title: Effects of passive heat stress on human somatosensory processing.
abstract: Herein, we investigated the effects of passive heat stress on human somatosensory processing recorded by somatosensory-evoked potentials (SEPs). Fifteen healthy subjects received a median nerve stimulation at the left wrist under two thermal conditions: Heat Stress and normothermic Time Control. The latencies and amplitudes of P14, N20, P25, N35, P45, and N60 at C4' and P14, N18, P22, and N30 at Fz were evaluated. Under the Heat Stress condition, SEPs were recorded at normothermic baseline (1st), early in heat stress (2nd), when esophageal temperature had increased by ~1.0°C (3rd) and ~2.0°C (4th), and after heat stress (5th). In the Time Control condition, SEPs were measured at the same time intervals as those in the Heat Stress condition. The peak latencies and amplitudes of SEPs did not change early in heat stress. However, the latencies of P14, N20, and N60 at C4' and P14, N18, and P22 at Fz were significantly shorter in the 4th session than in the 1st session. Furthermore, the peak amplitudes of P25 and N60 at C4', and P22 and N30 at Fz decreased with increases in body temperature. On the other hand, under the Time Control condition, no significant differences were observed in the amplitudes or latencies of any component of SEPs. These results suggested that the conduction velocity of the ascending somatosensory input was accelerated by increases in body temperature, and hyperthermia impaired the neural activity of cortical somatosensory processing.
authors.affiliation: Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University, Nara, Japan; and.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakata
authors.affiliation: Graduate School of Humanities and Sciences, Nara Women's University, Nara, Japan.
authors.forename: Misaki
authors.initials: M
authors.lastname: Oshiro
authors.affiliation: Graduate School of Humanities and Sciences, Nara Women's University, Nara, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Namba
authors.affiliation: Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University, Nara, Japan; and shiba@cc.nara-wu.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Shibasaki
mesh_terms: D000344:Afferent Pathways / Q000503:physiopathology; D001833:Body Temperature Regulation; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D009431:Neural Conduction; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: central fatigue; conduction velocity; hyperthermia; somatosensory evoked potentials; tactile