title: Adaptation of cortical activity to sustained pressure stimulation on the fingertip.
abstract: BACKGROUND
  Tactile adaptation is a phenomenon of the sensory system that results in temporal desensitization after an exposure to sustained or repetitive tactile stimuli. Previous studies reported psychophysical and physiological adaptation where perceived intensity and mechanoreceptive afferent signals exponentially decreased during tactile adaptation. Along with these studies, we hypothesized that somatosensory cortical activity in the human brain also exponentially decreased during tactile adaptation. The present neuroimaging study specifically investigated temporal changes in the human cortical responses to sustained pressure stimuli mediated by slow-adapting type I afferents.
  
  
  METHODS
  We applied pressure stimulation for up to 15 s to the right index fingertip in 21 healthy participants and acquired functional magnetic resonance imaging (fMRI) data using a 3T MRI system. We analyzed cortical responses in terms of the degrees of cortical activation and inter-regional connectivity during sustained pressure stimulation.
  
  
  RESULTS
  Our results revealed that the degrees of activation in the contralateral primary and secondary somatosensory cortices exponentially decreased over time and that intra- and inter-hemispheric inter-regional functional connectivity over the regions associated with tactile perception also linearly decreased or increased over time, during pressure stimulation.
  
  
  CONCLUSIONS
  These results indicate that cortical activity dynamically adapts to sustained pressure stimulation mediated by SA-I afferents, involving changes in the degrees of activation on the cortical regions for tactile perception as well as in inter-regional functional connectivity among them. We speculate that these adaptive cortical activity may represent an efficient cortical processing of tactile information.
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Anam-5ga, Seongbuk-gu, Seoul, 136-713, Republic of Korea. uskeywest@korea.ac.kr.
authors.forename: Yoon Gi
authors.initials: YG
authors.lastname: Chung
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Anam-5ga, Seongbuk-gu, Seoul, 136-713, Republic of Korea. realhsw@korea.ac.kr.
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Han
authors.affiliation: Department of Biomedical Engineering, BK21+ Research Institute of Biomedical Engineering, College of Biomedical & Health Science, Konkuk University, Chungju, 380-701, Republic of Korea. hskim98@kku.ac.kr.
authors.forename: Hyung-Sik
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Biomedical Engineering, BK21+ Research Institute of Biomedical Engineering, College of Biomedical & Health Science, Konkuk University, Chungju, 380-701, Republic of Korea. scchung@kku.ac.kr.
authors.forename: Soon-Cheol
authors.initials: SC
authors.lastname: Chung
authors.affiliation: Center for Neuroscience Imaging Research, Institute of Basic Science (IBS), Sungkyunkwan University, Suwon, 440-746, Republic of Korea. jyparu@skku.edu.|Department of Global Biomedical Engineering, Sungkyunkwan University, Suwon, 440-746, Republic of Korea. jyparu@skku.edu.
authors.forename: Jang-Yeon
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Anam-5ga, Seongbuk-gu, Seoul, 136-713, Republic of Korea. wallraven@korea.ac.kr.
authors.forename: Christian
authors.initials: C
authors.lastname: Wallraven
authors.affiliation: Department of Human and Systems Engineering, Ulsan National Institute of Science and Technology, UNIST-gil 50, Ulsan, 689-798, Republic of Korea. spkim@unist.ac.kr.
authors.forename: Sung-Phil
authors.initials: SP
authors.lastname: Kim
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D005385:Fingers / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013003:Somatosensory Cortex / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult