Lecture 10-Sensation

Question 1

Sensation & Perception

Three events are common characteristics of all sensory processes:

Answer 1

adequate physical stimulus.

Processes that convert information in physical stimulus into information encoded by neural signals.

Specificbody response to the message as conscious sense (perception).

Question 2

stimulus transduction

Answer 2

• All sensory systems are organized by the same general plan:
• Receptor is translating the energy of stimuli into electrochemicalenergy/action potentials.

Question 3

4 Categories of sensory receptors

Answer 3

•chemoreceptors,

photoreceptors,

mechanoreceptors, and

thermoreceptors.

transduce the signal into an electrical action potential. This action potential then travels along afferent neurons to specific brain regions

Question 4

Distance vs direct Chemoreceptors

Answer 4

• Distance chemoreceptors are integral to receiving stimuli in the olfactorysystem.
• Direct chemoreceptors are taste buds in the gustatorysystem.

Question 5

Mechanoreceptors:

Answer 5

•Sensory receptors which respond to mechanical forces, such as pressure or distortion.

Groupedinto four categories:

•Slowly adapting type 1 receptors have small receptive fields and respond to static stimulation. Used in the sensations of form and roughness.

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•Slowly adapting type 2 receptors have large receptive fields and respond to stretch. Producesustainedresponsesto a continued stimuli.

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•Rapidly adapting receptors have small receptive fields and underlie the perception of slip.

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•Pacinian receptors have large receptive fields and are the predominant receptors for high-frequency vibration.

Question 6

Slowly adapting type 1 receptors

(Mechanoreceptors)

Answer 6

•have small receptive fields and respond to static stimulation. Used in the sensations of form and roughness.

Question 7

Slowly adapting type 2 receptors

(Mechanoreceptors)

Answer 7

•have large receptive fields and respond to stretch. Producesustainedresponsesto a continued stimuli.

Question 8

RA 1 receptor

Answer 8

Rapidly adapting receptors have small receptive fields and underlie the perception of slip.

Rapidly adapting type I mechanoreceptors have multiple Meissner corpuscle end-organs.

Question 9

Pacinian receptors

Answer 9

•Pacinian receptors have large receptive fields and are the predominant receptors for high-frequency vibration.

(RA 2) Rapidly adapting type II mechanoreceptors (usually called Pacinian) have single Pacinian corpuscle end-organs.

Question 10

Thermoreceptors

Which respond to temps above/below body temp?

Answer 10

• Sensory receptors which respond to varying temperatures:
• The end-bulb of Krause, or bulboidcorpuscle, detects temperatures abovebody temperature.
• Ruffini’s end organ detectstemperaturesbelowbody temperature.

Question 11

Nociceptors

Answer 11

• Respond to potentially damaging stimuli by sending signals to the spinal cord and brain.
• Causes the perception of pain.
• Those that only respond when tissues are damaged are known as “sleeping” or “silent” nociceptors (These receptors are normally unresponsive to noxious mechanical stimulation but become “awakened” (responsive) to mechanical stimulation during inflammation and after tissue injury).
• Thermal nociceptors are activated by noxious heat or cold at various temperatures.
• Mechanical nociceptors respond to excess pressure or mechanical deformation.
• Chemical nociceptors respond to a wide variety of chemicals, some of which are signs of tissue damage.

Question 12

Main sensory cortices for the 5 traditional senses:

Answer 12

the somatosensory cortex (post-central gyrus, parietal),

the visual cortex,

the auditory cortex,

the primary olfactory cortex (The olfactory cortex is located on the medial aspect of the temporal lobe, in the uncus (aka piriform lobe).

the gustatory cortex (The gustatory cortex is made up of two smaller substructures, the anterior insula and the frontal operculum. These substructures are found in the insular and the frontal lobes of the brain).

the vestibular cortex (The two major cortical functions of the vestibular system are spatial orientation and self-motion perception).

