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Proprioception
Perception of the body mediated by kinaesthetic and vestibular receptors
Somatosensation
A collective term used for all sensory signals from the body plus the vestibular system
Skin
Largest sensory organ
Touch Receptors
Embedded in the outer layer (epidermis) and underlying layer (dermis) of the skin
Types of Tactile Receptors
Meissner Corpuscles
FA I
Fast adapting type I, small receptive field
FA II
Fast adapting type II, large receptive field
SA I
Slow adapting type I, small receptive field
SA II
Slow adapting type II, large receptive field
Kinesthetic receptors
Play important role in sense of where limbs are, what kinds of movements are made
Spindles
Convey the rate at which the muscle fibres are changing in length
Type Ia sensory fibre
Adapts, signals change in stretch, connects to spindles
Type II sensory fiber
Does not adapt, signals amount of stretch (position of the muscle fibres)
Ian Waterman
Got a viral infection that destroyed the Kinesthetic mechanoreceptors
unable to walk but learned to walk again, dependent of vision for the limb position
Cutaneous nerves that connected his mechanoreceptors to brain was destroyed
Thermoreceptors
Sensory receptors that signal information about changes in skin temperature
Nociceptors
Sensory receptors that transmit information about noxious (painful) stimulation yay causes damage or potential damage to the skin
Analgesia
Decreasing pain sensation during conscious experience
Gate Control Theory
System that transmits pain that incorporated modulating signals from the brain
feedback circuit located in substantial gelatinosa of the dorsal horn of the spinal cord
Gate neurons that block pain transmission can be activated by extreme pressure, cold, other noxious stimulation applied to another site distant from source of pain
Hyperalgesia
Once damage has occurred, site can become more sensitive; increase in pain
Neuropathic Pain
Pain as a result of damage to or dysfunction of the nervous system
“Nociceptive” Pain
Nociceptors provide signal when there is impending or ongoing damage to body’s tissue
Anterior Cingulate Cortex
Generally carries the signal if something wrong, can be pain or error in a cognitive task
Secondary pain effect
Emotional response associated with long-term suffering (associated with the prefrontal cortex)
Discriminative Touch
The classic touch sensations of tactile, thermal, pain, and itch experiences
Social Touch
mediated by unmyelinated peripheral C fibers — C tactile afferents
Respond best to slowly moving, lightly applied forced
Processed in the orbitofrontal cortex
Spinothalamic
slower, evolutionary older
Heat, pain, temperature, crude touch
Multiple synapses
Dorsal-column-medial-lemniscal
faster
Tactile and proprioceptive information
Fewer synapses- fast transmission
Spinothamic Pathway
Dorsal Horn of spinal cord —> lateral spinothalamic tract —> connection in ventral posterior nucleus of the thalamius —> travels to cerebral cortex
several synapses
Provides mechanisms for pain inhibition
DCML Pathway
Dorsal Horn of the spinal cord —> connection in the gracile nucleus (on the cuneate nucleus) —> travels to medial leminscus —> thalamus —> somatosensory cortex
wider axons
Fewer synapses
Used for planning and execution of fast movements
Primary Somatosensory Cortex (S1)
on the post central sulcus
Adjacent on the pre central sulcus are the corresponding motor areas
Phantom Limb
Perceived sensation from a physically amputated limb of the body
real pain might be felt if they perceived their phantom limbs to be in uncomfortable positions
Can be felt in area adjacent to the amputated limb (eg. Sensations of hand felt on arm)
Max von Frey
Developed an elegant way to measure mechanical pressure
used calibrated stimuli: horse and human hairs
Modern Research of Mechanical Pressure
Use nylon monofilaments of varying diameters
use hair to poke on your lips vs thighs or upper arm or sole of feet
Two-point touch threshold
The minimum distance at which two stimuli are just perceived as separate
Grating Orientation
Participants must tell if the grating orientation when pressed on a certain body area
Deciding Temporal Details
method to decide whether two events are simultaneous or sequential
Typically 5ms (if they are both apart)
Better than vision (25 ms) but worse than audition (0.01 ms)
Haptic Perception
Knowledge of the world that is derived from sensory receptors in skin, muscles, tendons and joints, usually interaction with eh environment
Lateral Motion
Back and forth motion, find out the texture of the object
Pressure
Press finger into an object to finger out the hardness
Static Contact
Finger on object to determine the temperature
Unsupported Holding
Hold the object in our hand to discover the weight
Enclosure
Enclosing the object with our hands to discover shape, volume
Contour Following
Moving hands around the object to determine the contour and its global shape/exact shape
What system (ventral)
material properties of objects are crucial for haptic recognition
