Standard Experimental Paradigm Research Articles

Dynamical mechanisms of how an RNN keeps a beat, uncovered with a low-dimensional reduced model

Despite music’s omnipresence, the specific neural mechanisms responsible for perceiving and anticipating temporal patterns in music are unknown. To study potential mechanisms for keeping time in rhythmic contexts, we train a biologically constrained RNN, with excitatory (E) and inhibitory (I) units, on seven different stimulus tempos (2–8 Hz) on a synchronization and continuation task, a standard experimental paradigm. Our trained RNN generates a network oscillator that uses an input current (context parameter) to control oscillation frequency and replicates key features of neural dynamics observed in neural recordings of monkeys performing the same task. We develop a reduced three-variable rate model of the RNN and analyze its dynamic properties. By treating our understanding of the mathematical structure for oscillations in the reduced model as predictive, we confirm that the dynamical mechanisms are found also in the RNN. Our neurally plausible reduced model reveals an E-I circuit with two distinct inhibitory sub-populations, of which one is tightly synchronized with the excitatory units.

Portfolio framing and diversification in a disposition effect experiment

We experimentally test an intervention designed to reduce investors’ disposition effect by prompting them to identify their worst asset, from the standpoint of its impact on future portfolio performance. We find that this intervention is mildly effective, and significantly more so for participants who correctly identify their worst asset, and/or sell the asset they identify. We also find that participants who correctly understand diversification in a financial literacy questionnaire exhibit larger disposition effects in the experiment. The latter finding raises concerns over the external validity of standard experimental paradigms used to study the disposition effect.

Is your stress my stress? A standardized, randomized-controlled paradigm to study physiological stress contagion based on direct stress observation

Background & objectivesExisting research indicates that not only own stress leads to physiological stress reactions, but also observing stress in others. So far, a standardized paradigm to reliably induce physiological stress contagion based on direct face-to-face stress observation compared to an active placebo-stress observing control condition is lacking. Here, we tested a standardized randomized placebo-controlled experimental paradigm to investigate physiological reactivity to direct stress observation and characterized the stress contagion response of the major endocrine stress systems, including full reactivity kinetics. MethodsHealthy young male participants were randomly assigned to (1) undergo an adapted version of the Trier Social Stress Test (“TSST participants”, n = 20), (2) observe it (“stress observers”, n = 36), or (3) observe a corresponding placebo-stress control condition (“placebo-stress observers”, n = 30). We repeatedly assessed heart rate, salivary alpha-amylase, salivary cortisol, and salivary aldosterone. ResultsStress observers exhibited greater physiological reactivity to stress observation as compared to placebo-stress observers to placebo-stress observation in heart rate, salivary alpha-amylase, and cortisol (p’s ≤ .027), but not in aldosterone. We observed similar reactivity kinetics in TSST participants and stress observers but less pronounced in stress observers. DiscussionExtending previous literature, our findings indicate that independent of secondary effects of the observation setting, direct observation of stress in other individuals induces activation of the hypothalamus-pituitary-adrenal axis and the sympathetic-adrenal-medullary axis. Moreover, the physiological stress contagion response resembles the physiological reactivity to first-hand stress but is less pronounced. Potential implications of physiological stress contagion regarding health, cognition, or behavior, as well as modulating factors need to be further elucidated.

Reliability and minimal detectable change of dynamic temporal summation and conditioned pain modulation using a single experimental paradigm.

