Chapter 7 sensory system and perception

Question 1

What are the sensory areas of the cortex?

Answer 1

Primary – input mainly from thalamic relay nuclei
Example: Primary visual cortex receives input from the lateral geniculate nucleus (LGN) of the thalamus.

• Secondary –input mainly from primary and secondary cortex within the sensory system
• Association – input from more than one sensory system, usually from secondary sensory cortex

Question 2

What principles guide the Interactions of Sensory Cortex?

In the context of sensory system organization, explain what is meant by each of the following terms: hierarchical organization, functional segregation, and parallel processing. Summarize the current model of sensory system organization.

Answer 2

Hierarchical Organization: a system whose members can be assigned to specific levels or ranks in relation of one another
*Based on specificity and complexity of function
*Each individual level receives input from a lower level
* Specificity and complexity increases with each level

Sensation – detecting a stimulus

Perception – understanding the stimulus

Functional Segregation: Sensory systems are characterized by functional segregation—each level contains distinct areas that specialize in different types of analysis.
*Primary, secondary, and association areas are no longer thought to be homogeneous but instead specialize in different functions.

Parallel Processing: occurs in sensory systems, meaning information flows through multiple pathways simultaneously, allowing for different types of analyses to happen at the same time.

Question 3

Explain the Organization of the Sensory System

Answer 3

Multiple specialized areas, at multiple levels, interconnected by multiple parallel pathways

• The binding problem – how does the brain make sense of all this?
• While there is no final integrator of information, there are pathways that allow higher areas to influence lower areas

Question 4

Talk to me about the visual cortex bitch

Answer 4

Primary (V1) – posterior occipital lobe
* Secondary
* Prestriate cortex – a band of tissue
surrounding V1
* Inferotemporal cortex
* Tertiary – various areas, largest single
area is in posterior parietal cortex

Question 5

What are Scotomas?

Answer 5

Scotoma – an area of blindness
resulting from damage to visual cortex
* Blind in corresponding contralateral
visual field of both eyes
* Deficit may not be readily detected due to phenomenon of completion

Question 6

What is blindsight?
How does it work

Answer 6

The ability to respond to a visual stimulus even with no conscious awareness of the stimulus (due to a scotoma)
* May be that some connections still exist in V1, allowing for reactions without awareness
* May be that message gets to the brain by connections that do not pass through the damaged area (i.e., LGN to V2)

Question 7

Dorsal and Ventral Streams

Answer 7

Dorsal stream – “where”/control of behavior
* V1 to dorsal prestriate cortex to posterior parietal
* Ventral stream – “what”/conscious perception
* V1 to ventral prestriate cortex to
inferotemporal cortex
* Both “where”/“what” and behavior/perception distinctions are supported by effects of
damage

Question 8

What are the two theories on the dorsal and ventricle streams, and what do they predict?

Answer 8

“Where” vs. “What” Theory:
Dorsal stream specializes in visual spatial perception,
Ventral stream specializes in visual pattern recognition

Predicts
* Damage to dorsal stream disrupts visual spatial perception
* Damage to ventral stream disrupts visual pattern recognition

“Control of Behaviour” vs. “Conscious Perception” Theory:
Dorsal stream specializes in visually guided behaviour
Ventral stream specializes in conscious visual perception

Predicts
* Damage to dorsal stream disrupts visually guided behaviour but not conscious visual perception
* Damage to ventral stream disrupts conscious visual perception but not visually guided behaviour

Question 9

Expliain: “Control of behavior” vs. “conscious perception”

What is Prosopagnosia?
What is Agnosia?
Visual Agnosia?

Answer 9

• Agnosia – failure of recognition
• Visual agnosia – able to see, but unable to recognize
• Prosopagnosia – a specific type of agnosia for faces. Its face blindness, is a neurological condition that impairs a person’s ability to recognize faces.
  ex. man who mistook his wife for a hat

This aligns with the idea that behavioural responses to stimuli can occur without conscious awareness, reinforcing the separation of conscious perception from unconscious visual processing.

Question 10

Is Prosopagnosia limited to faces?

Answer 10

Prosopagnosics are unable to recognize
particular faces – they also are unable to recognize other specifics – which chair, which cow, etc.
* There is an inability to recognize specific objects belonging to a complex class of objects
* Note – some cases where deficits are limited to faces have been observed

Question 11

How does Prosopagnosia occur?

