The second exteroceptive suppression is affected by psychophysiological factors

The effect of experimental emotion induction on experimental pain: a systematic review and meta-analysis

ABSTRACT

The idea that emotions can influence pain is generally recognized. However, a synthesis of the numerous individual experimental studies on this subject is lacking. The aim of the present systematic review and meta-analysis was to synthesize the existing evidence on the effect of experimental emotion induction on experimental pain in nonclinical adults. PsycInfo and PubMed were searched up until April 10, 2023, for studies assessing differences in self-reported pain between emotion induction groups and/or control groups or between conditions within group. Risk of bias was assessed for the individual studies. The literature search yielded 78 relevant records of 71 independent studies. When compared with control conditions, the pooled results revealed a statistically significant pain-attenuating effect of positive emotion induction (between-group: Hedges g = -0.48, 95% CI: -0.72; -0.25, K = 9; within-group: g = -0.24, 95% CI: -0.32; -0.15, K = 40), and a statistically significant pain-exacerbating effect of negative emotion induction in within-group analyses but not between-group analyses (between-group: g = -0.29, 95% CI: -0.66; 0.07, K = 10; within-group: g = 0.14, 95% CI: 0.06; 0.23, K = 39). Bayesian meta-analysis provided strong support for an effect of positive emotion induction but weak support for an effect of negative emotion induction. Taken together, the findings indicate a pain-attenuating effect of positive emotion induction, while the findings for negative emotion induction are less clear. The findings are discussed with reference to theoretical work emphasizing the role of motivational systems and distraction for pain. Limitations include considerable heterogeneity across studies limiting the generalizability of the findings.

Responses to External Emotions or their Transitions at Central to Peripheral Nervous System Levels: A Methodological Contribution to Mental Health

Background:

Responses to external emotional-stimuli or their transitions might help to elucidate the scientific background and assist the clinical management of psychiatric problems, but pure emotional-materials and their utilization at different levels of neurophysiological processing are few.

Objective:

We aimed to describe the responses at central and peripheral levels in healthy volunteers and psychiatric patients when facing external emotions and their transitions.

Methods:

Using pictures and sounds with pure emotions of Disgust, Erotica, Fear, Happiness, Neutral, and Sadness or their transitions as stimuli, we have developed a series of non-invasive techniques, i.e., the event-related potentials, functional magnetic resonance imaging, excitatory and inhibitory brainstem reflexes, and polygraph, to assess different levels of neurophysiological responses in different populations.

Results:

Sample outcomes on various conditions were specific and distinguishable at cortical to peripheral levels in bipolar I and II disorder patients compared to healthy volunteers.

Conclusions:

Methodologically, designs with these pure emotions and their transitions are applicable, and results per se are specifically interpretable in patients with emotion-related problems.

Inhibitory brainstem reflexes under external emotional-stimuli in bipolar I and II disorders

BACKGROUND

Bipolar disorder types I (BD I) and II (BD II) might present different dysfunctions of the cortex and brainstem, as reflected by the second exteroceptive suppression period of temporalis muscle activity (ES2) under different stimuli of external emotions.

METHODS

This study included 30 BD I and 20 BD II patients, and 40 healthy volunteers. All participants were invited to answer the Mood Disorder Questionnaire, the Hypomania Checklist-32, and the Plutchik-van Praag Depression inventory, as well as to undergo the ES2 test under external emotional-stimuli (emotional pictures plus sounds) of Disgust, Erotica, Fear, Happiness, and Sadness.

RESULTS

The scale scores were elevated in both patient groups, but were not correlated with ES2 parameters. Compared to healthy controls, BD I showed prolonged ES2 latency under Erotica, and their perceived happiness and sadness intensities were negatively correlated with the respective ES2 durations, while BD II showed prolonged ES2 latencies under Disgust and Happiness, and shortened ES2 durations under Disgust, Happiness and Sadness. Moreover, ES2 duration under Sadness was significantly shorter in BD II than that in BD I.

CONCLUSIONS

The cortico-brainstem inhibitory dysfunctions in BD I and BD II was different, and this difference was independent of the patient's ongoing emotions. Our study thus provides some hints to distinguish the two types of bipolar disorders.

Study of exteroceptive suppression of voluntary muscular activity in healthy volunteers and patients with paroxysmal neuropathic pain

The exteroceptive suppression of voluntary electromyographic activity of the masseter and temporal muscles was studied in healthy volunteers and patients with paroxysmal neuropathic pain (trigeminal neuralgia). The latent period of the exteroceptive suppression was prolonged and the duration of its late fragment was shortened in the patients in comparison with normal subjects. A short exteroceptive suppression period in patients with trigeminal neuralgia reflected deficient activity of inhibitory interneurons of the reflector loop and excessive activity of the antinociceptive system of the brain stem, while prolongation of the latent period reflected prolongation of inhibitory interneurons activation. A direct correlation between the degree of changes in the exteroceptive suppression parameters and pain intensity, evaluated by the patients by the visual analog scale, was detected.

Iatrogenic damage to the mandibular nerves as assessed by the masseter inhibitory reflex

Iatrogenic injury of the inferior alveolar or lingual nerves frequently leads to legal actions for damage and compensation for personal suffering. The masseter inhibitory reflex (MIR) is the most used neurophysiological tool for the functional assessment of the trigeminal mandibular division. Aiming at measuring the MIR sensitivity and specificity, we recorded this reflex after mental and tongue stimulations in a controlled, blinded study in 160 consecutive patients with sensory disturbances following dental procedures. The MIR latency was longer on the affected than the contralateral side (P < 0.0001). The overall specificity and sensitivity were 99 and 51%. Our findings indicate that MIR testing, showing an almost absolute specificity, reliably demonstrates nerve damage beyond doubt, whereas the relatively low sensitivity makes the finding of a normal MIR by no means sufficient to exclude nerve damage. Probably, the dysfunction of a small number of nerve fibres, insufficient to produce a MIR abnormality, may still engender important sensory disturbances. We propose that MIR testing, when used for legal purposes, be considered reliable in one direction only, i.e. abnormality does prove nerve damage, normality does not disprove it.