Reproductive hormones in relation to white matter hyperintensity volumes among midlife women.

INTRODUCTION: Although reproductive hormones are implicated in cerebral small vessel disease in women, few studies consider measured hormones in relation to white matter hyperintensity volume (WMHV), a key indicator of cerebral small vessel disease. Even fewer studies consider estrone (E1), the primary postmenopausal estrogen, or follicle-stimulating hormone (FSH), an indicator of ovarian age. We tested associations of estradiol (E2), E1, and FSH to WMHV among women. METHODS: Two hundred twenty-two women (mean age = 59) underwent hormone assays (E1, E2, FSH) and 3T brain magnetic resonance imaging. Associations of hormones to WMHV were tested with linear regression. RESULTS: Higher E2 (B[standard error (SE)] = -0.17[0.06], P = 0.008) and E1 (B[SE] = -0.26[0.10], P = 0.007) were associated with lower whole-brain WMHV, and higher FSH (B[SE] = 0.26[0.07], P = 0.0005) with greater WMHV (covariates age, race, education). When additionally controlling for cardiovascular disease risk factors, associations of E1 and FSH to WMHV remained. DISCUSSION: Reproductive hormones, particularly E1 and FSH, are important to women's cerebrovascular health. HIGHLIGHTS: Despite widespread belief that sex hormones are important to women's brain health, little work has considered how these hormones in women relate to white matter hyperintensities (WMH), a major indicator of cerebral small vessel disease. We considered relations of estradiol (E2), estrone (E1), and follicle-stimulating hormone (FSH) to WMH in midlife women. Higher E2 and E1 were associated with lower whole-brain WMH volume (WMHV), and higher FSH with higher whole-brain WMHV. Associations of E1 and FSH, but not E2, to WMHV persisted with adjustment for cardiovascular disease risk factors. Findings underscore the importance of E2 and FSH to women's cerebrovascular health.

Glucocorticoid receptors orchestrate a convergence of host and cellular stress signals in triple negative breast cancer.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks expression of the nuclear steroid receptors that bind estrogens (ER) and progestogens (PRs) and does not exhibit HER2 (Human epidermal growth factor 2) receptor overexpression. Even in the face of initially effective chemotherapies, TNBC patients often relapse. One primary cause for therapy-resistant tumor progression is the activation of cellular stress signaling pathways. The glucocorticoid receptor (GR), a corticosteroid-activated transcription factor most closely related to PR, is a mediator of both endocrine/host stress and local tumor microenvironment (TME)-derived and cellular stress responses. Interestingly, GR expression is associated with a good prognosis in ER+ breast cancer but predicts poor prognosis in TNBC. Classically, GR's transcriptional activity is regulated by circulating glucocorticoids. Additionally, GR is regulated by ligand-independent signaling events. Notably, the stress-activated protein kinase, p38 MAP kinase, phosphorylates GR at serine 134 (Ser134) in response to TME-derived growth factors and cytokines, including HGF and TGFß1. Phospho-Ser134-GR (p-Ser134-GR) associates with cytoplasmic and nuclear signaling molecules, including 14-3-3ζ, aryl hydrocarbon receptors (AhR), and hypoxia-inducible factors (HIFs). Phospho-GR/HIF-containing transcriptional complexes upregulate gene sets whose protein products include the components of inducible oncogenic signaling pathways (PTK6) that further promote cancer cell survival, chemoresistance, altered metabolism, and migratory/invasive behavior in TNBC. Recent studies have implicated liganded p-Ser134-GR (p-GR) in dexamethasone-mediated upregulation of genes related to TNBC cell motility and dysregulated metabolism. Herein, we review the tumor-promoting roles of GR and discuss how both ligand-dependent and ligand-independent/stress signaling-driven inputs to p-GR converge to orchestrate metastatic TNBC progression.

Foals of mares vaccinated for Hendra virus have a suboptimal response to HeV vaccination.

