6-2 Flashcards
Measuring tactile acuity
(a) Two-point threshold - minimum separation needed between two points to perceive them as two units
(b) Grating acuity - placing a grooved stimulus on the skin and asking the participant to indicate the
orientation of the grating
Tactile acuity thresholds are determined by
Merkel receptors
The tip of the finger has high concentrations
SAI and FAIs,
while SAIIs and FAIIs are more equally distributed
Receptor mechanisms for tactile
acuity
High density of Merkel receptor/SA1
fibers in the fingertips
Merkel receptors are densely packed
on the fingertips
Both two-point thresholds and grating
acuity studies show these results
Body surfaces with higher density of
receptors with smaller receptive fields
have
lower 2-point discrimination
thresholds
what do small receptive fields permit
high resolution of spatial details
Receptive field sizes correlate
tactile spatial acuity
Sensation
occurs when the
peripheral receptors are stimulated
Perception
occurs when the brain
interprets the sensory stimulation
Thalamus:
Relay information from the
sensory receptors to areas
of the cortex
Medial lemniscal
pathway consists of large fibers that carry
proprioceptive and touch information
Spinothalamic
pathway consists of smaller fibers that carry
temperature and pain information
Tactile acuity decreases
thresholds increase) from the index to the
pinky, but the density of Merkel receptors is the same across the
fingers
Homunculi reflect sensitivity & function
Across species, the somatosensory cortex map of the body reflects the
density of peripheral receptors, representation within the Somatosensory
cortex & has clear functional relevance
SOMATOSENSORY HOMUNCULUS
Lips, tongue, hands, feet and genitals are
considerably more sensitive than other
parts of the body