Quantitative sensory tests (QST) are frequently used to explore alterations in somatosensory systems. Static and dynamic QST like pain threshold and temporal summation (TS) and conditioned pain modulation (CPM) are commonly used to evaluate excitatory and inhibitory mechanisms involved in pain processing. The aim of the present study was to document the reliability and the minimal detectable change (MDC) of these dynamic QST measurements using a standardized experimental paradigm. Forty-six (46) pain-free participants took part in 2 identical sessions to collect TS and CPM outcomes. Mechanical (pressure pain threshold [PPT]) and thermal (constant 2-minute heat pain stimulation [HPS]) nociceptive stimuli were applied as test stimuli, before and after a cold-water bath (conditioning stimulus). TS was interpreted as the change in pain perception scores during HPS. CPM were determined by calculating the difference in pain perception between pre- and post- water bath for both PPT and HPS. Relative and absolute reliability were analyzed with intra-class correlation coefficient (ICC2, k), standard error of the measurements (SEMeas) and MDC. Results revealed a good to excellent relative reliability for static QST (ICC ≥ 0.73). For TS, a poor to moderate relative reliability depending on the calculation methods (ICC = 0.25 ≤ ICC ≤ 0.59), and a poor relative reliability for CPM (ICC = 0.16 ≤ ICC ≤ 0.37), both when measured with mechanical stimulation (PPT) and thermal stimulation (HPS). Absolute reliability varied from 0.73 to 7.74 for static QST, 11 to 22 points for TS and corresponded to 11.42 points and 1.56 points for thermal and mechanical-induced CPM, respectively. MDC analyses revealed that a change of 1.58 to 21.46 point for static QST, 31 to 52 points for TS and 4 to 31 points for CPM is necessary to be interpreted as a real change. Our approach seems well-suited to clinical use. Although our method shows equivalent relative and absolute reliability compared to other protocols, we found that the reliability of endogenous pain modulation mechanisms is vulnerable, probably due to its dynamic nature.

FNIRS-Driven Depression Recognition Based on Cross-Modal Data Augmentation.

Early diagnosis and intervention of depression promote complete recovery, with its traditional clinical assessments depending on the diagnostic scales, clinical experience of doctors and patient cooperation. Recent researches indicate that functional near-infrared spectroscopy (fNIRS) based on deep learning provides a promising approach to depression diagnosis. However, collecting large fNIRS datasets within a standard experimental paradigm remains challenging, limiting the applications of deep networks that require more data. To address these challenges, in this paper, we propose an fNIRS-driven depression recognition architecture based on cross-modal data augmentation (fCMDA), which converts fNIRS data into pseudo-sequence activation images. The approach incorporates a time-domain augmentation mechanism, including time warping and time masking, to generate diverse data. Additionally, we design a stimulation task-driven data pseudo-sequence method to map fNIRS data into pseudo-sequence activation images, facilitating the extraction of spatial-temporal, contextual and dynamic characteristics. Ultimately, we construct a depression recognition model based on deep classification networks using the imbalance loss function. Extensive experiments are performed on the two-class depression diagnosis and five-class depression severity recognition, which reveal impressive results with accuracy of 0.905 and 0.889, respectively. The fCMDA architecture provides a novel solution for effective depression recognition with limited data.

Standard experimental paradigm designs and data exclusion practices in cognitive psychology can inadvertently introduce systematic “shadow” biases in participant samples

Standard cognitive psychology research practices can introduce inadvertent sampling biases that reduce the reliability and generalizability of the findings. Researchers commonly acknowledge and understand that any given study sample is not perfectly generalizable, especially when implementing typical experimental constraints (e.g., limiting recruitment to specific age ranges or to individuals with normal color vision). However, less obvious systematic sampling constraints, referred to here as “shadow” biases, can be unintentionally introduced and can easily go unnoticed. For example, many standard cognitive psychology study designs involve lengthy and tedious experiments with simple, repetitive stimuli. Such testing environments may 1) be aversive to some would-be participants (e.g., those high in certain neurodivergent symptoms) who may self-select not to enroll in such studies, or 2) contribute to participant attrition, both of which reduce the sample’s representativeness. Likewise, standard performance-based data exclusion efforts (e.g., minimum accuracy or response time) or attention checks can systematically remove data from participants from subsets of the population (e.g., those low in conscientiousness). This commentary focuses on the theoretical and practical issues behind these non-obvious and often unacknowledged “shadow” biases, offers a simple illustration with real data as a proof of concept of how applying attention checks can systematically skew latent/hidden variables in the included population, and then discusses the broader implications with suggestions for how to manage and reduce, or at a minimum acknowledge, the problem.

Reward Accelerates the Preparation of Goal-directed Actions under Conflict.

Our goals sometimes conflict with our prepotent habitual responses, which often leads to impaired performance on a variety of tasks. People are better at exerting cognitive control to overcome prepotent and automatic responses when they are motivated by the prospect of reward. The standard experimental paradigms used to study this phenomenon examine free RTs that allow participants to select a variety of response strategies including delaying response initiation to avoid committing errors. However, this approach makes it difficult to determine which control processes are affected by reward. Does reward lead to improved performance via the inhibition of prepotent responses or the facilitation of goal-directed processing? Here, we use a forced-response paradigm to fix response initiation and systematically vary the time available for the cognitive processing necessary for response preparation. Using a probabilistic model that dissociates the preparation of habitual and goal-directed responses, we obtain evidence across multiple experiments (n = 87 people) that reward selectively accelerates the preparation of goal-directed actions in the context of conflict.

