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PubMed2000

Velocity constancy in a virtual reality environment.

During everyday life the brain is continuously integrating multiple perceptual cues in order to allow us to make decisions and to guide our actions. In this study we have used a simulated (virtual reality--VR) visual environment to investigate how cues to speed judgments are integrated. There are two sources that could be used to provide signals for velocity constancy: temporal-frequency or distance cues. However, evidence from most psychophysical studies favours temporal-frequency cues. Here we report that two depth cues that provide a relative object--object distance--disparity and motion parallax--can provide a significant input to velocity-constancy judgments, particularly when combined. This result indicates that the second mechanism can also play a significant role in generating velocity constancy. Furthermore, we show that cognitive factors, such as familiar size, can influence the perception of object speed. The results suggest that both low-level cues to spatiotemporal structure and depth, and high-level cues, such as object familiarity, are integrated by the brain during velocity estimation in real-world viewing.

Cues↗

PubMed2000

Involuntary orienting to sound improves visual perception.

To perceive real-world objects and events, we need to integrate several stimulus features belonging to different sensory modalities. Although the neural mechanisms and behavioural consequences of intersensory integration have been extensively studied, the processes that enable us to pay attention to multimodal objects are still poorly understood. An important question is whether a stimulus in one sensory modality automatically attracts attention to spatially coincident stimuli that appear subsequently in other modalities, thereby enhancing their perceptual salience. The occurrence of an irrelevant sound does facilitate motor responses to a subsequent light appearing nearby. However, because participants in previous studies made speeded responses rather than psychophysical judgements, it remains unclear whether involuntary auditory attention actually affects the perceptibility of visual stimuli as opposed to postperceptual decision and response processes. Here we provide psychophysical evidence that a sudden sound improves the detectability of a subsequent flash appearing at the same location. These data show that the involuntary orienting of attention to sound enhances early perceptual processing of visual stimuli.

Adult↗

PubMed1997

A comparison of Cox proportional hazards and artificial neural network models for medical prognosis.

Modeling survival of populations and establishing prognoses for individual patients are important activities in the practice of medicine. For patients with diseases that may extend for several years, in particular, accurate assessment of survival probabilities is essential. New methods, such as neural networks, have been used increasingly to model disease progression. Their advantages and disadvantages, when compared to statistical methods such as Cox proportional hazards, have seldom been explored in real-world data. In this study, we compare the performances of a Cox model and a neural network model that are used as prognostic tools for a set of people living with AIDS. We modeled disease progressions for patients who had AIDS (according to the 1993 CDC definition) in a set of 588 patients in California, using data from the ATHOS project. We divided the study population into 10 training and 10 test sets and evaluated the prognostic accuracy of a Cox proportional hazards model and of a neural network model by determining sensitivities, specificities, positive and negative predictive values for an arbitrary threshold (0.5), and the areas under the receiver operating characteristics (ROC) curves that utilized all possible thresholds for intervals of 1 yr following the diagnosis of AIDS. There was no evidence that the Cox model performed better than did the neural network model or vice versa, but the former method had the advantage of providing some insight on which variables were most influential for prognosis. Nevertheless, it is likely that the assumptions required by the Cox model may not be satisfied in all data sets, justifying the use of neural networks in certain cases.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Nursing scripts and the organizational influences on critical thinking: report of a study of neonatal nurses' clinical reasoning.

During 1995-1997 a study was undertaken to explore the extent to which theoretical knowledge acquired through a distance education programme in neonatal nursing was brought to bear in the real-world clinical reasoning of course participants. The study utilized a think aloud technique and included both concurrent (on-the-job) and retrospective verbal reports at 0, 6 and 12 months into the programme. Participants (n=4) were also interviewed individually on completion of the study. Results indicated that important inconsistencies existed between participants' theoretical knowledge and their practice; they also pointed to some organizational influences on these theory-practice inconsistencies. Script (or schema) theory provided a useful explanatory framework for these results. The paper includes a brief description of data collection and analysis techniques; its main emphasis, however, is on these theory-practice inconsistencies and their explanation in terms of the nature and acquisition of nursing practice scripts. The implications of nursing scripts for the promotion of critical thinking and evidence-based practice are discussed.

