Posterior Insular Cortex Research Articles

Gestational CBD Shapes Insular Cortex in Adulthood.

Many expectant mothers use CBD to alleviate symptoms like nausea, insomnia, anxiety, and pain, despite limited research on its long-term effects. However, CBD passes through the placenta, affecting fetal development and impacting offspring behavior. We investigated how prenatal CBD exposure affects the insular cortex (IC), a brain region involved in emotional processing and linked to psychiatric disorders. The IC is divided into two territories: the anterior IC (aIC), processing socioemotional signals, and the posterior IC (pIC), specializing in interoception and pain perception. Pyramidal neurons in the aIC and pIC exhibit sex-specific electrophysiological properties, including variations in excitability and the excitatory/inhibitory balance. We investigated IC's cellular properties and synaptic strength in the offspring of both sexes from mice exposed to low-dose CBD during gestation (E5-E18; 3 mg/kg, s.c.). Prenatal CBD exposure induced sex-specific and territory-specific changes in the active and passive membrane properties, as well as intrinsic excitability and the excitatory/inhibitory balance, in the IC of adult offspring. The data indicate that in utero CBD exposure disrupts IC neuronal development, leading to a loss of functional distinction between IC territories. These findings may have significant implications for understanding the effects of CBD on emotional behaviors in offspring.

Chemogenetic inhibition of pain-related neurons in the posterior insula cortex reduces mechanical hyperalgesia and anxiety-like behavior during acute pain

Pain is a complex phenomenon that involves sensory, emotional, and cognitive components. The posterior insula cortex (pIC) has been shown to integrate multisensory experience with emotional and cognitive states. However, the involvement of the pIC in the regulation of affective behavior in pain remains unclear. Here, we investigate the role of pain-related pIC neurons in the regulation of anxiety-like behavior during acute pain. We combined a chemogenetic approach with targeted recombination in active populations (TRAP) in mice. Global chemogenetic inhibition of pIC neurons attenuates chemically-induced mechanical hypersensitivity without affecting pain-related anxiety-like behavior. In contrast, inhibition of pain-related pIC neurons reduces both mechanical hypersensitivity and pain-related anxiety-like behavior. The present study provides important insights into the role of pIC neurons in the regulation of sensory and affective pain-related behavior.

Ventral posteromedial nucleus of the thalamus gates the spread of trigeminal neuropathic pain

BackgroundWidespread neuropathic pain usually affects a wide range of body areas and inflicts huge suffering on patients. However, little is known about how it happens and effective therapeutic interventions are lacking.MethodsWidespread neuropathic pain was induced by partial infraorbital nerve transection (p-IONX) and evaluated by measuring nociceptive thresholds. In vivo/vitro electrophysiology were used to evaluate neuronal activity. Virus tracing strategies, combined with optogenetics and chemogenetics, were used to clarify the role of remodeling circuit in widespread neuropathic pain.ResultsWe found that in mice receiving p-IONX, along with pain sensitization spreading from the orofacial area to distal body parts, glutamatergic neurons in the ventral posteromedial nucleus of the thalamus (VPMGlu) were hyperactive and more responsive to stimulations applied to the hind paw or tail. Tracing experiments revealed that a remodeling was induced by p-IONX in the afferent circuitry of VPMGlu, notably evidenced by more projections from glutamatergic neurons in the dorsal column nuclei (DCNGlu). Moreover, VPMGlu receiving afferents from the DCN extended projections further to glutamatergic neurons in the posterior insular cortex (pIC). Selective inhibition of the terminals of DCNGlu in the VPM, the soma of VPMGlu or the terminals of VPMGlu in the pIC all alleviated trigeminal and widespread neuropathic pain.ConclusionThese results demonstrate that hyperactive VPMGlu recruit new afferents from the DCN and relay the extra-cephalic input to the pIC after p-IONX, thus hold a key position in trigeminal neuropathic pain and its spreading. This study provides novel insights into the circuit mechanism and preclinical evidence for potential therapeutic targets of widespread neuropathic pain.

Gestational CBD shapes insular cortex in adulthood.

