Associations between infant amygdala functional connectivity and social engagement following a stressor: A preliminary investigation.

Functional architecture of the infant brain, especially functional connectivity (FC) within the amygdala network and between the amygdala and other networks (i.e., default-mode [DMN] and salience [SAL] networks), provides a neural basis for infant socioemotional functioning. Yet, little is known about the extent to which early within- and between-network amygdala FC are related to infant stress recovery across the first year of life. In this study, we examined associations between amygdala FC (i.e., within-network amygdala connectivity, and between-network amygdala connectivity with the DMN and SAL) at 3 months and infant recovery from a mild social stressor at 3, 6 and 9 months. At 3 months, thirty-five infants (13 girls) underwent resting-state functional magnetic resonance imaging during natural sleep. Infants and their mothers completed the still-face paradigm at 3, 6, and 9 months, and infant stress recovery was assessed at each time point as the proportion of infant social engagement during the reunion episode. Bivariate correlations indicated that greater positive within-network amygdala FC and greater positive amygdala-SAL FC, but not amygdala-DMN FC, at 3 months predicted lower levels of stress recovery at 3 and 6 months, but were nonsignificant at 9 months. These findings provide preliminary evidence that early functional synchronization within the amygdala network, as well as segregation between the amygdala and the SAL, may contribute to infant stress recovery in the context of infant-mother interaction.

Functional neural network connectivity at 3 months predicts infant-mother dyadic flexibility during play at 6 months.

Early functioning of neural networks likely underlies the flexible switching between internal and external orientation and may be key to the infant's ability to effectively engage in social interactions. To test this hypothesis, we examined the association between infants' neural networks at 3 months and infant-mother dyadic flexibility (denoting the structural variability of their interaction dynamics) at 3, 6, and 9 months. Participants included thirty-five infants (37% girls) and their mothers (87% White). At 3 months, infants participated in a resting-state functional magnetic resonance imaging session, and functional connectivity (FC) within the default mode (DMN) and salience (SN) networks, as well as DMN-SN internetwork FC, were derived using a seed-based approach. When infants were 3, 6, and 9 months, infant-mother dyads completed the Still-Face Paradigm where their individual engagement behaviors were observed and used to quantify dyadic flexibility using state space analysis. Results revealed that greater within-DMN FC, within-SN FC, and DMN-SN anticorrelation at 3 months predicted greater dyadic flexibility at 6 months, but not at 3 and 9 months. Findings suggest that early synchronization and interaction between neural networks underlying introspection and salience detection may support infants' flexible social interactions as they become increasingly active and engaged social partners.

A hydrolyzed lipid blend diet promotes myelination in neonatal piglets in a region and concentration-dependent manner.

The impact of early life nutrition on myelin development is of interest given that cognitive and behavioral function depends on proper myelination. Evidence shows that myelination can be altered by dietary lipid, but most of these studies have been performed in the context of disease or impairment. Here, we assessed the effects of lipid blends containing various levels of a hydrolyzed fat (HF) system on myelination in healthy piglets. Piglets were sow-reared, fed a control diet, or a diet containing 12%, 25%, or 53% HF consisting of cholesterol, fatty acids, monoglycerides, and phospholipid from lecithin. At postnatal day 28/29, magnetic resonance imaging (MRI) was performed to assess changes to brain development, followed by brain collection for microscopic analyses of myelin in targeted regions using CLARITY tissue clearing, immunohistochemistry, and electron microscopy techniques. Sow-reared piglets exhibited the highest overall brain white matter volume by MRI. However, a 25% HF diet resulted in the greatest total myelin density in the prefrontal cortex based on 3D modeling analysis of myelinated filaments. Nodal gap length and g-ratio were inversely correlated with percentage of HF in the corpus callosum, as well as in the PFC and internal capsule for g-ratio, indicating that a 53% HF diet resulted in the thickest myelin per axon and a 0% HF control diet the thinnest in specific brain regions. These findings indicate that HF promoted myelination in the neonatal piglet in a region- and concentration-dependent manner.

Rowing exercise increases cardiorespiratory fitness and brachial artery diameter but not traditional cardiometabolic risk factors in spinal cord-injured humans.

