Analysis for distinctive activation patterns of pain and itchy in the human brain cortex measured using near infrared spectroscopy (NIRS)

PLoS One. 2013 Oct 3;8(10):e75360. doi: 10.1371/journal.pone.0075360. eCollection 2013.

Abstract

Pain and itch are closely related sensations, yet qualitatively quite distinct. Despite recent advances in brain imaging techniques, identifying the differences between pain and itch signals in the brain cortex is difficult due to continuous temporal and spatial changes in the signals. The high spatial resolution of positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) has substantially advanced research of pain and itch, but these are uncomfortable because of expensiveness, importability and the limited operation in the shielded room. Here, we used near infrared spectroscopy (NIRS), which has more conventional usability. NIRS can be used to visualize dynamic changes in oxygenated hemoglobin and deoxyhemoglobin concentrations in the capillary networks near activated neural circuits in real-time as well as fMRI. We observed distinct activation patterns in the frontal cortex for acute pain and histamine-induced itch. The prefrontal cortex exhibited a pain-related and itch-related activation pattern of blood flow in each subject. Although it looked as though that activation pattern for pain and itching was different in each subject, further cross correlation analysis of NIRS signals between each channels showed an overall agreement with regard to prefrontal area involvement. As a result, pain-related and itch-related blood flow responses (delayed responses in prefrontal area) were found to be clearly different between pain (τ = +18.7 sec) and itch (τ = +0.63 sec) stimulation. This is the first pilot study to demonstrate the temporal and spatial separation of a pain-induced blood flow and an itch-induced blood flow in human cortex during information processing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cerebral Cortex / metabolism
  • Cerebral Cortex / pathology*
  • Cerebral Cortex / physiopathology*
  • Female
  • Hemoglobins / metabolism
  • Humans
  • Male
  • Nerve Net / pathology
  • Nerve Net / physiopathology
  • Neuroimaging / methods*
  • Oxyhemoglobins / metabolism
  • Pain / metabolism
  • Pain / pathology*
  • Pain / physiopathology*
  • Pruritus / metabolism
  • Pruritus / pathology*
  • Pruritus / physiopathology*
  • Spectrophotometry, Infrared

Substances

  • Hemoglobins
  • Oxyhemoglobins
  • deoxyhemoglobin

Grants and funding

This work was supported by grants from the National Science Council (NSC95-2314-B-037-024, NSC96-2314-B-037-043 and NSC97-2320-B-010-013-MY3); National Health Research Institute (NHRI-EO-096-PP-11; NHRI CN-PD-9611P); Kaohsiung Medical University (KMU)(KMU-QA096005); and KMU Center of Excellence for Environmental Medicine (98.2b). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.