Many expectant mothers use CBD to alleviate symptoms like nausea, insomnia, anxiety, and pain, despite limited research on its long-term effects. However, CBD passes through the placenta, affecting fetal development and impacting offspring behavior. We investigated how prenatal CBD exposure affects the insular cortex (IC), a brain region involved in emotional processing and linked to psychiatric disorders. The IC is divided into two territories: the anterior IC (aIC), processing socioemotional signals, and the posterior IC (pIC), specializing in interoception and pain perception. Pyramidal neurons in the aIC and pIC exhibit sex-specific electrophysiological properties, including variations in excitability and the excitatory/inhibitory balance. We investigated IC's cellular properties and synaptic strength in the offspring of both sexes from mice exposed to low-dose CBD during gestation (E5-E18; 3mg/kg, s.c.). Prenatal CBD exposure induced sex-specific and territory-specific changes in the active and passive membrane properties, as well as intrinsic excitability and the excitatory/inhibitory balance, in the IC of adult offspring. The data indicate that in-utero CBD exposure disrupts IC neuronal development, leading to a loss of functional distinction between IC territories. These findings may have significant implications for understanding the effects of CBD on emotional behaviors in offspring.

The Posterior Insular Cortex is Necessary for Feeding-Induced Jejunal Myoelectrical Activity in Male Rats

The gastrointestinal tract exhibits coordinated muscle motility in response to food digestion, which is regulated by the central nervous system through autonomic control. The insular cortex is one of the brain regions that may regulate the muscle motility. In this study, we examined whether, and how, the insular cortex, especially the posterior part, regulates gastrointestinal motility by recording jejunal myoelectrical signals in response to feeding in freely moving male rats. Feeding was found to induce increases in jejunal myoelectrical signal amplitudes. This increase in the jejunal myoelectrical signals was abolished by vagotomy and pharmacological inhibition of the posterior insular cortex. Additionally, feeding induced a decrease and increase in sympathetic and parasympathetic nervous activities, respectively, both of which were eliminated by posterior insular cortical inhibition. These results suggest that the posterior insular cortex regulates jejunal motility in response to feeding by modulating autonomic tone.

General and anxiety-linked influences of acute serotonin reuptake inhibition on neural responses associated with attended visceral sensation

Ordinary sensations from inside the body are important causes and consequences of our affective states and behaviour, yet the roles of neurotransmitters in interoceptive processing have been unclear. With a within-subjects design, this experiment tested the impacts of acute increases of endogenous extracellular serotonin on the neural processing of attended internal sensations and the links of these effects to anxiety using a selective serotonin reuptake inhibitor (SSRI) (20 mg citalopram) and a placebo. Twenty-one healthy volunteers (fourteen female, mean age 23.9) completed the Visceral Interoceptive Attention (VIA) task while undergoing functional magnetic resonance imaging (fMRI) with each treatment. The VIA task required focused attention on the heart, stomach, or visual sensation. The relative neural interoceptive responses to heart sensation [heart minus visual attention] (heart-IR) and stomach sensation [stomach minus visual attention] (stomach-IR) were compared between treatments. Visual attention subtraction controlled for the general effects of citalopram on sensory processing. Citalopram was associated with lower interoceptive processing in viscerosensory (the stomach-IR of bilateral posterior insular cortex) and integrative/affective (the stomach-IR and heart-IR of bilateral amygdala) components of interoceptive neural pathways. In anterior insular cortex, citalopram reductions of heart-IR depended on anxiety levels, removing a previously known association between anxiety and the region’s response to attended heart sensation observed with placebo. Preliminary post hoc analysis indicated that citalopram effects on the stomach-IR of the amygdalae corresponded to acute anxiety changes. This direct evidence of general and anxiety-linked serotonergic influence on neural interoceptive processes advances our understanding of interoception, its regulation, and anxiety.

The Role of 3' Regulatory Region Flanking Kinectin 1 Gene in Schizophrenia.