Hendra virus (HeV) is lethal to horses and a zoonotic threat to humans in Australia, causing severe neurological and/or respiratory disease with high mortality. An equine vaccine has been available since 2012. Foals acquire antibodies from their dams by ingesting colostrum after parturition, therefore it is assumed that foals of mares vaccinated against HeV will have passive HeV antibodies circulating during the first several months of life until they are actively vaccinated. However, no studies have yet examined passive or active immunity against HeV in foals. Here, we investigated anti-HeV antibody levels in vaccinated mares and their foals. Testing for HeV neutralising antibodies is cumbersome due to the requirement for Biosafety level 4 (BSL-4) containment to conduct virus neutralisation tests (VNT). For this study, a subset of samples was tested for HeV G-specific antibodies by both an authentic VNT with infectious HeV and a microsphere-based immunoassay (MIA), revealing a strong correlation. An indicative neutralising level was then applied to the results of a larger sample set tested using the MIA. Mares had high levels of HeV-specific neutralising antibodies at the time of parturition. Foals acquired high levels of maternal antibodies which then waned to below predictive protective levels in most foals by 6 months old when vaccination commenced. Foals showed a suboptimal response to vaccination, suggesting maternal antibodies may interfere with active vaccination. The correlation analysis between the authentic HeV VNT and HeV MIA will enable further high throughput serological studies to inform optimal vaccination protocols for both broodmares and foals.

A systematic umbrella review and meta-meta-analysis of eHealth and mHealth interventions for improving lifestyle behaviours.

The aim of this meta-meta-analysis was to systematically review randomised controlled trial (RCT) evidence examining the effectiveness of e- and m-Health interventions designed to improve physical activity, sedentary behaviour, healthy eating and sleep. Nine electronic databases were searched for eligible studies published from inception to 1 June 2023. Systematic reviews with meta-analyses of RCTs that evaluate e- and m-Health interventions designed to improve physical activity, sedentary behaviour, sleep and healthy eating in any adult population were included. Forty-seven meta-analyses were included, comprising of 507 RCTs and 206,873 participants. Interventions involved mobile apps, web-based and SMS interventions, with 14 focused on physical activity, 3 for diet, 4 for sleep and 26 evaluating multiple behaviours. Meta-meta-analyses showed that e- and m-Health interventions resulted in improvements in steps/day (mean difference, MD = 1329 [95% CI = 593.9, 2065.7] steps/day), moderate-to-vigorous physical activity (MD = 55.1 [95% CI = 13.8, 96.4] min/week), total physical activity (MD = 44.8 [95% CI = 21.6, 67.9] min/week), sedentary behaviour (MD = -426.3 [95% CI = -850.2, -2.3] min/week), fruit and vegetable consumption (MD = 0.57 [95% CI = 0.11, 1.02] servings/day), energy intake (MD = -102.9 kcals/day), saturated fat consumption (MD = -5.5 grams/day), and bodyweight (MD = -1.89 [95% CI = -2.42, -1.36] kg). Analyses based on standardised mean differences (SMD) showed improvements in sleep quality (SMD = 0.56, 95% CI = 0.40, 0.72) and insomnia severity (SMD = -0.90, 95% CI = -1.14, -0.65). Most subgroup analyses were not significant, suggesting that a variety of e- and m-Health interventions are effective across diverse age and health populations. These interventions offer scalable and accessible approaches to help individuals adopt and sustain healthier behaviours, with implications for broader public health and healthcare challenges.

Adults With Spina Bifida Fare Worse Than Young Adults: A Systemic Vulnerability in Urinary Tract Infection-Related Hospital Care.

PURPOSE: We aim to estimate the odds of UTI-related hospital care in spina bifida (SB) patients aged 18 to 25 years as compared with patients with SB in adolescence (11-17 years) or adulthood (26-35 years). We hypothesize that patients with SB in the typical transitional age, 18 to 25 years, will have higher odds of UTI-related hospital care as compared to adolescent SB patients or adult SB patients. MATERIALS AND METHODS: Using Cerner Real-World Data, we performed a retrospective cohort analysis comparing SB patients to age- and gender-matched controls. SB cases between 2015 and 2021 were identified and compared in 3 cohorts: 11 to 17 years (adolescents), 18 to 25 years (young adults [YA]), and 26 to 35 years (adults). Logistic regression analysis was used to characterize the odds of health care utilization. RESULTS: Of the 5497 patients with SB and 77,466 controls identified, 1839 SB patients (34%) and 3275 controls (4.2%) had at least 1 UTI encounter. UTI-related encounters as a proportion of all encounters significantly increased with age in SB patients (adolescents 8%, YA 12%, adult 15%; P < .0001). Adjusting for race, sex, insurance, and comorbidities, the odds of a UTI-related encounter in YA with SB were significantly higher than for adolescents with SB (adolescent odds ratio = 0.65, 95% CI: 0.57-0.75, P < .001). YA had lower odds of a UTI-related encounter as compared with adults with SB (adult odds ratio = 1.31, 95% CI: 1.16-1.49, P < .001). CONCLUSIONS: YA with SB have higher odds of UTI-related hospital care than adolescents, but lower odds of UTI-related hospital care when compared with adults.