2D pictures or objects are recognized easily visually but poorly haptically
Braille Alphabet
dot optimized for touch perception
Discrimination between letters in the dot patterns
Jack Loomis
Touch acts like blurred vision when the fingertips explore a raised pattern
visual stimuli blurred to match the acuity of fingertip skin
Visual stimuli and haptic stimuli showed the same confusion errors
The accuracy of touch feels like blurry vision
Tactile Agnosia
Inability to identify objects by touch
caused by lesion to the parietal lobe (where S1 and S2 are)
Patient by Reed and Caselli
Could not recognize weight and roughness of either hand
Lacked a connection b tween sensation and recognition systems on the impaired side: unable to integrate perceived properties about objects
Where system (parietal)
knowing where objects are in the environment when only using touch perception
Frame of reference
Egocenter
Frame of reference
The coordinate system used to define locations in space
Egocenter
The centre of a reference frame used to represent all locations relative to the body (where you are and how you encode locations of objects relative to your body)
Body Image
The impression or our body in space
our body is highly changeable
Possible to induce an out-of-body experience
Tacoma Method
Speech perception for deaf and blind people
thumb on speaker’s lips, fingers along jawline, littler finger feels vibrations of the throat
Invented by Sophie Alcorn
Olfaction
The sense of smell
Gustation
The sense of taste
Odorant
Any specific aromantic chemical
chemical compounds
Must be volatile, small, and hydrophobic
Olfactory Cleft
A narrow space at the back of the noise into which air flows, where the main olfactory epithelium is located
Olfactory Epithelium
A secretory mucosa in the humans nose whose primary function is to detect odourants in the inspired air; the “retina” of the nose
Supporting cells
Provide metabolic and physical support from the olfactory sensory neurons
Basal Cells
Precursor cells to olfactory sensory neurons
Olfactory Sensory neurons (OSNs)
The main cell type in the olfactory epithelium
located beneath a watery mucous layer in ther olfactory epithelium
Have 5-10 million
Cribriform Plate
Bony structure riddled with tiny holes, at the level of the eyebrows, that separates the nose from the brain. Axons of OSNs pass through the tiny holes to enter the brain
Cilia
Hairlike protrusions on the dendrites of OSNs, contain receptor sites for odourant molecules
Olfactory Receptor (OR)
Region on the cilia of OSNs where odorant molecules bind
takes 7-8 odorous molecules binding to a receptor to initiate an action potential
Takes about 40 events to perceive an odor
Olfactory Sensory Neuron Measured
pipette inside the cell
Records the membrane potential of the cell
Reliever an odourant through a pipette to the cilia of the olfactory sensory neurons
Record action potential and realization when it occurs
Olfactory Nerves
First pair of cranial nerves, formed by the axons of the olfactory sensory neurons that bundle together after passing from the cribiform plate to form the olfactory nerve
Olfactory Bulb
Blueberry-sized extension of the brain just above the nose, where olfactory info is first processes
two olfactory bulbs one in each brain hemisphere
Connections are ipsilateral unlike vision, hearing, or touch
Mitral cells
Main projective output neurons in the olfactory bulbs
axons in these cells carry the information further into the brain into the primary olfactory cortex and other brain structures
Glomeruli
Spherical conglomerates containing the incoming axons of the OSNs
axons for the olfactory sensory neurons make first synapse here
Many of them
Primary Olfactory Cortex
Neural area where olfactory information is first processed, which includes the amygdala, parahippocampal gyrus and interconnected areas, and also entorhinal cortex
Entorhinal Cortex
Phylogenetically old cortical region that provides the major sensory association input into the hippocampus. Also receives direct projections from olfactory regions
Lambic System
Direct and intimate connection with the olfaction system
Involved many aspects of emotion and memory
Why sense tends to have a strong emotional sensation association
Sensation vs Perception
Sensation occurs when scent is neurally registered
Perception occurred when becoming aware of sensations several 100 ms later (lot of time)
Trigeminal Nerve
Cranial nerve V, sensations of the scent mediated
Shape-pattern Theory
Different scents activate different arrays of olfactory receptors in the olfactory epithelium as a function of odorant-shape to OR-shape fit
Combinatorial Neural Code
Detect the pattern of activity across various receptor toes
intensity of odorant also a changes which receptors will be activities
Specific time order of activations of the activation of the olfactory receptors is also important
Binaral Rivalry
Competition between the two nostrils for odor perception
when a diff scent is presented to each nostril, we experience one scent at a time, not a combination
Similar to binocular rivalry
Zhou et al.
