Pain Perception Is Increased in Congenital but Not Late Onset Blindness

Abstract

There is now ample evidence that blind individuals outperform sighted individuals in various tasks involving the non-visual senses. In line with these results, we recently showed that visual deprivation from birth leads to an increased sensitivity to pain. As many studies have shown that congenitally and late blind individuals show differences in their degree of compensatory plasticity, we here address the question whether late blind individuals also show hypersensitivity to nociceptive stimulation. We therefore compared pain thresholds and responses to supra-threshold nociceptive stimuli in congenitally blind, late blind and normally sighted volunteers. Participants also filled in questionnaires measuring attention and anxiety towards pain in everyday life. Results show that late blind participants have pain thresholds and ratings of supra-threshold heat nociceptive stimuli similar to the normally sighted, whereas congenitally blind participants are hypersensitive to nociceptive thermal stimuli. Furthermore, results of the pain questionnaires did not allow to discriminate late blind from normal sighted participants, whereas congenitally blind individuals had a different pattern of responses. Taken together, these results suggest that enhanced sensitivity to pain following visual deprivation is likely due to neuroplastic changes related to the early loss of vision.

Enhanced heat discrimination in congenital blindness

“…We propose that blind individuals have learned to better use these thermal cues in order to prevent thermal injuries. This is supported by our recent findings that congenitally blind individuals are hypersensitive to thermal pain [18,19]. The same studies, however, indicated that thresholds for innocuous thermal perception in congenitally blind and sighted participants were not different.…”

“…Since we tested the volar forearm, a body region that is unlikely being used extensively by the blind in temperature discrimination tasks, it seems rather unlikely that our results are due to training-induced plasticity. Alternatively, the increased thermal sensitivity in congenital blindness might be explained by their hypersensitivity to nociceptive stimulation [18,19]. Indeed, a more efficient computing of rapid temperature raises will help in avoiding possible encounters with noxious thermal stimuli.…”

“…Therefore, a rapid increase in temperature, even within the innocuous range, can be encoded as dangerous. Since congenitally blind individuals have lower heat pain thresholds compared to the sighted [18,19], they may be more attentive to temperature shifts that may be indicative for an impeding painful stimulus.…”

Viewing the body modulates both pain sensations and pain responses

“…While our findings demonstrate that viewing the body can increase reported pain levels, other studies have shown that a complete absence of visual experience also increases perceived pain intensity. The congenitally blind have lower pain thresholds and give higher pain ratings to noxious thermal stimuli than the normally sighted and those with late-onset blindness (Slimani et al 2013 , 2014 ). Early visual deprivation induces structural and functional changes in neural organization which may underlie the heightened pain experiences of the congenitally blind.…”

Testing the exteroceptive function of nociception: the role of visual experience in shaping the spatial representations of nociceptive inputs

“…This would lead to qualitatively different ways of processing threatening information and perceiving pain. Accordingly, several studies have assumed that early blind people might display differences in their sensitivity to pain as compared to normally sighted individuals (Slimani, Danti, Ptito, & Kupers, 2014;Slimani, Ptito, & Kupers, 2015). However, further reports suggested that hypersensitivity to pain in early blindness might be restricted to changes in the processing of C-fibre inputs (Slimani, Plaghki, Ptito, & Kupers, 2016) and would be related to differences in anxiety levels and attention between blind and sighted participants (Holten-Rossing, Slimani, Ptito, Danti, & Kupers, 2018).…”