Schizophrenia is often associated with volumetric reductions in cortices and expansions in basal ganglia, particularly the putamen. Recent genome-wide association studies have highlighted the significance of variants in the 3' regulatory region adjacent to the kinectin 1 gene (KTN1) in regulating gray matter volume (GMV) of the putamen. This study aimed to comprehensively investigate the involvement of this region in schizophrenia. We analyzed 1136 single-nucleotide polymorphisms (SNPs) covering the entire 3' regulatory region in 4 independent dbGaP samples (4604 schizophrenia patients vs. 4884 healthy subjects) and 3 independent Psychiatric Genomics Consortium samples (107 240 cases vs. 210 203 controls) to identify consistent associations. Additionally, we examined the regulatory effects of schizophrenia-associated alleles on KTN1 mRNA expression in 16 brain areas among 348 subjects, as well as GMVs of 7 subcortical nuclei in 38 258 subjects, and surface areas (SA) and thickness (TH) of the entire cortex and 34 cortical areas in 36 936 subjects. The major alleles (f > 0.5) of 25 variants increased (β > 0) the risk of schizophrenia across 2 to 5 independent samples (8.4 × 10-4 ≤ P ≤ .049). These schizophrenia-associated alleles significantly elevated (β > 0) GMVs of basal ganglia, including the putamen (6.0 × 10-11 ≤ P ≤ 1.1 × 10-4), caudate (8.7 × 10-4 ≤ P ≤ 9.4 × 10-3), pallidum (P = 6.0 × 10-4), and nucleus accumbens (P = 2.7 × 10-5). Moreover, they potentially augmented (β > 0) the SA of posterior cingulate and insular cortices, as well as the TH of frontal (pars triangularis and medial orbitofrontal), parietal (superior, precuneus, and inferior), and temporal (transverse) cortices, but potentially reduced (β < 0) the SA of the whole, frontal (medial orbitofrontal), and temporal (pole, superior, middle, and entorhinal) cortices, as well as the TH of rostral middle frontal and superior frontal cortices (8.9 × 10-4 ≤ P ≤ .050). Our findings identify significant and functionally relevant risk alleles in the 3' regulatory region adjacent to KTN1, implicating their crucial roles in the development of schizophrenia.

Sex differences in neuronal activation in the cortex and midbrain during quinine-adulterated alcohol intake.

Continued alcohol consumption despite negative consequences is a core symptom of alcohol use disorder. This is modeled in mice by pairing negative stimuli with alcohol, such as adulterating alcohol solution with quinine. Mice consuming alcohol under these conditions are considered to be engaging in aversion-resistant intake. Previously, we have observed sex differences in this behavior, with females more readily expressing aversion-resistant consumption. We also identified three brain regions that exhibited sex differences in neuronal activation during quinine-alcohol drinking: ventromedial prefrontal cortex (vmPFC), posterior insular cortex (PIC), and ventral tegmental area (VTA). Specifically, male mice showed increased activation in vmPFC and PIC, while females exhibited increased activation in VTA. In this study, we aimed to identify what specific type of neurons are activated in these regions during quinine-alcohol drinking. We assessed quinine-adulterated alcohol intake using the two-bottle choice procedure. We also utilized RNAscope in situ hybridization in the three brain regions that previously exhibited a sex difference to examine colocalization of Fos, glutamate, GABA, and dopamine. Females showed increased aversion-resistant alcohol consumption compared to males. We also found that males had higher colocalization of glutamate and Fos in vmPFC and PIC, while females had greater dopamine and Fos colocalization in the VTA. Collectively, these experiments suggest that glutamatergic output from the vmPFC and PIC may have a role in suppressing, and dopaminergic activity in the VTA may promote, aversion-resistant alcohol consumption. Future experiments will examine neuronal circuits that contribute to sex differences in aversion resistant consumption.

Dysfunction of M channels in the insular cortex is involved in pathogenesis of primary hypertension