PURPOSE: This study assessed the effects of upper-body rowing exercise on cardiorespiratory fitness, traditional cardiometabolic risk factors, and vascular health in individuals with spinal cord injury (SCI). METHODS: Seventeen male and female adults with chronic (> 1 yr) motor-complete and incomplete SCI (level of injury: C4-L3) were randomized to control (CON, n = 9) or exercise (UBROW, n = 8). Participants in UBROW performed 12-week, 3 weekly sessions of 30-min upper-body ergometer rowing exercise, complying with current exercise guidelines for SCI. Cardiorespiratory fitness ([Formula: see text]O2peak), traditional risk factors (lipid profile, glycemic control) as well as inflammatory and vascular endothelium-derived biomarkers (derived from fasting blood samples) were measured before and after 6 (6W) and 12 weeks (12W). Brachial artery resting diameter and flow-mediated dilation (FMD) were determined by ultrasound as exploratory outcomes. RESULTS: UBROW increased [Formula: see text]O2peak from baseline (15.1 ± 5.1 mL/kg/min; mean ± SD) to 6W (16.5 ± 5.3; P < 0.01) and 12W (17.5 ± 6.1; P < 0.01). UBROW increased resting brachial artery diameter from baseline (4.80 ± 0.72 mm) to 12W (5.08 ± 0.91; P < 0.01), with no changes at 6W (4.96 ± 0.91), and no changes in CON. There were no significant time-by-group interactions in traditional cardiometabolic blood biomarkers, or in unadjusted or baseline diameter corrected FMD. Explorative analyses revealed inverse correlations between changes (∆12W-baseline) in endothelin-1 and changes in resting diameter (r = - 0.56) and FMD% (r = - 0.60), both P < 0.05. CONCLUSION: These results demonstrate that 12 weeks of upper-body rowing complying with current exercise guidelines for SCI improves cardiorespiratory fitness and increases resting brachial artery diameter. In contrast, the exercise intervention had no or only modest effects on traditional cardiometabolic risk factors. The study was registered at Clinicaltrials.gov (N-20190053, May 15, 2020).

Validation of Metabolic Models for Estimation of Energy Expenditure During Isolated Concentric and Eccentric Muscle Contractions.

Musculoskeletal modeling uses metabolic models to estimate energy expenditure of human locomotion. However, accurate estimation of energy expenditure is challenging, which may be due to uncertainty about the true energy cost of eccentric and concentric muscle contractions. The purpose of this study was to validate three commonly used metabolic models, using isolated isokinetic concentric and eccentric knee extensions/flexions. Five resistance-trained adult males (25.6 ± 2.4 year, 90.6 ± 7.5 kg, 1.81 ± 0.09 m) performed 150 repetitions at four different torques in a dynamometer. Indirect calorimetry was used to measure energy expenditure during these muscle contractions. All three models underestimated the energy expenditure (compared with indirect calorimetry) for up to 55.8% and 78.5% for concentric and eccentric contractions, respectively. Further, the coefficient of determination was in general low for eccentric contractions (R2 < 0.46) indicating increases in the absolute error with increases in load. These results show that the metabolic models perform better when predicting energy expenditure of concentric contractions compared with eccentric contractions. Thus, more knowledge about the relationship between energy expenditure and eccentric work is needed to optimize the metabolic models for musculoskeletal modeling of human locomotion.

Sex differences in microvascular function across lower leg muscles in humans.

Studies have reported sex-based differences in conduit artery function, however little is known about possible sex-based differences in microvascular function, and possible influence of muscle group. Blood-oxygen-level-dependent (BOLD) MR images acquired during ischemia-reperfusion assess the reactive hyperemic response in the microvasculature of skeletal muscle. We tested the hypothesis that women have greater microvascular reactivity, reflected by faster time-to-peak (TTP) and time-to-half-peak (TTHP) of the BOLD response, across all lower leg muscles. In healthy, young men (n = 18) and women (n = 12), BOLD images of both lower legs were acquired continuously during 30 s of rest, 5 min of cuff occlusion and 2 min of reperfusion, in a 3 T MR scanner. Segmentation of tibialis anterior (TA), soleus (SO), gastrocnemius medial (GM), and the peroneal group (PG) were performed using image registration, and TTP and TTHP of the BOLD response were determined for each muscle. Overall, women had faster TTP (p = 0.001) and TTHP (p = 0.01) than men. Specifically, women had shorter TTP and TTHP in TA (27.5-28.4%), PG (33.9-41.6%), SO (14.7-19.7%) and GM (15.4-18.8%). Overall, TTP and TTHP were shorter in TA compared with PG (25.1-31.1%; p ≤ 0.007), SO (14.3-16%; p ≤ 0.03) and GM (15.6-26%; p ≤ 0.01). Intra class correlations analyses showed large variation in absolute agreement (range: 0.10-0.81) of BOLD parameters between legs (within distinct muscles). Faster TTP and TTHP across all lower leg muscles, in women, provide novel evidence of sex-based differences in microvascular function of young adults matched for age, body mass index, and physical activity level.

