The role of the dorsolateral prefrontal cortex in the motor placebo effect

Abstract

The neural correlates of the placebo effect in the motor domain are still unknown. The aim of this study was to tackle the role of a frontal cortical region, the dorsolateral prefrontal cortex (dlPFC). To this end, we stimulated the cortical site corresponding to the left dlPFC with transcranial direct current stimulation (tDCS) during a placebo procedure and measured any change in the motor placebo effect in all the participants and more specifically in placebo‐responders. Three different experiments were conducted in which healthy volunteers performed a force motor task with the index finger. The placebo treatment consisted of transcutaneous electrical nerve stimulation (TENS). In Experiment 1 (expectation alone), participants were only verbally suggested about the positive effects of TENS. In Experiment 2 (expectation and conditioning), participants were verbally suggested about TENS and conditioned with a surreptitious increase in a visual feedback of force. In Experiment 3 (control procedure), participants were told that TENS was inefficient. Each participant was tested in three different days with anodal, cathodal and sham tDCS over the dlPFC. Results showed that in Experiment 1 and 2 force increased after the procedure, independently of tDCS. By focusing on placebo‐responders, we found that in Experiment 1 force remained stable after active tDCS, whereas it increased after inactive tDCS. These findings bring new evidence on the neural underpinnings of the motor placebo effect, by showing that independently of the polarity, active tDCS over the left dlPFC may undermine the expectation‐induced enhancement of force in placebo‐responders.

Neuroenhancement of surgeons during robotic suturing

“…This improvement was also retained in 48-h retention tests suggesting positive and lasting neurophysiological impact [ 18 ]. Moreover, recent findings suggest that tDCS applied to the PFC may actually nullify placebo-induced enhancement of motor force [ 59 ]. Dampening down of motor placebo effects through our stimulation protocol provides further evidence to support the validity of the increased KTS being attributable to the application of active tDCS.…”

Context matters: the psychoneurobiological determinants of placebo, nocebo and context-related effects in physiotherapy

“…Emergent studies have suggested a mechanical and neurophysiological mechanism (peripheral, spinal and supraspinal) as the base of the effects induced by the therapeutic interventions adopted by the physiotherapists [35][36][37]. Considering the supraspinal mechanisms, placebo and nocebo effects were indicated as important top-down modulators of patient's symptoms, mainly pain and motor performance [38][39][40][41][42][43][44], thus becoming elements that physiotherapists should attentively consider in their clinical practice [17].…”

The Role of Expectation and Beliefs on the Effects of Non-Invasive Brain Stimulation

“…Using this framework, it is reasonable to hypothesize that subjective expectations could induce a particular brain state that in turn interacts with the effect of the magnetic or electrical stimulation. With respect to this, it is well established that the dorsolateral prefrontal cortex (dlPFC) is involved in elaborating expectations [ 48 , 125 ] and plays a prominent role, together with other brain regions, in the placebo effect [ 48 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 ]. Moreover, this associative brain area is involved in many higher-order cognitive functions, such as working memory [ 134 , 135 ], strategic planning ability [ 136 ], and attention [ 137 ], and plays a significant role in the executive top-down control of behavior [ 138 ].…”