Top Hat module 4

Question 1

Sensation

Answer 1

The conversion of physical properties of the world or body into a neural code by the peripheral nervous system. It’s the first step of perception

Question 2

Perception

Answer 2

The processing and interpretation of sensory information into a form that can meaningfully guide behavioral decisions.

Question 3

Exteroception

Answer 3

The sensing and processing of information from the external environment by the five basic senses: vision, audition, touch, taste, and smell. We have these different forms of exteroception because the various types of stimuli provide information that has distinct advantages and disadvantages.

Question 4

Interoception

Answer 4

The sensing and processing of information from inside the body. This includes proprioception (the perception of the location of the limbs in space), nociception (the perception of pain due to internal bodily damage), and equilibrioception (the perception of bodily balance)

Question 5

Types of sensory receptors

Answer 5

• Chemoreceptors: Sensory receptors with nerve endings specialized to respond to chemicals in the environment.
• Mechanoreceptors: Sensory receptors specialized to respond to mechanical force.
• Thermoreceptors: Sensory receptors specialized to respond to heat.
• Photoreceptors: Sensory receptors specialized to respond to light.

Question 6

Perceptual process

Answer 6

1) transduction of physical energy into a neural code by the senses,
2) transmission to the brain through subcortical and then cortical structures,
3) processing in the cortex to generate behavior.

Question 7

Exterior anatomy of eye

Answer 7

• Cornea: A transparent rubbery layer of tissue at the front of the eyeball that bends light to focus it on the retina.
• Iris: A ring of colored muscle around the pupil that contracts or relaxes in order to determine the size of the pupil.
• Pupil: A small hole at the center of the iris that controls how much light is allowed to pass into the eye.

Question 8

Focus

Answer 8

A property of an image in which specific locations in the environment correspond to specific locations on the imaging device.

Question 9

Photoreceptors

Answer 9

Sensory receptors (neurons) specialized to respond to light.

Question 10

Types of photoreceptors

Answer 10

• Rods: A type of photoreceptor in the retina, outside of central vision, that responds to lower light but with reduced spatial acuity and no color differentiation.
• Cones: A type of photoreceptor, largely contained in the central fovea of the retina, that supports high spatial resolution and color vision under higher lighting conditions.

Question 11

Fovea

Answer 11

A depression in the retina that is densely packed with cone photoreceptors and is responsible for seeing detailed properties.

Question 12

Retina

Answer 12

A structure in the back of the eye consisting of multiple layers of neurons, including photoreceptors in the final layer which transduce light. The retina begins as part of the brain during development and then detaches and migrates away. It is considered par of the CNS.

Question 13

Retina “pre-processing” purpose

Answer 13

Compress or reduce the amount of information that the retina needs to send to the brain. This compression is necessary because the visual information needs to be sent to the back of the eye through the optic nerve, a bundle of axons that pass from the retina to the brain. It can’t be too fat, or it would restrict the movement of the eye and the number of photoreceptors that the retina can contain (because the optic nerve must pass through the retina, forming a “hole” in the layer of photoreceptors where it exits in order to reach the brain).

Question 14

Thalamus

Answer 14

A subcortical region of the brain that serves as a way-station between sensory inputs and the cortex. Around 99% of all the visual information sent from the retina to the brain goes through it.

Question 15

Primary visual cortex (V1)

Answer 15

The first region of the cortex to receive visual input. It contains neurons that respond to fairly simple patterns mostly consisting of oriented edges of particular sizes. As a general rule, as we travel up in the visual system, away from the original sensory input, the properties that neurons respond to grow more complex and more specific.

Question 16

Agnosias

Answer 16

A disability in which an individual has difficulty recognizing or perceiving certain kinds of objects. Examples:
- Prosopagnosia: A visual deficit that leads to an inability or difficulty in recognizing faces.
- Semantic agnosia: A visual deficit leading to the inability to recognize objects.

Question 17

Fusiform face area (FFA)

Answer 17

A region in the inferior temporal cortex that shows greatest activity when a subject is performing face-specific tasks (like naming people from a picture of their face). Some researchers have argued that the FFA is not concerned with faces per se, but rather with the ability to discriminate between visually similar stimuli (“visual expertise”). It is activated for faces because most people become face experts due to the social importance of being able to distinguish people.

Question 18

Lateral OccupitL Cortex (LOC)

Answer 18

A region in the occipital cortex that shows greatest activity when a subject is performing object-recognition tasks. The presence of such specialized brain activity has suggested to some researchers that these parts of the brain are geared towards processing particular classes of objects.

Question 19

Streams of information

Answer 19

• The dorsal stream projects upward and terminates in the parietal lobe. Helps identify where objects are.
• The ventral stream projects downward and terminates in the temporal lobe. Helps identify what objects are.

Question 20

Controversies about stream functions

Answer 20

Many times determining what something is depends on analyzing where its parts are in relation to one another. Other researchers have argued that the division between the dorsal and ventral streams is not one of “what” versus “where,” but rather “perception” versus “action”. This suggests that perhaps we should think of the division of information in the brain not only in terms of the kind of information that is being taken in but also in terms of what the information will be used for.