Carbon Plate Shoes Improve Metabolic Power and Performance in Recreational Runners.

This study compared metabolic power (MP) and time trial (TT) running performance between Adidas Adizero Adios (AAA) and Nike VaporFly 4% (NVP). Thirty-seven runners completed three laboratory sessions and two field sessions (n=30). After familiarization (visit 1), participants completed eight 6-min treadmill running bouts (four with each shoe, counterbalanced) at their preferred pace, and MP was assessed using indirect calorimetry (visits 2 and 3). During visits 4 and 5, participants completed two outdoor TTs (~3.5 km) in NVP and AAA (counterbalanced). Compared with AAA, NVP exhibited superior MP (NVP: median=13.88 (Q1-Q3=12.90-15.08 W/kg; AAA: median=14.08 (Q1-Q3=13.12-15.44 W/kg; z=-4.81, p<.001, effect size=.56) and TT (NVP=793±98 s; AAA=802±100 s, p=.001; effect size=.09). However, there was no relationship between changes in MP and changes in TT between shoes (r=.151 p=.425, 95% confidence interval=[-.22; .48]). Our results demonstrate that NVP, compared with AAA, improves MP and TT in recreational runners. The lack of correlation between changes in MP and TT indicates that factors other than improved MP contribute to faster short-distance TT with NVP.

Reliability of Running Economy Measurements: Influence of Shoe Familiarisation.

The purpose was to investigate differences in reliability of running economy measurements between familiar and unfamiliar shoes. Thirty-seven runners were included who all ran in familiar and unfamiliar running shoes while running economy was measured at steady state using a treadmill. Each participant was tested on two different visits (three sessions in total), with two trials in each of the three shoe conditions completed at each visit. Coefficient of variation, standard deviation of differences, and limits of agreement of running economy were used to quantify the repeatability (within-visit variation) and reproducibility (between-visit variation). The coefficient of variation showed a marginal difference in reproducibility across shoe conditions, whereas no differences were seen in coefficient of variation, standard deviation of the differences, or limits of agreement for repeatability across shoes. All three shoe conditions showed greater repeatability than reproducibility for running economy, and enhanced repeatability at visit 3 compared to visit 2. Our results indicate that familiarisation to shoes might not be needed for reliable measurements of running economy. Based on our results, when evaluating benefits in running shoes we suggest that running economy be assessed within the same day. Further, our data suggest a beneficial effect of using multiple familiarisation sessions if small differences between shoe conditions are expected.

Ischemic Preconditioning Attenuates Rating of Perceived Exertion But Does Not Improve Maximal Oxygen Consumption or Maximal Power Output.

