Measurement of magnesium absorption in man using stable 26MG as a tracer

The stable isotope ²⁶Mg was compared to the radioisotope ²⁸Mg to estimate magnesium absorption in four healthy male subjects confined to a metabolic ward and consuming a constant diet for 146 days. Two isotopes tests were carried out in each subject on days 66 and 109 of the constant-diet period. In test 1, a solution containing 50 mg ²⁶Mg and 30 μC ²⁸Mg were taken orally during breakfast. In test 2, 50 mg ²⁶Mg were administered orally followed three hours later by an i.v. injection of 20 μC ²⁸Mg.True magnesium absorption was estimated by: (1) oral/i.v. ratios of ²⁸Mg in plasma and urine, or oral/i.v. ²⁶Mg/²⁸Mg ratios in urine; (2) the difference between intake and fecal excretion of total dietary magnesium over a period of 10 days, or of a single dose of either isotope, corrected for endogenous fecal magnesium. Estimates made in individual subjects by different procedures based on data derived solely by use of ²⁸Mg varied as much as estimates made by comparable procedures with data derived from either ²⁶Mg or ²⁸Mg. Measurements of ²⁶Mg enrichment in urine and feces were made by neutron activation analysis which loses precision at enrichment levels below 10% above natural abundance. With the doses used in this investigation only fecal samples collected within 3–4 days and urine samples taken wihin 2–24 h contained adequately detectable ²⁶Mg enrichment levels. Despite this limitation, ²⁶Mg significantly expands the scope of investigation of magnesium absorption in man beyond that possible with the short lived ²⁸Mg alone.     

Alteration in the response properties of primary somatosensory cortex related to differential aversive Pavlovian conditioning

The effects of differential aversive Pavlovian conditioning on the functional organization of primary somatosensory cortex (SI) were examined in 17 healthy participants. Neuroelectric source imaging from 60 electrodes was employed while nine subjects received an innocuous electric stimulus (conditioned stimulus, CS) to one finger (left or right) that was followed by painful electric shock to the lower back (unconditioned stimulus, US) and an innocuous stimulus to the other finger that was never followed by pain. Eight subjects received a presentation of the innocuous and painful stimuli with equal probability to both fingers (control group). The data included the electromyogram (EMG) from the left m. corrugator, and judgments of intensity, aversiveness, and CS-US contingency. Only the experimental group displayed EMG conditioning, differential contingency judgments, as well as a change of dipole orientation for the CS and an enhanced dipole moment for the US in the electroencephalogram. Intensity and unpleasantness ratings were altered in a more unspecific manner and did not differ between groups and stimulus conditions. The data suggest that SI contributes to memory processes in associative learning. Pavlovian conditioning of tactile responses might be important in the altered processing of painful stimuli in chronic pain patients where enhanced conditioning has been demonstrated.     

Elasticity of the smallest noncapillary pulmonary blood vessels in the cat

We have previously described the compliance behavior of the pulmonary interalveolar capillary blood vessels in the cat and now characterize the compliance coefficient of the pulmonary arterioles and venules less than 50 μm in diameter in that species. These observations are unclassified with respect to arterioles and venules. Our method of silicone rubber microvascular casting under 0 to 23.75 cm H₂O pressures was used and diameter measurements were made from histological slides. Since the exact position of the vessels in branching hierarchy was not known, we called these vessels juxta-alveolar. The diameters of the smallest noncapillary blood vessels were measured and were analyzed by extreme-value statistics. We obtain a compliance coefficient, α, of 0.274 μm/cm H₂O over the pressure range measured, and a mean diameter of 14.5 μm for the smallest noncapillary blood vessels, 0Δp. These vessels are compliant.     