Adult↗

PubMed1999

Object identification is isolated from scene semantic constraint: evidence from object type and token discrimination.

Two models of the interaction between scene meaning and object identification were tested: the description enhancement model and the criterion modulation model. The former proposes that the early activation of a scene schema facilitates the initial perceptual analysis of schema-consistent objects, the latter that schema activation modulates the amount of information necessary to indicate the presence of an object of a particular perceptual type. In Experiment 1, we employed a forced-choice, type-discrimination paradigm. Participants were asked to determine which of two semantically consistent objects or which of two semantically inconsistent objects had appeared in a briefly presented scene. Contrary to the prediction derived from both of these models, discrimination performance was better for semantically inconsistent versus consistent objects. In Experiments 2 and 3 we introduced a forced-choice, token-discrimination paradigm to further test the description enhancement model. Contrary to the prediction of that model, discrimination performance was no better for semantically consistent versus inconsistent tokens. These results suggest that both the initial perceptual analysis of an object and the matching of an object's constructed visual description to stored descriptions are isolated from stored knowledge about real-world contingencies between scenes and objects.

Adult↗

PubMed2026

Survey on the current status of novel cancer drug therapies for gynecological cancers in Japan: a nationwide survey by the Japan Society of Obstetrics and Gynecology (JSOG).

OBJECTIVE: To characterize real-world implementation of novel therapies in gynecological oncology in Japan and identify actionable gaps through a nationwide survey. METHODS: A cross-sectional questionnaire was distributed to Japan Society of Obstetrics and Gynecology-affiliated institutions. The items covered institution characteristics; use of poly (ADP-ribose) polymerase (PARP) inhibitors, immune checkpoint inhibitors (ICIs), kinase inhibitors, and antibody-based agents; local adverse event (AE) manuals; availability of expert panels and immune-related adverse event (irAE) teams; and perceptions of educational sufficiency. RESULTS: Valid responses were obtained from 245 institutions, spanning universities, cancer centers, and general hospitals. Most institutions reported the routine use of PARP inhibitors, ICIs, kinase inhibitors, and antibody drugs. However, only 40.4% of institutions had an in-hospital irAE management team, 57.1% had an AE/irAE manual, and 31.0% and 12.2% considered prior educational opportunities sufficient for physicians and nurses/other medical staff, respectively. High-volume institutions and academic centers were significantly more likely to have medical oncology support, expert-panel access, irAE teams, manuals, and higher self-rated evidence-based management capacity. The majority favored e-learning and society-led case conferences, and 76.3% supported the development of drug therapy subspecialties in gynecologic oncology. CONCLUSION: Innovative drug modalities are widely implemented across Japanese gynecological oncology services. However, critical gaps persist in multidisciplinary irAE management, standardized manuals, and practical education. Coordinated society-led programs to expand irAE teams, streamline companion diagnostics, disseminate ready-to-use algorithms, and provide credential-targeted training may enhance safety, equity, and evidence-concordant care nationwide.

Immune Checkpoint Inhibitors↗

PubMed2026

Associations between smart infusion pump-electronic health record interoperability and healthcare outcomes: A systematic review.

OBJECTIVE: This study synthesized available evidence on the associations between smart infusion pump-electronic health record (EHR) interoperability and healthcare outcomes. METHODS: A systematic review of PubMed, CINAHL, Embase, and Scopus databases identified 901 records, which were imported into Rayyan® for duplicate removal, independent screening by three reviewers, and resolution of discrepancies. Eligible studies were peer-reviewed, data-driven, and reported associations between smart infusion pump-EHR interoperability and healthcare outcomes. Studies focused solely on technical validation or interoperability prototypes were excluded. A backward citation search identified additional studies. Two reviewers independently extracted and cross-validated study characteristics using standardized templates. Methodological quality was assessed with the Joanna Briggs Institute Critical Appraisal Tools. RESULTS: Twenty records of 14 full-text studies and 6 conference proceedings were included. Most records reported positive associations between smart infusion pump-EHR interoperability and outcomes related to safety (e.g., medication administration errors, safety-reported events, pump alerts, and compliance with interoperability and drug library), operational efficiency (e.g., programming and documentation time and technical issues), financial performance (e.g., charges captured, and cost avoided), and user experience domains. Most studies used observational designs, reflecting real-world interoperability implementations, where controlling confounding factors is challenging. Limited reporting of baseline characteristics, pump type, and sample sizes limited comparability across studies. CONCLUSIONS: Smart infusion pump-EHR interoperability was associated with improvements in patient safety, efficiency, charge capture, and user experience, with variable findings across studies. Future research should use rigorous methodologies and standardized measures, examine relationships across outcome domains, assess limitations of pump-EHR interoperability, and evaluate underexplored outcomes, including team communication, cognitive workload, and AI-enabled pumps. IMPLICATIONS FOR CLINICAL PRACTICE: Interoperability should be viewed as a component of a broader sociotechnical system, in which technology, user, workflow, clinical content, and organizational practices collectively determine overall effectiveness.