ABSTRACT: ter Beek, F, Jokumsen, PS, Sloth, BN, Thomas Stevenson, AJ, and Larsen, RG. Ischemic preconditioning attenuates rating of perceived exertion but does not improve maximal oxygen consumption or maximal power output. J Strength Cond Res 36(9): 2479-2485, 2022-Brief consecutive periods of limb ischemia and reperfusion, known as ischemic preconditioning (IPC), have been reported to increase maximal power output (MPO) during cycling. However, the underlying mechanisms are unclear. Therefore, the purpose of the study was to investigate the effects of IPC on MPO, maximal oxygen consumption (V̇ o2 max), muscle oxygenation, and rating of perceived exertion (RPE) during an incremental cycling test. Fourteen healthy young men participated in this double-blinded, randomized crossover study, involving IPC (250 mm Hg; four 5-minute cycles of ischemia) and sham (20 mm Hg) treatment followed by an incremental cycling test to exhaustion. During the cycling test, V̇ o2 , RPE, heart rate (HR), blood lactate (BL), and muscle oxygenation and deoxygenation (near-infrared spectroscopy) were measured. MPO, V̇ o2 max, HRmax, and muscle deoxygenation did not change with IPC (all p -values > 0.13). Furthermore, IPC had no significant effect on V̇ o2 , HR, or muscle oxygenation during the incremental cycling test (all p -values > 0.18). However, IPC attenuated RPE during cycling at 210 W (IPC: median 17.0 [interquartile range 15.3-19.0]; sham: 17.5 [17.0-19.0]; p = 0.007) and 245 W (IPC: 18.0 [17.0-18.8]; sham: 19.0 [18.0-19.8]; p = 0.011). A single session of IPC did not improve MPO, V̇ o2 max, or measures of oxygen consumption during the cycling test. However, IPC lowered RPE at 210 and 245 W, suggesting that IPC may attenuate the perception of effort at higher submaximal exercise intensities.

Proof-of-concept evidence for trimodal simultaneous investigation of human brain function.

The link between spatial (where) and temporal (when) aspects of the neural correlates of most psychological phenomena is not clear. Elucidation of this relation, which is crucial to fully understand human brain function, requires integration across multiple brain imaging modalities and cognitive tasks that reliably modulate the engagement of the brain systems of interest. By overcoming the methodological challenges posed by simultaneous recordings, the present report provides proof-of-concept evidence for a novel approach using three complementary imaging modalities: functional magnetic resonance imaging (fMRI), event-related potentials (ERPs), and event-related optical signals (EROS). Using the emotional oddball task, a paradigm that taps into both cognitive and affective aspects of processing, we show the feasibility of capturing converging and complementary measures of brain function that are not currently attainable using traditional unimodal or other multimodal approaches. This opens up unprecedented possibilities to clarify spatiotemporal integration of brain function.

Quantification of magnetic resonance spectroscopy data using a combined reference: Application in typically developing infants.

Quantification of proton magnetic resonance spectroscopy (1 H-MRS) data is commonly performed by referencing the ratio of the signal from one metabolite, or metabolite group, to that of another, or to the water signal. Both approaches have drawbacks: ratios of two metabolites can be difficult to interpret because study effects may be driven by either metabolite, and water-referenced data must be corrected for partial volume and relaxation effects in the water signal. Here, we introduce combined reference (CRef) analysis, which compensates for both limitations. In this approach, metabolites are referenced to the combined signal of several reference metabolites or metabolite groups. The approach does not require the corrections necessary for water scaling and produces results that are less sensitive to the variation of any single reference signal, thereby aiding the interpretation of results. We demonstrate CRef analysis using 202 1 H-MRS acquisitions from the brains of 140 infants, scanned at approximately 1 and 3 months of age. We show that the combined signal of seven reference metabolites or metabolite groups is highly correlated with the water signal, corrected for partial volume and relaxation effects associated with cerebral spinal fluid. We also show that the combined reference signal is equally or more uniform across subjects than the reference signals from single metabolites or metabolite groups. We use CRef analysis to quantify metabolite concentration changes during the first several months of life in typically developing infants.

Multiple-day high-dose beetroot juice supplementation does not improve pulmonary or muscle deoxygenation kinetics of well-trained cyclists in normoxia and hypoxia.

Dietary nitrate (NO3-) supplementation via beetroot juice (BR) has been reported to lower oxygen cost (i.e., increased exercise efficiency) and speed up oxygen uptake (VO2) kinetics in untrained and moderately trained individuals, particularly during conditions of low oxygen availability (i.e., hypoxia). However, the effects of multiple-day, high dose (12.4 mmol NO3- per day) BR supplementation on exercise efficiency and VO2 kinetics during normoxia and hypoxia in well-trained individuals are not resolved. In a double-blinded, randomized crossover study, 12 well-trained cyclists (66.4 ± 5.3 ml min-1∙kg-1) completed three transitions from rest to moderate-intensity (~70% of gas exchange threshold) cycling in hypoxia and normoxia with supplementation of BR or nitrate-depleted BR as placebo. Continuous measures of VO2 and muscle (vastus lateralis) deoxygenation (ΔHHb, using near-infrared spectroscopy) were acquired during all transitions. Kinetics of VO2 and deoxygenation (ΔHHb) were modeled using mono-exponential functions. Our results showed that BR supplementation did not alter the primary time constant for VO2 or ΔHHb during the transition from rest to moderate-intensity cycling. While BR supplementation lowered the amplitude of the VO2 response (2.1%, p = 0.038), BR did not alter steady state VO2 derived from the fit (p = 0.258), raw VO2 data (p = 0.231), moderate intensity exercise efficiency (p = 0.333) nor steady state ΔHHb (p = 0.224). Altogether, these results demonstrate that multiple-day, high-dose BR supplementation does not alter exercise efficiency or oxygen uptake kinetics during normoxia and hypoxia in well-trained athletes.