To gamble or not to gamble: at risk for craving and relapse--learned motivated attention in pathological gambling

In recent research similarities between pathological gambling and drug addiction have been identified, suggesting excessive gambling to constitute an addiction. So far, we have insufficient knowledge concerning the psychophysiological mechanisms underlying this kind of non-substance-related addiction. The objective of the study was to investigate emotional processing of gambling-relevant and -irrelevant stimuli in pathological gamblers and non-gambling controls using an EEG cue-reactivity paradigm. Whereas gambling-irrelevant stimuli were processed similarly in non-gambling controls (HC) and pathological gamblers (PG), PG showed significantly stronger gambling-relevant stimulus-induced psychophysiological cue-reactivity (larger gambling stimulus-induced late positive potential, LPP, higher arousal and more positively toned valence ratings as well as higher stimulus-induced craving for gambling cues compared to HC - but not the expectable increase of general craving over time and after stimulus presentation). Our findings suggest enhanced cue-reactivity in pathological gamblers indicative of learned motivated attention that may induce subjective craving and relapse.     

Effects of different viewing perspectives on somatosensory activations during observation of touch

Previous studies showed that neurons in the monkey premotor cortex became active when performing a particular action and also when observing the same action performed by others. These findings suggest a mirror system for action observation. Recently, bimodal neurons, sensitive both to visual and tactile stimulation, were reported in the parietal cortex, suggesting a potential mirror neuron system for observing and experiencing tactile stimulation. Subsequently, a mirror neuron system for observed touch has been suggested. The current study was designed to determine whether the activation of a sensory mirror system during touch observation is affected by possible attributions of the observed touch to oneself (subjective view) or to somebody else (objective view). In the study, healthy volunteers observed video clips of a touched or nontouched hand either in an egocentric or in an allocentric perspective during functional magnetic resonance imaging. Results showed activation of somatosensory cortices when observing the hand being touched in egocentric as well as in the allocentric perspectives. Moreover, somatosensory responses differed depending on the perspective of the observed touch. We discuss the results in terms of a possible mirror neuron system for observed and experienced touch. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.     

Emotional learning during dissociative states in borderline personality disorder

Background

Neurobiological findings and clinical data suggest that dissociative experience inhibits conditioning processes, but experimental studies are lacking. The aim of our study was to determine whether high states of dissociative experience would specifically alter emotional learning, but not declarative knowledge.

Methods

We used an aversive differential delay conditioning procedure in 33 unmedicated patients with borderline personality disorder (BPD) and 35 healthy controls.

Results

Patients with BPD who had high state dissociative experiences (BPD D+) showed diminished acquisition of differential aversive delay conditioning with respect to emotional learning compared with those who did not experience dissociative symptoms (BPD D−) and healthy controls (skin conductance response; interaction dissociation × quadratic time × type, p = 0.009). Specifically, the control group and the BPD D− subgroup showed an increase in valence and arousal to the conditioned stimulus (CS+) during the conditioning procedure (all p < 0.012) and demonstrated differential skin conductance responses in the acquisition and extinction phases. In contrast, the BPD D+ subgroup showed no increase in valence and arousal to CS+ or differential response regarding skin conductance. We examined general psychopathology, trauma history, perceptual differences and posttraumatic stress disorder as confounding factors, but we found no evidence of bias.

Limitations

Subdividing the BPD group reduced power. In addition, because our sample included only women, the generalizability of our results is constrained. Furthermore, we performed no separate analysis of the influence of different aspects of dissociation on the learning process.

Conclusion

Emotional, amygdala-based learning processes seem to be inhibited during state dissociative experience. State dissociative experience may alter acquisition and extinction processes and should be closely monitored in exposure-based psychotherapy.     

