Effects of self movement on absolute and masked thresholds in the pacinian channel

Abstract

Bu tezde, ki³i periyodik olarak hareket ederken Paçini kanalnn mutlak vemaskeli e³ik de§erlerini ölçerek aktif dokunma duyusunu olu³turmaya çal³tk. Öncekiara³trmalardan yola çkarak mutlak e³ik de§erlerinin dü³mesini ve maskeleme etkinli§inin artmasn snadk. Deneklerin sol orta parmak uçlar yarçap 0.685 cm olan biraluminyum kontak ucuyla mekanik olarak uyarlm³tr. Psikoziksel e³ik de§erlerininölçümü üç ayr durumda tekrarlanm³tr: statik durum, yava³ hareket (0.1-0.2 m/s),hzl hareket (0.5-0.6 ms/s). Hareketli durumdaki (yava³: -20.8 dB; hzl: -21.8 dB)e³ik seviyeleri pasif (-17.9 dB) duruma kyasla daha dü³ük çkm³tr. E³li t testlerihareketli e³ik de§erlerinin pasif durumdan istatistiksel olarak farkl oldu§unu göstermi³tir (pasif ve yava³: p=0.023, pasif ve hzl: p=0.024). Ayrca maskeyle olu³an e³ikyükselmesi hareketle artm³tr (pasif: 2.9 dB, yava³: 7.9 dB, hzl: 9.2 dB). Pasif durumve hareketli durumlar arasndaki maskeleme etkisi istatistiksel olarak anlaml çkm³tr.Bu sonuçlara göre öz-hareketin Paçini kanalndan kaynaklanan dokunma duyusunu iyile³tirdi§i söylenebilir ancak hzn pek etkisi olmad§ görülmü³tür. Maskeleme etkisihareketle artm³tr. Bu da duyudaki iyile³menin hem e³ik seviyesinde hem de e³iküstünde olabildi§ini göstermektedir fakat öz-hareket srasnda hem proprioseptif hemde motor sinyaller olu³tu§u için bu iyile³menin tam kayna§ ³u an bilinmemektedir.Anahtar Sözcükler: Psikozik, bedensel duyu, titre³imsel uyar, Paçini, insan, aktifdokunma.

In this thesis, we simulated active touch by measuring absolute and maskedthresholds in the Pacinian channel during cyclic self-movement. Based on previouswork we hypothesized improvement in the absolute thresholds and increase of maskingeciency compared to passive touch condition. An aluminum contactor (r=0.685cm) was used for the stimulation of the left middle ngertip of the subjects. Themeasurements of the psychophysical thresholds were repeated for three conditions: nomovement, slow self-movement (0.1-0.2 m/s), and fast self-movement (0.5-0.6 m/s).The slow movement condition (-20.8 dB) and the fast movement condition (-21.8 dB)yielded on average lower thresholds than the passive condition (-17.9 dB). Paired t-testsshowed that the dierences between the movement conditions and the passive conditionwere signicant (p=0.023 for passive vs. slow; p=0.024 passive vs. fast). Interestinglythe threshold shift due to masking increased with self-movement (2.9 dB for passive;7.9 dB for slow; 9.2 dB for fast). The dierences between the threshold shift due tomasking for passive and individual movement conditions were signicant. According tothese results, self-movement signicantly enhanced sensation in the Pacinian channel.However the speed of the self-movement did not matter. Forward- masking eciencyalso increased due to self-movement. Therefore this enhancement seems to operate atboth threshold and suprathreshold levels. Since self-movement involves both proprioceptiveand motor signals, the exact source of this enhancement currently cannot beidentied.Keywords: Psychophysics, somatosensation, vibratory stimulus, Pacinian, human,active touch.