Multisensory Flashcards
What are the skin layers?
Epidermis is the top layer
Then the Dermis
the Hypodermis is next and includes the hair follicles, sweat glands, fat and connective tissue)
Blood vessels branch from below the hypodermis and into the dermis
What are the types of skin receptors?
In both the dermis and hypodermis layers
Meissner corpuscle
Pacinian corpuscle
Ruffini organ
Merkel disks
Free nerve endings
What are unencapsulated and encapsulated nerve endings?
Un-encapsulated nerve endings: respond to temperature, pain and pressure, projects to the spinal cord, sensory afferents (slow)
Encapsulated nerve endings: respond to different vibration frequencies, pressure, tickle and hair bending, project to spinal cord, sensory afferents (fast)
What does FA, SA and RA stand for?
FA1 FA2 (fast adaptive type 1 or 2) can also have RA1 RA2 (rapid adaptive type 1 or 2)
SA1 SA2 (slow adaptive, type 1 or 2)
What is the classification of mechanoreceptors?
RA- meissner’s corpuscle - stroking movements
SA - merkel cells - steady pressure and texture
RA- pacinian corpuscle - senses vibration
SA- ruffini endings - skin stretch
What are mechanoreceptors, thermoreceptors, nociceptors and proprioceptors?
mechanoreceptors: sensitive to touch, pressure, vibration and skin stretching
thermoreceptors: heat, cold
proprioceptors: body position, muscle length
nociceptors: pain
What is somatosensory RF (receptive field)?
the portion of the skin which, when stimulated, activates a somatosensory neuron
What is the two point discrimination threshold procedure? What were the results?
2 sticks and touch the participants skin
ps is blindfolded
if the two touches were far apart, the ps will say they feel 2 touches
if the touches were close together, the ps will say one touch, even though they were touched with two sticks
This is due to the sticks touching in the same receptive field
What is the somatosensory pathway?
From the mechanoreceptor or the proprioceptors to the first order neuron (afferent) then to the spinal cord and the dorsal columns
Next the signal goes to the decussation of medial lemniscus, to the medulla oblongata, to the dorsal column nuclei
To the second order neuron, to the thalamus to the primary somatosensory cortex
What is the motor pathway?
Send signal to brain: Sensory endings in skin to the neuromuscular junction, to the spinal cord, to the interneuron, then thalamus and the cerebral cortex
From brain to hand:
From upper motor neuron in brain, to the spinal cord and then the lower motor neuron
What is somatotopy?
spatial topography of body preserved in the brain, adjacent parts of the skin surface represented by the adjacent parts of the cortex
What is the cortical magnification?
Proportion of the cortex devoted to the body parts is related to their sensitivity or functional importance, not their physical size
What was the procedure for monkeys digits being surgically fused and what does it show us about the plasticity of the RF organisation?
Clear RF boundaries in both digit 3 and 4
Digits 3 and 4 (middle and ring finger) in monkeys were surgically fused
Led to blurring of representational boundaries in those digits
After fingers were unfused, RF (receptive fields) were found to cover both digits
What was the procedure for monkeys digits being amputated and what does this tell us about the plasticity of the RF organisation?
Digit 3 amputated in monkey
Area which previously represented digit 3, invaded by representations of digit 2 and 4
Suggests that representations of different body parts are competitive
What is Aristotle’s illusion?
touch a pea, fingers are crossed to do this, move ball in circles, begin to feel two peas
What is the cutaneous rabbit tactile illusion?
Stimulation in P1 (wrist), P2 (forearm), P3 (elbow)
When P1, P2, P3 were touched, ps felt it. When P1 was stimulated first, then P3, ps felt P2 being touched, even if it wasn’t stimulated. When P1 was touched first, then P3 and then P1 again, P2 wasn’t stimulated and ps didn’t feel P2.
What are the terms multisensory, cross-modal and integration?
Multisensory: more than one sense modality is used in perception
Cross-model: interaction between different sense modalities
integration: merging of information from different sense modalities into unified percept
What is the Superior colliculus (SC)?
SC is in the midbrain
Contains neurons which respond to visual, auditory and tactile stimuli
This is unisensory, bisensory and trisensory
Merges information from different modalities to enable efficient reactions, like integration, localisation, rapid and automatic orienting of attention and orienting behaviour
What is topographic organisation and saptial and temporal selectivity? How does this relate to the SC? How are multisensory RFs formed?
Multisensory RF are formed by converging input from unisensory neurons
Topographic organisation: neurons with RF respond to stimulation from a certain direction and are in a certain area of the SC
Spatial and temporal selectivity: multisensory neurons react to stimuli arising from a similar location in space at about the same time
When a monkey’s cheek was experiencing a visual and tactile task, what happened in the brain?
Monkey as a ps
Tactile task: touch the cheek, tactile neuron would respond
Visual task: shine a light to the same cheek, visual neuron would respond
When a monkey touched lights that were shining in 2 different spots, what happened in the brain?
2 lights
Monkey moved hand to the first light, neurons fired in S1
Then moved to the next light, neurons fired in S2
No neurons fired in S1 or 2 when the monkey moved hand away from both lights
What is spatial congruence?
Reactions to a visual stimulus are faster and more accurate if an extra, task-irrelevant auditory stimulus is presented from the same location (vica versa)
Improved reactions, stronger integration and interpretated to arise from the same event
What is temporal congruence?
simultaneous stimuli are more likely to be integrated
Temporal window of integration, if stimuli goes out of this window, the brain recognises this as different stimuli. If the stimuli occurs within the window, the brain integrates and recognises the information as the same
What is semantic congruence?
Reactions are faster and more accurate to a stimulus if it is accompanies by a semantically congruent stimulus in another modality
Improved reactions, stronger integration and interpretated to arise from the same event
What is SC super additivity?
Superadditive multisensory responses
Works best for weak stimuli
Enhanced multisensory responses when unisensory stimuli from the same event are poorly detectable alone
What is the rubber hand illusion? What were the results? Why?
Real hand next to rubber hand
Both hands are stroked simultaneously
The ps watches this
The ps will feel the stroking sensation in both his real hands, when only one of this real hands are being stroked
This is because we tend to attribute the most meaning to information that we acquire via the visual senses
Another version of the rubber hand experiment includes beliefs. What was the procedure for this? What was found?
In this version of the rubber hand experiment, ps were asked if they believed they were feeling the stroking sensation
Ps admitted they didn’t believe the sensation but still felt the sensation
What is sensory substitution?
Blindfolded ps
Sensory substitution device which allowed them to navigate the environment by listening