Body Temperature Manipulation Increases Salivary Cortisol Independent of Exercise

The vast majority of circulating cortisol in the blood is bound and inactivated by binding proteins like corticosteroid-binding globulin (CBG) and albumin. The cortisol that is free of these binding proteins is secreted via saliva and other body fluids. Ex-vivo studies have shown that CBG binding to cortisol is temperature-dependent within the physiological range of human core body temperatures. Exercise is a standard experimental paradigm for inducing cortisol responses. However, these studies rarely consider that exercise-induced changes in core body temperature might increase free cortisol independent of psychological stress or physical exertion. We tested the effect of heat exposure without exertion or other stressors on saliva cortisol. 26 Participants (18 healthy and 8 with Major Depression MDD) sat motionless in a dry infrared sauna set to 65.5 degrees C (150 F). They had their tympanic membrane temperature and salivary cortisol measured as their body temperature increased. Exposure to exogenous heat significantly increased core body temperature from 36.93 C/98.48 F (95% CI 36.79-37.07 C, 98.23-98.73 F) to 38.42 C /101.16 F (95% CI 38.24-38.6 C, 100.83-101.48 F) after 45 minutes of heat exposure, F(15,42.33)=43.509, p<0.001. Concurrently saliva cortisol also increased significantly from 4.00 nmol/l (95%CI 1.89-6.11) to 9.87 nmol/l (95% CI 5.58-14.17), F(1,33.17)=6.64, p=0.015. Elevations in core body temperature can significantly increase free cortisol levels even in the absence of exercise or overt psychological stressors.

The Importance of the Treatment Rationale for Pain in Animal-Assisted Interventions: A Randomized Controlled Trial in Healthy Participants

Animal-assisted interventions (AAIs) is a promising treatment approach for pain, but possible mechanisms still need to be elucidated. This study set out to investigate the analgesic effects of an animal provided with a treatment rationale in a randomized controlled trial employing a standardized experimental heat-pain paradigm. We randomly assigned 128 healthy participants to: dog treatment (DT), placebo treatment (PT), dog and placebo treatment (DPT), and no treatment (NT). Primary outcomes were heat-pain tolerance and the corresponding self-reported ratings of pain unpleasantness and intensity. Results revealed no differences in heat-pain tolerance between the conditions. However, participants in the DT condition experienced heat-pain as significantly less unpleasant at the limit of their tolerance compared to participants in the NT condition (estimate = -0.96, CI = -1.58 to 0.34, P = .010). Participants in the DT condition also showed lower ratings of pain intensity at the limit of their tolerance compared to participants in the NT condition (estimate = -0.44, CI = -0.89 to 0.02, P = .060). This study indicates that a dog has analgesic effects on pain perception when integrated into the treatment rationale. We assume that providing a treatment rationale regarding the animal is important in AAIs for pain. PerspectiveThis study shows that the presence of an animal is not sufficient for animal-assisted interventions (AAIs) to have an analgesic effect on pain unless they are provided with a treatment rationale. This could imply that not only the animal but also contextual factors are important in AAIs. Trial registrationClinical Trials NCT04361968.

Incidental findings in relation to subsequent search misses in visual search

Incidental findings defined as valuable findings that are not searched purposely by the experts were originally discovered by radiologists. Despite the importance and great practical value of this phenomenon for visual search, it was almost not studied by cognitive psychologists and vision science experts. The current study aimed to examine experimentally incidental findings in visual search. The main objective was to clarify independence of incidental findings from subsequent search misses, another well-known visual search phenomenon. In order to do that, the standard experimental paradigm for detecting subsequent search misses was used. At the same time the stimuli material and tasks were created to closely fit the definition of incidental findings. The participants were asked to find the images of plastic bags and paper wastes (targets) among the images of leaves and snags (distractors) on the computer screen in a simulated “garbage collection” task. Their accuracy and reaction times were analyzed. Specifically, the trials with a single target were compared with dual-target trials. The findings revealed that subsequent search misses, but not incidental findings, were observed. The results suggest that incidental findings may be closely related to subsequent search misses. As well as that, the difficulty of the task, particularly induced by target-distractor similarity, may be one of the major factors leading to the emergence of subsequent search misses instead of incidental findings.

