Do we perceive sensations inside and outside of our body differently? Perceptual, emotional, and behavioral differences between visceral and somatic sensation, discomfort, and pain

BACKGROUND

Experimental research evaluating differences between the visceral and somatic stimulation is limited to pain and typically uses different induction methods for visceral and somatic stimulation (e.g., rectal balloon distention vs. tactile hand stimulation). Our study aimed to compare differences in response time, intensity, unpleasantness, and threat between identical electrical visceral and somatic stimulations at both painful and non-painful perceptual thresholds.

METHODS

Electrical stimulation was applied to the wrist and distal esophagus in 20 healthy participants. A double pseudorandom staircase determined perceptual thresholds of Sensation, Discomfort, and Pain for the somatic and visceral stimulations, separately. Stimulus reaction time (ms, via button press), and intensity, unpleasantness, and threat ratings were recorded after each stimulus. General linear mixed models compared differences in the four outcomes by stimulation type, threshold, and the stimulation type-by-threshold interaction. Sigmoidal maximum effect models evaluated differences in outcomes across all delivered stimulation intensities.

KEY RESULTS

Overall, visceral stimulations were perceived as more intense, threatening, and unpleasant compared to somatic stimulations, but participants responded faster to somatic stimulations. There was no significant interaction effect, but planned contrasts demonstrated differences at individual thresholds. Across all delivered intensities, higher intensity stimulations were needed to reach the half-maximum effect of self-reported intensity, unpleasantness, and threat ratings in the visceral domain.

CONCLUSIONS AND INFERENCES

Differences exist between modalities for both non-painful and painful sensations. These findings may have implications for translating paradigms and behavioral treatments from the somatic domain to the visceral domain, though future research in larger clinical samples is needed.

Expectations underlie the effects of unpredictable pain: a behavioral and electroencephalogram study

ABSTRACT

Previous studies on the potential effects of unpredictability on pain perception and its neural correlates yielded divergent results. This study examined whether this may be explained by differences in acquired expectations. We presented 41 healthy volunteers with laser heat stimuli of different intensities. The stimuli were preceded either by predictable low, medium, or high cues or by unpredictable low-medium, medium-high, or low-high cues. We recorded self-reports of pain intensity and unpleasantness and laser-evoked potentials (LEPs). Furthermore, we investigated whether dynamic expectations that evolved throughout the experiment based on past trials were better predictors of pain ratings than fixed (nonevolving) expectations. Our results replicate previous findings that unpredictable pain is higher than predictable pain for low-intensity stimuli but lower for high-intensity stimuli. Moreover, we observed higher ratings for the medium-high unpredictable condition than the medium-low unpredictable condition, in line with an effect of expectation. We found significant interactions (N1, N2) for the LEP components between intensity and unpredictability. However, the few significant differences in LEP peak amplitudes between cue conditions did not survive correction for multiple testing. In line with predictive coding perspectives, pain ratings were best predicted by dynamic expectations. Surprisingly, expectations of reduced precision (increased variance) were associated with lower pain ratings. Our findings provide strong evidence that (dynamic) expectations contribute to the opposing effects of unpredictability on pain perception; therefore, we highlight the importance of controlling for them in pain unpredictability manipulations. We also suggest to conceptualize pain expectations more often as dynamic constructs incorporating previous experiences.

The effect of unpredictability on the perception of pain: a systematic review and meta-analysis

ABSTRACT

Despite being widely assumed, the worsening impact of unpredictability on pain perception remains unclear because of conflicting empirical evidence, and a lack of systematic integration of past research findings. To fill this gap, we conducted a systematic review and meta-analysis focusing on the effect of unpredictability on pain perception. We also conducted meta-regression analyses to examine the moderating effect of several moderators associated with pain and unpredictability: stimulus duration, calibrated stimulus pain intensity, pain intensity expectation, controllability, anticipation delay, state and trait negative affectivity, sex/gender and age of the participants, type of unpredictability (intensity, onset, duration, location), and method of pain induction (thermal, electrical, mechanical pressure, mechanical distention). We included 73 experimental studies with adult volunteers manipulating the (un)predictability of painful stimuli and measuring perceived pain intensity and pain unpleasantness in predictable and unpredictable contexts. Because there are insufficient studies with patients, we focused on healthy volunteers. Our results did not reveal any effect of unpredictability on pain perception. However, several significant moderators were found, ie, targeted stimulus pain intensity, expected pain intensity, and state negative affectivity. Trait negative affectivity and uncontrollability showed no significant effect, presumably because of the low number of included studies. Thus, further investigation is necessary to clearly determine their role in unpredictable pain perception.

