13. touchy-feely sensation & perception - bryan burnham · title: microsoft powerpoint - 13....
TRANSCRIPT
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Material properties Weight, density, roughness, warmth, etc.
Different firing rates
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Touch is our only non-localized sensory system
MechanoreceptorSkin Location
Adaptation Rate
RF Size
Response Type
Functions (Aids in Perception of)
Merkel Superficial Slow Small SA-I Texture perceptionMeissner Superficial Fast Small FA-I Finger positionRuffini Deep Slow Large SA-II Grasping & stretching, low
frequency vibrationPacinian Deep Fast Large FA-II High frequency vibration
Bell–Magendie Law explains the division between efferent and afferent pathways Ventral root to muscles Dorsal root is sensory
▪ Spinothalamic Pathway (Anterolateral Pathway)▪ Dorsal Column Medial-Lemniscal Pathway
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Somatosensory Area 1 (S1) is the Primary Tactile Receiving Area
Tactile sensitivity varies across body, and is based on cortical representation
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Tactile acuity also varies across the body, and is related to receptive field size
BodyLocation
AbsoluteThreshold (g)
Two-pointthreshold (mm)
Forehead 1.4 15.0Nose 0.5 8.0Lip 0.9 5.5Cheek 1.0 7.0Shoulder 10.0 41.1Upper Arm 16.0 44.5Forearm 13.3 38.5Thumb 9.0 3.5Digit 1 11.4 3.0Digit 2 6.8 2.5Digit 3 7.9 4.0Digit 4 5.7 4.5
Klatzky, et al. (1985) examined ability to distinguish tactile features
Detect local and global temperature changes Physiological zero (~98.6°F)
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20 25 30 35 40 45 50
Temperature (C)
Ac
tio
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ote
nti
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Pe
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on
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Cold
Warmth
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Ronald Melzack and Patrick Wall (1965, 1998) Nociceptors
▪ Aδ fibers▪ C fibers
Analgesia
Cortical Model of Pain Perception
TI
From Brain To Brain
Aα/Aβ
C/Aδ (nociceptors)
(mechanoreceptors)
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