Answer 11

• A result of bilateral damage to the
  ventral “what”/conscious perception
  stream
• Thus, unconscious recognition can be
  preserved
• altered skin conductance responses to
  familiar vs. unfamiliar faces

Question 12

Explain how we recognize Specific Classes of
Objects
* Fusiform face area

Answer 12

• Fusiform face area – activity increased
  during face recognition but not
  recognition of other objects

The ventral stream (the “what” pathway) contains regions that specialize in recognizing different categories, such as humans, animals (e.g., cats), and buildings (e.g., houses).
These areas respond preferentially to specific object classes but are not exclusively dedicated to them.

• Areas in ventral stream may be specific to humans, cats, or houses
• But – more than one area responds to
  each class and there is great overlap

Question 13

Wtf is the Fusiform Gyrus???

Question 14

What is audation?
What is frequency?
What is pitch?

Answer 14

Audition:the sense of hearing
Frequency:the number of complete wavelengths that pass a point in a given time
Pitch: a tone’s highness or lowness
depends on frequency

Question 15

Parts of the ear

Answer 15

Middle Ear:chamber between eardrum and cochlea containing three tiny bones (hammer, anvil,
stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window
Inner Ear: innermost part of the ear, containing the cochlea, semicircular canals, and vestibular
sacs

Question 16

Anatomy of the ear

Answer 16

Tympanic membrane - eardrum
Ossicles - bones in middles ear
 malleus (hammer)
 incus (anvil)
 stapes (stirrup)
Cochlea - snail shaped structure which
contains hair cells
Oval Window - place on cochlea where the
stapes presses

Question 17

What is the organ of corti

Answer 17

The primary sensory organ of hearing, located on the basilar membrane in the cochlea. It contains hair cells, which convert sound vibrations into neural signals.

Question 18

What are hair cells?

Answer 18

The receptive cells of hearing. Their cilia bend in response to sound waves, triggering electrical signals sent to the brain.

Question 19

What is the function of the basilar membrane?

Answer 19

Supports the Organ of Corti and vibrates in response to sound. Different regions detect different frequencies:

Base (near oval window) → High frequencies
Apex (far end) → Low frequencies

Question 20

What is the tectorial membrane?

Answer 20

A gel-like structure above the basilar membrane. The cilia of hair cells push against it when the basilar membrane vibrates, leading to signal transduction.

Question 21

Basilar membrane, tectorial membrane
ion channels of auditory nerve
How do these structures work together to process sound?

Answer 21

Sound waves enter the cochlea and vibrate the basilar membrane.
This causes hair cells to bend against the tectorial membrane.
Bending opens ion channels, generating electrical signals.
Signals travel via the auditory nerve to the brain for interpretation.

Question 22

Overview of the cochlea

Answer 22

Organ of Corti - organ on the basilar
membrane which contains hair cells
Hair cell - receptive cell
Basilar membrane - a membrane in the cochlea that contains the organ of corti
Tectorial membrane - above the basilar membrane, cilia of hair cells move against the tectorial membrane

Question 23

Where are hair cells located?

Answer 23

Inside cochlear coil

Question 24

What are tip links?

Answer 24

Tiny protein filaments that connect the tips of adjacent stereocilia (cilia of hair cells). They help open ion channels when the hair bundle moves.

Question 25

What happens when the hair bundle is straight?

Answer 25

When the bundle is straight there is a 10% chance of ion channels being open

Question 26

What happens when the hair bundle moves toward the tallest cilium?

Answer 26

As the bundle moves toward the tallest cillia the ion channels allow more K+ and Ca+ to enter and depolarize the cell

Question 27

Cochlear nerve What is it? Are hair cells important to it?

Answer 27

Cochlear nerve - bipolar neuron whose cell body is located in the cochlear nerve ganglion 95% of neurons in the cochlear nerve are from inner hair cells, which are myelinated The other 5% originate in outer hair cells and are unmyelinated

Question 28

The 6 steps of hearing (wowww)

Answer 28

Step 1: Sound Wave Entry Sound waves enter the outer ear and travel down the auditory canal. The tympanic membrane (eardrum) vibrates in response. Step 2: Middle Ear Vibration Transmission Vibrations pass through the ossicles: Malleus (hammer) → Incus (anvil) → Stapes (stirrup) The stapes transmits vibrations to the oval window, moving cochlear fluid. Step 3: Cochlear Processing The cochlea is a snail-shaped, fluid-filled structure housing the Organ of Corti (auditory receptor organ). Pressure waves travel through the cochlear fluid, affecting the basilar membrane. Step 4: Organ of Corti Activation The Organ of Corti has two key membranes: Basilar membrane – Holds hair cells (receptors). Tectorial membrane – Rests above hair cells. Vibrations bend hair cell cilia, opening ion channels. Step 5: Neural Signal Transmission Depolarization occurs as K+ and Ca²+ enter the hair cells. This increases auditory nerve firing, sending signals to the brain. Step 6: Frequency Coding in the Cochlea Different frequencies activate different regions of the basilar membrane: High frequencies → Base (near oval window). Low frequencies → Apex (tip of cochlea). Multiple auditory neurons carry frequency-specific signals to the brain for processing.