Examining the impact of cue similarity and fear learning on perceptual tuning

Past research on the effects of associative aversive learning on discrimination acuity has shown mixed results, including increases, decreases, and no changes in discrimination ability. An animal study found that the type of learning experience determined the direction and extent of learning-induced changes. The current preregistered web-based study aimed to translate these findings to humans. Experiment 1 (N = 245) compared changes in stimulus discrimination between simple learning (only one oriented grating cue), coarse differential conditioning (physically distinct cues), and fine differential conditioning (physically similar cues) as well as to their three respective control groups. The discrimination task consisted of a two-alternative-forced-choice task with oriented grating stimuli. During learning, a specific orientation was paired with unpleasant pictures. Our analysis using generative modeling demonstrated weak to moderate evidence that aversive learning did not alter discrimination acuity in any of the groups. In a follow-up experiment (N = 121), we replicated these findings despite successful learning trajectories in all three groups and a more detailed assessment of discrimination acuity. Contrary to prior assumptions, our findings indicate that aversive learning does not enhance perceptual discrimination, and the presence of additional safety cues does not appear to moderate this effect.

The idiosyncratic nature of how individuals perceive, represent, and remember their surroundings and its impact on learning-based generalization

The current study adopted a multimodal assessment approach to map the idiosyncratic nature of how individuals perceive, represent, and remember their surroundings and to investigate its impact on learning-based generalization. During an online differential conditioning paradigm, participants (n = 105) learned the pairing between a blue color patch (CS +) and an outcome (i.e., shock symbol) and the unpairing between a green color patch and the same outcome. After the learning task, the generalization of outcome expectancies was assessed to 14 stimuli spanning the entire blue-green color spectrum. Hereafter, a stimulus identification task assessed the ability to correctly identify the CS + among this stimulus range. Continuous and binary color category membership judgments of the stimuli were assessed preconditioning. We found that a response model with color perception and identification performance as sole predictors was preferred to contemporary approaches that use stimulus as a predictor. Interestingly, incorporating interindividual differences in color perception, CS identification, and color categories significantly improved the models' ability to account for different generalization patterns. Our findings suggest that insight into the idiosyncratic nature of how individuals perceive, represent, and remember their surroundings provides exciting opportunities to understand post-learning behaviors better. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

From transabdominal to totally extra-peritoneal robotic ventral hernia repair: observations and outcomes

PURPOSE

While robotic-assisted hernia repair has increased the popularity of minimally invasive hernia surgery, selecting between the types of approaches is a challenge for both experts and novices alike. In this study, we compared a single surgeon's early experience transitioning from transabdominal hernia repair with sublay mesh in either the pre-peritoneal or retrorectus space (TA-SM) and enhanced-view totally extra-peritoneal (eTEP) ventral hernia repair in the peri-operative and long-term post-operative time periods.

METHODS

We conducted a retrospective review of 50 eTEP and 108 TA-SM procedures to collect demographics, intraoperative details, and 30-day and 1-year post-operative outcomes. Statistical analysis was performed utilizing Chi-square analysis, Fisher's test, and two sample t-tests with equal variances.

RESULTS

There were no significant differences in patient demographics or comorbidities. eTEP patients had larger defects (109.1 cm² vs. 31.8 cm², p = 0.043) and mesh used (432.8 cm² vs. 137.9 cm², p = 0.001). Operative times were equivalent (158.3 ± 90.6 min eTEP and 155.8 ± 65.2 min TA-SM, p = 0.84), but conversion to alternate procedure type was higher for the transabdominal approach (4% eTEP vs. 22% TA-SM, p < 0.05). Hospital stay was less in the eTEP cohort (1.3 days vs. 2.2 days, p < 0.05). Within 30 days, there were no significant differences in emergency visits or hospital readmissions. There was a greater propensity for eTEP patients to develop seromas (12.0% vs. 1.9%, p < 0.05). At 1 year, there was no statistically significant difference in recurrence rate (4.56% eTEP vs. 12.2% TA-SM, p = 0.28) respective to average time to recurrence (9.17 months eTEP vs. 11.05 months TA-SM).