Question 13

What is the hierarchical Organisation of Sensation

(Former and Current model)

Answer 13

Association Cortex

Secondary Sensory Cortex

Primary Sensory Cortex

Thalamus

Receptors

Question 14

three levels of the sensory cortex

Answer 14

primary, secondary, association

Question 15

Visual Areas of Brain

Answer 15

•Visual perception is localized to the parietal/occipital lobes.

Question 16

Retina

Answer 16

the layered structure at the back of the eye that contains five different types of cells (receptors, horizontal cells, bipolar cells, amacrine cells, and retinal ganglion cells).

Question 17

Rods/Cones Receptors

Answer 17

•responsible for converting light energy into neural responses which are then transmitted to brain via retinal ganglion cells.

Receptors in retina are specialised (rods and cones).

Question 18

Amacrineand horizontal cells

Answer 18

responsible for lateral communication between the various cells.

Question 19

Bipolar cells

Answer 19

•synapse on the receptors and they in turn synapse on the retinal ganglion cells whose axons leave the retina via the optic nerve.

Question 20

Rods

Answer 20

•typically active in low light, very sensitive to movement.

Question 21

Cones

Answer 21

•: active in medium to bright light and are responsible for high acuity vision (vision that provides rich details and colour).

Question 22

Colour Blindness

Answer 22

• Color blindness occurs when light-sensitive cells in the retina fail to respond appropriately to variations in wavelengths of light that enable people to see an array of colors.
• The 6 to 7 million cones in the human retina are responsible for color vision, and these photoreceptors are concentrated in the central zone of the retina called the macula.
• Inherited forms of color blindness often are related to deficiencies in certain types of cones or outright absence of these cones.

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Question 23

Visual information from the retina is relayed through the _______ of the _______ to the ____________cortex

Answer 23

(Retina) > Lateral geniculate nucleus > thalamus > primary visual cortex

Question 24

•Visual signals are fed into at least three separate processing systems. One system appears to process information mainly about _______; a second, mainly about ______; and a third, ________, ________, and _________ ____________.

Answer 24

shape

color

movement, location, & spatial organization

Question 25

Lateral Geniculate Nucleus

its layers

Answer 25

• A six layered nucleus of the thalamus that receives info from the retina.
• Top four layers = neurons that have small cell bodies: parvocellular or P layers. Responsive to colour, detail and stationary or slowly moving objects.
• Bottom two layers = neurons that have large cell bodies: magnocellular or M layers. Responsive to movement and orientation but does not respond to colour or detail.

Question 26

How the brain integrates visual info to produce the perception of the object as a whole:

Answer 26

The visual field of each eye has the left and right hemifields.

Throughthe optic chiasm, the visual signals from the left hemifieldsof both eyes are sent to the right hemisphere of the brain, while the signals from the right hemifieldsof both eyes are sent to the left hemisphere of the brain.

So each hemisphere of the brain is responsible for processing the visual information in the opposite visual field from both eyes.

The pathways stay this way all the way up to the visual cortex.

Question 27

names for primary visual cortex

Answer 27

V1, broddman area 17

Striate cortex

Question 28

what is the macula?

where is it represented?

Answer 28

the most sensitive portion of the center of the retina, is represented at the posterior tip of the occipital lobe. The upper part of the world projects to the lower part of the striate cortex.

Question 29

Theprimary visual cortex projects to where

Answer 29

•cortical areas surrounding it, called the visual association areas (V2, V3; areas 18 and 19), where signals are interpreted and form is recognized.

Question 30

Visual Dorsal and Ventral Stream areas

Answer 30

•The dorsal stream includes areas V2 and V5, and is used in interpreting visual ‘where’ and ‘how.’

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•The ventral stream includes areas V2 and V4, and is used in interpreting ‘what.’

Question 31

Dorsal Stream

Answer 31

• Extremely sensitive to movement.
• Known as the “where pathway”.
• Main output for neurons from this pathway is the posterior parietal cortex, which is implicated in directing visual attention to specific points in space.

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Specialised for processing spatial relations through:

• Neurons responding to both visual fields, allowing for the computation of an objects exact position in space.
• Neurons can also track moving objects and respond differentially to direction and speed of movement.
• Posterior parietal cortex thought to be responsible for creating stable maps of the world and placing items within that map, resulting in knowledge of where an object is in space.

