Irritable bowel syndrome: low dose antidepressant improves symptoms.

The studyFord AC, Wright-Hughes A, Alderson SL, et al. Amitriptyline at low-dose and titrated for irritable bowel syndrome as second-line treatment in primary care (ATLANTIS): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet 2023;402:1773-85.To read the full NIHR Alert, go to: https://evidence.nihr.ac.uk/alert/irritable-bowel-syndrome-low-dose-antidepressant-improves-symptoms/.

Postprandial symptoms in disorders of gut-brain interaction and their potential as a treatment target.

Postprandial, or meal-related, symptoms, such as abdominal pain, early satiation, fullness or bloating, are often reported by patients with disorders of gut-brain interaction, including functional dyspepsia (FD) or irritable bowel syndrome (IBS). We propose that postprandial symptoms arise via a distinct pathophysiological process. A physiological or psychological insult, for example, acute enteric infection, leads to loss of tolerance to a previously tolerated oral food antigen. This enables interaction of both the microbiota and the food antigen itself with the immune system, causing a localised immunological response, with activation of eosinophils and mast cells, and release of inflammatory mediators, including histamine and cytokines. These have more widespread systemic effects, including triggering nociceptive nerves and altering mood. Dietary interventions, including a diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols, elimination of potential food antigens or gluten, IgG food sensitivity diets or salicylate restriction may benefit some patients with IBS or FD. This could be because the restriction of these foods or dietary components modulates this pathophysiological process. Similarly, drugs including proton pump inhibitors, histamine-receptor antagonists, mast cell stabilisers or even tricyclic or tetracyclic antidepressants, which have anti-histaminergic actions, all of which are potential treatments for FD and IBS, act on one or more of these mechanisms. It seems unlikely that food antigens driving intestinal immune activation are the entire explanation for postprandial symptoms in FD and IBS. In others, fermentation of intestinal carbohydrates, with gas release altering reflex responses, adverse reactions to food chemicals, central mechanisms or nocebo effects may dominate. However, if the concept that postprandial symptoms arise from food antigens driving an immune response in the gastrointestinal tract in a subset of patients is correct, it is paradigm-shifting, because if the choice of treatment were based on one or more of these therapeutic targets, patient outcomes may be improved.

Effect of Brain-Gut Behavioral Treatments on Abdominal Pain in Irritable Bowel Syndrome: Systematic Review and Network Meta-analysis.

BACKGROUND & AIMS: Some brain-gut behavioral treatments (BGBTs) are beneficial for global symptoms in irritable bowel syndrome (IBS). United States management guidelines suggest their use in patients with persistent abdominal pain, but their specific effect on this symptom has not been assessed systematically. METHODS: We searched the literature through December 16, 2023, for randomized controlled trials (RCTs) assessing efficacy of BGBTs for adults with IBS, compared with each other or a control intervention. Trials provided an assessment of abdominal pain resolution or improvement at treatment completion. We extracted data as intention-to-treat analyses, assuming dropouts to be treatment failures and reporting pooled relative risks (RRs) of abdominal pain not improving with 95% confidence intervals (CIs), ranking therapies according to the P score. RESULTS: We identified 42 eligible randomized controlled trials comprising 5220 participants. After treatment completion, the BGBTs with the largest numbers of trials and patients recruited demonstrating efficacy for abdominal pain, specifically, included self-guided/minimal contact cognitive behavioral therapy (CBT) (RR, 0.71; 95% CI, 0.54-0.95; P score, 0.58), face-to-face multicomponent behavioral therapy (RR, 0.72; 95% CI, 0.54-0.97; P score, 0.56), and face-to-face gut-directed hypnotherapy (RR, 0.77; 95% CI, 0.61-0.96; P score, 0.49). Among trials recruiting only patients with refractory global IBS symptoms, group CBT was more efficacious than routine care for abdominal pain, but no other significant differences were detected. No trials were low risk of bias across all domains, and there was evidence of funnel plot asymmetry. CONCLUSIONS: Several BGBTs, including self-guided/minimal contact CBT, face-to-face multicomponent behavioral therapy, and face-to-face gut-directed hypnotherapy may be efficacious for abdominal pain in IBS, although none was superior to another.