CONCLUSION

The eTEP approach can be adopted safely and efficiently, and may have superior peri-operative outcomes including fewer conversions and reduced hospital stay.

Individual differences in stimulus identification, rule induction, and generalization of learning

In the field of stimulus generalization, an old yet unresolved discussion pertains to what extent stimulus misidentifications contribute to the pattern of conditioned responding. In this article, we perform cluster analysis on six datasets (four published datasets and two unpublished datasets, included N = 950) to examine the relationship between interindividual differences in (a) stimulus identification, (b) patterns of generalized responding, and (c) verbalized generalization rules. The datasets were obtained from online predictive learning tasks where participants learned associations between colored cues and the presence or absence of a hypothetical outcome. In these datasets, stimulus identification and expectancy ratings were assessed in separate phases to a range of colors varying between blue-green. Using cluster analyses on performance during stimulus identification, we identified different subgroups of participants (good vs. bad identifiers). In all six datasets, we found a close relationship between the pattern of stimulus identification and the shape of the expectancy gradient across the test dimension between the identified subgroups. Furthermore, participants classified as good identifiers were more likely to report a similarity generalization rule than a relational or linear rule, suggesting that individual differences in stimulus identification are related to individual differences in generalization rules. These findings suggest that greater consideration should be given to interindividual variability in stimulus identification, inductive rules, and their relationship in explaining patterns of generalized responses. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Epidemiology and impact of frailty in patients with atrial fibrillation in Europe

BACKGROUND

Frailty is a medical syndrome characterised by reduced physiological reserve and increased vulnerability to stressors. Data regarding the relationship between frailty and atrial fibrillation (AF) are still inconsistent.

OBJECTIVES

We aim to perform a comprehensive evaluation of frailty in a large European cohort of AF patients.

METHODS

A 40-item frailty index (FI) was built according to the accumulation of deficits model in the AF patients enrolled in the ESC-EHRA EORP-AF General Long-Term Registry. Association of baseline characteristics, clinical management, quality of life, healthcare resources use and risk of outcomes with frailty was examined.

RESULTS

Among 10,177 patients [mean age (standard deviation) 69.0 (11.4) years, 4,103 (40.3%) females], 6,066 (59.6%) were pre-frail and 2,172 (21.3%) were frail, whereas only 1,939 (19.1%) were considered robust. Baseline thromboembolic and bleeding risks were independently associated with increasing FI. Frail patients with AF were less likely to be treated with oral anticoagulants (OACs) (odds ratio 0.70, 95% confidence interval 0.55-0.89), especially with non-vitamin K antagonist OACs and managed with a rhythm control strategy, compared with robust patients. Increasing frailty was associated with a higher risk for all outcomes examined, with a non-linear exponential relationship. The use of OAC was associated with a lower risk of outcomes, except in patients with very/extremely high frailty.

CONCLUSIONS

In this large cohort of AF patients, there was a high burden of frailty, influencing clinical management and risk of adverse outcomes. The clinical benefit of OAC is maintained in patients with high frailty, but not in very high/extremely frail ones.