Does Speeded Decision-Making Reveal Tacit Teleological Tendencies?

Previous research suggests that people implicitly believe that biological and nonbiological natural entities exist to fulfil certain functions (i.e., people hold implicit teleological beliefs). The standard experimental paradigm used to demonstrate this is to compare rates of teleological acceptance in an un-speeded condition to acceptance in a speeded condition. As speeded decision-making limits the opportunity to engage in reflective thought, increased rates of teleological acceptance relative to the un-speeded condition are said to provide evidence of implicit teleological beliefs. Across two large online studies, we show that due to the exclusion criteria typically used in this paradigm, the included and excluded participants vary systemically in important ways between conditions, and that increased rates of teleological acceptance during speeded responding does not provide evidence of implicit teleological beliefs. Rather, the difference between conditions can be explained by increased acceptance of explanations which are objectively false. Furthermore, we show that a key assumption underpinning the use of this paradigm – that accepting teleological explanations should be effortless and rejecting them should require effort – is not supported by the data. These results highlight not only a methodological issue, but also a theoretical issue in the current literature. We discuss the implications of these findings in the context of existing theoretical and empirical literature on teleological reasoning and dual-process theory more generally.

Meta-Analysis of Seven Standard Experimental Paradigms Comparing Student to Non-student

This study embarked on the very challenging proposition of systematically organizing and classifying an assortment of experimental economics essays pertinent to seven experiments performed with both non-student and student populations. The experiments were the Dictator game, Stag Hunt – Coordination game, Risk Aversion Measurement (as measured by the players type of lottery choice), Trust game, Guessing game, Prudence Measurement, and the Guessing game. This meta-analysis reviewed 126 published and unpublished papers collected from several journals and papers provided by several authors via the Google Groups "Economic Science Association - Experimental Methods Discussion" group. Ultimately, only 39 studies were utilized due to methodological alignment. While some studies showed statistically significant differences between non-students and students as indicated by their respective 95% confidence intervals, the overall random-effects model of each of the seven games showed not to be statistically significant. This study contributes to the literature in three important ways. First, the study generates a comprehensive inventory and review of experiments comparing student to non-student populations for the last four decades; second, the study points out a possible limitation when combining several studies of the same game, despite following similar protocols, suggesting that compounded contextual complexities might diminish aggregate effects of the individuals’ behavioral responses to the financial incentives, and third, the study indicates that generalizations from one experimental economic study, may not render a solid base for extending statistical extrapolations applicable to the total population since the aggregate effects do not indicate substantial differences.

Hippocampus and cortex are involved in the retrieval of a spatial memory under full and partial cue availability

Retaking routes after a period of time usually occurs in an environment which has suffered from spatial configuration modifications. Thus, the original visual stimuli that allowed us to establish cognitive mapping using an allocentric strategy during the acquisition phase may not remain physically identical at the time of retrieval. However, in the standard experimental paradigms the cues are typically maintained constant. In this study, we explored memory retrieval with spatial modifications from learning in the Morris Water Maze. We trained rats on a reference memory protocol with five cues placed on black curtains that surrounded the pool, and seven days later, we tested memory retrieval under different conditions: maintenance of the five cues, removal of two and four of them, and the addition of three extra ones. Under full-cue and partial cue-conditions, rats showed successful memory retrieval, whereas adding extra cues resulted in impaired retrieval. Furthermore, we assessed brain oxidative metabolism through cytochrome c oxidase (CCO) histochemistry and found that, under full- and partial-cue conditions, there is an enhancement of the hippocampal, prefrontal, retrosplenial, parietal, and rhinal cortex metabolism. Rats that failed to retrieve spatial information in the extra cues condition showed similar or lower CCO activity than controls across many limbic areas. It is suggested that the presence of a partial portion of visual stimuli from learning makes it possible to reactivate the entire memory trace, but extra spatial information hinders retrieval, making it difficult to disengage the novel information from the older knowledge and establish a contextual generalization.

