No perceptual prioritization of non-nociceptive vibrotactile and visual stimuli presented on a sensitized body part

Abstract

High frequency electrical conditioning stimulation (HFS) is an experimental method to induce increased mechanical pinprick sensitivity in the unconditioned surrounding skin (secondary hyperalgesia). Secondary hyperalgesia is thought to be the result of central sensitization, i.e. increased responsiveness of nociceptive neurons in the central nervous system. Vibrotactile and visual stimuli presented in the area of secondary hyperalgesia also elicit enhanced brain responses, a finding that cannot be explained by central sensitization as it is currently defined. HFS may recruit attentional processes, which in turn affect the processing of all stimuli. In this study we have investigated whether HFS induces perceptual biases towards stimuli presented onto the sensitized arm by using Temporal Order Judgment (TOJ) tasks. In TOJ tasks, stimuli are presented in rapid succession on either arm, and participants have to indicate their perceived order. In case of a perceptual bias, the stimuli presented on the attended side are systematically reported as occurring first. Participants performed a tactile and a visual TOJ task before and after HFS. Analyses of participants’ performance did not reveal any prioritization of the visual and tactile stimuli presented onto the sensitized arm. Our results provide therefore no evidence for a perceptual bias towards tactile and visual stimuli presented onto the sensitized arm.

No evidence of widespread mechanical pressure hyperalgesia after experimentally induced central sensitization through skin nociceptors

“…We used this scale because in previous studies, pinprick stimuli delivered with a force of 128 mN were on average not perceived as painful at baseline, but in some cases became painful after HFS. 8,23,31,32 The present scale allows for the quantification of sensations changing from being nonpainful to being painful. To avoid sensitization of the stimulated skin, the pinprick stimulus was not applied twice on the same location.…”

Use-Dependent Plasticity Enhances Nociceptive and Non-Nociceptive Somatosensory Cortical Responses in Healthy Individuals

“…The underlying mechanisms following sustained nociceptive HFS have been associated with long-term potentiation (LTP) of excitatory synaptic transmission, a key feature for improving signal processing and sensory transmission (Froemke et al, 2013), between peripheral nociceptive fibers within dorsal horn neurons projecting to the parabrachial area in the brainstem (Ikeda et al, 2003). In addition, sustained nociceptive HFS can also enhance the non-nociceptive evoked N100 peak amplitude (the negative peak recorded between 100–200 ms and equivalent to N140 and N200) in response to vibrotactile (van den Broeke and Mouraux, 2014) and visual stimulation (Torta et al, 2018, 2017), suggesting that sustained nociceptive stimulation may also engage LTP mechanisms in supra-spinal multisensory areas, such as the insula and ACC (Zhuo, 2014).…”

High cognitive load may prevent the development of nociceptive hypersensitivity

“…Sixty-four healthy participants were enrolled; four stopped during the sensitization procedure due to unbearable pain (two in experiment 1 and 2 in experiment 2). The final sample was composed of sixty participants: Twenty took part in experiment 1, (14 women, 6 men; median age 22 years, range 19-37), 19 in experiment 2 (15 women, 4 men; median age 22 years, range 18-40), 20 in experiment 3 (10 women, 11 men; median age 26, range [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. None of the participants took part in more than one experiment.…”

“…Indeed, albeit to a lesser extent, an enhancement in the magnitude of cortical potentials in response to stimuli presented on the sensitized arm has been also observed for visual stimuli [27], and changes in brain responses are uncorrelated with the changes in pain reports [1]. Currently, it remains unclear which processes lead to an increase in the magnitude of the brain response after HFS and capsaicin [25,32,33,35]. A previous study [25] investigated whether sensitization procedures (HFS in that case) would increase attentional allocation towards the sensitized arm, thereby resulting in a prioritization of stimuli presented on the sensitized arm over those presented on the control arm.…”

“…Currently, it remains unclear which processes lead to an increase in the magnitude of the brain response after HFS and capsaicin [25,32,33,35]. A previous study [25] investigated whether sensitization procedures (HFS in that case) would increase attentional allocation towards the sensitized arm, thereby resulting in a prioritization of stimuli presented on the sensitized arm over those presented on the control arm.…”