Heightened sympathetic nerve activity is critically involved in the pathogenesis of primary hypertension. However, the sources driving increased sympathetic vasomotor tone remain unclear. The posterior insular cortex (PIC) is a brain region involved in regulating blood pressure and sympathetic tone. Neurons in the PIC project to the rostral ventrolateral medulla (RVLM), a key brain stem region in regulating sympathetic nerve activity and blood pressure. The non-inactivating voltage-dependent K+ channels, M channels (Kv7/KCNQ channel family) encoded by KCNQ2/3 genes, play a unique role in stabilizing the neuronal membrane potential and regulating neuronal excitability. Here, we determined if the M channel activity of neurons in the PIC is altered in a primary hypertension. Compared with Wistar-Kyoto (WKY) rats, the mRNA and protein expression levels of Kv7.2/Kv7.3 in the PIC tissue were significantly reduced in spontaneously hypertensive rats (SHRs). Microinjection of M channel blocker 10, 10-bis (4-pyridinylmethyl)-9(10H)-anthracnose (XE-991) into the PIC increased arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) in anesthetized WKY rats, while induced minimal changes of ABP and RSNA in SHRs. M currents recorded from PIC neurons in brain slices labeled by retrograde tracer, Fluospheres, injected into the RVLM were significantly smaller in SHRs than in WKY rats. Furthermore, bath application of specific M channel blocker XE-991 increased the firing rate of PIC-RVLM output neurons in WKY rats while caused a minimal increase in firing rate of PIC-RVLM output neurons in SHRs. In addition, M currents recorded from PIC-RVLM output neurons in SHRs were significantly smaller than those recorded from WKY rats. These data suggest that M channel activity is diminished in PIC-RVLM output neurons in SHRs, and the diminished Kv7 channel activity contributes to elevated sympathetic outflow in primary hypertension. This novel information provides new a mechanistic insight into the pathogenesis of neurogenic hypertension. Supported by grants from National Institutes of Health (HL139523, HL142133, and HL159157 to DPL). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Secondary somatosensory and posterior insular cortices: a somatomotor hub for object prehension and manipulation movements.

The secondary somatosensory cortex (SII) and posterior insular cortex (pIC) are recognized for processing touch and movement information during hand manipulation in humans and non-human primates. However, their involvement in three-dimensional (3D) object manipulation remains unclear. To investigate neural activity related to hand manipulation in the SII/pIC, we trained two macaque monkeys to grasp three objects (a cone, a plate, and a ring) and engage in visual fixation on the object. Our results revealed that 19.4% (n = 50/257) of the task-related neurons in SII/pIC were active during hand manipulations, but did not respond to passive somatosensory stimuli. Among these neurons, 44% fired before hand-object contact (reaching to grasping neurons), 30% maintained tonic activity after contact (holding neurons), and 26% showed continuous discharge before and after contact (non-selective neurons). Object grasping-selectivity varied and was weak among these neurons, with only 24% responding to fixation of a 3D object (visuo-motor neurons). Even neurons unresponsive to passive visual stimuli showed responses to set-related activity before the onset of movement (42%, n = 21/50). Our findings suggest that somatomotor integration within SII/pIC is probably integral to all prehension sequences, including reaching, grasping, and object manipulation movements. Moreover, the existence of a set-related activity within SII/pIC may play a role in directing somatomotor attention during object prehension-manipulation in the absence of vision. Overall, SII/pIC may play a role as a somatomotor hub within the lateral grasping network that supports the generation of intentional hand actions based on haptic information.

Sexual differences in neuronal and synaptic properties across subregions of the mouse insular cortex

BackgroundThe insular cortex (IC) plays a pivotal role in processing interoceptive and emotional information, offering insights into sex differences in behavior and cognition. The IC comprises two distinct subregions: the anterior insular cortex (aIC), that processes emotional and social signals, and the posterior insular cortex (pIC), specialized in interoception and perception of pain. Pyramidal projection neurons within the IC integrate multimodal sensory inputs, influencing behavior and cognition. Despite previous research focusing on neuronal connectivity and transcriptomics, there has been a gap in understanding pyramidal neurons characteristics across subregions and between sexes.MethodsAdult male and female C57Bl/6J mice were sacrificed and tissue containing the IC was collected for ex vivo slice electrophysiology recordings that examined baseline sex differences in synaptic plasticity and transmission within aIC and pIC subregions.ResultsClear differences emerged between aIC and pIC neurons in both males and females: aIC neurons exhibited distinctive features such as larger size, increased hyperpolarization, and a higher rheobase compared to their pIC counterparts. Furthermore, we observed variations in neuronal excitability linked to sex, with male pIC neurons displaying a greater level of excitability than their female counterparts. We also identified region-specific differences in excitatory and inhibitory synaptic activity and the balance between excitation and inhibition in both male and female mice. Adult females demonstrated greater synaptic strength and maximum response in the aIC compared to the pIC. Lastly, synaptic long-term potentiation occurred in both subregions in males but was specific to the aIC in females.ConclusionsWe conclude that there are sex differences in synaptic plasticity and excitatory transmission in IC subregions, and that distinct properties of IC pyramidal neurons between sexes could contribute to differences in behavior and cognition between males and females.

Insula→Amygdala and Insula→Thalamus Pathways Are Involved in Comorbid Chronic Pain and Depression-Like Behavior in Mice.

The comorbidity of chronic pain and depression poses tremendous challenges for the treatment of either one because they exacerbate each other with unknown mechanisms. As the posterior insular cortex (PIC) integrates multiple somatosensory and emotional information and is implicated in either chronic pain or depression, we hypothesize that the PIC and its projections may contribute to the pathophysiology of comorbid chronic pain and depression. We show that PIC neurons were readily activated by mechanical, thermal, aversive, and stressful and appetitive stimulation in naive and neuropathic pain male mice subjected to spared nerve injury (SNI). Optogenetic activation of PIC neurons induced hyperalgesia and conditioned place aversion in naive mice, whereas inhibition of these neurons led to analgesia, conditioned place preference (CPP), and antidepressant effect in both naive and SNI mice. Combining neuronal tracing, optogenetics, and electrophysiological techniques, we found that the monosynaptic glutamatergic projections from the PIC to the basolateral amygdala (BLA) and the ventromedial nucleus (VM) of the thalamus mimicked PIC neurons in pain modulation in naive mice; in SNI mice, both projections were enhanced accompanied by hyperactivity of PIC, BLA, and VM neurons and inhibition of these projections led to analgesia, CPP, and antidepressant-like effect. The present study suggests that potentiation of the PIC→BLA and PIC→VM projections may be important pathophysiological bases for hyperalgesia and depression-like behavior in neuropathic pain and reversing the potentiation may be a promising therapeutic strategy for comorbid chronic pain and depression.

Pharmacological Manipulation of Corticotropin-Releasing Factor Receptors in the Anterior and Posterior Subregions of the Insular Cortex Differently Affects Anxiety-Like Behaviors in the Elevated Plus Maze in Rats.

Neuroimaging data in humans and neurobiological studies in rodents have suggested an involvement of the insular cortex (IC) in anxiety manifestations. However, the local neurochemical mechanisms involved are still poorly understood. Corticotropin-releasing factor (CRF) neurotransmission has been described as a prominent neurochemical mechanism involved in the expression of anxiety-like behaviors, but the brain sites related are poorly understood. Additionally, several findings indicate that control of physiological and behavioral responses by the IC occurs in a site-specific manner along its rostrocaudal axis. Thus, this study is aimed at evaluating the effect of CRF receptor agonism and antagonism within the anterior and posterior subregions of the IC in controlling anxiety-related behaviors in the elevated plus maze (EPM). For this, independent groups (six groups) of animals received bilateral microinjections of vehicle, the selective CRF1 receptor antagonist CP376395, or CRF into either the anterior or posterior subregions of the IC. Ten minutes later, the behavior in the EPM was evaluated for five minutes. Treatment of the anterior IC with CP376395, but not with CRF, increased the time and number of entries into the open arms of the EPM. CRF, but not the CRF1 receptor antagonist, microinjected into the posterior IC also increased exploration of the EPM open arms. Taken together, these data indicate that CRFergic neurotransmission in the anterior IC is involved in the expression of anxiety-related behaviors in the EPM. This neurochemical mechanism does not seem to be activated within the posterior IC during exposure to the EPM, but the effects caused by CRF microinjection indicate that activation of CRF receptors in this IC subregion might evoke anxiolytic-like effects.

Systematic reduction of gray matter volume in anorexia nervosa, but relative enlargement with clinical symptoms in the prefrontal and posterior insular cortices: a multicenter neuroimaging study