Endogenous estrogens and brain activation during verbal memory encoding and recognition in the postmenopause.

OBJECTIVE: Determine associations of endogenous estrogens with memory systems in the postmenopausal brain and evaluate clinical significance. STUDY DESIGN: In the MsBrain cohort (n=199, mean age 59.3+3.9 years, 83.9% white), we examined the cross-sectional association of serum estradiol and estrone, measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS), during a functional magnetic resonance imaging (fMRI) task of word encoding and recognition. To characterize the clinical significance of those associations, we examined the magnitude of activation in relation to a neuropsychological measures of memory and affect. RESULTS: Endogenous estradiol was positively associated with activation in temporal and frontal cortices during encoding and negatively associated with one prefrontal region during recognition (p<.05). Activation in the left inferior frontal gyrus was associated with memory performance (ß(SE)= 0.004(0.002), p<.05), and anxiety (ß(SE)= -0.100(0.050), p<.05). The left middle frontal gyrus was associated with memory performance (ß(SE)= 0.006(0.002), p<.01), depression, and anxiety. The left superior temporal gyrus (STG) was associated with depression (ß(SE)= -0.083(0.036), p<.05) and anxiety (ß(SE)= -0.134(0.058), p<.05). Estrone was positively associated with activation in a range of brain areas including bilateral STG and right superior frontal gyrus during encoding (p<.05). Activation of the left insula an precental gyrus were associated with symptoms of depression and anxiety. None related to memory. CONCLUSION: The function of brain areas critical to memory performance varies with estrogen levels in the postmenopause, even though those levels are low. Higher levels of estradiol may facilitate memory performance through enhanced function of temporal and frontal cortices during encoding of verbal material.

Degradation in Binaural and Spatial Hearing and Auditory Temporal Processing Abilities as a Function of Aging.

Objectives: Sensorineural hearing loss is common with advancing age, but even when hearing is normal or near normal in older persons, performance deficits are often seen for suprathreshold listening tasks such as understanding speech in background noise or localizing the direction sounds are coming from. This suggests there is also a more central source of the problem. Objectives of this study were to examine as a function of age (young adult to septuagenarian) performance on: 1) a spatial acuity task examining lateralization ability, and a spatial speech-in-noise (SSIN) recognition task, both measured in a hemi-anechoic sound field using a circular horizontal-plane loudspeaker array, and 2) a suprathreshold auditory temporal processing task and a spectro-temporal processing task, both measured under headphones. Further, we examined any correlations between the measures. Design: Subjects were 48 adults, aged 21 to 78, with either normal hearing or only a mild sensorineural hearing loss through 4000 Hz. The lateralization task measured minimum audible angle (MAA) for 500 and 4000 Hz narrowband noise (NBN) bursts in diffuse background noise for both an on-axis (subject facing 0°) and off-axis (facing 45°) listening condition at signal-to-noise ratios (SNRs) of -3, -6, -9, and -12 dB. For 42 of the subjects, SSIN testing was also completed for key word recognition in sentences in multi-talker babble noise; specifically, the separation between speech and noise loudspeakers was adaptively varied to determine the difference needed for 40% and 80% correct performance levels. Finally, auditory temporal processing ability was examined using the Temporal Fine Structure test (44 subjects), and the Spectro-Temporal Modulation test (46 subjects). Results: Mean lateralization performances were poorer (larger MAAs) in older compared to younger subjects, particularly in the more adverse listening conditions (i.e., for 4000 Hz, off-axis, and at poorer SNRs). Performance variability was notably higher for older subjects than for young adults. The 4000 Hz NBN bursts produced larger MAAs than did 500 Hz NBN bursts. The SSIN data also showed declining mean performance with age at both criterion levels, with greater variability again found for older subjects. Spearman rho analyses revealed some low to moderate, but significant correlation coefficients for age versus MAA and for age versus SSIN results. Results from both the TFS and STM showed decreased mean performance with aging, and revealed moderate, significant correlations, with the strongest relationship shown with the TFS test. Finally, of note, extended-high-frequency (EHF) hearing loss (measured between 9000 and 16,000 Hz) was found to increase with aging, but was not seen in the young adult subjects. Conclusions: Particularly for more adverse listening conditions, age-related deficits were found on both of the spatial hearing tasks and in temporal and spectro-temporal processing abilities. It may be that deficits in temporal processing ability contribute to poorer spatial hearing performance in older subjects due to inaccurate coding of binaural/interaural timing information sent from the periphery to the brainstem. In addition, EHF hearing loss may be a coexisting factor that impacts performance in older subjects.

Gyrification across psychotic disorders: A bipolar-schizophrenia network of intermediate phenotypes study.

BACKGROUND: The profiles of cortical gyrification across schizophrenia, bipolar I disorder, and schizoaffective disorder have been studied to a limited extent, report discordant findings, and are rarely compared in the same study. Here we assess gyrification in a large dataset of psychotic disorder probands, categorized according to the DSM-IV. Furthermore, we explore gyrification changes with age across healthy controls and probands. METHODS: Participants were recruited within the Bipolar-Schizophrenia Network of Intermediate Phenotypes study and received T1-MPRAGE and clinical assessment. Gyrification was measured using FreeSurfer 7.1.0. Pairwise t-tests were conducted in R, and age-related gyrification changes were analyzed in MATLAB. P values <0.05 after false discovery rate correction were considered significant. RESULTS: Significant hypogyria in schizophrenia, bipolar disorder, and schizoaffective disorder probands compared to controls was found, with a significant difference bilaterally in the frontal lobe between schizophrenia and bipolar disorder probands. Verbal memory was associated with gyrification in the right frontal and right cingulate cortex in schizophrenia. Age-fitted gyrification curves differed significantly among psychotic disorders and controls. CONCLUSIONS: Findings indicate hypogyria in DSM-IV psychotic disorders compared to controls and suggest differential patterns of gyrification across the different diagnoses. The study extends age related models of gyrification to psychotic disorder probands and supports that age-related differences in gyrification may differ across diagnoses. Fitted gyrification curves among probands categorized by DSM-IV significantly deviate from controls, with the model capturing early hypergyria and later hypogyria in schizophrenia compared to controls; this suggests unique disease and age-related changes in gyrification across psychotic disorders.

Signal Regulatory Protein α Expression in Systemic Vasculitis.

OBJECTIVE: Signal regulatory protein α (SIRPα) is found primarily on myeloid cells, including macrophages and neutrophils; binds to CD47; and regulates phagocytosis, antigen presentation, cellular fusion, cell proliferation, and migration. Therefore, SIRPα may be involved in the pathogenesis of autoimmune diseases, including systemic vasculitis. This study aimed to assess SIRPα expression in tissue samples from patients with vasculitis. METHODS: Immunohistochemical staining for SIRPα was performed on temporal artery (TA), kidney, and lung biopsy samples from patients with giant cell arteritis (GCA), patients with microscopic polyangiitis (MPA), patients with granulomatosis with polyangiitis (GPA), and patients without vasculitis. A score of SIRPα+ expression was calculated, derived from the percentages of monocytes, macrophages, and dendritic cells and neutrophils with different staining intensities in affected tissues. RESULTS: A total of 46 samples from patients with different vasculitides (GCA, MPA, and GPA) were included in the study. Tissue samples included TA samples from 15 patients with GCA; kidney samples from 11 and 9 patients with GPA and MPA, respectively; and lung samples from 11 patients with GPA. Most tissue samples from patients with active vasculitis (15 of 15 TA samples, 17 of 20 kidney samples, and 9 of 11 lung samples) showed SIRPα staining. SIRPα staining intensity was less in kidney samples compared to TA and lung samples. CONCLUSION: This study demonstrates high-level expression of SIRPα in macrophages and monocytes in affected tissue in systemic vasculitis. These findings provide a foundation for further studies exploring the role of the SIRPα-CD47 pathway in the pathogenesis of systemic vasculitis and the potential for the blockade of SIRPα and/or the depletion of SIRPα+ cells as treatment of systemic vasculitis.

Feedback and observational learning differ in effectiveness during category learning in early school aged children and adults.

When learning new categories, do children benefit from the same types of training as adults? We compared the effects of feedback-based training with observational training in young adults (ages 18-25) and early school aged children (ages 6-7) across two different multimodal category learning tasks: conjunctive rule based and information integration. We used multimodal stimuli that varied across a visual feature (rotation speed of the "planet" stimulus) and an auditory feature (pitch frequency of a pure tone stimulus). We found an interaction between age and training type for the rule-based category task, such that adults performed better in feedback training than in observational training, whereas training type had no significant effect on children's category learning performance. Overall adults performed better than children in learning both the rule based and information integration category structures. In information integration category learning, feedback versus observational training did not have a significant effect on either adults' or children's category learning. Computational modelling revealed that children defaulted to univariate rules in both tasks. The finding that children do not benefit from feedback training and can learn successfully via observational learning has implications for the design of educational interventions appropriate for children.

Outcomes in solid organ transplant recipients receiving organs from a donor with Fusarium solani species complex meningitis.

BACKGROUND: Five organs (heart, right lung, liver, right, and left kidneys) from a deceased patient were transplanted into five recipients in four US states; the deceased patient was identified as part of a healthcare-associated fungal meningitis outbreak among patients who underwent epidural anesthesia in Matamoros, Mexico. METHODS: After transplant surgeries occurred, Fusarium solani species complex, a fungal pathogen with a high case-mortality rate, was identified in cerebrospinal fluid from the organ donor by metagenomic next-generation sequencing (mNGS) and fungal-specific polymerase chain reaction and in plasma by mNGS. RESULTS: Four of five transplant recipients received recommended voriconazole prophylaxis; four were monitored weekly by serum (1-3)-ß-d-glucan testing. All five were monitored for signs of infection for at least 3 months following transplantation. The liver recipient had graft failure, which was attributed to an etiology unrelated to fungal infection. No fungal DNA was identified in sections of the explanted liver, suggesting that F. solani species complex did not contribute to graft failure. The remaining recipients experienced no signs or symptoms suggestive of fusariosis. CONCLUSION: Antifungal prophylaxis may be useful in preventing donor-derived infections in recipients of organs from donors that are found to have Fusarium meningitis.

Evaluation of the "15 Minute Challenge": A Workplace Health and Wellbeing Program.

The 15 Minute Challenge is an mHealth workplace wellness initiative, employing gamification to promote physical activity, aiming to enhance health outcomes and overall well-being. This retrospective cohort study evaluated the effectiveness of the program among employees at various Australian, New Zealand, and UK workplaces. Real-world data from 11,575 participants across 73 companies were analyzed. The program encouraged daily 15 min physical activity sessions over six weeks. Participants self-reported their physical activity and fitness, energy, overall health, sleep quality, and mood at baseline and 6 weeks. Program satisfaction, engagement rates, and adherence to the program were also assessed. Effectiveness was evaluated using multi-level mixed-effects linear regression analyses. The intervention showed significant increases in physical activity, with 95% of participants meeting or exceeding international physical activity guidelines, up from 57% at baseline (p < 0.05). Self-reported fitness, energy, overall health, sleep quality, and mood significantly improved (between 7.1 and 14.0% improvement; all p < 0.05). High satisfaction was reported, with 92% of participants recommending the program. The 15 Minute Challenge effectively increased physical activity levels and improved self-reported health outcomes among participating employees. The high satisfaction rates and significant health improvements highlight the potential of workplace wellness programs to combat sedentary behavior and promote a healthier, more active lifestyle.

Oral Lipid Nanocrystal Amphotericin B (MAT2203) for the Treatment of Invasive Fungal Infections.

Amphotericin B (AmB) has broad fungicidal activity against many fungi, but the high incidence of adverse events, particularly nephrotoxicity, and the need for intravenous administration restrict its use for many patients. MAT2203, an investigational oral AmB formulation available under a compassionate use program, uses a lipid nanocrystal bilayer structure to deliver AmB with lower toxicity. We present a synopsis of clinical characteristics, treatment course, and outcomes for 5 patients who were treated with MAT2203. Outcomes were positive, with cure of infection noted in 4 patients and improvement in 1 patient who remains on therapy. MAT2203 was well tolerated with only modest gastrointestinal adverse effects. This new oral formulation might provide a safer treatment option for patients requiring extended courses of AmB.

Spatial transcriptomics implicates impaired BMP signaling in NF1 fracture pseudarthrosis in murine and patient tissues.

