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Psychophysics of CNS pain-related activity: binary and analog channels and memory encoding.

The forebrain neuronal system signaling pain has been poorly characterized. The pain pathway afferent to the thalamus may be a labeled line consisting of neurons in the pain-signaling pathway to the brain (spinothalamic tract, STT) that respond only to painful stimuli. It has recently been proposed that the STT contains a series of analog-labeled lines, each signaling a different aspect of the internal state of the body (interoception), for example, visceral/cold/itch sensations. In this view, pain is the unpleasant emotion produced by disequilibrium of the internal state. The authors now show that stimulation of an STT receiving zone (thalamic principal somatic sensory nucleus, ventral caudal) in awake humans produces two different exteroceptive responses. The first is a binary response signaling the presence of painful stimuli. The second is an analog response in which nonpainful and painful sensations are graded with intensity of the stimulus. Such stimulation can evoke both the sensory and emotional components of previously experienced pain. These results illustrate the diverse functions of human pain signaling pathways.

Animals↗

Validity of the Arabic version of the eating disorders inventory (EDI).

BACKGROUND: We aimed to validate the Eating Disorders Inventory (EDI) in Arabic. METHODS: Subjects were chosen randomly from female school students. Only healthy Saudi students were included. They were asked to fill the EDI and undergo a semi-structured interview by a psychiatrist who was unaware of the EDI scores. Of 146 students approached 12 did not meet our criteria and were excluded; 16 other students were excluded for incomplete responses. RESULTS: The difference between the two diagnostic methods in the proportion of caseness was statistically significantly (P < 0.0001). The scores on Perfectionism, Maturity Fears and Interoceptive Awareness were significantly higher in the Saudi students compared with Canadians (P < 0.05). CONCLUSIONS: The EDI-DT subscale has a sensitivity of 100% and a specificity of 85%. Despite its low positive predictive value of 5%, it may be useful for screening large non-clinical groups for eating disorders.

Adolescent↗

Clinical implications of neuroscience research in PTSD.

The research showing how exposure to extreme stress affects brain function is making important contributions to understanding the nature of traumatic stress. This includes the notion that traumatized individuals are vulnerable to react to sensory information with subcortically initiated responses that are irrelevant, and often harmful, in the present. Reminders of traumatic experiences activate brain regions that support intense emotions, and decrease activation in the central nervous system (CNS) regions involved in (a) the integration of sensory input with motor output, (b) the modulation of physiological arousal, and (c) the capacity to communicate experience in words. Failures of attention and memory in posttraumatic stress disorder (PTSD) interfere with the capacity to engage in the present: traumatized individuals "lose their way in the world." This article discusses the implications of this research by suggesting that effective treatment needs to involve (a) learning to tolerate feelings and sensations by increasing the capacity for interoception, (b) learning to modulate arousal, and (c) learning that after confrontation with physical helplessness it is essential to engage in taking effective action.

Arousal↗

Emotion awareness and identification skills in adolescent girls with bulimia nervosa.

This study examined emotion-identification skills in 19 adolescent girls (M age=16 years, 8 months) diagnosed with a Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM-IV], American Psychiatric Association, 1994) diagnosis of bulimia nervosa or eating disorder not otherwise specified in the bulimic spectrum, 19 age-matched girls with a DSM-IV diagnosis of unipolar depression, and 19 age-matched girls without a mental health history. Findings revealed that girls with bulimia nervosa compared to girls in the depressed and community control groups endorsed significantly greater reluctance to express emotions and inferior interoceptive awareness. Moreover, they exhibited significantly longer latencies to retrieve information regarding their emotional state in self-generated situations. When provided with a list of emotion labels, girls with bulimia endorsed significantly more labels to describe their responses to typical adolescent situations than girls in the control groups.

Adolescent↗

Abnormal forebrain activity in functional bowel disorder patients with chronic pain.