Question 32

Ventral Stream

Answer 32

• Area V4 is the origin of this stream.
• Known as the “what pathway”.
• Responsive to both colour and patterns.
• The main output for neurons in V4 is the inferior temporal cortex, which has cells that are very complex and tend to be selective for shape, colour and texture.

Question 33

Neural Olfactory Processing

Answer 33

• When an odorant stimulates the chemoreceptors in the nose that detect smell, they pass on electrical impulses to the brain.
• The brain then interprets patterns in electrical activity as specific odors and olfactory sensation becomes perception;something we can recognize as smell.
• When an air current sweeps an odorant up through the nostrils, the molecules hit the olfactory epithelium.

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• Olfactory receptor cells areneurons. Olfactory hairs that bind with odorants cover the dendrites of these olfactory receptor cells.
• When an odorant stimulates a receptor cell, the cell sends an electrical impulse to the olfactory bulb through the axon at its base.

Question 34

•People have about_____ different types of olfactory receptors.

Answer 34

450

•Each receptor can be activated by many different odor molecules, and each odor molecule can activate several different types of receptors.

The complexity of receptors and their interactions with odor molecules are what allow us to detect a wide variety of smells.

Question 35

How does the brain recognize, categorize and memorize the huge variety of odors?

Answer 35

•Each olfactory receptor type sends its electrical impulse to a particular microregionof the olfactory bulb.

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•The microregionthat receives the information then passes it on to other parts of the brain which interpret the “odorant patterns“.

Question 36

Where is the Primary Olfactory Cortex

Answer 36

temporal lobe

Question 37

Peripheral mechanisms of Olfaction:

Answer 37

• Involve olfactory receptor neurons which transduce a chemical signal along the olfactory nerve, which terminates in the olfactory bulb.
• The chemo-receptors involved in olfactory nervous cascade involve using G-protein receptors to send their chemical signals down said cascade.

Question 38

Central mechanisms of olfaction:

Answer 38

•Include the convergence of olfactory nerve axons into glomeruli in the olfactory bulb, where the signal is then transmitted to the anterior olfactory nucleus, the piriform cortex, the medial amygdala, and the entorhinal cortex, all of which make up the primary olfactory cortex.

Question 39

Olfactory Bulb

Answer 39

•This neural code begins with the nose’s sensory neurons.

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•Once an odor molecule binds to a receptor, it sends Aps to the olfactory bulb, a structure at the base of the forebrain that relays the signal to other brain areas for additional processing.

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•One of these areas is the piriform cortex, a collection of neurons located just behind the olfactory bulb that works to identify the smell.

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•From those areas, olfactory information via polysynaptic pathways can reach other brain areaseg. orbitofrontal cortex, thalamus, lateral hypothalamus, septum, brain stem.

Question 40

how many smells can the average person smell?

Answer 40

• One study created different mixes from 128 different odor molecules.
• They used this data to estimate that the average person can detect at least one trillion different smells.

Question 41

Smell and Emotion

Answer 41

• Smell is also intimately linked to the parts of the brain that process emotion and associative learning.
• The olfactory bulb in the brain, which sorts sensation into perception, is part of the limbicsystem;a system that includes the amygdala and hippocampus.

Question 42

How is smell linked with emotion?

Answer 42

• Smell is also intimately linked to the parts of the brain that process emotion and associative learning.
• The olfactory bulb in the brain, which sorts sensation into perception, is part of the limbic system;

(a system that includes the amygdala and hippocampus)

Question 43

Smell and memory

Answer 43

•Because the olfactory bulb is part of the brain’s limbic system, smellcan call up memories and powerful responses almost instantaneously.

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•Role of conditioned responses.

Question 44

Smell and memory study

Answer 44

•One study tested the olfactory effects on memory encoding and retrieval (Cannand Ross, 1989).

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•Male college students were shown a series of slides of pictures of females, whose attractiveness they were asked to rate on a scale.