Question 29

lecture version: Auditory pathway

Answer 29

Step 1: Cochlear Nucleus First relay station in the brainstem. Receives input from the auditory nerve. Step 2: Superior Olivary Complex Located in the medulla. Codes for spatial location by comparing signals from both ears (sound localization). Step 3: Lateral Lemniscus A fiber tract that carries auditory information through the medulla and pons. Sends signals to the inferior colliculus. Step 4: Inferior Colliculus Located in the midbrain. Processes reflexive responses to sound and sound localization. Step 5: Medial Geniculate Nucleus (MGN) Located in the thalamus. Acts as a relay station for auditory signals before reaching the cortex. Step 6: Auditory Cortex Located in the temporal lobe. Responsible for sound perception, interpretation, and recognition.

Question 30

What is the role of the Inferior Colliculus?

Answer 30

Located in the midbrain. Processes sound localization and reflexive responses to auditory stimuli. Relays auditory signals from the lateral lemniscus to the medial geniculate nucleus.

Question 31

What is the Medial Geniculate Nucleus (MGN)?

Answer 31

Part of the thalamus. Final relay station for auditory signals before they reach the auditory cortex. Refines and processes auditory information, maintaining frequency selectivity.

Question 32

What is the Auditory Cortex?

Answer 32

Located in the temporal lobe. Responsible for sound perception, recognition, and interpretation. Organized tonotopically—different areas process specific frequencies of sound.

Question 33

What is Tonotopic Representation?

Answer 33

A topographical organization of sound frequencies in the auditory system. High frequencies processed at the base of the cochlea and the front of the auditory cortex. Low frequencies processed at the apex of the cochlea and the back of the auditory cortex. Helps in distinguishing pitch and tone.

Question 34

What is Phase Difference?

Answer 34

Phase difference refers to the difference in the arrival times of sound waves at each of the ear drums. It helps the brain detect the direction of sound sources, especially for low-frequency sounds.

Question 35

How is Phase Difference Detected?

Answer 35

Detected by the medial superior olivary complex (MSO). The MSO compares the timing of sound arrivals at each ear to locate the sound source. difference in arrival times of sound waves at each of the ear drums

Question 36

What are Intensity Differences?

Answer 36

Intensity differences occur when a sound is louder in one ear than the other. They help the brain determine the lateral location of a sound source, especially for high-frequency sounds.

Question 37

How are Intensity Differences Detected?

Answer 37

Detected by the lateral superior olivary complex (LSO). The LSO compares the intensity of sounds arriving at both ears to detect the direction of the sound source.

Question 38

What are the three separate systems in somatosensory

Answer 38

Exteroreceptive – external stimuli * Proprioceptive – body position * Interoceptive – body conditions (e.g., temperature and blood pressure) * Exteroreceptive – 3 divisions

Question 39

Exteroreceptive System: 3 devisions

Answer 39

Touch (mechanical stimuli) * Temperature (thermal stimuli) * Pain (nociceptive stimuli) * Specialized receptors respond to the various stimuli

Question 40

Cutaneous Receptors

Answer 40

* Free nerve ending: * temperature and pain * Pacinian corpuscles * adapt rapidly, large and deep; onion-like * sudden displacements of the skin * Merkel’s disks – gradual skin indentation * Ruffini endings – gradual skin stretch Stereognosis – identifying objects by touch * Dermatome – the area of the body innervated by the left and right dorsal roots of a given segment of spinal cord

Question 41

Story to help you with cutaneous receptors

Answer 41

When you touch an object, your skin acts as a sensory organ, detecting different types of stimuli. The cutaneous receptors in your skin play a key role in helping you feel and respond to the world around you. First, as your skin encounters a change in temperature or pressure, free nerve endings spring into action. These simple, unprotected nerve endings are sensitive to pain and temperature, alerting you when something is too hot, too cold, or painful. For example, if you accidentally touch something sharp, these free nerve endings will immediately send a signal to your brain, causing a painful sensation. Now, if you touch something more subtle, like the surface of a pillow, you have other receptors that help detect texture or the movement of the skin. The Pacinian corpuscles, which are deep and onion-like in structure, respond to sudden skin displacement—such as when you press into the pillow. These receptors adapt rapidly to vibrations or pressure, helping you feel even the smallest shift in your environment, like when the pillow shifts as you lay your head down. If you apply a more gradual pressure, like gently pressing your hand against a smooth surface, Merkel’s disks are the receptors that detect that gradual skin indentation. These receptors are sensitive to light touch and help you feel things like the texture of a fabric or the detailed surface of an object.