Population coding of time-varying sounds in the nonlemniscal inferior colliculus.

The inferior colliculus (IC) of the midbrain is important for complex sound processing, such as discriminating conspecific vocalizations and human speech. The IC's nonlemniscal, dorsal "shell" region is likely important for this process, as neurons in these layers project to higher-order thalamic nuclei that subsequently funnel acoustic signals to the amygdala and nonprimary auditory cortices, forebrain circuits important for vocalization coding in a variety of mammals, including humans. However, the extent to which shell IC neurons transmit acoustic features necessary to discern vocalizations is less clear, owing to the technical difficulty of recording from neurons in the IC's superficial layers via traditional approaches. Here, we use two-photon Ca2+ imaging in mice of either sex to test how shell IC neuron populations encode the rate and depth of amplitude modulation, important sound cues for speech perception. Most shell IC neurons were broadly tuned, with a low neurometric discrimination of amplitude modulation rate; only a subset was highly selective to specific modulation rates. Nevertheless, neural network classifier trained on fluorescence data from shell IC neuron populations accurately classified amplitude modulation rate, and decoding accuracy was only marginally reduced when highly tuned neurons were omitted from training data. Rather, classifier accuracy increased monotonically with the modulation depth of the training data, such that classifiers trained on full-depth modulated sounds had median decoding errors of ∼0.2 octaves. Thus, shell IC neurons may transmit time-varying signals via a population code, with perhaps limited reliance on the discriminative capacity of any individual neuron.NEW & NOTEWORTHY The IC's shell layers originate a "nonlemniscal" pathway important for perceiving vocalization sounds. However, prior studies suggest that individual shell IC neurons are broadly tuned and have high response thresholds, implying a limited reliability of efferent signals. Using Ca2+ imaging, we show that amplitude modulation is accurately represented in the population activity of shell IC neurons. Thus, downstream targets can read out sounds' temporal envelopes from distributed rate codes transmitted by populations of broadly tuned neurons.

Chronic Visceral Pain: New Peripheral Mechanistic Insights and Resulting Treatments.

Chronic visceral pain is one of the most common reasons for patients with gastrointestinal disorders, such as inflammatory bowel disease or disorders of brain-gut interaction, to seek medical attention. It represents a substantial burden to patients and is associated with anxiety, depression, reductions in quality of life, and impaired social functioning, as well as increased direct and indirect health care costs to society. Unfortunately, the diagnosis and treatment of chronic visceral pain is difficult, in part because our understanding of the underlying pathophysiologic basis is incomplete. In this review, we highlight recent advances in peripheral pain signaling and specific physiologic and pathophysiologic preclinical mechanisms that result in the sensitization of peripheral pain pathways. We focus on preclinical mechanisms that have been translated into treatment approaches and summarize the current evidence base for directing treatment toward these mechanisms of chronic visceral pain derived from clinical trials. The effective management of chronic visceral pain remains of critical importance for the quality of life of suffers. A deeper understanding of peripheral pain mechanisms is necessary and may provide the basis for novel therapeutic interventions.

Utility of irritable bowel syndrome subtypes and most troublesome symptom in predicting disease impact and burden.