Binocular rivalry stimulus of markers in one eye and and a rose in the other eye
when exposed to smell of marker of rose
timing was now bias to the binocular rivalry
Subjects saw corresponding stimulus more often
Odor Imagery
Humans have little to no ability to conjure odoro “images”
cannot think in smells well
Do not imagine smells well— dreams with it are very rare
Other animals whom smell plays a more central role may do better than humans
Amosmia
Totally inability to smell, most often resulting from sinus illness or head trauma
lead to depression, loss of libido
Early symptom of Covid-19 (55%)
Congenital anosmia
Children often pretend to be able to smell
Specific Anosmia
Inability to smell one specific compound amid otherwise normal smell perception
Aromatherapy
Contention that doors can influence, improve, and alter mood, performance, and well-being, as well as the physiological correlates of emotion such as heart rate, blood pressure, and sleep.
can make you feel energized
No evidence for pharmacological effect of odors in humans
Vomeronasal organ (VNO)
Chemical sensing organ at the base of the nasal cavity of many animals with a curved tubular shape.
evolved to detect chemicals that cannot be processed by the olfactory epithelium such as large and/or aqueous molecules, types of molecules that constitutes pheromones
Pheromones
Signals for chemical communication between members of the same species that do not need to have any smell
Retronasal olfactory sensation
Sensation of an odor that is perceived when chewing and swallowing force an odorant in the mounts up behind the palate into the nose
odor sensations are perceived as originating from the mount, even though the actual contact of the odorant and receptor occurs at the olfactory mucosa
Flavor
The combo of true taste (sweet, slaty, dour, bitter, umami) and retronasal olfaction
Chords tympani
Blanch of the cranial nerve VII (7th, facial nerve) that carries taste information from the anterior, mobile tongue
Tastant
Any stimulus that can be tasted
some can be made up of small, charged particles of salty or sour
Other tastants are perceived via G protein-couples receptors (GPCRs) similar to that in the olfactory system, molecules taste sweet, bitter or savoury
Taste buds
Create neural signals conveyed to brain by taste nerves
embedded in structures of papillae
Arch taste bud contains taste receptor cells
Info is sent to brain via cranial nerves
Microvilli
Slender projections on the tips of some taste bud cells tat extend into the taste pore
contain the sites that bind to taste substances
Not tiny hairs, extensions of the cell membrane
Taste receptors cells
Insular cortex
Primary cortical processing area for taste, the part of the cortex that first receives taste information
Orbitofrontal cortex
The part of the frontal lobe of the cortex that lies above the bone (orbit) containing the eyes
receives projections from insular cortex
Involved in processing of temperature, touch, smell, and taste, suggesting it may be an integration area
Arthur Fox
Discovered that phenylthiocarbamide (PTC) tastes dramatically different to different people
bitter taste to some but not others
Started using PROP (propylthioracil) bc its safer
individuals with two recessive genes are non tasters of PTC/PROP
Individuals with one or more of the genes are tasters of PTC/PROP
Supertaster
Individual who is a taster of PTC/PROP and has a high density of fungiform papillae
Specific hungers theory
Idea that deficiency of a given nutrient produces craving (a specific hunger) for that nutrient
cravings for salty or sweet are associated with deficiencies in those substances
Theory has not been supported for other nutrients
Only holds for sweet and salty foods
Orthonasal olfaction
Olfaction through the nostrils