MCAT Sensation, Perception, and Consciousness

Question 1

Transduction

Answer 1

When an environmental signal is turned into an electrical signal that’s sent to the brain.

Question 2

Sensory Adaptation

Answer 2

When the strength in the response to a stimulus decreases with prolonged exposure to the stimulus.

Question 3

Difference threshold (just noticeable difference)

Answer 3

The minimum threshold to differentiate two between two stimuli 50% of the time.

Question 4

Weber’s law

Answer 4

As the intensity of the stimulus increases so does the just noticeable difference.

Given by the following equation:

(Difference threshold)/ (original stimulus strength) = K

We can find the difference threshold of one stimulus by using the equation and calculating the constant, K.

Question 5

Absolute threshold

Answer 5

The threshold needed to detect a stimulus 50% of the time.

Question 6

Signal detection theory

Answer 6

Used to see how external stimuli effects our judgements and decision making.

• Hit = signal presented, correctly identified
• Miss = signal presented, not identified.
• False alarm = no signal present, signal identified.
• correct rejection = no signal, signal not identified.

Question 7

Sensory receptors, what are the four types?

Answer 7

Sensory receptors take internal and external stimuli and transduce them to the CNS.

• Mechanoreceptors- respond to mechanical stimuli such as pressure, vibrations, movement.
• Thermoreceptors - receptors that respond to a change in temperature.
• Photoreceptors - responds to light.
• Chemoreceptors - responds to chemicals like taste and smell.

Question 8

Role of the thalamus

Answer 8

Most sensory information is sent here first and then to the appropriate brain regions.

The exception is olfactory stimuli which is sent to the olfactory bulb and then directly to brain regions.

Question 9

Perception

Answer 9

Making a meaning of neural signals.

Question 10

Top- down processing

Answer 10

When someone uses previously encoded information in perception of stimuli.

Question 11

Perceptual set

Answer 11

When someone focus on certain parts of a stimuli but not others.

Question 12

Perceptual organization

Answer 12

When someone’s experiences and expectation effect their perception of a stimulus.

People can have different perceptions of a stimulus if they have difference experiences and expectations.

Question 13

Perceptual constancy

Answer 13

When nothing changes to the stimulus when slight changes are done to it when were observing it.

• Shape constancy
• Size constancy
• Color constancy
• Brightness constancy

Question 14

Depth perception

Answer 14

When a person sees in 3D from the brain’s interpretation of 2D information from the eyes.

Information of depth perception given by monocular cues and binocular cues.

Question 15

Describe the following monocular cues:
- Interposition

• Relative size
• Height in plane (relative height)
• Motion parallax (relative motion)
• Linear perspective

Answer 15

Monocular cues are cues from one eye that gives us information about depth perception.

• Interposition - When an object is partially blocked by another object the partially blocked object appears further away.
• Relative size - An object that is further away from another object appears smaller.
• Height in plane - objects lower the plane appears closer to us the objects further in the plane.
• Motion parallax - object that’s closer to us seem to be moving faster than objects further away. Think moving in a car.
• Linear perspective - parallel lines going off in the distance appears to come together.

Question 16

Describe the binocular cues

Answer 16

Binocular cues are cues on depth given by both eyes.

• Retinal disparity - information about depth caused by the slight difference in the images that falls on both eyes.
• Convergence - The brain interprets the angles created by the eyes when they come close together to view close objects and the increase in the angle as it views objects further away.

Question 17

Phi phenomenon

Answer 17

When adjacent flashing lights are perceived as moving.

Question 18

Gestalt principles. Describe each one:
1. Law of subjective contours

2. Law of similarity
3. Law of continuity
4. Law of closure
5. Law of proximity

Answer 18

Used to explain how the brain examines stimuli as a whole rather than its hearts.

• Law of subjective contours- we perceive the contours (edges) of an object even when it’s not filled in.
• Law of similarity- we group together objects that are similar.
• Law of continuity - we view stimuli as a continuous path, not broken paths.
• Law of closure- we view the whole object by filling in gaps (think “ closing in those gaps”).
• Law of proximity - we see objects that are close together as groups .

Question 19

What kind of waves is light?

Answer 19

Electromagnetic waves.
Wavelength determines it’s color (hue).

• Amplitude describes its intensity.

Question 20

Describe the following parts of the eye:
- The cornea
- The pupil
- The iris
- The sclera
- The lens

Answer 20

• The cornea covers the pupil
• The pupil is the opening of the eye that allows light the pass.
• The iris- determines the dilates or constricts the pupil. It’s colored and determines the color of our eyes.
• The sclera- the white part of the eye.
• The lens- changes shape to change how the image falls onto the retina.

Question 21

Accommodation

Answer 21

The process of the lens changing shape to change how the image falls onto the retina.

Question 22

Describe the photoreceptors of the eye

Answer 22

Rods responds to movement and white, black, and grey colors.

Cones has high visual acuity and responds to the other colors.
- Centermost region of cones is the fovea which is the highest visual acuity as it’s packed with cones. The middle of the fovea is the macula.

Question 23

Describe how visual information is passed among retinal cells?

Answer 23

Photoreceptors sends information to bipolar cells which synapses onto the ganglion cells whose axons come together and form the optic nerve. It goes to the thalamus and then to the visual cortex of the occipital lobe.

• The optic disk is where the optic nerve leaves for the thalamus and blood vessels supply blood to the retina. Because of this there’s a blind spot there.

Question 24

Describe the visual pathway in the brain

Answer 24

Optic nerve crosses over at the chiasm so that information is processed on the opposite side of the brain from where it was transduced.