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•Whilst viewing the slides, the participants were exposed to pleasant odor of aftershave or an unpleasant smell. Their recollection of the faces in the slides was later tested in an environment containing either the same or a different scent.

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•The results showed that participants were better able to recall memories when the scent at the time of encoding matched that at the time of recall. These findings suggest that a link between our sense of smell and memories remains.

Question 45

Anosmia

Answer 45

•The inability to smell.

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•Caused by: sinus disease, growths in the nasal passage, viral infections and head trauma.

Question 46

The taste map

Answer 46

• D.P. Hanigdeveloped the tongue map in 1901 by asking volunteers where they could perceive sensation.
• Other scientists later corroborated his findings but charted the results in such a way that areas of lowered sensitivity looked like areas of no sensitivity.
• Later it was determined that while the tongue did have varying degrees of sensitivity; some areas could perceive certain tastes better than others - there was no real truth to the strict tongue map.
• Although taste receptors usually react strongly to a single taste, many respond to multiple gustatory stimulations.

Question 47

What are Papillae

Question 48

What are papillae?

Name 4 types

Answer 48

• 1) Papillae filliformes- responsible for giving the tongue its texture and are responsible for the sensation of touch. Don’t have taste buds.
• 2) Papillae circumvallate
• 3) Papillae fungiform
• 4) Papillae foliatae

Question 49

Gustatory Pathway

Answer 49

•Starts with sensory cells of the taste bud.

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•First synapse is between basal surface of sensory cells and primary afferent neuron.

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Question 50

Neural Processing of Taste

Answer 50

•Taste begins with sensation in the form of electrical impulses.

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•Different stimuli activate different sensory receptors.

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•Chemical stimuli activate the chemoreceptorsresponsiblefor gustatory and olfactory perceptions.

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•Every gustatory receptor cell has a spindly protrusion called a gustatory hair. This taste hair reaches the outside environment through an opening called a taste pore. Molecules mix with saliva, enter the taste pore and interact with the gustatory hairs. This stimulates the sensation of taste.

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•Once a stimulus activates the gustatory impulse, receptor cells synapse with neurons and pass on electrical impulses to the gustatory area of the cerebral cortex. The brain then interprets the sensations as taste.

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Question 51

Describe the Gustatory Cortex and how it works

Answer 51

• The gustatory cortex is the primary receptive area for taste.
• The gustatory cortex consists of two primary structures: the anterior insula, located on the insular lobe, and the frontal operculum, located on the frontal lobe.

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How does it work?

• Peripheral taste receptors, located on the tongue, soft palate, pharynx, and esophagus, transmit the received signal to primary sensory axons.
• The signal is then transmitted to the thalamus, which in turn projects the signal to several regions of the neocortex, including the gustatory cortex.

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Question 52

The King and the Sausage?

(study of students who fasted 16 hours vs 1 hour on taste discernment)

Answer 52

•One study found that groups of students who had not eaten in 16 hours could perceive weaker sucrose and salt solutions than those who had eaten only an hour before.

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•In order to discern taste, students who had just eaten needed a sucrose concentration 50 percent higher and a salt concentration double that of those who had not eaten.

Question 53

What is a Supertaster?

Answer 53

• People with two or sometimes just one dominant allele for the gene TAS2R28. (should be TAS2R38)
• Can perceive more nuanced flavor in food than nontasters, they often find common foods too bitter, sweet or spicy.
• Eg. coffee, hoppy (bitter) beer and vegetables like Brussels sprouts might be too bitter; cake and ice cream might be too rich and chili peppers might be too hot.
• Less likely to crave junky food and eat less food overall – butalso skimp on leafy vegetables.

Question 54

Limbic system components,

specifically, define Amygdala

Answer 54

Limbic cortex – regulates autonomic functions, cognitive processing, attention, emotional behaviors, and spatial memory

Hippocampus – regulates long-term memory formation and retrieval

Amygdala – is associated mainly with various emotional behaviors, fear conditioning, emotional memory formation, and social recognition

Hypothalamus – regulates autonomic nervous system by synthesizing and releasing hormones as well as participates in maintaining circadian rhythms of the body