Humans↗

PubMed2026

Personalised Nutraceutical Treatment Guided by MTHFR Genotype in Mental Health: A Retrospective Cohort Study.

BACKGROUND & AIMS: One-carbon metabolism plays a central role in neurotransmitter synthesis, methylation capacity, and neurobiological resilience. Variants in the methylenetetrahydrofolate reductase (MTHFR) gene can reduce enzymatic activity, affecting folate- and methionine-cycle functions and potentially influencing biological pathways relevant to mood and anxiety disorders. Personalised nutraceutical treatment strategies, particularly those addressing methylation capacity through targeted B-vitamin, folate, and adjunctive metabolic interventions are increasingly implemented in integrative clinical practice, yet evidence regarding their clinical outcomes remains limited. METHODS: We conducted a retrospective cohort study of 50 adults attending an integrative general practice clinic for anxiety and/or depression. All received personalised nutraceutical treatment informed by clinical assessment, laboratory testing and, for 37/50 patients, MTHFR genotyping. Psychological distress was measured using the Kessler-10 (K10) scale at baseline and approximately three months later. Secondary analyses evaluated whether outcomes differed by MTHFR genotype, whether specific supplements (e.g., L-methylfolate and SAMe) were associated with greater improvement, whether biomarker changes correlated with symptom change, and the safety/tolerability profile. RESULTS: Across the full cohort, mean K10 scores significantly decreased by four points over the treatment period, with 72% of patients showing clinical improvement. Reductions in psychological distress were seen across all MTHFR genotypes, including individuals with homozygous variant genotypes. Supplement-specific analyses showed improvement among those receiving methylfolate or SAMe, although the differences were not statistically significant. Following nutraceutical treatment, biomarker analyses demonstrated significant increases in serum vitamin B12 and modest reductions in homocysteine, but biomarker shifts did not correlate strongly with K10 change. No serious adverse events or clinically significant abnormalities in liver or renal function were identified. CONCLUSIONS: In this real-world primary care cohort, personalised nutraceutical treatment, grounded in one-carbon metabolism support and applied alongside usual care, was associated with clinically meaningful reductions in psychological distress. Outcomes were comparable across MTHFR genotypes when treatments were appropriately tailored, suggesting that genotype and biomarker-informed nutraceutical strategies may mitigate potential metabolic disadvantages. These findings support further controlled research into precision nutraceutical psychiatry for anxiety and depression. Secondary analyses of genotype subgroup, specific supplements, and biomarker-outcome associations are reported alongside Benjamini-Hochberg FDR-adjusted p-values and should be interpreted as hypothesis-generating.

Humans↗

PubMedDate not supplied

Cost-effectiveness of initial therapy with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors to treat hypercholesterolemia in a primary care setting of a managed-care organization.