BACKGROUND: Abnormal cortical pain responses in patients with fibromyalgia and conversion disorder raise the possibility of a neurobiologic basis underlying so-called "functional" chronic pain. OBJECTIVE: To use percept-related fMRI to test the hypothesis that patients with a painful functional bowel disorder do not process visceral input or sensations normally or effectively at the cortical level. METHODS: Eleven healthy subjects and nine patients with irritable bowel syndrome (IBS) underwent fMRI during rectal distensions that elicited either a moderate level of urge to defecate or pain. Subjects continuously rated their rectal stimulus-evoked urge or pain sensations during fMRI acquisition. fMRI data were interrogated for activity related to stimulus presence and to specific sensations. RESULTS: In IBS, abnormal responses associated with rectal-evoked sensations were identified in five brain regions. In primary sensory cortex, there were urge-related responses in the IBS but not control group. In the medial thalamus and hippocampus, there were pain-related responses in the IBS but not control group. However, pronounced urge- and pain-related activations were present in the right anterior insula and the right anterior cingulate cortex in the control group but not the IBS group. CONCLUSIONS: Percept-related fMRI revealed abnormal urge- and pain-related forebrain activity during rectal distension in patients with irritable bowel syndrome (IBS). As visceral stimulation evokes pain and triggers unconscious processes related to homeostasis and reflexes, abnormal brain responses in IBS may reflect the sensory symptoms of rectal pain and hypersensitivity, visceromotor dysfunction, and abnormal interoceptive processing.

Adult↗

Pharmacological evidence for the potential of Daucus carota in the management of cognitive dysfunctions.

The present study was aimed at investigating the effects of Daucus carota seeds on cognitive functions, total serum cholesterol levels and brain cholinesterase activity in mice. The ethanolic extract of Daucus carota seeds (DCE) was administered orally in three doses (100, 200, 400 mg/kg) for seven successive days to different groups of young and aged mice. Elevated plus maze and passive avoidance apparatus served as the exteroceptive behavioral models for testing memory. Diazepam-, scopolamine- and ageing-induced amnesia served as the interoceptive behavioral models. DCE (200, 400 mg/kg, p.o.) showed significant improvement in memory scores of young and aged mice. The extent of memory improvement evoked by DCE was 23% at the dose of 200 mg/kg and 35% at the dose of 400 mg/kg in young mice using elevated plus maze. Similarly, significant improvements in memory scores were observed using passive avoidance apparatus and aged mice. Furthermore, DCE reversed the amnesia induced by scopolamine (0.4 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.). Daucus carota extract (200, 400 mg/kg, p.o.) reduced significantly the brain acetylcholinesterase activity and cholesterol levels in young and aged mice. The extent of inhibition of brain cholinesterase activity evoked by DCE at the dose of 400 mg/kg was 22% in young and 19% in aged mice. There was a remarkable reduction in total cholesterol level as well, to the extent of 23% in young and 21% in aged animals with this dose of DCE. Therefore, DCE may prove to be a useful remedy for the management of cognitive dysfunctions on account of its multifarious beneficial effects such as, memory improving property, cholesterol lowering property and anticholinesterase activity.

Acetylcholinesterase↗

Antiamnesic effects of Desmodium gangeticum in mice.

Dementia is a mental disorder characterized by loss of intellectual ability sufficiently severe enough to interfere with one's occupational or social activities. Desmodium gangeticum commonly known as Salparni, is widely used in ayurveda for the treatment of neurological disorders. The present work was designed to assess the potential of aqueous extract of D. gangeticum (DG) as a nootropic agent in mice. DG (50, 100 and 200 mg/kg, p.o.) was administered for 7 successive days to both young and older mice. Exteroceptive behavioral models such as elevated plus maze and passive avoidance paradigm were employed to evaluate learning and memory. Scopolamine (0.4 mg/kg, i.p.) induced amnesia and ageing induced amnesia were the interoceptive behavioral models. To delineate the mechanism by which DG exerts nootropic activity, the effect of DG on whole brain AChE activity was also assessed. Piracetam (200 mg/kg, i.p.) was used as a standard nootropic agent. Pretreatment with DG (50, 100 and 200 mg/kg p.o.) for seven successive days significantly improved learning and memory in mice and reversed the amnesia induced by both, scopolamine (0.4 mg/kg, i.p.) and natural ageing. DG also decreased whole brain acetyl cholinesterase activity. Hence, D. gangeticum appears to be a promising candidate for improving memory and it would be worthwhile to explore the potential of this plant in the management of dementia and Alzheimer disease.