The Neurofibromatosis Type 1 (NF1) RASopathy is associated with persistent fibrotic nonunions (pseudarthrosis) in human and mouse skeletal tissue. Here, we first performed spatial transcriptomics to define the molecular signatures across normal endochondral healing following fracture in mice. Within the control fracture callus, we observed spatially restricted activation of morphogenetic pathways, such as TGF-ß, WNT, and BMP. To investigate the molecular mechanisms contributing to Nf1-deficient delayed fracture healing, we performed spatial transcriptomic analysis on a Postn-cre;Nf1flox/- (Nf1Postn) fracture callus. Transcriptional analyses, subsequently confirmed through p-SMAD1/5/8 immunohistochemistry, demonstrated a lack of BMP pathway induction in Nf1Postn mice. To further inform the human disease, we performed spatial transcriptomic analysis of fracture pseudarthrosis tissue from a NF1 patient. Analyses detected increased MAPK signaling at the fibrocartilaginous-osseus junction. Similar to the Nf1Postn fracture, BMP pathway activation was absent within the pseudarthrosis tissue. Our results demonstrate the feasibility to delineate the molecular and tissue-specific heterogeneity inherent in complex regenerative processes, such as fracture healing, and to reconstruct phase transitions representing endochondral bone formation in vivo. Furthermore, our results provide in situ molecular evidence of impaired BMP signaling underlying NF1 pseudarthrosis, potentially informing the clinical relevance of off-label BMP2 as a therapeutic intervention.

Blockade of thromboxane A2 signaling attenuates ethanol-induced myocardial inflammatory response in mice.

BACKGROUND: Alcohol-associated cardiomyopathy (ACM) is a cardiac muscle disease characterized by inflammation and oxidative stress. Thromboxane-prostanoid receptor (TP-R) plays an important role in the pathogenesis of cardiovascular disease. Herein, we hypothesize that TP-R mediates alcohol-induced early cardiac injury. METHODS: Eight-week-old male C57BL/6 wild-type mice were fed a chronic ethanol (ET) or control diet (CON) for 10 days followed by a single binge of ethanol or maltose-dextrin through oral gavage. A cohort of ethanol-fed mice received SQ 29,548 (SQ), a TP-R antagonist. RNA sequencing, real-time PCR, and western blot analysis were performed on left ventricle to investigate alterations in genes and/or proteins mediating oxidative stress, inflammation, and cardiac remodeling. Sirius Red staining was performed to measure myocardial fibrosis. RESULTS: RNA-sequencing analysis of myocardium from CON and ET groups identified 142 genes that were significantly altered between the two groups. In particular, the gene expression of thioredoxin-interacting protein (TXNIP), a component of NLR family pyrin domain containing 3 (NLRP3) signaling, which mediates oxidative stress and inflammatory response, was upregulated in response to ethanol exposure. The myocardial protein levels of TP-R and thromboxane A2 synthase were increased upon alcohol exposure. Ethanol increased the levels of 4-hydroxynonenal, a marker of oxidative stress, with a concomitant increase in the protein levels of TXNIP and NLRP3, and administration of SQ attenuated these effects. Additionally, ethanol increased the protein levels of pro-inflammatory mediators, including tumor necrosis factor alpha and the NLRP3 downstream product, secretory interleukin 1 beta, and SQ blunted these effects. Finally, the Sirius red staining of the myocardium revealed an increase in collagen deposition in ethanol-fed mice which was attenuated by TP-R antagonism. CONCLUSION: This study demonstrates that ethanol promotes the NLRP3 signaling pathway within the myocardium, leading to a pro-inflammatory milieu that potentially initiates early myocardial remodeling, and TP-R antagonism attenuates this effect.

Prototype or Exemplar Representations in the 5/5 Category Learning Task.

Theories of category learning have typically focused on how the underlying category structure affects the category representations acquired by learners. However, there is limited research as to how other factors affect what representations are learned and utilized and how representations might change across the time course of learning. We used a novel "5/5" categorization task developed from the well-studied 5/4 task with the addition of one more stimulus to clarify an ambiguity in the 5/4 prototypes. We used multiple methods including computational modeling to identify whether participants categorized on the basis of exemplar or prototype representations. We found that, overall, for the stimuli we used (schematic robot-like stimuli), learning was best characterized by the use of prototypes. Most importantly, we found that relative use of prototype and exemplar strategies changed across learning, with use of exemplar representations decreasing and prototype representations increasing across blocks.