BACKGROUND: Little is known about the characteristics of individuals with irritable bowel syndrome (IBS) according to stool subtype or the most troublesome symptom reported by the individual, or whether these are useful in predicting the impact of IBS. METHODS: We collected demographic, gastrointestinal, and psychological symptoms, healthcare usage and direct healthcare costs, impact on work and activities of daily living, and quality of life data from individuals with Rome IV-defined IBS. KEY RESULTS: We recruited 752 people with Rome IV IBS. Individuals with IBS-D reported a poorer disease-specific quality of life than those with IBS-C or IBS-M (mean (SD) IBS-QOL 45.3 (23.0) for IBS-D, vs. 52.3 (19.9) for IBS-C, vs. 49.4 (22.0) for IBS-M, p = 0.005). Mean (SD) IBS-QOL scores were also lower amongst those who reported diarrhea (44.8 (22.3)) or urgency (44.6 (22.3)) as their most troublesome symptom, compared with those reporting abdominal pain (52.2 (22.9)), constipation (49.5 (21.8)), or abdominal bloating or distension (50.4 (21.3)). However, there were no differences in mean EQ-5D scores, IBS severity, levels of anxiety, depression, somatoform symptom-reporting, or gastrointestinal symptom-specific anxiety. Direct healthcare costs of IBS were similar across all subtypes and all most troublesome symptom groups, although some differences in work productivity and social leisure activities were detected. CONCLUSIONS AND INFERENCES: There appears to be limited variation in the characteristics of individuals with Rome IV IBS based on both stool subtypes and most troublesome symptom reported, suggesting that gastrointestinal symptoms alone have limited ability to predict disease impact and burden.

Assessing Diagnostic Performance of Modifications to the Rome IV Criteria for Irritable Bowel Syndrome.

The gold standard symptom-based criteria for diagnosis of irritable bowel syndrome (IBS) are the Rome IV criteria.1 These are more restrictive than their predecessor, Rome III, because the cardinal feature required to meet criteria for IBS was changed to presence of abdominal pain alone, rather than abdominal pain or discomfort.2 This change was made because discomfort was believed to be an ambiguous term, with no equivalent in some languages. In addition, symptom frequency required for the presence of abdominal pain was increased to 1 day per week from 2 to 3 days per month. This has led to reduced sensitivity for detecting IBS and a 50% decrease in the prevalence of the disorder in the community.3,4 In a cross-sectional survey applying both Rome IV and III criteria to people living with IBS, 89% of those with Rome III-defined IBS not meeting Rome IV criteria did not meet Rome IV criteria because of this change in pain frequency.5 Previous iterations of the Rome criteria have performed only modestly in predicting a diagnosis of IBS.6-8 However, in a validation study, the Rome IV criteria outperformed Rome III,9 largely because their more restrictive nature made them more specific than Rome III. We assessed whether modifications to the Rome IV criteria led to a better trade-off between sensitivity and specificity.

Novel Symptom Subgroups in Individuals With Irritable Bowel Syndrome Predict Disease Impact and Burden.

BACKGROUND & AIMS: Current classification systems based on bowel habit fail to capture the multidimensional nature of irritable bowel syndrome (IBS). We previously derived and validated a classification system, using latent class analysis, incorporating factors beyond bowel habit. We applied this in another cohort of people with IBS to assess its ability to capture the impact of IBS on the individual, the health care system, and society. METHODS: We collected demographic, symptom, and psychological health data from adults in the community self-identifying as having IBS, and meeting Rome IV criteria. We applied our latent class analysis model to identify the 7 subgroups (clusters) described previously, based on overall gastrointestinal symptom severity and psychological burden. We assessed quality of life, health care costs (£1 = $1.20), employment status, annual income, work productivity, and ability to perform work duties in each cluster. RESULTS: Of 1278 responders, 752 (58.8%) met Rome IV criteria. The 7-cluster model fit the data well. The patients in the 4 clusters with the highest psychological burden, and particularly those in cluster 6 with high overall gastrointestinal symptom severity and high psychological burden, showed lower educational levels, higher gastrointestinal symptom-specific anxiety, were more likely to have consulted a gastroenterologist, and used more drugs for IBS. IBS-related and generic quality of life were impaired significantly in these 4 clusters and significantly fewer individuals reported earning ≥£30,000 per year. Productivity and the ability to work, manage at home, engage in social and private leisure activities, and maintain close relationships all were impacted significantly, and IBS-related health care costs over the previous 12 months were highest in these 4 clusters. In those in cluster 6, costs were more than £1000 per person per year. CONCLUSIONS: Our clusters identify groups of individuals with significant impairments in quality of life, earning potential, and ability to work and function socially, who are high utilizers of health care.