Acetylcholinesterase↗

Behavioral analysis of zopiclone on the basis of their discriminative stimulus properties in the rat.

Zopiclone is a new cyclopyrrolone derivative which exerts pharmacological activities similar to those of benzodiazepines in behavioral and biochemical studies. In order to clarify the discriminative stimulus properties of zopiclone, 8 rats were trained to discriminate the interoceptive stimulus induced by zopiclone (3.2 mg/kg, i.p.) from those of saline. Following discrimination acquisition, administration of zopiclone resulted in drug-appropriate responding with an ED50 of 1.3 (1.0-1.8) mg/kg. The zopiclone discriminative stimulus generalized to the benzodiazepines diazepam (1.8 mg/kg), nitrazepam (10 mg/kg) and alprazolam (10 mg/kg). A non-benzodiazepine, suriclone, at 3.2 mg/kg, generalized to the zopiclone stimulus in 5 out of 7 rats, but meprobamate, hydroxyzine, tracazolate and muscimol did not. The benzodiazepine antagonist Ro 15-1788 (1 mg/kg) completely blocked zopiclone stimulus. In contrast, however, bicuculline and pentetrazol failed to antagonize it. The serotonin antagonist cinanserin and ritanserin neither generalized to the zopiclone stimulus nor did they exhibit antagonism. These results suggest that the zopiclone discriminative stimulus is mediated by binding to benzodiazepine receptors and appears not to be related to GABAergic or serotonergic system.

Animals↗

Ascorbic Acid: a promising memory-enhancer in mice.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by a gradual decline in memory. The occurrence of Alzheimer's disease is commonplace among the Asian population, particularly among senior citizens. The present study was undertaken to assess the potential of ascorbic acid as a memory-enhancer. Swiss mice of either sex were employed in the present investigation. Elevated plus-maze and passive-avoidance apparatus served as the exteroceptive behavioral models, and diazepam-, scopolamine-, and aging-induced amnesia served as the interoceptive behavioral models. Ascorbic acid (60, 120 mg/kg) injected for 3 and 8 consecutive days improved learning and memory of aged mice as indicated by decreased transfer-latency and increased step-down latency. Furthermore, ascorbic acid provided protection to the young animals from scopolamine- and diazepam-induced impairment of memory. Ascorbic acid was found to be more potent than piracetam as reflected by the smaller dose, more pronounced effect, and quicker onset of action. Ascorbic acid has shown promise as a powerful memory-improving agent particularly effective in aged animals. Hence, ascorbic acid might prove to be a useful memory-restorative agent in the treatment of dementia seen in elderly individuals. The underlying mechanism of action of ascorbic acid may be attributed to its antioxidant property.

Aging↗

Eating behavior and the experience of hunger following gastric bypass surgery for morbid obesity.

BACKGROUND: Numerous different factors may contribute to the varying degrees of success observed following gastric bypass surgery. It is likely that alterations in the subjective experiences of hunger and satiety, as well as behavioral factors, are important. Our aim was to investigate the association of several factors, including qualitative aspects of hunger and satiety, eating patterns, and the emotional valence of different foods, to the weight loss that occurred following obesity surgery. METHODS: A questionnaire covering aspects of hunger, eating and satiety was administered to three groups: (1) a group of people who had undergone gastric bypass surgery with an acceptable weight loss; (2) a morbidly obese group of patients prior to their surgical intervention; (3) a group of people of normal weight. RESULTS: There were significant differences amongst the three groups in scoring on standardized eating disorder scales, in the amount they could eat, and in the experience of hunger. The presurgery, waiting-list group was more receptive to food-related than interoceptive cues when deciding to stop eating. 'Eating styles' also differed across the groups. CONCLUSIONS: It is concluded that changes in specific food-related behaviors and other psychological variables interact with the physical restriction to eating. The relative weighting of other variables needs further exploration.