Cortico-Brainstem Mechanisms of Biased Perceptual Decision-Making in the Context of Pain

Prior expectations can bias how we perceive pain. Using a drift diffusion model, we recently showed that this influence is primarily based on changes in perceptual decision-making (indexed as shift in starting point). Only during unexpected application of high-intensity noxious stimuli, altered information processing (indexed as increase in drift rate) explained the expectancy effect on pain processing. Here, we employed functional magnetic resonance imaging to investigate the neural basis of both these processes in healthy volunteers. On each trial, visual cues induced the expectation of high- or low-intensity noxious stimulation or signaled equal probability for both intensities. Participants categorized a subsequently applied electrical stimulus as either low- or high-intensity pain. A shift in starting point towards high pain correlated negatively with right dorsolateral prefrontal cortex activity during cue presentation underscoring its proposed role of "keeping pain out of mind". This anticipatory right dorsolateral prefrontal cortex signal increase was positively correlated with periaqueductal gray (PAG) activity when the expected high-intensity stimulation was applied. A drift rate increase during unexpected high-intensity pain was reflected in amygdala engagement and increased functional connectivity between amygdala and PAG. Our findings suggest involvement of the PAG in both decision-making bias and altered information processing to implement expectancy effects on pain. PERSPECTIVE: Modulation of pain through expectations has been linked to changes in perceptual decision-making and altered processing of afferent information. Our results suggest involvement of the dorsolateral prefrontal cortex, amygdala, and periaqueductal gray in these processes.

When experience is not enough: learning-based cognitive pain modulation with or without instructions

ABSTRACT

The effects of expectations on pain perception are often studied using large differences in pain probabilities between experimental conditions, although they may be far more subtle in clinical contexts and, therefore, more difficult to detect. The current study aimed to investigate at which point subtle differences in pain probabilities can be detected and lead to differentiable expectations and perceptions. Furthermore, we investigated whether instructions can aid learning from experience and enhance subsequent pain modulatory effects. During a predictive learning task, participants were presented with 5 different cues, followed by either a high and low noxious stimulus. They learned about the different cue-stimulus contingencies either solely through experience (LEARN, N = 40) or a combination of experience and explicit information about the cue-stimulus contingencies (INSTRUCT, N = 40). We found that without explicit information, picking up the different pain probabilities was challenging, while explicit instruction significantly improved their detection. As revealed by drift diffusion modeling, learning from experience was insufficient for the development of a bias towards low pain even when it was highly likely. By contrast, when explicit information was provided, perception became more nuanced with the direction and extent of bias, capturing the subtle differences in pain probabilities. These findings highlight that the use of instructions to foster the detection of subtle pain improvements during pain treatment to enhance their cognitive pain modulatory effects warrant further investigation.

Improving the quality of discharge care plan in the heart failure with reduced ejection fraction (HFrEF) cohort: a quality improvement study

Background

High-quality heart failure (HF) discharge summary (DS) is the cornerstone of effective communication during the transition from specialists to primary care. The combination of continuing involvement of multidisciplinary members, varying individual tolerance to treatments, and the need for multiple investigations beget intricate HFrEF management. The quality of the information included in DS following HF-related hospitalisation varies widely and may be sub-optimal in communicating patient's in-hospital care, leading to inadequate compliance to guideline-directed medical therapy (GDMT) and increased risk of re-hospitalisation. Notwithstanding this real-world observation, there remains a paucity of consensus on the standard of measurements of HF DS.

Purpose

We aimed to optimise the transmission of information between patients and HF multidisciplinary members to improve adherence to GDMT, follow-up (F/U) care coordination and patient education in line with the National Institute for Health and Care Excellence (NICE) and the European Society of Cardiology (ESC) recommendations.

Methods

A random sampling of the HFrEF cohort discharged from the cardiac unit at our institution following HF-related hospitalisation was performed across four distinct time points matched with respective interventions. Three iterative cycles (baseline analysis and two educational interventions – departmental teaching and dissemination of innovative mnemonics sheets – THE WET TO DRY [Figure 1]) were completed using Plan-Do-Study-Act (PDSA) methodology. The quality of patients DS was objectively analysed based on the inclusion of physiological and investigation parameters, in-patient treatment, initiation/titration of GDMT, F/U care coordination, and patient education.

Results

Sixty-six patients, mean±SD age 74.6±12.8y were enrolled between 2018–2021. The baseline reporting of presenting complaints, trigger and investigation findings were high and consistent throughout all cycles. A positive trend was observed in the reporting of physiological parameters and in-patient treatment post-interventions. Patient education and vaccines offered remained low despite improving compliance. As such, a consensus on the provision of nurse-led pre-discharge review label and interactive patient personal passport (Figure 1) was achieved via a group of cardiologists and HF specialist nurses to address identified practice gap from preceding PDSA cycles. Full adherence to GDMT and the inclusion of F/U pathway were observed following the provision of nurse-led review label (Figure 2).

