Date Published: September 22, 2014
Publisher: Public Library of Science
Author(s): Hocine Slimani, Sabrina Danti, Maurice Ptito, Ron Kupers, Matthew Longo.
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.
In a recent study we showed that congenitally blind individuals have reduced thresholds to heat and cold pain, and rate supra-threshold nociceptive stimuli as more painful compared to normally sighted individuals . In sharp contrast, thresholds for innocuous cold and warmth perception were not altered, suggesting a specific effect for noxious thermal processing. These results add to a growing body of evidence that vision may affect pain processing –. The purpose of this study is to examine whether the loss of vision later in life also causes a hypersensitivity to pain.
The purpose of the present study was to investigate if individuals with acquired blindness show thermal hypersensitivity to noxious thermal stimulation as previously reported in congenital blindness . In contrast with our hypothesis, late blind and sighted participants showed similar heat and cold pain thresholds and supra-threshold pain ratings. This indicates that onset of blindness, and not blindness per se, is the driving factor of thermal pain hypersensitivity in individuals lacking vision.