Unit 11 Tactile, Haptic, Gustatory and Olfactory Perception

Question 1

What happens to people that have autoimmune diseases that damage neurones loose the ability to consciously experience sensation?

Answer 1

the skin suffers constant bruises and broken bones as they receive no warning from touch

-> no feedback from skin means worse and harmful performance in mundane activities

Question 2

What is the somatosensory system responsible for?

Answer 2

Proprioception: ability to sense position of body
Kinesthesis: ability to sense movement of body
Cutaneous (skin) sense: responsible for perceiving touch and pain

Question 3

What does the skin do?

Answer 3

->prevents body fluid from escaping
-> bateria, chemical agents, and dirt from penetrating our bodies
-> PROVIDES INFORMATION OF WHAT OUR BODIES ARE TOUCHING

Question 4

-> WHAT ARE the 2 layers of the skin
-> what are the four mechnoreceptors

Answer 4

-> Epidermis (dead skin at the surface of the skin)
-> Dermis (inner layer of skin)

=> Merkel Receptors and Meissner corpuscles (in epidermis)
=> Ruffini cylinders and Pacinian corpuscles (in Dermis)

Question 5

Merkel Receptors and Meissner corpuscles

Answer 5

MR = When stimulated, the neurones CONNECT with the purpose of firing continously (nerve fibres called Slowly Adapting fibres [SA])
-> for perceiving fine details, shapes and textures

MC = neurones connect to ONLY FIRE WHEN stimulation is applied, then again when it is removed (Rapidly Adapting fibres [RA])
-> contributes to controlling handgrip and perceiving motion across skin

Question 6

Ruffini cylinders and Pacinian corpuscles

Answer 6

locating deeper in skin and have larger CUTANEOUS RECEPTIVE FIELDS

RC = respond continuously to stimulation
-> help us perceive stretching of skin

PC = responds when stimulation is applied and removed
-> responsible for sensing vibrations and helping us perceive fine texture

Question 7

Tactile Acuity

Answer 7

the accuracy of touch perception

-> highly depends on the properties of mechanoreceptors and the brain

-> less space between receptors gives greater spatial acuity

Merkel receptors are in high density in finger, there is just as much in the thumb as there is in the little finger, BUT due to the large portion go primary somatosensory cortex dedicated to processing -> it gives it greater tactile acuity

Question 8

Two-point threshold

Answer 8

classic measure for tactile acuity

-> the minimum separation between two points on the skin to be perceived between two different points

Question 9

Passive touch and Haptic exploration

Answer 9

-> Passive touch: when we are touched with no intention of identifying what it is

-> Haptic exploration: is actively touching trying to find or explore an object trying to recognise it using its shapes

Question 10

Haptic explorations three system

Answer 10

1) somatosensory system: detecting touch, temperature, texture, movement, positions of fingers and hands
2) motor system: controlling finger and hand movements
3) cognitive system: making decisions based on the information provided by the somatosensory and motor systems, long-term memory, attention, etc.)

Question 11

Exploratory procedures

Answer 11

common object takes 1 to 2s and a no. of movements to recognise

movements: lateral motion, pressure, enclosure, contour following

we chose movements depending on our judgement of their texture and shape

for texture = lateral motion and contour
for shape = enclosure and contour following

Question 12

Pain and it’s three types

Answer 12

Scholz and Woolf (2002 in Goldstein, 2017)
-> inflammatory: pain bcs of damage to tissue, inflammation of joints, or tumour cells
-> Neuropathic: pain bcs of lesions to the nervous system (carpal tunnel syndrome)
-> Nociceptive: pain bcs of activation of skin receptors (nociceptors) in response to heat, chemical, severe pressure and cold stimuli

Question 13

traditional view of pain perception and now

Answer 13

we used to think that there was direct pathway between nociceptors and the brain
-> this changed slightly when it was reported the that WW2 soldiers felt no pain in severe wounds
-> and phantom limb, even after nerves carrying pain information from amputated limbs to brain were severed

MODERN: an interaction between the input from pain receptors and brain activity which is explained by Gate Control Model of pain