From January 1994 through May 1995, Prudential HealthCare-North Texas prospectively studied 299 member patients diagnosed with hypercholesterolemia for whom pharmacotherapy with one of four 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, also known as statins, was prescribed. The purpose of this study was to measure the relative cost-effectiveness (CE) of these drugs in a real-world setting. This study provides information to assist decision makers in managed-care organizations (MCO) in making formulary selections. The study used a prospective, randomized, balanced cohort design, examining patients who had been prescribed initial therapy with a statin drug as monotherapy. Costs (direct medical and indirect costs) and effectiveness (percent reduction in low-density lipoprotein cholesterol levels) were based on approximately the first 6 months of initial therapy. Both the MCO and patient perspectives were considered. In the base case, mean CE ratios were significantly lower for fluvastatin compared with lovastatin, pravastatin, and simvastatin from both the managed-care perspective and the patient perspective. Sensitivity analysis did not alter the CE conclusions, even under conditions of varying cost structures. Although differences were found in the effectiveness of lovastatin, pravastatin, and simvastatin measured in this study versus efficacy measured for these drugs in controlled clinical trials, sensitivity analysis suggests that these differences alone do not determine the superior CE of fluvastatin. Finally, this study supports the idea that well-designed formularies should consider drug CE (based on safety, effectiveness, and cost) and that integration of the pharmacy benefit management with other medical management is essential. These results provide evidence that fluvastatin may represent a more cost-effective formulary choice among statin products used for initial monotherapy of hypercholesterolemia.

Adult↗

PubMed2001

Effects of cost sharing on physician utilization under favourable conditions for supplier-induced demand.

The effects of cost sharing on the demand for ambulatory care in experimental circumstances are well understood since the Rand Health Insurance Experiment (HIE). However, in a non-experimental real-world context, supplier-induced demand of doctors might erode some of the significant negative out-of-pocket price elasticity identified in the HIE. Belgium is an interesting test case for this hypothesis because it has relatively high rates of patient cost sharing in its public health insurance system and a very high density of physicians, all remunerated fee-for-service. We have exploited the price variation generated by a substantial increase in patient co-payment rates in 1994 to estimate out-of-pocket price elasticities for three groups of users, and for three types of services using a fixed-effects model in levels and in differences. We obtain significant out-of-pocket price elasticities for the general population in the range from -0.39 to -0.28 for GP home visits, -0.16 to -0.12 for GP office visits and -0.10 for specialist visits. The estimates were generally lower and less significant for the groups of elderly and disabled. The differences we find in price responsiveness appear to be fairly robust and consistent with the HIE predictions. These results suggest that--at least in the short run--non-experimental utilization effects of cost sharing are very similar to the experimental evidence, even in a situation of favourable conditions for supplier-induced demand.

Ambulatory Care↗

PubMed2026

Temporal shifts in gyrA mutation types and sublineage replacement in ST11 Salmonella enterica serovar Enteritidis over a decade (2014-2023): A genomic epidemiological study in Guangxi, China.

The overuse or abuse of antibiotics drives the global health threat of antimicrobial resistance. Although bans on certain veterinary antibiotics, such as colistin, have proven effective, the impact of fluoroquinolone stewardship on the evolution of the foodborne pathogen Salmonella enterica serovar Enteritidis (S. Enteritidis) remains unclear. Here, we conducted a decade-long (2014-2023) retrospective longitudinal genomic epidemiological analysis of 441 ST11 S. Enteritidis isolates from Guangxi, China, alongside a global reference dataset of 4297 genomes. Our aim was to elucidate the effect of real-world antibiotic stewardship on the shift of gyrA point mutations and lineage distribution. Surveillance identified three global epidemic clade sublineages (GEC-L2, L3, L4), with the multidrug-resistant GEC-L4 (i.e., GC-c or MMC2), characterized by the gyrA mutation with amino acid substitution D87Y, being domestically dominant (70.07%, 309/441). Following China's 2016 ban on the veterinary use of critical fluoroquinolones, the proportion of the highly resistant GEC-L4 sublineage decreased continuously (from 86.84% in 2017 to 56.00% in 2023), while the less resistant GEC-L3 sublineage (i.e., GC-b or MMC1), mainly characterized by gyrA D87G, increased simultaneously (from 13.16% to 44.00%). This phenomenon might be attributed to the fact that the GEC-L4 sublineage exhibited a higher fitness cost compared with the GEC-L3 sublineage, as confirmed by the competition assay. A Random Forest Model validated that the gyrA mutation with amino acid substitution D87Y was the paramount feature for these sublineages' identification. In contrast, global data showed a continuous increase in gyrA mutations (from 8.63% in 2006 to 68.85% in 2024), primarily D87Y (from 1.44% to 31.15%) and D87N (from 4.32% to 22.95%), correlating with rising average fluoroquinolone consumption. This study provides direct genomic evidence that national-level antibiotic stewardship can drive the replacement of highly resistant sublineages with moderately resistant ones. These findings offer crucial scientific evidence for evaluating the impact of antibiotic management policies and inform strategies for the rational use of antimicrobials.

