The Relationship Between Emotion Processing and Flexor Afferent Responses in Upper Limbs

Background: This study investigates the influence of emotional processing on flexor reflex responses in the upper limbs, focusing on cutaneomuscular reflexes (CMRs) and the cutaneous silent period (CSP) in patients with chronic neuropathic pain. The modulation of motor reflexes by emotions remains unclear. Methods: Fifty-one patients with chronic upper limb neuropathic pain (carpal tunnel syndrome, other neuropathies, post-burn hypertrophic scars) and twenty healthy controls underwent standardized electrodiagnostic signal acquisition. Neurophysiological assessments (CMRs, CSP, standard nerve conduction tests) and psychological evaluations (anxiety, depression, emotion processing) were conducted. Neurophysiological signal acquisition included median and ulnar nerve conduction studies recorded with an electrodiagnostic system (48 kHz sampling rate; 30-3000 Hz bandpass). CSP and CMRs were recorded from the abductor pollicis brevis using surface electrodes (bipolar belly-tendon montage) and were evoked by electrical stimulation delivered through ring electrodes, with individualized perceptual-threshold calibration. Statistical analyses examined correlations between neurophysiological and psychological measures. Results: Patients showed significantly longer duration and higher intensity of CMRs and CSP than controls (p < 0.01). CMR and CSP durations correlated positively with anxiety, depression, and alexithymia scores, and negatively with facial emotion recognition. General Linear Model analyses indicated these relations were mediated by tactile and pain perception thresholds. Conclusions: The findings support that spinal reflex responses in the upper limbs are modulated by emotional and cognitive-affective processes, especially in chronic pain contexts. This highlights the complex interaction between emotion regulation and motor control in neuropathic pain conditions.