 86.9 at one, two, 3 years, respectively. Among them, ten patients underwent FEM-FEM bypass only (group 1). The other 17 patients needed a concomitant FEM-POP bypass and these patients were classified into three groups (group 2, ipsilateral FEM-POP, n = 5; group 3, crossover FEM-POP, n = 6; and group 4, bilateral FEM-POP, n = 6) The comparison of the primary patency of group 1 with the concomitant FEM-POP groups (sum of groups 2, 3, and 4, that is, group 5, n = 17) revealed a statistically significant improved patency for FEM-FEM bypasses not requiring concomitant infra-inguinal bypass (p = .036). Among the concomitant FEM-POP groups, group 2 had the lowest primary patency of the FEM-FEM bypass significantly (p = 0.07). The limb salvage rate of group 4 was significantly low. CONCLUSIONS: A concomitant FEM-POP bypass influenced the outcome of FEM-FEM bypass surgery. In conclusion, compromised infra-inguinal runoff at either extremity requiring concomitant FEM-POP bypass significantly worsens long-term FEM-FEM bypass patency. In addition, a concomitant bilateral FEM-POP bypass is a risk factor affecting the limb salvage rate in FEM-FEM bypass.

Childhood maltreatment is associated with increased neural response to ambiguous threatening facial expressions in adulthood: Evidence from the late positive potential.

Childhood maltreatment increases lifetime vulnerability for psychopathology. One proposed mechanism for this association is that early maltreatment increases vigilance for and attention to subtle threat cues, persisting outside of the environment in which maltreatment occurs. To test this possibility, the present study examined neural responses to ambiguous and nonambiguous threatening facial expressions in a sample of 25 adults reporting a history of low-to-moderate levels of abuse in childhood and 46 reporting no or low levels of childhood maltreatment. The measure of neural response used was the late positive potential (LPP), a neural marker of sustained attention to motivationally salient information that is sensitive to subtle variation in emotional content. Participants passively viewed angry-neutral and fearful-neutral face blends and rated emotional intensity for each face. In the maltreated group, as fearful faces increased in emotional intensity, the LPP similarly increased, suggesting increased sensitivity to subtle variation in threatening content. Moreover, the LPP at each level of emotional intensity was not related to current symptoms of anxiety and depression. However, contrary to our hypotheses, adults with a history of abuse did not rate angry or fearful faces as more threatening, nor did they exhibit a larger LPP to angry faces, compared to controls. These findings suggest that childhood maltreatment may be associated with increased sensitivity to ambiguous threatening information in adulthood.

Rethinking simultaneous suppression in visual cortex via compressive spatiotemporal population receptive fields.

When multiple visual stimuli are presented simultaneously in the receptive field, the neural response is suppressed compared to presenting the same stimuli sequentially. The prevailing hypothesis suggests that this suppression is due to competition among multiple stimuli for limited resources within receptive fields, governed by task demands. However, it is unknown how stimulus-driven computations may give rise to simultaneous suppression. Using fMRI, we find simultaneous suppression in single voxels, which varies with both stimulus size and timing, and progressively increases up the visual hierarchy. Using population receptive field (pRF) models, we find that compressive spatiotemporal summation rather than compressive spatial summation predicts simultaneous suppression, and that increased simultaneous suppression is linked to larger pRF sizes and stronger compressive nonlinearities. These results necessitate a rethinking of simultaneous suppression as the outcome of stimulus-driven compressive spatiotemporal computations within pRFs, and open new opportunities to study visual processing capacity across space and time.

Characterizing spatiotemporal population receptive fields in human visual cortex with fMRI.

The use of fMRI and computational modeling has advanced understanding of spatial characteristics of population receptive fields (pRFs) in human visual cortex. However, we know relatively little about the spatiotemporal characteristics of pRFs because neurons' temporal properties are one to two orders of magnitude faster than fMRI BOLD responses. Here, we developed an image-computable framework to estimate spatiotemporal pRFs from fMRI data. First, we developed a simulation software that predicts fMRI responses to a time varying visual input given a spatiotemporal pRF model and solves the model parameters. The simulator revealed that ground-truth spatiotemporal parameters can be accurately recovered at the millisecond resolution from synthesized fMRI responses. Then, using fMRI and a novel stimulus paradigm, we mapped spatiotemporal pRFs in individual voxels across human visual cortex in 10 participants. We find that a compressive spatiotemporal (CST) pRF model better explains fMRI responses than a conventional spatial pRF model across visual areas spanning the dorsal, lateral, and ventral streams. Further, we find three organizational principles of spatiotemporal pRFs: (i) from early to later areas within a visual stream, spatial and temporal integration windows of pRFs progressively increase in size and show greater compressive nonlinearities, (ii) later visual areas show diverging spatial and temporal integration windows across streams, and (iii) within early visual areas (V1-V3), both spatial and temporal integration windows systematically increase with eccentricity. Together, this computational framework and empirical results open exciting new possibilities for modeling and measuring fine-grained spatiotemporal dynamics of neural responses in the human brain using fMRI.