Conclusion

This study demonstrates that educational interventions – departmental teaching and innovative mnemonics can be effective in improving the quality of HF DS. Structured nurse-led review label and interactive patient personal passport are feasible interventions, which can be implemented at minimal cost to sustain adherence to GDMT, F/U care coordination and individualised patient education.

Funding Acknowledgement

Type of funding sources: None.

Differences in perceptual memory determine generalization patterns

Although memory of past experiences is crucial for the ability to transfer knowledge to new situations, surprisingly little research has directly investigated the relationship between memory and generalization. The present study sought to investigate how the perceptual memory of a trained stimulus influences generalization to similar stimuli. Forty participants underwent a fear conditioning procedure on Day 1, and separate memory recall and generalization tests on Day 2. We focused on two aspects of perceptual memory: namely memory bias (i.e., over- or underestimation of stimulus magnitude) and uncertainty. We found that memory bias predicted the pattern of generalized self-reported (expectancy ratings) and psychophysiological responses (fear-potentiated startle responses). Memory uncertainty was measured in two ways: self-reported uncertainty ratings and variability in stimulus recall. We found that higher levels of self-reported memory uncertainty corresponded with a broader generalization gradient on US expectancy, while greater variability in memory recall was associated with a broader generalization gradient on fear-potentiated startle responses. Taken together, our findings suggest that memory is an important determinant of generalized behavior and illustrate the need to account for these interindividual differences in perceptual memory when examining the generalization of learned responses.

Characteristics and health status of patients with and without confirmed HFpEF

Aims

Patients with heart failure with preserved ejection fraction (HFpEF) are usually older and multi-morbid and diagnosis can be challenging. The aims of this cohort study were to confirm diagnosis of HFpEF in patients with possible HFpEF recruited from primary care, to compare characteristics and health status between those with and without HFpEF, and to determine factors associated with health status in patients with HFpEF.

Methods

Patients with presumed HFpEF were recruited from primary care practices and underwent clinical assessment and diagnostic evaluation as part of a longitudinal cohort study. Health status was measured by Montreal Cognitive Assessment (MOCA), 6-minute walk test, symptoms, and the Kansas City Cardiomyopathy Questionnaire (KCCQ), and quality of life (QoL) by EQ-5D-5L visual analogue scale (VAS).

Results

151 patients (mean age 78.5±8.6 years, 40% women, mean EF 56% + 9.4) were recruited and 93 (61.6%) were confirmed HFpEF (those without HFpEF had other HF and cardiac diagnoses). Patients with and without HFpEF did not differ by age, MOCA, blood pressure, heart rate, NYHA class, proportion with atrial fibrillation, Charlson Comorbidity Index, or NT-ProBNP levels. Patients with HFpEF were more likely to be women, overweight or obese, frail, and to be more functionally impaired by 6 minute walk distance and gait speed than those without. Although not statistically significant, patients with HFpEF had clinically significant differences (&gt;5 points) on the physical limitations, symptom burden and clinical summary subscales of the KCCQ, but did not differ by other subscales or by EQ-5D-5L VAS (70±17 vs 73±19, p=0.385). More patients with HFpEF reported daytime dyspnoea (63% vs 46%, p=0.035) and fatigue (81% vs 61%, p=0.008), but not other symptoms compared to those without HFpEF. For both groups BMI was moderately negatively correlated with KCCQ subscale scores, and 6 minute walk distance was positively correlated with KCCQ subscales.

