title: Effects of face/head and whole body cooling during passive heat stress on human somatosensory processing.
abstract: We herein investigated the effects of face/head and whole body cooling during passive heat stress on human somatosensory processing recorded by somatosensory-evoked potentials (SEPs) at C4' and Fz electrodes. Fourteen healthy subjects received a median nerve stimulation at the left wrist. SEPs were recorded at normothermic baseline (Rest), when esophageal temperature had increased by ~1.2°C (heat stress: HS) during passive heating, face/head cooling during passive heating (face/head cooling: FHC), and after HS (whole body cooling: WBC). The latencies and amplitudes of P14, N20, P25, N35, P45, and N60 at C4' and P14, N18, P22, and N30 at Fz were evaluated. Latency indicated speed of the subcortical and cortical somatosensory processing, while amplitude reflected the strength of neural activity. Blood flow in the internal and common carotid arteries (ICA and CCA, respectively) and psychological comfort were recorded in each session. Increases in esophageal temperature due to HS significantly decreased the amplitude of N60, psychological comfort, and ICA blood flow in the HS session, and also shortened the latencies of SEPs (all,P< 0.05). While esophageal temperature remained elevated, FHC recovered the peak amplitude of N60, psychological comfort, and ICA blood flow toward preheat baseline levels as well as WBC. However, the latencies of SEPs did not recover in the FHC and WBC sessions. These results suggest that impaired neural activity in cortical somatosensory processing during passive HS was recovered by FHC, whereas conduction velocity in the ascending somatosensory input was accelerated by increases in body temperature.
authors.affiliation: Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University, Nara, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakata
authors.affiliation: Graduate School of Humanities and Sciences, Nara Women's University, Nara, Japan; and.
authors.forename: Mari
authors.initials: M
authors.lastname: Namba
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
authors.affiliation: Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University, Nara, Japan; shiba@cc.nara-wu.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Shibasaki
mesh_terms: D001783:Blood Flow Velocity; D001833:Body Temperature Regulation; D002343:Carotid Artery, Internal / Q000503:physiopathology; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory; D005145:Face; D006257:Head; D064368:Healthy Volunteers; D018882:Heat Stress Disorders / Q000503:physiopathology* / Q000523:psychology; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D009431:Neural Conduction; D011930:Reaction Time; D012039:Regional Blood Flow; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: central fatigue; conduction velocity; hyperthermia; somatosensory-evoked potentials; tactile