~Chapter 14 - Lecture Section 14.2 Flashcards
What is Tactile Acuity?
Our ability to detect details on the skin. Important for coding object shape and texture by touch.
How is Tactile Acuity psychophysically measured?
Using the two-point threshold, where two probes/pencils are poked into your skin, and you are asked if you perceive one point or two.
In order to perceive two points, each point has to stimulate a ___ pool of receptive fields.
significantly different
If the two points stimulate ___ receptive fields, they’ll be perceived as a single point being pushed into your skin.
overlapping
The parts of the body that have the lowest two-point thresholds have the ___ receptive fields, and the ___ representation in Somatosensory Cortex.
smallest // largest
The hands, lips, nose, cheek and face have a very ___ two-point threshold
low
When you reach areas which have a ___ representation in the Cortex, such as the back, the calf, thigh, or arms, they have ___ two-point thresholds.
smaller // very large
What is the two-point threshold of your pointer finger?
Your pointer finger has a two-point threshold of around 3mm
So if you got the two points pressed into your finger at 1mm apart, you couldn’t tell the difference between 1 or 2 points
For the center of your back, in order for the two points to be detected as two distinct areas of the skin being stimulated, those probes have to be separated by about ___.
4cm
What are two methods of testing Tactile Acuity?
Two-Point Threshold and Grading Acuity
How is Grading Acuity performed?
A textured probe is pressed into the skin, and you’d have to determine whether the grating is vertically or horizontally orientated.
When performing Grading Acuity, in order to perceive the orientation of the grating as horizontal or vertical you must detect the spacing between the ___ and the ___.
bars // elongated contour
In terms of perceiving details, ___ have ideal response properties to signal shape.
Merkel Receptors (SA1 afferents)
There is a good correlation between ___ and the spacing of ___.
Tactile Acuity // SA1 afference
There is ___ Tactile Acuity where there is ___ spacing at the fingertip, where there is ___ packing.
high // low // very dense
At the base of the finger where there is ___ dense packing, there is ___ high Acuity.
less // less
At the palm of the hand, there is the ___ Acuity, where the packing of the receptors is the most ___.
lowest // sparse
What is one thing which makes Merkel Receptors really good at detecting details?
They respond linearly to static skin indentation.
This means that the relationship between the amount that the skin is pressed in and the number of action potentials that the receptor is firing make a nice straight line relationship.
Likely due to the branched structure of the Merkel Receptors, that for stimuli that are smaller than the ___, these are likely just stimulating a ___ terminal branch.
receptive field (2-5mm) // single
When the corner of a probe is being pressed into the Merkel Receptor, there is a ___ in spike.
large elevation
When the flat bit of a probe is being pressed into the receptive field of a Merkel Receptor, the response is fairly ___.
low
The Merkel Receptor (SA1) detects each ___ of the stimulus.
gap/bump
The Pacinian corpuscle (RA2) responds ___ to all parts of the stimulus.
equally
___ are capable of carrying information about fine details of the probe, whereas the ___ are not capable of transmitting the details of the probe.
Merkel Receptors // Pacinian Corpuscles
2-point stimulation (arrows) needs to activate ___ pools of cortical neurons to be perceived as 2 locations on the skin.
different
There is a relationship between the Receptive Field size at the ___ and the ___.
Skin // Cortex
The Finger, which has small receptive fields, in response to the two points of stimulation, there are ___ receptive fields between the two points, which means that when we go to the neural activation anatomically, there are ___ neurons that reside between the two populations of ___ neurons, and so they will perceive ___ point(s).
non-stimulated // non-activated // activated // 2
The Forearm, which has large receptive fields, the two points which are the same spacing are now activating ___ receptive fields. In the Cortex, this will produce activation of a cluster of neighbouring Neurons with no ___ neurons in-between, and therefore, it will be perceived as ___ point(s).
overlapping // non-activated // a single
Pacinian Corpuscle (RA2 afferents) is ___, and responds really well to ___.
extremely sensitive // vibration
The Pacinian Corpuscle can respond to as little as ___ of skin motion as long as its vibrating fast enough, in the range of ___.
10nm // 200Hz
The responses of the Pacinian Corpuscle are ___.
Transient
The Pacinian Corpuscle has an ___ structure which surrounds the ___.
onion-like // unmyelinated nerve ending
When there is stimulation from the outside to the Pacinian Corpuscle, the layers of the onion-like outer bulb contain a ___ which ___ static forces
viscous fluid // dampen
If a probe is pressed into the Pacinian Corpuscle, there will be a ___ as that energy is transmitted to the Mechanoreceptors along the unmyelinated part of the neuron. Then everything settles and that pressure is absorbed, so there’s ___ firing. And then when the probe is removed, the layers shift again and cause a disruption to allow the Mechanoreceptors to shift and ___ ion flux, and so then there is a ___ of activity when the probe is removed. This is the ___.
burst // no more // allow // burst // Rapidly Adapting Response
