Placebo effects induced by auditory cues decrease parkinsonian rigidity in patients with subthalamic stimulation

• We analyzed parkinsonian rigidity in patients treated with deep brain stimulation.
• We evaluated conditioned auditory cues as triggers of placebo effects.
• We measured viscoelastic stiffness as an indicator of rigidity.
• The values of viscoelastic stiffness decreased due to placebo effect.
• Simple auditory cues can affect the clinical status due to placebo effect.

Placebo effects are the consequence of an interaction between an organism and its surroundings and may be influenced by cues from the environment. Our study was designed to analyze if conditioned auditory cues could trigger placebo effects and affect parkinsonian rigidity as measured by viscoelastic properties of skeletal muscles in patients treated with subthalamic stimulation. We found that after repeatedly associating with the effect of deep brain stimulation on rigidity, a common dial phone signal itself was able to reduce the mean values of viscoelastic stiffness in the placebo stage (368.8 ± 50.4 N m−1) as compared to the stimulation-off conditions (383.7 ± 61.2 N m−1) (q = 4.18; p < 0.05) in ten patients with Parkinson’s disease. Thus, it appears that due to associative learning processes environmental cues can acquire the capacity to trigger placebo effects affecting the clinical status of the patients.