Attitude↗

Involvement of the dorsal striatum in cue-controlled cocaine seeking.

Through association with the interoceptive effects of drugs of abuse, neutral environmental stimuli can gain motivational properties themselves, becoming conditioned reinforcers that can evoke craving and relapse to drug seeking. Nucleus accumbens dopamine (DA) neurotransmission plays an important role in the reinforcing effect of cocaine itself, but, unlike nucleus accumbens glutamate, it seems not to mediate the conditioned reinforcing properties of cocaine-paired stimuli. Dorsal striatal DA transmission, in contrast, has been shown to be enhanced during cocaine seeking under a second-order schedule of reinforcement, which depends on the conditioned reinforcing properties of cocaine-associated stimuli. Therefore, the aim of the present study was to evaluate the role of DA and glutamate transmission in the dorsal striatum in cue-controlled cocaine seeking. Infusion of the DA receptor antagonist alpha-flupenthixol into the dorsal striatum decreased cocaine seeking under a second-order schedule of reinforcement. In addition, intradorsal striatal infusion of the AMPA/kainate (KA) receptor antagonist LY293558 (3SR, 4aRS, 6RS, 8aRS-6-[2-(iH-tetrazol-5-yl)ethyl]-1,2,3,4,4a,5,6,7,8,8a-decahydroiso-quinoline-3-carboxylic acid), but not the NMDA receptor antagonist AP-5, also decreased cue-controlled cocaine seeking. These data show that stimulation of DA and AMPA/KA receptors in the dorsal striatum is critical for well established drug seeking that depends on the reinforcing effects of cocaine-associated stimuli. In addition, given the importance of the dorsal striatum in stimulus-response habit learning, these data suggest that the habitual or compulsive quality of persistent drug seeking depends on dorsal striatal mechanisms.

Animals↗

Glucagon-like peptide 1 excites hypocretin/orexin neurons by direct and indirect mechanisms: implications for viscera-mediated arousal.

Glucagon-like peptide 1 (GLP-1) is produced by neurons in the caudal brainstem that receive sensory information from the gut and project to several hypothalamic regions involved in arousal, interoceptive stress, and energy homeostasis. GLP-1 axons and receptors have been detected in the lateral hypothalamus, where hypocretin neurons are found. The electrophysiological actions of GLP-1 in the CNS have not been studied. Here, we explored the GLP-1 effects on GFP (green fluorescent protein)-expressing hypocretin neurons in mouse hypothalamic slices. GLP-1 receptor agonists depolarized hypocretin neurons and increased their spike frequency; the antagonist exendin (9-39) blocked this depolarization. Direct GLP-1 agonist actions on membrane potential were abolished by choline substitution for extracellular Na+, and dependent on intracellular GDP, suggesting that they were mediated by sodium-dependent conductances in a G-protein-dependent manner. In voltage clamp, the GLP-1 agonist Exn4 (exendin-4) induced an inward current that reversed near -28 mV and persisted in nominally Ca2+-free extracellular solution, consistent with a nonselective cationic conductance. GLP-1 decreased afterhyperpolarization currents. GLP-1 agonists enhanced the frequency of miniature and spontaneous EPSCs with no effect on their amplitude, suggesting presynaptic modulation of glutamate axons innervating hypocretin neurons. Paraventricular hypothalamic neurons were also directly excited by GLP-1 agonists. In contrast, GLP-1 agonists had no detectable effect on neurons that synthesize melanin-concentrating hormone (MCH). Together, our results show that GLP-1 agonists modulate the activity of hypocretin, but not MCH, neurons in the lateral hypothalamus, suggesting a role for GLP-1 in the excitation of the hypothalamic arousal system possibly initiated by activation by viscera sensory input.