Conclusions

Nearly 40% were not confirmed as HFpEF indicating the challenges of diagnosis. Patients with confirmed HFpEF differed by sex, overweight/obesity, frailty, functional impairment, and symptoms but not by age or comorbidities from those without HFpEF. These differences were reflected in some subscale scores of the KCCQ, but not how patients reported their quality of life on the KCCQ QoL subscale and EQ-5D-5L VAS. Older patients with HFpEF reported relatively high QoL despite poor health status by functional impairment, frailty and symptoms.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institute of Health Research School of Primary Care Research

P1419Persistent atrial fibrillation terminates during ablation more often using dispersion mapping than with fractionated electrogram mapping

Introduction

Persistent AF termination rates have increased since the advent of AF driver mapping, with a recent meta-analysis (Baykaner Circ AE 2018) of over 3200 patients showing improved 12 month freedom from AF/AT.  However,  recent randomised clinical trials have cast doubt on the efficacy of complex fractionated atrial electrograms (CFAE) based mapping strategies. We

set out to study a consecutive single centre series pre-and post- use of spatio-temporal dispersion (STD) to identify termination rates between the two approaches.

Methods

We recruited consecutive patients over 18 months at a single high volume tertiary centre undergoing first redo ablation for persistent AF. Patients were all

mapped using Pentarray to mark areas of substrate using the spatio-temporal dispersion (STD) method (Seitz JACC 2017).

Ablation was performed by a single operator using catheters to standardise equipment and workflow, to enable true

comparison of mapping and ablation results in a consecutive series.

Results

In total 38 patients were studied at redo ablation for persistent AF (age 69, 87% male, LA diameter 4.5cm). Termination of persistent

AF to SR (30%) or AT (70%) was obtained in 30/38 (79%) of the group with STD based substrate ablation vs. 1/38 (3%) in patients mapped

with CFAE targeting using identical equipment and operator (p &lt; 0.001). Procedure time was no different between STD and CFAE based

approaches (263 vs. 248 mins, p = ns). Figure shows STD patterns (red arrows) on Pentarray in a 67 year old man anterior to left inferior

pulmonary vein (A), where ablation terminated AF to sinus rhythm. At 12 month follow up, 30/38 (79%) patients were in sinus rhythm with no AF detected on ECG or continuous monitoring.

Conclusions

In this single centre series of persistent AF ablations, the use of STD mapping increased rates of termination compared to a fractionation based mapping strategy alone, without increasing overall procedure time. Clinical outcome data suggest this translates into better 12 month clinical outcomes, and motivate prospective randomised trials to definitively study this technique.

Abstract Figure.

The use of stimulus perception to account for variability in skin conductance responses to interoceptive stimuli

Activity of the electrodermal response system is customarily expressed in relation to physical stimulus properties and not to perceived features. In situations where the delivery of physically identical stimuli can be challenging, such as in interoception research, this variability might pose a challenge for contemporary SCR analyses. Therefore, we investigated the extent to which activity in the electrodermal response system triggered by the delivery of interoceptive stimuli is better predicted by perceived intensity rather than physical input. For this purpose, we reanalyzed data from the baseline phase of a previous study (n = 60) in which skin conductance responses (SCRs) to innocuous esophageal stimulations of high and low intensities were recorded in addition to categorizations based on their perceived intensity (high or low). Using both peak scoring and model inversion methods, we found that the inclusion of stimulus perception as a predictor of the magnitude of the SCR increased model fit. These findings suggest that the inclusion of perception is a promising avenue to better model variability in psychophysiological responses to interoceptive stimuli.

Direct and indirect effects of perception on generalization gradients

For more than a century, researchers have attempted to understand why organisms behave similarly across situations. Despite the robust character of generalization, considerable variation in conditioned responding both between and within humans remains a challenge for contemporary generalization models. The current study aims to investigate the extent to which variation in behavior in a context of generalization can be attributed to differences in perception. We combined a fear conditioning and generalization procedure with a perceptual decision task in humans. We found that the failure to perceive a novel stimulus as different from the trained fear-evoking stimulus led to increased conditioned responding. Furthermore, perceptual errors yielded perceived stimulus-outcome contingencies that differed substantially from the objective contingencies. Final, the impact of a perceptual error was dependent upon these perceived contingencies. These findings suggest that generalization across a perceptual dimension is to a large extent driven by perceptual errors that directly affect behavior but also indirectly as they yield different learning experiences between individuals.