Maternal Dietary Intake of Omega-3 Fatty Acids Correlates Positively with Regional Brain Volumes in 1-Month-Old Term Infants.

Maternal nutrition is an important factor for infant neurodevelopment. However, prior magnetic resonance imaging (MRI) studies on maternal nutrients and infant brain have focused mostly on preterm infants or on few specific nutrients and few specific brain regions. We present a first study in term-born infants, comprehensively correlating 73 maternal nutrients with infant brain morphometry at the regional (61 regions) and voxel (over 300 000 voxel) levels. Both maternal nutrition intake diaries and infant MRI were collected at 1 month of life (0.9 ± 0.5 months) for 92 term-born infants (among them, 54 infants were purely breastfed and 19 were breastfed most of the time). Intake of nutrients was assessed via standardized food frequency questionnaire. No nutrient was significantly correlated with any of the volumes of the 61 autosegmented brain regions. However, increased volumes within subregions of the frontal cortex and corpus callosum at the voxel level were positively correlated with maternal intake of omega-3 fatty acids, retinol (vitamin A) and vitamin B12, both with and without correction for postmenstrual age and sex (P < 0.05, q < 0.05 after false discovery rate correction). Omega-3 fatty acids remained significantly correlated with infant brain volumes after subsetting to the 54 infants who were exclusively breastfed, but retinol and vitamin B12 did not. This provides an impetus for future larger studies to better characterize the effect size of dietary variation and correlation with neurodevelopmental outcomes, which can lead to improved nutritional guidance during pregnancy and lactation.

Physical Activity Barriers in Danish Manual Wheelchair Users: A Cross-sectional Study.

OBJECTIVE: To identify physical activity barrier prevalence and severity among manual wheelchair users (MWCUs) and test whether barrier impact is associated with self-reported physical activity level (PAL). DESIGN: Cross-sectional survey. The Barriers to Physical Activity Questionnaire for People with Mobility Impairments (BPAQ-MI) was translated from English to Danish and administered online. The BPAQ-MI includes barriers within 4 domains and 8 subdomains and queries if an item hindered physical activity participation in the last 3 months (yes/no). If "yes," participants graded barrier severity from very small (1) to very big (5). Barrier impact scores were summed within and across domains. SETTING: General community. PARTICIPANTS: Danish MWCUs (N=181; 52.5% female, mean age, 48±14y.). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: PAL was rated from not active (1) to extremely active (10). Individual barrier prevalence (frequency, %) and severity (median [interquartile range]) was computed. Unadjusted (Spearman rank correlations, domains, subdomains) and adjusted (multivariate linear regression, subdomains) associations between PAL and barrier impact were computed. RESULTS: The 5 most prevalent barriers were reported by ≥49.6% of participants (2 intrapersonal and 3 community). The 5 most severe barriers all had a median of 5 (1 organizational and 4 community). Unadjusted analysis showed that PAL was inversely associated with total intrapersonal (r=-0.487, P<.01) and overall (r=-0.241, P<.01) impact and the intrapersonal "health" (r=-0.477, P<.01) and "beliefs/attitudes"(r=-0.307, P<.01) subdomains. Adjustment for shared variance revealed only the "health" subdomain impact score was independently associated with PAL (P<.001). CONCLUSIONS: Intrapersonal barriers were highly prevalent. Health-related barriers were inversely related to PAL. When organizational and community barriers were present, they were rated as particularly severe. These results provide novel information that can guide the design of future interventions aiming to increase MWCUs PALs.

The effects of organic grass and grass-birdsfoot trefoil pastures on Jersey heifer development: Heifer growth, performance, and economic impact.