Action Potentials↗

Pain encoding in the human forebrain: binary and analog exteroceptive channels.

The neuronal system signaling pain has often been characterized as a labeled line consisting of neurons in the pain-signaling pathway to the brain [spinothalamic tract (STT)] that respond only to painful stimuli. It has been proposed recently that the STT contains a series of analog labeled lines, each signaling a different aspect of the internal state of the body (interoception) (e.g., visceral-cold-itch sensations). In this view, pain is the unpleasant emotion produced by disequilibrium of the internal state. We now show that stimulation of an STT receiving zone in awake humans (66 patients) produces two different responses. The first is a binary response signaling the presence of painful stimuli. The second is an analog response in which nonpainful and painful sensations are graded with intensity of the stimulus. Compared with the second pathway, the first was characterized by higher pain ratings and stimulus-evoked sensations covering more of the body surface (projected fields). Both painful responses to stimulation were described in terms usually applied to external stimuli (exteroception) rather than to internal or emotional phenomena, which were infrequently evoked by stimulation of either pathway. These results are consistent with those of functional imaging studies that have identified brain regions activated in a binary manner by the application of a specific, painful stimulus while increases in stimulus intensity do not produce increased activation. Such binary pain functions could be involved in pain-related alarm-alerting functions, which are independent of stimulus amplitude.

Chronic Disease↗

Anxiogenic effect of disulfiram evaluated in an animal model.

The present experiment was designed to determine whether disulfiram produced an interoceptive discriminative stimulus (IDS) in rats similar to that exhibited by the anxiogenic drug pentylenetetrazol (PTZ). Rats were trained to discriminate PTZ (20 mg/kg IP) from saline, according to an FR10 schedule of food reinforcement. After training criteria had been met, discrimination testing revealed that disulfiram (100 mg/kg, IP) produced a PTZ-like IDS that fully substituted for PTZ 4 hours after injection, decaying to baseline values by the third day. The metabolite of disulfiram, diethyl dithiocarbamate (100 mg/kg, IP), followed much the same temporal pattern, but only showed partial substitution for PTZ. When ethanol (1 g/kg, gavage) or the monoamine oxidase inhibitor pargyline (50 mg/kg, IP) were administered in combination with disulfiram, no significant change of the PTZ-like stimulus was observed. Pargyline (100 mg/kg, IP) or acetaldehyde (200 mg/kg, IP), given alone, did not significantly substitute for PTZ. These data show that disulfiram produces an IDS in rats similar to that produced by other anxiogenic drugs. These data also suggest that the mechanism by which disulfiram produces its anxiogenic effect may not be entirely based upon the disulfiram metabolite diethyl dithiocarbamate, elevated acetaldehyde levels or stimulation of the catecholaminergic system.

Acetaldehyde↗

Self-stimulatory behavior and perceptual reinforcement.

Self-stimulatory behavior is repetitive, stereotyped, functionally autonomous behavior seen in both normal and developmentally disabled populations, yet no satisfactory theory of its development and major characteristics has previously been offered. We present here a detailed hypothesis of the acquisition and maintenance of self-stimulatory behavior, proposing that the behaviors are operant responses whose reinforcers are automatically produced interoceptive and exteroceptive perceptual consequences. The concept of perceptual stimuli and reinforcers, the durability of self-stimulatory behaviors, the sensory extinction effect, the inverse relationship between self-stimulatory and other behaviors, the blocking effect of self-stimulatory behavior on new learning, and response substitution effects are discussed in terms of the hypothesis. Support for the hypothesis from the areas of sensory reinforcement and sensory deprivation is also reviewed. Limitations of major alternative theories are discussed, along with implications of the perceptual reinforcement hypothesis for the treatment of excessive self-stimulatory behavior and for theoretical conceptualizations of functionally related normal and pathological behaviors.