Question 14

Gate control Model

Answer 14

pain signals s are sent from the body to the spinal cord and then sent up ascending pathways to brain

-> additional pathways located in the dorsal horn the spine cord grey matter, open or close like a gate -> determining strength of pain (functions from receiving input from mechanoreceptors and nociceptors in skin )

Question 15

Transmission cells responsibility

Answer 15

gates close and open based on the command of transmission cells, located in dorsal horn of spinal cord (send excitatory or inhibitory input)

-> when noxious stimulus detected by nociceptors exiting transmission cells, resulting pain signals
-> when non-painful stimuli is detected by mechanoreceptors, they inhibit transmission cells, resulting in less or no pain signals being sent

Question 16

what does the central control do?

Answer 16

CC fibres carry signals from the brain to the dorsal horn of spinal cord grey matter. These signals concern cognitive processes like expectations and attention

-> Central control fibre stimulate inhibitory cells that reduce the firing of transmission cells, resulting in less pain signals being sent

Question 17

How does expectation and attention influence pain perception

Answer 17

-> effects of expectation are demonstrated by placebo effects, many patients w/ pathological pain get relief from taking a placebo (belief resulting in expectation)

-> effects of attention: burn patients given virtual reality headsets to distract them while having their bandages changed (smt rlly painful) report feeling less pain than patients that were not distracted

Question 18

Chemical sense - olfaction and gustatory perception systems

Answer 18

• molecule detectors (we smell things bcs molecules enter our nose and we taste things bcs molecules stimulate our tongue)

-> help identify things for survival like smelling or tasting smt that is gross possibly deadly

smells and taste accompanied by emotions
-> constant exposure to bacteria and dirt so they have a relatively faster neurogenesis cycle
OLFACTORY 5-7 weeks
TASTE 1-2 weeks

Question 19

Taste

Answer 19

Occurs when molecules enter the mouth in solid or liquid -> stimulate taste receptors on the tongue
-> salty, sour, sweet, bitter, umami (brothy)

surface of the tongue has protrusions called PAPILLAE which have taste buds (-> send taste signals to brain when chemicals in saliva bind to the taste pore of taste buds)

Question 20

Macrosmatic and microsmatic olfactory sense

Answer 20

other animals are macrosmatic -> keen sense of smell important for survival ( orient them in space, mark territory and guide them to food sources and detection of pheromones)

humans -> macrosmatic animals (less)
(t-shirts worn by women for 3 consecutive nights when they were ovulating compared when they were not ovulating were rated as smelling more pleasant by men)

Question 21

Detection threshold

Answer 21

For odours is the lowest concentration at which an odorant’s can be detected
-> T-butyl mercaptan: added natural gas detected in very small concentrations <1 part per billion air molecules
-> Methanol: (non-drinkable alcohol) can be detected 141,000 parts per billion
-> Nail polish: detected in 15,000 parts per billion

=> Humans have ~10,000,000, whereas dogs have ~1,000,000,000

Question 22

what is the process of olfaction

Answer 22

Odorant molecules entering the nose and stimulating receptors in the olfactory mucosa; a small region located on the roof of the nasal cavity just below the olfactory bulb in the brain

mucosa are dotted with olfactory receptors (10,000 each type)

Percieved odour depends on the pattern of stimulation across these different receptors allowing us to discriminate > 1 trillion olfactory stimuli

Question 23

Flavour

Answer 23

experience resulting from the combination of stimulation of taste receptors in the tongue, and olfactory receptors in the nose

TASTE AND OLFACTORY INFORMATION ARE COMBINED IN THE CORTEX,

eating also releases odarant molecules that reach the olfactory mucosa via retronasal route that connects the back of the throat to the nasal cavity

Question 24

Proust effect

Answer 24

happens when taste and olfaction unloack potent memories

-> Subjects who were presented olfactory cues rated their memories as more emotional than subjects who were presented visual cues

-> brain structures involved in processing taste and olfaction are connected to brain structures involved in processing emotions (e.g. amygdala) and memories (e.g. hippocampus), resulting in strong connections between taste and olfactory cues, and emotions and memories
* However, the Proust effect is still not completely understood (