Question 42

Stereognosis vs * Dermatome

Answer 42

Stereognosis – identifying objects by touch * Dermatome – the area of the body innervated by the left and right dorsal roots of a given segment of spinal cord

Question 43

What is the Dorsal-Column Medial-Lemniscus System?

Answer 43

It processes touch and proprioception (sense of body position). The first synapse occurs in the dorsal column nuclei of the medulla. It carries information about fine touch and vibration.

Question 44

What is the Anterolateral System?

Answer 44

It processes pain and temperature sensations. The first synapse occurs immediately upon entering the spinal cord.

Question 45

What Are the 3 Tracts of the Anterolateral System?

Answer 45

Spinothalamic tract – carries pain and temperature information to the thalamus. Spinoreticular tract – involved in arousal and attention to painful stimuli. Spinotectal tract – directs attention to painful stimuli, particularly related to visual and sensory processing.

Question 46

Somatosensory cortex: Where is the Primary Somatosensory Cortex (SI) Located? How is it organized? Contralateral impute? Role of SII? Output to Association Cortex?

Answer 46

Location of SI: The Primary Somatosensory Cortex (SI) is located on the postcentral gyrus of the brain. Somatotopic Organization: The sensory areas of the body are mapped onto the cortex. This mapping is somatotopic, meaning that each area of the body has a corresponding area on the cortex. Areas of the body that are more sensitive (like the fingertips or lips) have a larger cortical representation. Contralateral Input: Sensory input to the SI is contralateral—meaning that the left side of the body sends sensory information to the right SI, and vice versa. Role of SII: The Secondary Somatosensory Cortex (SII) receives input from SI. SII also follows a somatotopic organization but receives input from both sides of the body. Output to Association Cortex: The output from SI and SII is directed to the association cortex in the posterior parietal lobe, where higher-level processing and integration of sensory information occurs.

Question 47

What is Asterognosia ?

Answer 47

inability to recognize objects by touch * pure cases are rare – other sensory deficits are usually presen

Question 48

Asomatognosia what is it?

Answer 48

The failure to recognize parts of one’s own body – the case of the man who fell out of bed

Question 49

Descending Pain Control Circuit * 3 discoveries made this possible

Answer 49

Electrical stimulation of the periaqueductal gray (PAG) has analgesic (pain-blocking) effects * PAG and other brain areas have opiate receptors * Existence of endogenous opiates (natural analgesics) - endorphins

Question 50

chemical senses what two does food act on

Answer 50

Olfaction (smell) * detects airborne chemicals * Gustation (taste) * Responds to chemicals in the mouth * Food acts on both systems to produce flavor

Question 51

Pheromones

Answer 51

Chemicals that influence the behavior of conspecifics (members of the same species) * Evidence of human pheromones? * Changes in olfactory sensitivity across and menstrual cycle * Synchronization of menstrual cycles * Sex differences in odors * Men can identify menstrual stage by smell

Question 52

Olfaction

Answer 52

Receptors embedded in the olfactory mucosa of the nose * Thousands of olfactory receptor proteins * New receptors are created throughout life

Question 53

Gustation

Answer 53

Receptors in tongue and oral cavity in clusters of about 50 called taste buds * > 4 (sweet, sour, salty, bitter) primary tastes – 5th is umami, meat or savory * Many tastes not created by combining primaries * Salty and sour don’t have receptors, they merely act on ion channels

Question 54

Anosmia and Ageusia what are they?

Answer 54

* Anosmia – inability to smell * Most common cause is a blow to the head that damages olfactory nerves * Incomplete deficits seen with a variety of disorders * Ageusia – inability to taste * Rare due to multiple pathways carrying taste information

Question 55

Selective Attention: What is it? What are the types? What is Change Blindness?

Answer 55

Selective attention is the process by which we focus on certain pieces of information while ignoring others. Endogenous Attention: Driven by internal cognitive processes (e.g., focusing on a task or goal). Exogenous Attention: Driven by external events or stimuli (e.g., something catching your eye in the environment). Change blindness refers to the phenomenon where people fail to notice changes in a visual scene because they were not attending to the area where the change occurred. This occurs because there is no memory of what was not attended to, and the brain does not retain information about it.