Autistic Disorder↗

Effects of body weight on discriminative-stimulus control by phencyclidine in the pigeon.

Using a color-tracking procedure with responses reinforced under a second-order schedule, the discriminative-stimulus properties of phencyclidine were studied in pigeons maintained at 70%, 80%, or 90% of their free-feeding weights. The generalization curves for phencyclidine were similar at all three body weights. Generalization curves for pentobarbital, d-amphetamine, and saline were also unrelated to body weight. These data suggest that food deprivation may not influence the discriminative-stimulus properties of drugs in the way that it influences the reinforcing-stimulus properties of drugs. The reason may be that during discrimination training interoceptive stimuli resulting from food deprivation do not become conditioned to the stimulus properties of the drug, because the food-deprivation stimuli are paired equally often with the presence and absence of drug stimuli.

Animals↗

Navigation in the Morris swim task as a baseline for drug discrimination: a demonstration with morphine.

A morphine versus saline discrimination was demonstrated using the Morris swim task as the behavioral baseline. The apparatus was a large circular pool filled with water made opaque by floating polypropylene pellets. Rats were placed in the tank in randomly selected locations (12 trials per session) and could escape by swimming to a platform submerged 2 cm below the surface. Morphine (5.6 mg/kg) or saline was injected prior to training sessions. The position of the platform in a given session depended on the drug condition, thus forming the basis for discriminative responding. Three of the 4 rats acquired the discrimination, as evidenced by direct swims to the condition-appropriate platform. Generalization probe sessions were conducted following acquisition. Probe sessions were preceded by injections of morphine (0, 1.0, 3.0, 5.6, or 10.0 mg/kg) and involved placing the rat in the pool for 1 min without a platform. Swim patterns revealed a gradient, with probe swimming more concentrated in the area of the morphine platform position after higher morphine doses. In addition, dose-dependent increases in the likelihood of swimming first to the morphine-associated platform location were obtained. These results illustrate the generality of drug discrimination across different behavioral procedures, and of particular interest with respect to spatial learning, demonstrate interoceptive stimulus control of navigation.

Animals↗

An empirical delineation of the heterogeneity of chronic unexplained fatigue in women.

OBJECTIVES: To test the hypothesis that medically unexplained chronic fatigue and chronic fatigue syndrome (CFS) are heterogeneous conditions, and to define the different conditions using both symptom and laboratory data. METHODS: We studied 159 women from KS, USA. A total of 51 of these suffered from fatigue consistent with established criteria for CFS, 55 had chronic fatigue of insufficient symptoms/severity for a CFS diagnosis and 53 were healthy controls matched by age and body mass index (BMI) against those with CFS. We used principal components analyses to define factors that best described the variable space and to reduce the number of variables. The 38 most explanatory variables were then used in latent class analyses to define discrete subject groups. RESULTS: Principal components analyses defined six discrete factors that explained 40% of the variance. Latent class analyses provided several interpretable solutions with four, five and six classes. The four-class solution was statistically most convincing, but the six-class solution was more interpretable. Class 1 defined 41 (26%) subjects with obesity and relative sleep hypnoea. Class 2 were 38 (24%) healthy subjects. Class 3 captured 24 (15%) obese relatively hypnoeic subjects, but with low heart rate variability and cortisol. Class 4 were 23 (14%) sleep-disturbed and myalgic subjects without obesity or significant depression. The two remaining classes with 22 (14%) and 11 (7%) subjects consisted of the most symptomatic and depressed, but without obesity or hypnoea. Class 5 had normal sleep indices. Class 6 was characterized by disturbed sleep, with low sleep heart rate variability, cortisol, and sex hormones. CONCLUSION: Chronic medically unexplained fatigue is heterogeneous. The putative syndromes were differentiated by obesity, sleep hypnoea, depression, physiological stress response, sleep disturbance, interoception and menopausal status. If these syndromes are externally validated and replicated, they may prove useful in determining the causes, pathophysiology and treatments of CFS.

Adult↗