Learned Fear of Gastrointestinal Sensations in Healthy Adults

BACKGROUND & AIMS

Gastrointestinal symptom-specific fear and anxiety are important determinants of gastrointestinal symptom perception. We studied learning of fear toward innocuous gastrointestinal sensations as a putative mechanism in the development of gastrointestinal symptom-specific fear and anxiety.

METHODS

Fifty-two healthy subjects (26 women) received 2 types of esophageal balloon distention at a perceptible but nonpainful intensity (conditioned stimulus [CS], the innocuous sensation) and at a painful intensity (unconditioned stimulus [US]). Subjects were assigned randomly to 1 of 2 groups. During the learning phase, the innocuous CS preceded the painful US in the experimental group (n = 26). In the control group (n = 26), on the contrary, the US never followed the CS directly. During a subsequent extinction phase, both groups received only CS distention-the painful US was no longer administered. Indexes of fear learning toward the innocuous CS distention included the skin conductance response, fear-potentiated startle (measured by the eye-blink electromyogram), and self-reported expectancy of the US.

RESULTS

During the learning phase, only the experimental group learned to fear the innocuous gastrointestinal CS, based on the increase in US expectancy (compared with the control group, P = .04), increased skin conductance response (compared with the control group, P = .03), and potentiated startle reflex (compared with the control group, P = .001) in response to the CS. The differences between the experimental and control groups in US expectancy and skin conductance, but not fear-potentiated startle, disappeared during the extinction phase.

CONCLUSIONS

Fear toward innocuous gastrointestinal sensations can be established through associative learning in healthy human beings. This may be an important mechanism in the development of fear of gastrointestinal symptoms, implicated in the pathophysiology of functional gastrointestinal disorders.

Interoceptive cues predicting exteroceptive events

The growing body of research on interoceptive conditioning has predominantly focused on associative learning paradigms that investigated the formation of intero-interoceptive or extero-interoceptive associations. Yet, little research has explored whether interoceptive sensations can enter an intero-exteroceptive association. Therefore, in an interoceptive conditioning paradigm, healthy participants experienced a respiratory resistance for 8s, causing mild dyspnea (interoceptive conditioned stimulus, CS), that was either paired to an aversive electrocutaneous stimulus (unconditioned stimulus, US) (experimental condition, n=25), or presented in an unpaired fashion (control condition, n=25) during the acquisition phase. In a subsequent extinction phase, the US was not delivered anymore. US-expectancy, skin conductance responses (SCR), and eyeblink startle EMG were used as indices of associative learning. During acquisition, we observed stronger US expectancies during the CS as compared to the intertrial interval in the experimental group, but not in the control group, nor during extinction. In line, only in the experimental group did skin conductance responses to the CS increase across acquisition. The pattern of the eyeblink startle data did not reach statistical significance. In sum, interoceptive sensations can become associated with exteroceptive events.

Perceptual discrimination in fear generalization: Mechanistic and clinical implications

For almost a century, Pavlovian conditioning is the imperative experimental paradigm to investigate the development and generalization of fear. However, despite the rich research tradition, the conceptualization of fear generalization has remained somewhat ambiguous. In this selective review, we focus explicitly on some challenges with the current operationalization of fear generalization and their impact on the ability to make inferences on its clinical potential and underlying processes. The main conclusion is that, despite the strong evidence that learning influences perception, current research has largely neglected the role of perceptual discriminability and its plasticity in fear generalization. We propose an alternative operationalization of generalization, where the essence is that Pavlovian conditioning itself influences the breadth of fear generalization via learning-related changes in perceptual discriminability. Hence a conceptualization of fear generalization is incomplete without an in-depth analysis of processes of perceptual discriminability. Furthermore, this highlights perceptual learning and discriminability as important future targets for pre-clinical and clinical research.