Dairy heifers developed in certified organic programs, especially those utilizing pasture-based management schemes, have lower rates of gain than heifers raised in nonorganic confinement production systems in temperate climates, such as in the Intermountain West region of the United States. This study investigates the effects that different forages in a rotational grazing system have on development of organically raised Jersey heifers. Over 3 years, 210 yearling Jersey heifers were randomly assigned to one of 9 treatments, including a conventional confinement control where animals were fed a total mixed ration or one of 8 pasture treatments: Cache Meadow bromegrass (Bromus riparius Rehmann), QuickDraw orchard grass (Dactylis glomerata L.), Amazon perennial ryegrass (Lolium perenne L.), or Fawn tall fescue (Schendonorus arundinaceus [Schreb.] Dumort) and each individual grass interseeded with birdsfoot trefoil (Lotus corniculatus L., BFT). Each treatment had 3 blocks/yr over the 3-yr period, with each block having a 0.4 ha pasture of each treatment. Every 35 d, over a 105-d period, heifers were weighed and measured for hip height, and blood samples were collected to determine serum insulin-like growth factor-1 and blood urea nitrogen concentrations. Fecal egg counts were also assessed. Heifer body weight (BW), blood urea nitrogen, and insulin-like growth factor-1 concentrations were affected by treatment when analyzed over time. Heifers on grass-BFT pastures had increased BW compared with heifers on monoculture grass pastures. Heifers receiving a total mixed ration or perennial ryegrass+BFT had increased BW gain over the 105-d period compared with heifers grazing tall fescue+BFT, orchard grass, perennial ryegrass, meadow bromegrass, or tall fescue. Individually for all grass species, heifers grazing +BFT pastures had greater ending BW and weight gain than heifers grazing the respective grass monocultures. Furthermore, weight gain for heifers on perennial ryegrass+BFT, meadow bromegrass+BFT, and orchard grass+BFT were not different from those on a total mixed ration. Heifers grazing grass-BFT pastures had increased blood urea nitrogen compared with heifers grazing monoculture grass pastures. Heifer hip height and fecal egg counts were not affected by treatment. These results show that the addition of BFT to organic pasture improves growth of grazing replacement heifers. Economic analyses also demonstrate that interseeding grass pastures with BFT results in an increased economic return compared with grazing monoculture grass pastures. Grass pastures interseeded with BFT may be a sustainable option to achieve adequate growth of Jersey heifers raised in an organic pasture scenario in a temperate climate.

The Impact of Focused Attention on Emotional Experience: A Functional MRI Investigation.

Emotional well-being depends on the ability to adaptively cope with various emotional challenges. Most studies have investigated the neural mechanisms of emotion regulation strategies deployed relatively later in the timing of processing that leads to full emotional experiences. However, less is known about strategies that are engaged in earlier stages of emotion processing, such as those involving attentional deployment. We investigated the neural mechanisms associated with self-guided Focused Attention (FA) in mitigating subjective negative emotional experiences. Functional magnetic resonance imaging (fMRI) data were recorded while participants viewed a series of composite negative and neutral images with distinguishable foreground (FG) and background (BG) areas. Participants were instructed to focus either on the FG or BG components of the images, and then rated their emotional experiences. Behavioral results showed that FA was successful in decreasing emotional ratings for negative images viewed in BG Focus condition. At the neural level, the BG Focus was associated with increased activity in regions typically implicated in top-down executive control (dorsolateral prefrontal cortex and lateral parietal cortex) and decreased activity in regions linked to affective processing (amygdala and ventrolateral prefrontal cortex). Dissociable brain activity linked to FA also was identified in visual cortices, including between the parahippocampal and fusiform gyri, showing increased versus decreased activity, respectively, during the BG Focus. These findings complement the evidence from prior FA studies with recollected emotional memories as internal stimuli and further demonstrate the effectiveness of self-guided FA in mitigating negative emotional experiences associated with processing of external unpleasant stimuli.

System-Specific Patterns of Thalamocortical Connectivity in Early Brain Development as Revealed by Structural and Functional MRI.