Systematic Review and Meta-analysis: Efficacy of Mesalamine in Irritable Bowel Syndrome.

BACKGROUND & AIMS: Some patients with irritable bowel syndrome (IBS) demonstrate low-grade inflammation in the intestine. Mesalamine, which has anti-inflammatory effects, may be an efficacious treatment for IBS, but studies are conflicting. We conducted a systematic review and meta-analysis to assess efficacy and safety of mesalamine in IBS. METHODS: We searched the medical literature up to September 14, 2022, to identify randomized controlled trials (RCTs) of mesalamine in IBS. We judged efficacy and safety using dichotomous assessments of effect on global IBS symptoms, abdominal pain, bowel habit or stool frequency, and occurrence of any adverse event. We pooled data using a random effects model, with efficacy and safety reported as pooled relative risks (RRs) with 95% confidence intervals (CIs). RESULTS: We identified 8 eligible RCTs (820 patients). Mesalamine was more efficacious than placebo for global IBS symptoms (RR of global symptoms not improving, 0.86; 95% CI, 0.79-0.95; number needed to treat = 10; 95% CI, 6-27), but not for abdominal pain or bowel habit or stool frequency. Subgroup analyses demonstrated efficacy of mesalamine in IBS with diarrhea for global IBS symptoms (RR, 0.88; 95% CI, 0.79-0.99), but not patients with other predominant bowel habits or those with post-infection IBS. Adverse event rates were no higher with mesalamine (RR, 1.20; 95% CI, 0.89-1.63) but were reported in only 5 trials. CONCLUSIONS: Mesalamine may be modestly efficacious for global symptoms in IBS, particularly IBS with diarrhea, but quality of evidence was low. Adequately powered high quality RCTs of mesalamine in IBS are needed.

Maintenance of clinical remission with biologics and small molecules in inflammatory bowel disease according to trial design: Meta-analysis.

BACKGROUND AND AIMS: Design of randomised controlled trials (RCTs) examining maintenance of clinical remission in inflammatory bowel disease (IBD) varies, with some trials re-randomising patients who have responded to active drug during induction to either active drug or placebo and others treating patients through with active drug or placebo from baseline. Whether this influences therapeutic gain of drug over placebo is unknown. METHODS: We searched the literature to January 2023 for maintenance of remission trials of biologics or small molecules versus placebo in IBD. We extracted maintenance of remission rates according to trial design; either trials re-randomising patients or trials treating patients through. We pooled data in a meta-analysis for all patients, and according to type of IBD. We calculated the number needed to treat (NNT), with a 95% confidence interval (CI), to assess therapeutic gain of active drug over placebo according to trial design. RESULTS: We identified 37 maintenance of remission trials (12,075 patients). Rates of maintenance of clinical remission were higher (41.9% with active drug, versus 20.3% with placebo), and NNT lowest (5; 95% CI 4-6), in trials re-randomising patients compared with those treating through (maintenance of remission rate 30.9% with active drug versus 14.6% with placebo, NNT = 7; 95% CI 5-9). Results were similar when trials were analysed according to IBD type but were more marked in ulcerative colitis RCTs (maintenance of remission rates in re-randomised trials 39.4% with active drug versus 17.8% with placebo, NNT = 5; 95% CI 3-7; treat-through trials 27.3% with active drug versus 11.9% with placebo, NNT = 7; 95% CI 5-11.5). CONCLUSION: Trials re-randomising patients had generally higher maintenance of remission rates, lower NNTs, and greater therapeutic gains over placebo.