Now they’re referred to as tracts which goes to the lateral geniculate nucleus of the thalamus and then to the V1 (primary visual cortex)

Question 25

Feature detectors

Answer 25

Neurons within the V1 only fire when exposed to different features of a stimulus such as certain orientation of lines.

Question 26

Parallel processing

Answer 26

Processing the different information from feature detectors simultaneously.

Question 27

Parvocellular pathway v. Magno cellular pathway of the V1

Answer 27

Parvo pathway transmits information about fine details from the LGN to V1.

Magno pathway transmits information about motion from LGN to V1.

Question 28

Ventral stream v. Dorsal stream of V1

Answer 28

Ventral stream - projects information from V1 to the temporal lobe about what the of the stimulus (characteristics)

Dorsal stream- projects information from V1 to parietal lobe about the motion of the stimulus.

Question 29

What are the two theories about how we process color?

Answer 29

• Trichromatic theory- cones responds to one the following three colors: red, green, blue.
• Opponent - process theory - cones sense color in opposing pairs. Inhibition of one leads to activation of the other: red- green, blue- yellow

Question 30

What are the three sections of the ear?

Answer 30

Outer ear - contains the pinna which serves to funnel sound to the tympanic membrane (eardrum).

Middle ear - contains the tympanic membrane which vibrates the malleus, Incas, and stapes which are also in the middle ear.

Inner ear - contains the cochlea. Contains semicircular canals and otolith organs which are part of the vestibular system.

Question 31

Describe the cochlea

Answer 31

A three- chambered structure in the inner ear. The middle chamber contains the organ of Corti which contains mechanoreceptors and supporting cells that sits on the basilar membrane.

The fluid in the middle chamber is called endolymph and when hair cells move it causes depolarization allowing the auditory nerve to send signal to brain.

The receptors are also called hair cells because on top of the mechanoreceptors are cilia.

Question 32

What happens after auditory transduction?

Answer 32

The vestibulocochlear nerve sends signal from cochlea to medial geniculate nucleus (MGN) of the thalamus. From the thalamus it’s sent to the auditory cortex of the temporal lobe and to the inferior colliculus.

Question 33

What is the pitch of sound?
Frequency theory
Place theory

Answer 33

How high lor low a tone is, determined by frequency.

• Frequency theory - pitch perception occurs because of the frequency of interaction at the auditory nerve.
• Place theory- pitch is influenced on where receptors are located on the basilar membrane in the organ of corti.

Question 34

Somatosensation

Answer 34

The process of relaying sensory information from the environment to the brain. Specific receptors respond to specific stimuli.

Somatosensory neurons transduce sensory stimuli to electrical signal that’s sent to the primary somatosensory cortex (which is in the parietal lobe).

Most sensitive parts of the body take up more space in the somatosensory cortex.

Question 35

Hemispheric lateralization

Answer 35

Each brain region is specialized for a specific function.

Each side of the brain interprets somatosensory information from the opposite side of the body.

Question 36

Gate- control theory

Answer 36

pain is controlled by a “ neurological gate” that can be closed by another type of stimuli thereby decreasing the sensation of pain.

i.e. being distracted during a tattoo session decreases the perception of pain.

Question 37

Gustation

Answer 37

The process by which tastants bind to taste receptors within taste buds. Taste buds are organized into papillae on the tongue.

Taste receptors responds to a certain taste but there is multiple forms of taste receptors in each taste bud.

Question 38

What are the 5 primary tastes?

Answer 38

Sweet, bitter, umami ( savory flavor of meat), sour, salty

Question 39

Chemical senses

Answer 39

Food and odor molecules

Question 40

Describe the path that gustatory information travels to the brain?

Answer 40

Tastant binds to taste receptor and depolarizes it. This causes a signal to be sent to the gustatory afferent neuron which synapses onto the thalamus.

The thalamus then sends the information to the primary gustatory cortex which is located in the insular cortex of the frontal lobe.

Question 41

Sensory information

Answer 41

When sensory information influences each other.

Question 42

Olfaction

Answer 42

Occurs when an oderant binds to cilia of olfactory neurons. There neurons form the olfactory nerve which sends information to the olfactory bulb.

The axons of the olfactory bulb forms the olfactory tract which sends information directly to various brain regions.

Question 43

What is unique about olfaction?

Answer 43

It bypasses the thalamus

Question 44

Kinesthetic sense. How is it sensed?

Answer 44

The awareness of our body in space and our movement. Happens through proprioceptors.

Proprioceptors are mechanoreceptors that are located in skin, tendons, joints, and muscles and responds to mechanical stimuli.

Question 45

Describe the path of proprioceptor information transmition

Answer 45

Proprioceptors transmit information from the environment from afferent sensory neurons which sends it the the spinal cord.

The spinal cord sends information to thalamus via tracts.

From the thalamus it’s sent to the primary somatosensory cortex in the parietal lobe.

Question 46

Vestibular sense. How is it sensed?

Answer 46

Maintain’s body sense of balance.

Sensed from the semicircular canals and otolith organs of the inner ear.
There information is sent to the brain via the vestibulocochlear nerve.

Question 47

Semicircular canals v. otolith organs

Answer 47

Semicircular canals transmits information related to angular acceleration due to continous movement of the endolymph in the middle ear if we suddenly stop our angular momentum.

Otolith organs transmit information about linear acceleration.

Question 48

Sensory interaction

Answer 48

When our kinesthetic sense, vestibular sense, and sensory information all combined gives us information about proprioception and vestibular information.