Although brain morphological abnormalities have been reported in anorexia nervosa (AN), the reliability and reproducibility of previous studies were limited due to insufficient sample sizes, which prevented exploratory analysis of the whole brain as opposed to regions of interest (ROIs). Objective was to identify brain morphological abnormalities in AN and the association with severity of AN by brain structural magnetic resonance imaging (MRI) in a multicenter study, and to conduct exploratory analysis of the whole brain. Here, we conducted a cross-sectional multicenter study using T1-weighted imaging (T1WI) data collected between May 2014 and February 2019 in Japan. We analyzed MRI data from 103 female AN patients (58 anorexia nervosa restricting type [ANR] and 45 anorexia nervosa binge-purging type [ANBP]) and 102 age-matched female healthy controls (HC). MRI data from five centers were preprocessed using the latest harmonization method to correct for intercenter differences. Gray matter volume (GMV) was calculated from T1WI data of all participants. Of the 205 participants, we obtained severity of eating disorder symptom scores from 179 participants, including 87 in the AN group (51 ANR, 36 ANBP) and 92 HC using the Eating Disorder Examination Questionnaire (EDE-Q) 6.0. GMV reduction were observed in the AN brain, including the bilateral cerebellum, middle and posterior cingulate gyrus, supplementary motor cortex, precentral gyrus medial segment, and thalamus. In addition, the orbitofrontal cortex (OFC), ventromedial prefrontal cortex (vmPFC), rostral anterior cingulate cortex (ACC), and posterior insula volumes showed positive correlations with severity of symptoms. This multicenter study was conducted with a large sample size to identify brain morphological abnormalities in AN. The findings provide a better understanding of the pathogenesis of AN and have potential for the development of brain imaging biomarkers of AN. Trial Registration: UMIN000017456. https://center6.umin.ac.jp/cgi-open-bin/icdr/ctr_view.cgi?recptno=R000019303.

Neural sensitivity to translational self- and object-motion velocities.

The ability to detect and assess world-relative object-motion is a critical computation performed by the visual system. This computation, however, is greatly complicated by the observer's movements, which generate a global pattern of motion on the observer's retina. How the visual system implements this computation is poorly understood. Since we are potentially able to detect a moving object if its motion differs in velocity (or direction) from the expected optic flow generated by our own motion, here we manipulated the relative motion velocity between the observer and the object within a stationary scene as a strategy to test how the brain accomplishes object-motion detection. Specifically, we tested the neural sensitivity of brain regions that are known to respond to egomotion-compatible visual motion (i.e., egomotion areas: cingulate sulcus visual area, posterior cingulate sulcus area, posterior insular cortex [PIC], V6+, V3A, IPSmot/VIP, and MT+) to a combination of different velocities of visually induced translational self- and object-motion within a virtual scene while participants were instructed to detect object-motion. To this aim, we combined individual surface-based brain mapping, task-evoked activity by functional magnetic resonance imaging, and parametric and representational similarity analyses. We found that all the egomotion regions (except area PIC) responded to all the possible combinations of self- and object-motion and were modulated by the self-motion velocity. Interestingly, we found that, among all the egomotion areas, only MT+, V6+, and V3A were further modulated by object-motion velocities, hence reflecting their possible role in discriminating between distinct velocities of self- and object-motion. We suggest that these egomotion regions may be involved in the complex computation required for detecting scene-relative object-motion during self-motion.

Regular cannabis use alters the neural dynamics serving complex motor control.

Cannabis is the most widely used recreational drug in the United States and regular use has been linked to deficits in attention and memory. However, the effects of regular use on motor control are less understood, with some studies showing deficits and others indicating normal performance. Eighteen users and 23 nonusers performed a motor sequencing task during high-density magnetoencephalography (MEG). The MEG data was transformed into the time-frequency domain and beta responses (16-24 Hz) during motor planning and execution phases were imaged separately using a beamformer approach. Whole-brain maps were examined for group (cannabis user/nonuser) and time window (planning/execution) effects. As expected, there were no group differences in task performance (e.g., reaction time, accuracy, etc.). Regular cannabis users exhibited stronger beta oscillations in the contralateral primary motor cortex compared to nonusers during the execution phase of the motor sequences, but not during the motor planning phase. Similar group-by-time window interactions were observed in the left superior parietal, right inferior frontal cortices, right posterior insular cortex, and the bilateral motor cortex. We observed differences in the neural dynamics serving motor control in regular cannabis users compared to nonusers, suggesting regular users may employ compensatory processing in both primary motor and higher-order motor cortices to maintain adequate task performance. Future studies will need to examine more complex motor control tasks to ascertain whether this putative compensatory activity eventually becomes exhausted and behavioral differences emerge.