China↗

PubMed1985

Reporting presence or absence of named objects by a language-trained dolphin.

Referential "reporting" was defined as the transmission of information about the presence or absence of symbolically-referenced real-world objects. In Experiment 1 two bottlenosed dolphins (Tursiops truncatus), trained in earlier studies to carry out instructions conveyed by imperative sentences expressed in artificial gestural or acoustic languages, each gave spontaneous indications that an object referenced in an imperative was absent from their tank. In Experiment 2 the dolphin tutored in the gestural language was taught to make explicit reports of object absence by pressing a "No" paddle in response to imperatives referencing an absent object. Absence was reported correctly on 84% of 97 missing-object probes inserted at random intervals among 598 sentences referring to objects that were present. Reports were typically made after active search of the tank for an average of 15.0 sec. False reports, that objects present were absent, were few (7.5%). In Experiment 3, the dolphin was taught an interrogative sentence form that enabled us to ask direct questions about the presence or absence of specific objects. Responses by the dolphin on the No paddle indicated absence, while responses on a "Yes" paddle indicated presence. From one to three objects were shown the dolphin and then placed in the tank in a discrete-trial procedure. In response to the interrogative, reports or object presence or absence were better than 91% correct with a single object in the tank and either that object or some other object referenced; accuracy declined to 72-78% correct with three objects present, but was still well above chance. Several lines of evidence suggested that the dolphin was attempting to remember which objects it had been shown, rather than conducting an active environmental search as in Experiment 2. The memory strategy became less efficient as the number of objects to be remembered increased. Overall, the results evidenced the language-trained dolphin's understanding of references to present or absent objects, its ability to inventory its environment to seek information about those objects, and its ability to report its obtained knowledge to others.

Animal Communication↗

PubMed2026

HER2DX genomic assay in HER2-positive early breast cancer treated with trastuzumab and pertuzumab: A correlative analysis from a real-world cohort.

BACKGROUND: HER2DX genomic assay is a genomic tool developed for personalizing care in early-stage HER2-positive breast cancer. This real-world analysis examines its associations with pathological complete response (pCR) and invasive disease-free survival (IDFS) following trastuzumab- and pertuzumab-based neoadjuvant therapy. MATERIALS AND METHODS: Retrospective, observational, single-center study of 156 patients with stage I-III HER2-positive breast cancer treated with dual HER2 blockade-based neoadjuvant therapy between February 2015 and May 2022 at University Hospital A Coruña. HER2DX and clinicopathological variables were assessed in pretreatment tumor biopsies. Statistical analyses included Fisher's exact test, logistic regression, Cox proportional hazards models, and Kaplan-Meier estimates. RESULTS: HER2DX was performed in 111 tumors (71.2%). Overall pCR rate was 51.3%. Hormone receptor-positive disease was significantly associated with lower pCR (odds ratio [OR] 0.25, 95% CI 0.11-0.50; p < 0.001), whereas HER2 immunohistochemistry 3+ showed a non-significant trend toward higher pCR (OR 2.95, 95% CI 0.96-11.08; p = 0.075). Median IDFS was not reached, but hormone receptor-positive tumors showed better outcomes (hazard ratio [HR] 3.67, 95% CI 1.02-13.32; p = 0.004 by log-rank). The association between HER2DX pCR score and pCR appeared heterogeneous. The continuous score was significantly associated with pCR in univariable analysis, not in multivariable model. In contrast, medium-high HER2DX pCR category showed significantly higher pCR rates than low category (OR 4.83, 95% CI 1.72-14.65; p = 0.004). The continuous HER2DX risk score was independently associated with IDFS (HR 2.84, 95% CI 1.24-6.48; p = 0.010). CONCLUSIONS: In this cohort, HER2DX scores were associated with pCR and IDFS, supporting previous evidence and highlighting potential role in treatment stratification.

Humans↗

PubMed1997

Discrimination of complex patterns: orientation information is integrated across spatial scale; spatial-frequency and contrast information are not.