Left anterior descending artery dissection with retrograde aortic dissection during percutaneous coronary intervention: a case report.

Retrograde catheter-induced coronary artery dissection during percutaneous coronary intervention is an exceedingly rare occurrence, and the likelihood of it extending into the aorta is even more uncommon. Typically, surgical treatment involves aortic root replacement combined with coronary artery bypass grafting. However, in this particular case, a meticulous approach was employed. By carefully guiding wires into the true lumens and placing stents in the proximal left main and left anterior descending arteries, the immediate complications were averted by obstructing the retrograde flow in the false lumen. Subsequently, an off-pump coronary artery bypass was performed using the left internal mammary artery to the left anterior descending artery, without the need to manipulate the aorta. This approach resulted in a short operation time and the absence of any other complications.

Effect of acute and fractionated irradiation on hippocampal neurogenesis.

Ionizing radiation has become an inevitable health concern emanating from natural sources like space travel and from artificial sources like medical therapies. In general, exposure to ionizing radiation such as γ-rays is one of the methods currently used to stress specific model systems. In this study, we elucidated the long-term effect of acute and fractionated irradiation on DCX-positive cells in hippocampal neurogenesis. Groups of two-month-old C57BL/6 female mice were exposed to whole-body irradiation at acute dose (5 Gy) or fractional doses (1 Gy × 5 times and 0.5 Gy × 10 times). Six months after exposure to γ-irradiation, the hippocampus was analyzed. Doublecortin (DCX) immunohistochemistry was used to measure changes of neurogenesis in the subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). The number of DCX-positive cells was significantly decreased in all acute and fractionally irradiation groups. The long-term changes in DCX-positive cells triggered by radiation exposure showed a very different pattern to the short-term changes which tended to return to the control level in previous studies. Furthermore, the number of DCX-positive cells was relatively lower in the acute irradiation group than the fractional irradiation groups (approximately 3.6-fold), suggesting the biological change on hippocampal neurogenesis was more susceptible to being damaged by acute than fractional irradiation. These results suggest that the exposure to γ-irradiation as a long-term effect can trigger biological responses resulting in the inhibition of hippocampal neurogenesis.

The biological response of spermidine induced by ionization radiation.

Globally, there are concerns over the risks associated with radiation exposure, so it is important to understand the biological effects of radiation exposure. Driven by the need to detect the presence of radiation exposure, biomarkers to monitor potential exposure after radiological accidents can be developed and would be extremely valuable for biological response. In this study, the behavior of spermidine as a biomarker was investigated in a C57BL/6 mouse model exposed to an acute whole-body sublethal dose of 6 Gy. The spermidine content values in serum increased for up to two days after 6 Gy irradiation. However, the enhanced spermidine content observed on day +3 in irradiated mice returned to normal levels on the subsequent five days. The result indicates that spermidine can be used as a biomarker of biological response to radiation exposure.

Comparison of clinical outcomes of pharmaco-mechanical thrombectomy in iliac vein thrombosis with and without May-Thurner syndrome.

BACKGROUND: May-Thurner syndrome (MTS) has a different etiology from that of general deep vein thrombosis (DVT). However, few clinical comparisons of MTS-induced and non-MTS-induced DVT have been reported. The aim of this study was to analyze the clinical results of pharmaco-mechanical thrombectomy (PMT) in DVT with and without MTS. METHODS: Forty-seven iliac vein thrombosis patients treated with PMT between January 2008 and December 2013 were enrolled. 25 patients had DVT with MTS and 22 patients had iliac vein DVT without MTS. We retrospectively reviewed medical records and analyzed mid-term patencies and post-thrombotic syndrome (PTS) occurrence by Villalta Score. RESULTS: The median follow-up period was 48.4 (36~92) months. A venous stent was inserted in the iliac vein in all MTS patients. One-/two-/three-year primary patencies in the non-MTS group were 77.3% (N.=17) for all three years in the non-MTS group and were 96.0% (N.=24), 83.1% (N.=22), and 83.1% (N.=22) in the MTS group for years 1/2/3, respectively. One-/two-/three-year secondary patencies were 90.9% (N.=20) for all three years in the non-MTS group and were 96.0% (N.=24), 91.4% (N.=23), and 91.4% (N.=23) in the MTS group, respectively. One-, two-, and three-year Villalta Scores were 4.3, 3.9, and 3.4, respectively, in the non-MTS group, and 3.8, 3.7, and 4.0, respectively, in the MTS group. Primary and secondary patency and Villalta Score were not significantly different between the MTS and non-MTS groups. CONCLUSIONS: Although MTS and DVT have different etiologies, clinical results for both diseases using PMT were not significantly different. Therefore, PMT can be offered as an acceptable initial therapy in DVT patients with and without MTS.

Educational Disparities in Risk for Metabolic Syndrome.