Alterations of Cerebral Metabolites Are Associated with Frequency of Vasoocclusive Crises and Pain Sensitivity in Patients with Sickle Cell Disease

Purpose Sickle cell disease (SCD) is an inherited hemolytic disorder complicated by acute and chronic pain. Acute vasoocclusive crises (VOCs) associated with SCD are extremely painful episodes that are recurrent, unpredictable, and frequently require hospitalization and opioids for pain control. Changes in brain metabolites were identified in other chronic pain populations but haven't been well studied in SCD. Our ongoing trial (ClinicalTrials.gov Identifier: NCT05045820) aims to evaluate the characteristics of brain metabolites in SCD and understand the relationship between the altered cerebral metabolite(s) and clinical pain in patients with SCD. Materials and Methods Metabolite measurements from a single voxel (size: 2×3×3 cm 3) located within the posterior insula cortex (PIC) were acquired from 26 patients with SCD (31.9 ± 13.9 years, 14-73; 14 females) and 19 healthy controls (HCs) (37.9 ± 16.4 years, 17-62; 10 females) with PRESS (TR/TE = 3000/25 ms, Averages =128) and MEGA-PRESS (TR/TE = 3000/68 ms, Averages =256) sequences using a Siemens Prisma 3T scanner. Written consent was obtained from each participant before scanning. LCModel was used for PRESS analysis to obtain concentration values of glutamine + glutamate (Glx), total creatine (tCr), N-acetylaspartate (NAA), total choline (tCho), and myoinositol (MI). Gannet was used for processing MEGA-PRESS data to estimate GABA+. Ratios of each metabolite to tCr were also quantified. Tissue correction for cerebrospinal fluid was performed for each voxel using the tissue composition estimated from SPM12. The Cramer-Rao Lower Bounds of each metabolite analyzed with LCModel was less than 20%. The frequency of VOCs in the preceding 12 months was recorded for each participant. A moderate pressure pain stimuli (using a 0-100 scale with “0” representing “no pain” and “100” representing “most intense pain imaginable”, pain rating at 40-60 abbreviated as P40 is considered as moderate pain) was delivered via a pressure cuff to the gastrocnemius area of the non-dominant leg using a validated MR-compatible air compressor to induce a tonic pressure pain for 8 min right before MRS scan. Higher pressure intensity (mmHg) of P40 indicated higher pain tolerance and lower pain sensitivity. Correlation between the brain metabolites and pain-related outcomes was studied. Results Due to the large range of age in the SCD group, the brain metabolite profile was compared between 17 SCD patients and 17 ethnicity-, age- and gender-matched HCs. The concentration of Glx (p =0.012) and ratio of Glx to tCr (p =0.034) in PIC were significantly higher in patients with SCD compared to HCs (Figure 1). Within the SCD patient group, there was a significant positive correlation between frequency of VOCs in the preceding 12 months and Glx/tCr (r= 0.39, p=0.047, Spearman's), a significant negative correlation between P40 and Glx (r= -0.46, p=0.019, Spearman's). There were no group differences in any other metabolites. Conclusion We find increased Glx in the PIC in patients with SCD. Previous studies have also found increased Glx and/ or Glx/tCr in the PIC as well as other brain regions including the amygdala, the posterior cingulate, the ventral lateral prefrontal cortex and the anterior insula in fibromyolgia. The PIC is thought to be involved in discriminative activities of sensory pain, which suggests that Glx in PIC is related to pain processing in patients with SCD. Glx/tCr was correlated with frequency of VOCs in patients with SCD, indicating that the SCD patients with higher level of Glx/tCr had more VOCs in the preceding 12 months. In addition, the SCD patients with higher level of Glx had lower pressure intensity of P40, suggesting that elevated Glx in the PIC was related to higher pain sensitivity. Our preliminary data provide the first evidence of a link between alterations in excitatory neurotransmitter levels in the PIC in patients with SCD and indicates new information of potential brain markers for pain in SCD, which may guide treatment. Clinical Relevance Statement: Treatment of pain in SCD remains very challenging in part due to a lack of understanding of the underlying mechanisms and pathophysiology of pain. Brain excitatory neurotransmitters and their relationship with pain have been largely unexplored in SCD. These findings indicate that the relationship between clinical outcomes and excitatory brain neurotransmitters may be a potential objective outcome measure in SCD.

Estradiol mediates sex differences in aversion-resistant alcohol intake.