The normal development of thalamocortical connections plays a critical role in shaping brain connectivity in the prenatal and postnatal periods. Recent studies using advanced magnetic resonance imaging (MRI) techniques in neonates and infants have shown that abnormal thalamocortical connectivity is associated with adverse neurodevelopmental outcomes. However, all these studies have focused on a single neuroimaging modality, overlooking the dynamic relationship between structure and function at this early stage. Here, we study the relationship between structural and functional thalamocortical connectivity patterns derived from healthy full-term infants scanned with diffusion-weighted MRI and resting-state functional MRI within the first weeks of life (mean gestational age = 39.3 ± 1.2 weeks; age at scan = 24.2 ± 7.9 days). Our results show that while there is, in general, good spatial agreement between both MRI modalities, there are regional variations that are system-specific: regions involving primary-sensory cortices exhibit greater structural/functional overlap, whereas higher-order association areas such as temporal and posterior parietal cortices show divergence in spatial patterns of each modality. This variability illustrates the complementarity of both modalities and highlights the importance of multimodal approaches.

Body mass and cardiorespiratory fitness are associated with altered brain metabolism.

Magnetic Resonance Spectroscopy provides measures of brain chemistry that are sensitive to cardiorespiratory fitness and body composition. The concentration of N-acetyl aspartic acid (NAA) is of interest because it is a marker of neuronal integrity. The ratio of NAA to creatine, a standard reference metabolite, has been shown to correlate with measures of both cardiorespiratory fitness and body composition. However, previous studies have explored these effects in isolation, making it impossible to know which of these highly correlated measures drive the correlations with NAA/Cr. As a result, the mechanisms underlying their association remain to be established. We therefore conducted a comprehensive study to investigate the relative contributions of cardiorespiratory fitness and percent body fat in predicting NAA/Cr. We demonstrate that NAA/Cr in white matter is correlated with percent body fat, and that this relationship largely subsumes the correlation of NAA/Cr with cardiorespiratory fitness. These results underscore the association of body composition with axonal integrity and suggests that this relationship drives the association of NAA/Cr with physical fitness in young adults.

Chronic high-dose beetroot juice supplementation improves time trial performance of well-trained cyclists in normoxia and hypoxia.

Dietary nitrate (NO3-) supplementation via beetroot juice (BR) is known to improve endurance performance in untrained and moderately trained individuals. However, conflicting results exist in well-trained individuals. Evidence suggests that the effects of NO3- are augmented during conditions of reduced oxygen availability (e.g., hypoxia), thereby increasing the probability of performance improvements for well-trained athletes in hypoxia vs. normoxia. This randomized, double-blinded, counterbalanced-crossover study examined the effects of 7 days of BR supplementation with 12.4 mmol NO3- per day on 10-km cycling time trial (TT) performance in 12 well-trained cyclists in normoxia (N) and normobaric hypoxia (H). Linear mixed models for repeated measures revealed increases in plasma NO3- and NO2- after supplementation with BR (both p < 0.001). Further, TT performance increased with BR supplementation (∼1.6%, p < 0.05), with no difference between normoxia and hypoxia (p = 0.92). For respiratory variables there were significant effects of supplementation on VO2 (p < 0.05) and VE (p < 0.05) such that average VO2 and VE during the TT increased with BR, with no difference between normoxia and hypoxia (p ≥ 0.86). We found no effect of supplementation on heart rate, oxygen saturation or muscle oxygenation during the TT. Our results provide new evidence that chronic high-dose NO3- supplementation improves cycling performance of well-trained cyclists in both normoxia and hypoxia.

Multivariate Associations of Fluid Intelligence and NAA.

Understanding the neural and metabolic correlates of fluid intelligence not only aids scientists in characterizing cognitive processes involved in intelligence, but it also offers insight into intervention methods to improve fluid intelligence. Here we use magnetic resonance spectroscopic imaging (MRSI) to measure N-acetyl aspartate (NAA), a biochemical marker of neural energy production and efficiency. We use principal components analysis (PCA) to examine how the distribution of NAA in the frontal and parietal lobes relates to fluid intelligence. We find that a left lateralized frontal-parietal component predicts fluid intelligence, and it does so independently of brain size, another significant predictor of fluid intelligence. These results suggest that the left motor regions play a key role in the visualization and planning necessary for spatial cognition and reasoning, and we discuss these findings in the context of the Parieto-Frontal Integration Theory of intelligence.