Natural history and impact of irritable bowel syndrome-type symptoms in inflammatory bowel disease during 12 months of longitudinal follow-up.

BACKGROUND: Little is known about the natural history and impact of irritable bowel syndrome (IBS)-type symptoms on psychological health and quality of life in inflammatory bowel disease (IBD). We aimed to address this in a 12-month longitudinal follow-up study of secondary care patients. METHODS: We collected demographic, Rome III IBS-type symptom, psychological, and quality of life data, with questionnaires at 3-month intervals, over 12 months of follow-up in patients with IBD in clinical remission at baseline. We assessed the natural history of Rome III IBS-type symptoms over the 12 months of the study and compared psychological and quality of life data between those reporting Rome III IBS-type symptoms at each of the points of follow-up with those not reporting such symptoms. KEY RESULTS: Among 206 patients with IBD in clinical remission at baseline (104 [50.5%] women, mean age 56.9 years [range 18-83 years], 79 [38.3%] Crohn's disease), 33 (16.0%) reported Rome III IBS-type symptoms at baseline and 72 (35.0%) reported Rome III IBS-type symptoms at one or more time points. Among the 33 patients with Rome III IBS-type symptoms at baseline, symptoms resolved in 6 (18.2%) patients, were present throughout in 6 (18.2%) patients, and fluctuated in the remaining 21 (63.6%) patients. Among the 39 patients with new onset of Rome III IBS-type symptoms after baseline, 24 (65.1%) had symptoms at one point in time only, 10 (25.6%) at two points, four (10.3%) at three points, and one (2.6%) at four points. At each point in time, reporting IBS-type symptoms was associated with significantly higher anxiety, depression, or somatoform symptom-reporting scores, and/or lower quality of life scores. CONCLUSIONS & INFERENCES: In this 12-month follow-up study, one-third of patients with IBD reported presence of Rome III IBS-type symptoms at any point in time. Reporting such symptoms was associated with significant impacts on psychological health and/or quality of life.

Auditory Corticofugal Neurons Transmit Auditory and Non-auditory Information During Behavior.

Layer 5 pyramidal neurons of sensory cortices project "corticofugal" axons to myriad sub-cortical targets, thereby broadcasting high-level signals important for perception and learning. Recent studies suggest dendritic Ca2+ spikes as key biophysical mechanisms supporting corticofugal neuron function: these long-lasting events drive burst firing, thereby initiating uniquely powerful signals to modulate sub-cortical representations and trigger learning-related plasticity. However, the behavioral relevance of corticofugal dendritic spikes is poorly understood. We shed light on this issue using 2-photon Ca2+ imaging of auditory corticofugal dendrites as mice of either sex engage in a GO/NO-GO sound-discrimination task. Unexpectedly, only a minority of dendritic spikes were triggered by behaviorally relevant sounds under our conditions. Task related dendritic activity instead mostly followed sound cue termination and co-occurred with mice's instrumental licking during the answer period of behavioral trials, irrespective of reward consumption. Temporally selective, optogenetic silencing of corticofugal neurons during the trial answer period impaired auditory discrimination learning. Thus, auditory corticofugal systems' contribution to learning and plasticity may be partially nonsensory in nature.

Impact of Opioid Use on the Natural History of Inflammatory Bowel Disease: Prospective Longitudinal Follow-up Study.