Cognitive Multitasking: Inhibition in Task Switching Depends on Stimulus Complexity.

We report a series of three experiments investigating inhibition in task switching, using N-2 repetition costs as an empirical marker. The experiments were structurally identical, employing a standard experimental paradigm where participants switch between three different categorization tasks. The experiments differed with respect to the stimulus material. According to prominent theories of cognitive control, N-2 repetition costs should be observed in all three experiments. To our surprise, this is not what we observed: N-2 repetition costs did not occur in Experiment 1, where we used static pictures from a driving simulator environment showing an oncoming car, embedded in a car-driving scene. In contrast, we observed robust N-2 repetition costs in Experiment 2, where we used static pictures of faces, and in Experiment 3, where the identical car stimuli from Experiment 1 were used, but without the surrounding visual scene. These results suggest that N-2 repetition costs depend on the complexity of the stimulus material. We discuss two aspects of complexity: 1) When the relevant stimulus feature is embedded in a complex visual scene, task-irrelevant features in that scene might trigger additional task sets, and thus induce additional task switches, attenuating N-2 repetition costs among the instructed task sets. 2) The presence of distractors might lead to additional covert or overt shifts of spatial attention, which in turn might reduce the size of N-2 repetition costs. On a more general level, the results illustrate the difficulty of transferring laboratory tasks to settings that bear more similarity to everyday life situations.

Examining Four Experimental Paradigms for EEG-Based Sleep Quality Evaluation with Domain Adaptation.

With the quick development of dry electrode electroencephalography (EEG) acquisition technology, EEG-based sleep quality evaluation attracts more attention for its objective and quantitative merits. However, there hasn't been a standard experimental paradigm. This situation hinders the development of sleep quality evaluation method and technique. In this paper, we experimentally examine the performance of four typical experimental paradigms for EEG-based sleep quality evaluation and develop a new EEG dataset recorded by dry-electrode headset. To eliminate individual variation caused by subjects, we evaluate the four experimental paradigms using domain adaptation (DA) methods. Experimental results demonstrate that a relaxing paradigm is more effective than other attention concentration paradigms and achieves the average accuracy of 76.01%. Domain Adversarial Neural Network outperforms other DA methods and obtains 18.69% improvement on accuracy compared with transfer component analysis.

Putting a stereotype to the test: The case of gender differences in multitasking costs in task-switching and dual-task situations.

According to a popular stereotype, women are better at multitasking than men, but empirical evidence for gender differences in multitasking performance is mixed. Previous work has focused on specific aspects of multitasking or has not considered gender differences in abilities contributing to multitasking performance. We therefore tested gender differences (N = 96, 50% female) in sequential (i.e., task switching) and concurrent (i.e., dual tasking) multitasking, while controlling for possible gender differences in working memory, processing speed, spatial abilities, and fluid intelligence. Applying two standard experimental paradigms allowed us to test multitasking abilities across five different empirical indices (i.e., performance costs) for both reaction time (RT) and accuracy measures, respectively. Multitasking resulted in substantial performance costs across all experimental conditions without a single significant gender difference in any of these ten measures, even when controlling for gender differences in underlying cognitive abilities. Thus, our results do not confirm the widespread stereotype that women are better at multitasking than men at least in the popular sequential and concurrent multitasking settings used in the present study.

Higher trait reappraisal predicts stronger HPA axis habituation to repeated stress

Undergoing stress can be advantageous when it leads to adaptation and growth; however, failure of the hypothalamic-pituitary-adrenal (HPA) axis to habituate (i.e., nonhabituation) involves continuing to become highly activated in response to repeated exposure of the same stimulus and is considered maladaptive. Although 50–75% of individuals assessed in a laboratory exhibit adaptive habituation to repeated stress, variability in habituation suggests psychological processes used in response to stress may play a role, such as emotion regulation (ER). Nonetheless, no research to date has investigated whether ER strategies affect HPA axis habituation. We investigated whether tendency to use two ER strategies, reappraisal and suppression, influenced HPA axis habituation among 84 healthy young adults (60.7% female; Mage = 24.8 years, SD = 6.0) exposed to a standardized experimental stress paradigm on two consecutive days. HPA axis stress responses were assessed using salivary cortisol concentrations. We also examined whether non-manipulated state ER strategies (i.e., those used by the participant during and following the stressor on the first day) modulated HPA axis habituation over and above trait-use in a subsample (N = 60). Trait, but not state, reappraisal was associated with stronger HPA axis habituation. Neither trait nor state suppression were significantly associated with HPA axis habituation. These findings expand our current understanding of how ER can affect stress-related health outcomes and suggest habitual reappraisal plays an important role in adaption of the HPA axis to stress.