Real-world objects are complex, containing information at multiple orientations and spatial scales. It is well established that at initial cortical stages of processing, local information about an image is separately represented at multiple spatial scales. However, it is not yet established how these early representations are later integrated across scale to signal useful information about complex stimulus features, such as edges and textures. In the studies reported here, we investigate the scale-integration processes involved in distinguishing among complex patterns. We use a concurrent-response paradigm in which observers simultaneously judge two components of compound gratings that differ widely in spatial frequency. In different experiments, each component takes one of two slightly different values along the dimensions of spatial frequency, contrast, or orientation. Using analyses developed within the framework of a multivariate extension of signal-detection theory, we ask how information about the frequency, contrast, or orientation of the components is or is not integrated across the two grating components. Our techniques permit us to isolate and identify interactions due to excitatory or inhibitory processes from effects due to noise, and to separately assess any attentional limitations that might occur in processing. Results indicate that orientation information is fully integrated across spatial scales within a limited orientation band and that decisions are based entirely on the summed information. Information about spatial frequency and contrast is not summed over spatial scale; cross-scale results show sensory independence. However, our results suggest that observers cannot simultaneously use information about frequency or contrast when it is presented at different spatial scales. Our results provide direct evidence for the existence of a higher-level summing circuit tailored to signal information about orientation. The properties of this mechanism differ substantially from edge-detector mechanisms proposed by Marr and others.

Female↗

PubMed2026

A Smartphone-Based Ecological Momentary Intervention for Workplace Mental Health: Randomized Controlled Trial.

BACKGROUND: Work-related stress has been widely associated with an increased risk of various mental disorders and poor mental well-being. The fast-growing mobile health services industry has provided new opportunities for workplace mental health. OBJECTIVE: This randomized controlled trial examined the effectiveness of Neurum (Neurum Limited), a smartphone-based intervention tool featuring ecological momentary assessments and interventions that aims to reduce workplace stress in real-time and real-world settings. METHODS: A total of 201 working adults were recruited for a 4-week smartphone-based intervention that incorporated cognitive behavioral therapy, mindfulness exercises, and self-regulation exercises delivered on Neurum. A simple randomization procedure was used. Participants in the intervention group were encouraged to log mood journals, complete mental health exercises, and provide user feedback whenever applicable. The key outcome was measured by the Depression, Anxiety, and Stress Scale-21 items (DASS-21; Cronbach α=0.87). RESULTS: The intervention group consisted of 102 participants, while the control group consisted of 99 participants. More participants dropped out from the intervention group (n=21) than from the control group (n=2; χ21=18.259; P<.001). The final sample consisted of 178 participants (male: 85/178, 47.8%; female: 93/178, 52.2%; mean age of 34.65, SD 7.67 y). Analyses revealed that after the 4-week intervention, the DASS-21 scores decreased in the intervention group (mean difference [MD]post-pre intervention=-14.518) but increased in the control group (MDpost-pre intervention=3.319; F1,176=59.358, P<.001; η2=0.252). This effect was largely led by stress reduction (F1,176=64.679, P<.001; for the intervention group, MDpost-pre intervention=-6.692, while for the control group, MDpost-pre intervention=2.000). On average, participants completed 6.27 (SD 9.4) exercises and provided 9.74 (SD 18.2) mood journal logs, with a daily engagement of 4.95 (SD 6.89) minutes. However, the associations between the changes in DASS-21 scores and the numbers of exercises or mood journal logs did not reach statistical significance. CONCLUSIONS: This study primarily established the effectiveness of Neurum in alleviating depression, anxiety, and stress symptoms in noninstitutionalized working adults, with a satisfactory user retention rate. Despite potential health-related culture differences, Neurum contributed to evidence-based digital health in nonclinical settings for timely needs and general accessibility as an alternative to traditional, face-to-face, and high-cost mental health services. Future directions involving a personalized approach in online mental health services were discussed.

Humans↗

PubMed1995

Sparseness of the neuronal representation of stimuli in the primate temporal visual cortex.