BACKGROUND: Opioid use is increasingly prevalent amongst patients with inflammatory bowel disease (IBD), but whether opioids have deleterious effects, or their use is merely linked with more severe disease, is unclear. We conducted a longitudinal follow-up study examining this issue. METHODS: Data on demographics, gastrointestinal and psychological symptoms, quality of life, and opioid use were recorded at baseline. Data on healthcare use and adverse disease outcomes were obtained from a review of electronic medical records at 12 months. Characteristics at baseline of those using opioids and those who were not were compared, in addition to occurrence of flare, prescription of glucocorticosteroids, treatment escalation, hospitalization, or intestinal resection during the 12 months of follow-up. RESULTS: Of 1029 eligible participants, 116 (11.3%) were taking opioids at baseline. Medium (odds ratio [OR], 4.67; 95% confidence interval [CI], 1.61-13.6) or high (OR, 8.03; 95% CI, 2.21-29.2) levels of somatoform symptom-reporting and use of antidepressants (OR, 2.54; 95% CI, 1.34-4.84) or glucocorticosteroids (OR, 6.63; 95% CI, 2.26-19.5; P < .01 for all analyses) were independently associated with opioid use. Following multivariate analysis, opioid users were significantly more likely to undergo intestinal resection (hazard ratio,  7.09; 95% CI, 1.63 to 30.9; P = .009), particularly when codeine or dihydrocodeine were excluded (hazard ratio, 42.9; 95% CI, 3.36 to 548; P = .004). CONCLUSIONS: Opioid use in IBD is associated with psychological comorbidity and increased risk of intestinal resection, particularly in stronger formulations. Future studies should stratify the risk of individual opioids, so that robust prescribing algorithms can be developed and assess whether addressing psychological factors in routine IBD care could be an effective opioid avoidance strategy.

Of the 1029 patients with IBD in this study, opioid use exceeded 10% and was associated with psychological comorbidity and an increased risk of intestinal resection during longitudinal follow-up, particularly when more potent formulations were used.

Amitriptyline at Low-Dose and Titrated for Irritable Bowel Syndrome as Second-Line Treatment in primary care (ATLANTIS): a randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Most patients with irritable bowel syndrome (IBS) are managed in primary care. When first-line therapies for IBS are ineffective, the UK National Institute for Health and Care Excellence guideline suggests considering low- dose tricyclic antidepressants as second-line treatment, but their effectiveness in primary care is unknown, and they are infrequently prescribed in this setting. METHODS: This randomised, double-blind, placebo-controlled trial (Amitriptyline at Low-Dose and Titrated for Irritable Bowel Syndrome as Second-Line Treatment [ATLANTIS]) was conducted at 55 general practices in England. Eligible participants were aged 18 years or older, with Rome IV IBS of any subtype, and ongoing symptoms (IBS Severity Scoring System [IBS-SSS] score ≥75 points) despite dietary changes and first-line therapies, a normal full blood count and C-reactive protein, negative coeliac serology, and no evidence of suicidal ideation. Participants were randomly assigned (1:1) to low-dose oral amitriptyline (10 mg once daily) or placebo for 6 months, with dose titration over 3 weeks (up to 30 mg once daily), according to symptoms and tolerability. Participants, their general practitioners, investigators, and the analysis team were all masked to allocation throughout the trial. The primary outcome was the IBS-SSS score at 6 months. Effectiveness analyses were according to intention-to-treat; safety analyses were on all participants who took at least one dose of the trial medication. This trial is registered with the ISRCTN Registry (ISRCTN48075063) and is closed to new participants. FINDINGS: Between Oct 18, 2019, and April 11, 2022, 463 participants (mean age 48·5 years [SD 16·1], 315 [68%] female to 148 [32%] male) were randomly allocated to receive low-dose amitriptyline (232) or placebo (231). Intention-to-treat analysis of the primary outcome showed a significant difference in favour of low-dose amitriptyline in IBS-SSS score between groups at 6 months (-27·0, 95% CI -46·9 to -7·10; p=0·0079). 46 (20%) participants discontinued low-dose amitriptyline (30 [13%] due to adverse events), and 59 (26%) discontinued placebo (20 [9%] due to adverse events) before 6 months. There were five serious adverse reactions (two in the amitriptyline group and three in the placebo group), and five serious adverse events unrelated to trial medication. INTERPRETATION: To our knowledge, this is the largest trial of a tricyclic antidepressant in IBS ever conducted. Titrated low-dose amitriptyline was superior to placebo as a second-line treatment for IBS in primary care across multiple outcomes, and was safe and well tolerated. General practitioners should offer low-dose amitriptyline to patients with IBS whose symptoms do not improve with first-line therapies, with appropriate support to guide patient-led dose titration, such as the self-titration document developed for this trial. FUNDING: National Institute for Health and Care Research Health Technology Assessment Programme (grant reference 16/162/01).