Alcohol consumption despite negative consequences is a core symptom of alcohol use disorder. This can be modeled in mice by pairing aversive stimuli with alcohol consumption, such as adding the bitter tastant quinine to the alcohol solution. If an animal continues to drink alcohol despite such negative stimuli, this is typically considered aversion-resistant, or inflexible, drinking behavior. Previous studies in our lab have found that females are more aversion-resistant than males in that they tolerate higher concentrations of quinine before they suppress their alcohol intake. Interestingly, we did not observe any differences in intake across the estrous cycle. In regards to neuronal activation patterns during quinine-alcohol intake, we have found that male mice show higher levels of activation in the ventromedial prefrontal cortex and posterior insular cortex, while females show higher levels of activation in the ventral tegmental area. In the experiments presented here, we conducted ovariectomies to further examine the role of circulating sex hormones in aversion-resistant alcohol intake and neuronal activation patterns. Furthermore, we used hormonal addback of estradiol or progesterone to determine which ovarian sex hormone mediates aversion-resistant consumption. We found that ovariectomy reduced quinine-adulterated alcohol intake, demonstrating that circulating sex hormones play a role in this behavior. We also observed reduced neuronal activation in the VTA of ovariectomized mice compared to sham females, and that estradiol supplementation reversed the effect of ovariectomy on quinine-alcohol intake. Taken together with our prior data, these findings suggest that circulating estradiol contributes to the expression of aversion-resistant alcohol intake and neuronal activity in the VTA. However, since this behavior is not affected by the estrous cycle, we believe this is due to a threshold level of this hormone, as opposed to fluctuations that occur across the estrous cycle.

Chemogenetic Modulation of Posterior Insula CaMKIIa Neurons Alters Pain and Thermoregulation

The posterior insular cortex (PIC) is well positioned to perform somatosensory-limbic integration; yet, the function of neuronal subsets within the PIC in processing the sensory and affective dimensions of pain remains unclear. Here, we employ bidirectional chemogenetic modulation to characterize the function of PIC CaMKIIa-expressing excitatory neurons in a comprehensive array of sensory, affective, and thermoregulatory behaviors. Excitatory pyramidal neurons in the PIC were found to be sensitized under inflammatory pain conditions. Chemogenetic activation of excitatory CaMKIIa-expressing PIC neurons in non-injured conditions produced an increase in reflexive and affective pain- and anxiety-like behaviors. Moreover, activation of PIC CaMKIIa-expressing neurons during inflammatory pain conditions exacerbated hyperalgesia and decreased pain tolerance. However, Chemogenetic activation did not alter heat nociception via hot plate latency or body temperature. Conversely, inhibiting CaMKIIa-expressing neurons did not alter either sensory or affective pain-like behaviors in non-injured or under inflammatory pain conditions, but it did decrease body temperature and decreased hot plate latency. Our findings reveal that PIC CaMKIIa-expressing neurons are a critical hub for producing both sensory and affective pain-like behaviors and important for thermoregulatory processing. PerspectiveThe present study reveals that activation of the posterior insula produces hyperalgesia and negative affect, and has a role in thermal tolerance and thermoregulation. These findings highlight the insula as a key player in contributing to the multidimensionality of pain.

Vestibular mapping of the naturalistic head-centered motion spectrum.

Naturalistic head accelerations can be used to elicit vestibular evoked potentials (VestEPs). These potentials allow for analysis of cortical vestibular processing and its multi-sensory integration with a high temporal resolution. We report the results of two experiments in which we compared the differential VestEPs elicited by randomized translations, rotations, and tilts in healthy subjects on a motion platform. An event-related potential (ERP) analysis revealed that established VestEPs were verifiable in all three acceleration domains (translations, rotations, tilts). A further analysis of the VestEPs showed a significant correlation between rotation axes (yaw, pitch, roll) and the amplitude of the evoked potentials. We found increased amplitudes for rotations in the roll compared to the pitch and yaw plane. A distributed source localization analysis showed that the activity in the cingulate sulcus visual (CSv) area best explained direction-dependent amplitude modulations of the VestEPs, but that the same cortical network (posterior insular cortex, CSv) is involved in processing vestibular information, regardless of the motion direction. The results provide evidence for an anisotropic, direction-dependent processing of vestibular input by cortical structures. The data also suggest that area CSv plays an integral role in ego-motion perception and interpretation of spatial features such as acceleration direction and intensity.