1. To analyze the selectivity and the sparseness of firing to visual stimuli of single neurons in the primate temporal cortical visual area, neuronal responses were measured to a set of 68 visual stimuli in macaques performing a visual fixation task. The population of neurons analyzed had responses that occurred primarily to faces. The stimuli included 23 faces, and 45 nonface images of real-world scenes, so that the function of this brain region could be analyzed when it was processing natural scenes. 2. The neurons were selected to meet the previously used criteria of face selectivity by responding more than twice as much to the optimal face as to the optimal nonface stimulus in the set. Application of information theoretic analyses to the responses of these neurons confirmed that their responses contained much more information about which of 20 face stimuli had been seen (on average 0.4 bits) than about which (of 20) nonface stimuli had been seen (on average 0.07 bits). 3. The sparseness of the representation of a scene or object provided by each of these neurons (which can be thought of as the proportion of stimuli to which the neuron responds, and which is fundamental to understanding the network operation of the system) can be defined as [formula: see text] where ri is the firing rate to the ith stimulus in the set of n stimuli. The sparseness has a maximal value of 1.0. It was found that the sparseness of the representation of the 68 stimuli by each neuron had an average across all neurons of 0.65. This indicates a rather distributed representation. 4. If the spontaneous firing rate was subtracted from the firing rate of the neuron to each stimulus, so that the changes of firing rate, i.e., the responses of the neurons, were used in the sparseness calculation, then the "response sparseness" had a lower value, with a mean of 0.33 for the population of neurons, or 0.60 if calculated over the set of faces. 5. Multidimensional scaling to produce a stimulus space represented by this population of neurons showed that the different faces were well separated in the space created, whereas the different nonface stimuli were grouped together in the space. 6. The information analyses and multidimensional scaling provided evidence that what was made explicit in the responses of these neurons was information about which face had been seen.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1998

The social construction of cardiovascular reactivity.

One can view the "reactivity hypothesis" as having two basic forms: the individual difference or personality approach, which suggests that people who show exaggerated cardiovascular responses to stress are at increased risk of developing cardiovascular disease, and the situational or social psychological approach, which suggests that circumstances which give rise to unusually large responses are those that put people at risk of disease. Both versions rely on the generality of cardiovascular responses across situations. Evidence is presented from two studies which indicate that such generality may, however, be hard to come by. In the first study, examining the personality approach, we show that a simple change in setting dramatically attenuates the consistency of reactivity. In the second study, from the social psychological perspective, we show that subtle alterations in the situation have profound effects on group mean responses. In both cases, reactivity proved extremely sensitive to the context, suggesting that testing in arbitrary and artificial settings cannot be expected to generalize well to the real world. Instead, we argue, careful attention to psychological naturalism is essential, with the testing carefully matched to specific real-world phenomena of interest.

Adaptation, Psychological↗

PubMed1996

The interpretation of visual motion: evidence for surface segmentation mechanisms.

The independent motions of objects in a visual scene are commonly manifest as overlapping retinal motions. A consequence of this overlap is the creation of spurious retinal image features--such as corners and terminated contours--that bear no direct relation to the motions of the objects that give rise to them. To reconstruct object motions, these emergent features must be distinguished from the retinal motions of real object features. This process can be studied using visual stimuli known as plaid patterns, which provide a laboratory archetype for the ubiquitous real-world circumstance of two surfaces with overlapping retinal projections. By adjusting luminance relationships in a plaid pattern it is possible to influence the perceptual interpretation of image features, such that they are seen as either an emergent consequence of occlusion or as real variations in surface reflectance. In the former case, the plaid is most likely to be to perceived as two independently moving surfaces, whereas the latter generally elicits a percept of a single moving surface. This dependence of motion perception on luminance configuration can be viewed as evidence for the involvement of surface segmentation mechanisms, which distinguish between real and emergent image features by promoting a depth-ordered neural representation of surfaces. An alternative interpretation, which does not demand such depth-ordering and feature classification, asserts that the effect of luminance configuration can be accounted for by attendant variations in the distribution of moving Fourier components. To evaluate these two proposed mechanisms, we designed novel plaid stimuli in which surface segmentation cues could be varied independently of changes in the distribution of Fourier components. Perceived motion was found to be highly correlated with the presence of appropriate segmentation cues and uncorrelated with the distribution of Fourier components. These results refute the Fourier components hypothesis, and they support our proposal that surface segmentation plays a critical role in the interpretation of visual motion signals.

Contrast Sensitivity↗