BACKGROUND: The objective of this study was to evaluate the relationship between educational level as a surrogate marker of socioeconomic status and the risk of developing metabolic syndrome (MetS). METHODS: Study subjects were 1915 Korean adults (1193 women and 722 men) who participated in a cohort study. Educational level was categorized into two groups: (1) high education (more than 12 years of education), and (2) low education (less than 12 years of education). MetS was defined according to diagnostic criteria of the National Cholesterol Education Program (NCEP-III) and the International Diabetes Federation (IDF). Multiple logistic regression analysis and Cox proportional hazard analysis were performed to evaluate cross-sectional and prospective association between MetS or MetS components and educational level after adjusting for covariates. RESULTS: The overall prevalence of MetS at baseline was 15.0% in women and 20.4% in men. Incidence of MetS over 4.52 years was 16.6 per 1000 person-year in women and 27.6 per 1000 person-year in men. The prevalence and incidence of MetS were higher in the low educational group than those in the high educational group in both sexes. At baseline, the risk of MetS (odds ratio [OR]: 1.63, 95% confidence interval [CI]: 1.05-2.53 for NCEP criteria; OR: 2.30, 95% CI: 1.41-3.76 for IDF criteria) and abdominal obesity (OR: 2.62, 95% CI: 1.75-3.93) were higher in less educated women compared with those in more educated women. In men, there was no association between Mets or MetS components and educational level. Over 4.6 years of follow-up, the risk of developing MetS in women in the low education group (hazard ratio [HR]: 1.95, 95% CI: 1.12-3.50 for NCEP criteria; HR: 2.36, 95% CI: 1.14-4.86 for IDF criteria) was significantly higher than that in the high education group. In men, low education significantly increased the risk of developing impaired fasting glucose (HR: 1.95, 95% CI: 1.12-3.40). CONCLUSION: An inverse association between educational level and MetS was found in Korean women, suggesting that socioeconomic disparities might increase the risk of MetS development, especially in women.

Effects of a Proteasome Inhibitor on Cardiomyocytes in a Pressure-Overload Hypertrophy Rat Model: An Animal Study.

BACKGROUND: The ubiquitin-proteasome system (UPS) is an important pathway of proteolysis in pathologic hypertrophic cardiomyocytes. We hypothesize that MG132, a proteasome inhibitor, might prevent hypertrophic cardiomyopathy (CMP) by blocking the UPS. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and androgen receptor (AR) have been reported to be mediators of CMP and heart failure. This study drew upon pathophysiologic studies and the analysis of NF-κB and AR to assess the cardioprotective effects of MG132 in a left ventricular hypertrophy (LVH) rat model. METHODS: We constructed a transverse aortic constriction (TAC)-induced LVH rat model with 3 groups: sham (TAC-sham, n=10), control (TAC-cont, n=10), and MG132 administration (TAC-MG132, n=10). MG-132 (0.1 mg/kg) was injected for 4 weeks in the TAC-MG132 group. Pathophysiologic evaluations were performed and the expression of AR and NF-κB was measured in the left ventricle. RESULTS: Fibrosis was prevalent in the pathologic examination of the TAC-cont model, and it was reduced in the TAC-MG132 group, although not significantly. Less expression of AR, but not NF-κB, was found in the TAC-MG132 group than in the TAC-cont group (p<0.05). CONCLUSION: MG-132 was found to suppress AR in the TAC-CMP model by blocking the UPS, which reduced fibrosis. However, NF-κB expression levels were not related to UPS function.

Hemangioma originating from the main pulmonary artery.

In this study, we report the case of a 42-year-old female patient who was diagnosed with hemangioma in the pericardium connected to the main pulmonary artery. Chest CT revealed a hypodense, well-marginated, mass-like lesion, probably connected to the main pulmonary artery, and multiple heterogeneous attenuations were seen with contrast enhancement. The tumor was resected using conventional extracorporeal circulation for complete resection involving the main pulmonary artery wall. Pathologic examination revealed hemangioma. Because main pulmonary originated hemangioma is extremely rare, examination of these cases provides much needed data to further our understanding of this disease. We herein report such a case.

A relationship between Alzheimer's disease and type 2 diabetes mellitus through the measurement of serum amyloid-beta autoantibodies.

Increasing evidence suggests that type 2 diabetes mellitus (T2DM) is strongly correlated with Alzheimer's disease (AD). To examine the relationship between T2DM and AD, autoantibodies against amyloid-Abeta were measured in the serum of T2DM patients and age-matched controls. Levels of Abeta autoantibody were measured by ELISA in serum samples of T2DM patients (n=92) and age-matched control group (n=106). Abeta autoantibody levels were increased in T2DM compared with age-matched controls by 45.4 +/- 8.1% (p< 0.001). Females had higher Abeta autoantibody levels than males in both T2DM and control group. Abeta autoantibody levels in the T2DM group were positively correlated with the levels of cholesterol (p=0.011), low density lipoprotein cholesterol (p=0.020), and triglycerides (p=0.039). In conclusion, the level of Abeta autoantibody is dramatically elevated in patient serum of T2DM, and, as such, might be used as a possible biomarker for T2DM.