Sense of agency for movements.

In this paper, we argue that the comparator model is not a satisfactory model of sense of agency (SoA). We present a theoretical argument and experimental studies. We show (1) most studies of SoA neglect a distinction between SoA associated with movements (narrow SoA) and SoA associated with environmental events (broad SoA); (2) the comparator model emerges from experimental studies of sensory consequences narrowly associated with movements; (3) narrow SoA can be explained by a comparator model, but a motor signal model is simpler and explain narrow SoA equally well; and (4) standard experimental paradigms study only broad SoA. Finally, we present results from two experiments, where we have failed to induce illusory narrow SoA in healthy participants. We believe our experimental approaches should have led to illusory SoA, if the comparator model of SoA was correct. The results challenge proponents of the comparator model of narrow SoA.

High-Yield Purification, Preservation, and Serial Transplantation of Human Satellite Cells.

SummaryInvestigation of human muscle regeneration requires robust methods to purify and transplant muscle stem and progenitor cells that collectively constitute the human satellite cell (HuSC) pool. Existing approaches have yet to make HuSCs widely accessible for researchers, and as a result human muscle stem cell research has advanced slowly. Here, we describe a robust and predictable HuSC purification process that is effective for each human skeletal muscle tested and the development of storage protocols and transplantation models in dystrophin-deficient and wild-type recipients. Enzymatic digestion, magnetic column depletion, and 6-marker flow-cytometric purification enable separation of 104 highly enriched HuSCs per gram of muscle. Cryostorage of HuSCs preserves viability, phenotype, and transplantation potential. Development of enhanced and species-specific transplantation protocols enabled serial HuSC xenotransplantation and recovery. These protocols and models provide an accessible system for basic and translational investigation and clinical development of HuSCs.

Pharmacological inhibition of diacylglycerol acyltransferase-1 and insights into postprandial gut peptide secretion.

AIMTo examine the role that enzyme Acyl-CoA:diacylglycerol acyltransferase-1 (DGAT1) plays in postprandial gut peptide secretion and signaling.METHODSThe standard experimental paradigm utilized to evaluate the incretin response was a lipid challenge. Following a lipid challenge, plasma was collected via cardiac puncture at each time point from a cohort of 5-8 mice per group from baseline at time zero to 10 h. Incretin hormones [glucagon like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY) and glucose dependent insulinotropic polypeptide (GIP)] were then quantitated. The impact of pharmacological inhibition of DGAT1 on the incretin effect was evaluated in WT mice. Additionally, a comparison of loss of DGAT1 function either by genetic ablation or pharmacological inhibition. To further elucidate the pathways and mechanisms involved in the incretin response to DGAT1 inhibition, other interventions [inhibitors of dipeptidyl peptidase-IV (sitagliptin), pancreatic lipase (Orlistat), GPR119 knockout mice] were evaluated.RESULTSDGAT1 deficient mice and wildtype C57/BL6J mice were lipid challenged and levels of both active and total GLP-1 in the plasma were increased. This response was further augmented with DGAT1 inhibitor PF-04620110 treated wildtype mice. Furthermore, PF-04620110 was able to dose responsively increase GLP-1 and PYY, but blunt GIP at all doses of PF-04620110 during lipid challenge. Combination treatment of PF-04620110 and Sitagliptin in wildtype mice during a lipid challenge synergistically enhanced postprandial levels of active GLP-1. In contrast, in a combination study with Orlistat, the ability of PF-04620110 to elicit an enhanced incretin response was abrogated. To further explore this observation, GPR119 knockout mice were evaluated. In response to a lipid challenge, GPR119 knockout mice exhibited no increase in active or total GLP-1 and PYY. However, PF-04620110 was able to increase total GLP-1 and PYY in GPR119 knockout mice as compared to vehicle treated wildtype mice.CONCLUSIONCollectively, these data provide some insight into the mechanism by which inhibition of DGAT1 enhances intestinal hormone release.