Context conditioning and extinction in humans: differential contribution of the hippocampus, amygdala and prefrontal cortex

Functional magnetic resonance imaging was used to investigate the role of the hippocampus, amygdala and medial prefrontal cortex (mPFC) in a contextual conditioning and extinction paradigm provoking anxiety. Twenty-one healthy persons participated in a differential context conditioning procedure with two different background colours as contexts. During acquisition increased activity to the conditioned stimulus (CS+) relative to the CS− was found in the left hippocampus and anterior cingulate cortex (ACC). The amygdala, insula and inferior frontal cortex were differentially active during late acquisition. Extinction was accompanied by enhanced activation to CS+ vs. CS− in the dorsal anterior cingulate cortex (dACC). The results are in accordance with animal studies and provide evidence for the important role of the hippocampus in contextual learning in humans. Connectivity analyses revealed correlated activity between the left posterior hippocampus and dACC (BA32) during early acquisition and the dACC, left posterior hippocampus and right amygdala during extinction. These data are consistent with theoretical models that propose an inhibitory effect of the mPFC on the amygdala. The interaction of the mPFC with the hippocampus may reflect the context-specificity of extinction learning.     

Psychophysiological responses to drug-associated stimuli in chronic heavy cannabis use

Due to learning processes originally neutral stimuli become drug-associated and can activate an implicit drug memory, which leads to a conditioned arousing 'drug-seeking' state. This condition is accompanied by specific psychophysiological responses. The goal of the present study was the analysis of changes in cortical and peripheral reactivity to cannabis as well as alcohol-associated pictures compared with emotionally significant drug-unrelated and neutral pictures in long-term heavy cannabis users. Participants were 15 chronic heavy cannabis users and 15 healthy controls. Verbal reports as well as event-related potentials of the electroencephalogram and skin conductance responses were assessed in a cue-reactivity paradigm to determine the psychophysiological effects caused by drug-related visual stimulus material. The evaluation of self-reported craving and emotional processing showed that cannabis stimuli were perceived as more arousing and pleasant and elicited significantly more cannabis craving in cannabis users than in healthy controls. Cannabis users also demonstrated higher cannabis stimulus-induced arousal, as indicated by significantly increased skin conductance and a larger late positivity of the visual event-related brain potential. These findings support the assumption that drug-associated stimuli acquire increased incentive salience in addiction history and induce conditioned physiological patterns, which lead to craving and potentially to drug intake. The potency of visual drug-associated cues to capture attention and to activate drug-specific memory traces and accompanying physiological symptoms embedded in a cycle of abstinence and relapse – even in a 'so-called' soft drug – was assessed for the first time.     

Responder criteria for operant and cognitive-behavioral treatment of fibromyalgia syndrome

OBJECTIVE: To predict the effects of cognitive-behavioral therapy (CBT) and operant-behavioral therapy (OBT) in fibromyalgia syndrome (FMS). METHODS: A total of 125 patients who fulfilled the American College of Rheumatology FMS criteria were randomly assigned to CBT (n = 42), OBT (n = 43), or attention placebo (AP; n = 40). The pretreatment to 12-month followup reliability change index was used to determine clinically meaningful changes in pain intensity and physical impairment. Multinominal logistic regression analyses were used to determine the predictors of improvement in pain intensity and physical impairment for the entire sample. Analyses of variance were computed to compare the characteristics of responders and nonresponders in each of the 3 interventions. RESULTS: At the 12-month followup, 53.5%, 45.2%, and 5% of patients in the OBT, CBT, and AP groups, respectively, reported clinically meaningful improvements in pain intensity. Similarly, 58.1%, 38.1%, and 7.5% of patients treated with OBT, CBT, and AP, respectively, reported clinically significant improvements in physical impairment. Prior to treatment, the OBT physical impairment responders displayed significantly more pain behaviors, physical impairment, physician visits, solicitous spouse behaviors, and level of catastrophizing compared with nonresponders. The CBT physical impairment responders, compared with nonresponders, reported higher levels of affective distress, lower coping, less solicitous spouse behavior, and lower pain behaviors. CONCLUSION: The results of this study suggest that pretreatment patient characteristics are important predictors of treatment response and may serve as a basis for matching treatments to patient characteristics. Prospective outcome studies are needed to confirm whether the tailoring of treatment actually leads to better outcomes for patients with FMS.