Novel symptom clusters predict disease impact and healthcare utilisation in inflammatory bowel disease: Prospective longitudinal follow-up study.

BACKGROUND: Predicting adverse disease outcomes and high-volume users of healthcare amongst patients with inflammatory bowel disease (IBD) is difficult. AIMS: The aim of this study is to use latent class analysis to create novel clusters of patients and to assess whether these predict outcomes during 6.5 years of longitudinal follow-up. METHODS: Baseline demographic features, disease activity indices, anxiety, depression, and somatoform symptom-reporting scores were recorded for 692 adults. Faecal calprotectin (FC) was analysed at baseline in 348 (50.3%) patients (<250 mcg/g defined biochemical remission). Using baseline gastrointestinal and psychological symptoms, latent class analysis identified specific patient clusters. Rates of glucocorticosteroid prescription or flare, escalation, hospitalisation, or intestinal resection were compared between clusters using multivariate Cox regression. RESULTS: A three-cluster model was the optimum solution; 132 (19.1%) patients had below-average gastrointestinal and psychological symptoms (cluster 1), 352 (50.9%) had average levels of gastrointestinal and psychological symptoms (cluster 2), and 208 (30.1%) had the highest levels of both gastrointestinal and psychological symptoms (cluster 3). Compared with cluster 1, cluster 3 had significantly increased risk of flare or glucocorticosteroid prescription (hazard ratio (HR): 2.13; 95% confidence interval (CI): 1.46-3.10), escalation (HR: 1.92; 95% CI: 1.34-2.76), a composite of escalation, hospitalisation, or intestinal resection (HR: 2.05; 95% CI: 1.45-2.88), or any of the endpoints of interest (HR: 2.06; 95% CI: 1.45-2.93). Healthcare utilisation was highest in cluster 3. CONCLUSIONS: Novel model-based clusters identify patients with IBD at higher risk of adverse disease outcomes who are high-volume users of healthcare.

Population coding of time-varying sounds in the non-lemniscal Inferior Colliculus.

The inferior colliculus (IC) of the midbrain is important for complex sound processing, such as discriminating conspecific vocalizations and human speech. The IC's non-lemniscal, dorsal "shell" region is likely important for this process, as neurons in these layers project to higher-order thalamic nuclei that subsequently funnel acoustic signals to the amygdala and non-primary auditory cortices; forebrain circuits important for vocalization coding in a variety of mammals, including humans. However, the extent to which shell IC neurons transmit acoustic features necessary to discern vocalizations is less clear, owing to the technical difficulty of recording from neurons in the IC's superficial layers via traditional approaches. Here we use 2-photon Ca2+ imaging in mice of either sex to test how shell IC neuron populations encode the rate and depth of amplitude modulation, important sound cues for speech perception. Most shell IC neurons were broadly tuned, with a low neurometric discrimination of amplitude modulation rate; only a subset were highly selective to specific modulation rates. Nevertheless, neural network classifier trained on fluorescence data from shell IC neuron populations accurately classified amplitude modulation rate, and decoding accuracy was only marginally reduced when highly tuned neurons were omitted from training data. Rather, classifier accuracy increased monotonically with the modulation depth of the training data, such that classifiers trained on full-depth modulated sounds had median decoding errors of ~0.2 octaves. Thus, shell IC neurons may transmit time-varying signals via a population code, with perhaps limited reliance on the discriminative capacity of any individual neuron.