Influence of prior information on pain involves biased perceptual decision-making

Prior information about features of a stimulus is a strong modulator of perception. For instance, the prospect of more intense pain leads to an increased perception of pain, whereas the expectation of analgesia reduces pain, as shown in placebo analgesia and expectancy modulations during drug administration [1]. This influence is commonly assumed to be rooted in altered sensory processing and expectancy-related modulations in the spinal cord [2], are often taken as evidence for this notion. Contemporary models of perception, however, suggest that prior information can also modulate perception by biasing perceptual decision-making — the inferential process underlying perception in which prior information is used to interpret sensory information. In this type of bias, the information is already present in the system before the stimulus is observed [3]. Computational models can distinguish between changes in sensory processing and altered decision-making as they result in different response times for incorrect choices in a perceptual decision-making task (Figure S1A,B) [4]. Using a drift-diffusion model, we investigated the influence of both processes in two independent experiments. The results of both experiments strongly suggest that these changes in pain perception are predominantly based on altered perceptual decision-making.

Reprint of "Learning to breathe? Feedforward regulation of the inspiratory motor drive"

Claims have been made that breathing is in part controlled by feedforward regulation. In a classical conditioning paradigm, we investigated anticipatory increases in the inspiratory motor drive as measured by inspiratory occlusion pressure (P100). In an acquisition phase, an experimental group (N = 13) received a low-intensity resistive load (5 cmH2O/l/s) for three consecutive inspirations as Conditioned Stimulus (CS), preceding a load of a stronger intensity (20 cmH2O/l/s) for three subsequent inspirations as unconditioned stimulus (US). The control group (N = 11) received the low-intensity load for six consecutive inspirations. In a post-acquisition phase both groups received the low-intensity load for six consecutive inspirations. Responses to the CS-load only differed between groups during the first acquisition trials and a strong increase in P100 during the US-loads was observed, which habituated across the experiment. Our results suggest that the disruption caused by adding low to moderate resistive loads to three consecutive inspirations results in a short-lasting anticipatory increase in inspiratory motor drive.

Effect of seated trunk posture on eye blink startle and subjective experience: comparing flexion, neutral upright posture, and extension of spine

Postures are known to be able to affect emotion and motivation. Much less is known about whether (affective) modulation of eye blink startle occurs following specific postures. The objective of the current study was to explore this. Participants in the present study were requested to assume three different sitting postures: with the spine flexed (slouched), neutral upright, and extended. Each posture was assumed for four minutes, and was followed by the administration of brief self-report questionnaires before proceeding to the next posture. The same series of postures and measures were repeated prior to ending the experiment. Results indicate that, relative to the other postures, the extended sitting posture was associated with an increased startle, was more unpleasant, arousing, had smaller levels of dominance, induced more discomfort, and was perceived as more difficult. The upright and flexed sitting postures differed in the level of self-reported positive affect, but not in eye blink startle amplitudes.

Value of FNAC in diagnosis of different types of thyroiditis and its comparison with clinical and biochemical findings

FNAC has developed tremendous improvement in the diagnosis of thyroiditis. The present study was designed to asses the usefulness of FNAC to diagnose various types of thyroiditis and to study their smear patterns. Over a period of one-year, 70 cases of thyroiditis have been evaluated on the basis of cytomorphological criteria and clinical findings of patients. The age ranged from 12-60 years. Majority of the cases were between 21 to 30 years of age with female preponderance in each group of thyroiditis. Among 70 cases, 26(37.14%) cases were Hashimoto's thyroiditis, 21(30%) cases were lymphocytic thyroiditis, seven (10%) cases as granulomatous thyroiditis and 16(22.8%) were non-specific thyroiditis. Further study was carried out in these 70 cases regarding biochemical thyroid status, ultrasonography and radionucleotide scan. Blood was drawn from all patients for estimation of antibody titer to compare with cytological diagnosis. It was found that, clinical examination and history of patients had limited value in the diagnosis of thyroiditis. Ultrasonography and thyroid scan could not reliably differentiate between patients with autoimmune thyroiditis and those with simple and nodular goiter. Biochemically hypothyroidism is more frequently evaluated with Hashimoto's diseases. On the other hand, hyperthyroidism was observed in most other types of thyroiditis. Cytologically diagnosed 78.72% cases of autoimmune thyroiditis had positive antibody titer. From the present study it is concluded that FNAC is a safe, reliable, cost effective and time saving method in the diagnosis of thyroiditis. Being a benign condition also reduce the rate of unnecessary operation, which can be treated conservatively.