Question 21

Outer ear anatomy

Answer 21

• Pinna: The visible portion of ear made up of folded cartilage; it serves to gather and transmit sound into the ear canal.
• Ear canal: A narrow tube following from the pinna that amplifies certain sound frequencies and transmits them to the eardrum.

Question 22

Middle ear anatomy

Answer 22

• Eardrum: A thin piece of tissue separating the ear canal from the inner ear that amplifies certain frequencies and passes them to a series of tiny bones called the ossicles.
• Ossicles: A set of three tiny bones that amplifies certain frequencies and relays them to the cochlea.

Question 23

Inner ear anatomy

Answer 23

• Cochlea: A coiled, bony structure in the inner ear that is filled with fluid and contains the basilar membrane.
• Basilar membrane: A strip of tissue inside the cochlea that contains the hair cells that transduce sound.

Question 24

Hair cell

Answer 24

A type of mechanacoreceptors situated in the basilar membrane that are stimulated by vibrations in the fluid in the cochlea, which they convert into a neural signal that is sent to the brain.

Question 25

Why is the cochlea full of fluid?

Answer 25

The answer likely lies in the fact that that the fluid-filled environment of the cochlea preserves the underwater conditions in which brains first evolved. The problem is that sound loses a lot of its amplitude when it moves from air to fluid. The purpose of the structure of the ear is to amplify the sound so that the original frequencies and amplitudes are preserved in the cochlea.

Question 26

Tonotopic map

Answer 26

A spatial arrangement of neural structures (such as hair cells) in which locations are organized based on the frequency of sound they encode.

Question 27

Primary auditory cortex (A1)

Answer 27

A region in the temporal lobe of the cortex that is the first to receive auditory information in the cortex.

Question 28

Sound waves

Answer 28

Oscillating movement in the air caused by vibrations of objects in the environment. That vibration propagates as waves in the air. Different movements of different objects lead to telltale patterns of vibrations. The perceptual system uses these patterns of vibrations in order to infer certain properties of the world.

Question 29

Properties (dimensions) of sound waves

Answer 29

• Frequency: A measure of the lengths of a wave defined as the distance between the crests of sequential waves. A low-frequency sound has a low pitch, while a high-frequency sound has a higher pitch.
• Amplitude: The length from the trough of a wave to its crest. The length from the trough of a wave to its crest. A more powerful vibration will lead to higher amplitudes, resulting in a louder sound.

Question 30

Chemical senses

Answer 30

• Olfaction: the sense of smell. It measures chemicals that have travelled through the air (sometimes over a long distance)
• Gustation: the sense of taste. It measures the presence of certain chemicals that have already been ingested into the mouth.
  These senses are much less involved in cognition. They came first and the other senses likely developed evolutionarily as extensions of these more “primitive” sensing abilities. Thus, there are likely many clues to the origins and structure of other perceptual systems contained within these systems.

Question 31

Taste buds

Answer 31

Structures on the surface of the tongue that contain the sensory receptors for taste. We have five basic taste receptors types: sweetness, sourness, saltiness, bitterness, and savoriness (also known as umami). These sensory neurons send their signal through the brainstem, rather than the spinal cord, through devoted nerve fibers. Each nerve fiber carries a mix of signals which the brain sorts out to generate our perceived tastes.

Question 32

Primary gustatory cortex

Answer 32

The first region of the cortex to receive information from the gustatatory sensory system. It contains 2 substructures: one on the lateral sulcus (a deep fissure that divides both the frontal and parietal lobes from the temporal lobe) and one on the frontal lobe. The functional divisions of the gustatory cortex are not well understood, but a small portion have been found to encode specific tastes

Question 33

Olfactory epithelium

Answer 33

A strip of tissue in the nasal cavity that contains the chemical sensory receptors that support the sense of smell. There is a very wide array of olfactory receptor types, each with its own tuning to different chemicals. By comparing the patterns across these different receptors, it is estimated we can differentiate a trillion different odors.

Question 34

Olfactory bulb

Answer 34

A specialized brain structure at the bottom of the forebrain that receives the information from the olfactory epithelium. The olfactory bulb is a layered structure that is generally assumed to act like something of a filter for the neural signals. However, its function is still not well understood. The olfactory bulb projects to several other brain structures including the amygdala, which is involved in emotional processing, and the hippocampus, which is involved in memory formation.

Question 35

Tactile exteroception

Answer 35

Spread throughout our skin are tiny mechanoreceptors, receptors that respond to different kinds of physical stimulation. There are four kinds of tactile receptors that respond to different kinds of stimulation, from small light touches (these are concentrated in places like your fingertips) to large, sustained pressure (these are found in places like your trunk).

Question 36

Somatosensory cortex

Answer 36

A region of the brain, located in the temporal lobe, that receives multiple sources of sensory information from across the body, including sensation of touch.

Question 37

Cortical homonculus

Answer 37

A spatially organized map of the human body, contained within the somatosensory cortex, that processes touch information. Different locations on this map respond to specific regions of the body when they are touched. This representation is enlarged for portions of the body that are dense with sensory receptors and large for those with sparse receptors. We need more information from some parts of our body than others, and the more sensory information coming in from a location, the more neural resources that are needed to process it.

Question 38

Constructive perception

Answer 38

A model of perception in which the sensory information is used to generate a mental model of the environment that is assumed to have caused the sensory stimulus. Behavioral decisions are then based on the inferred model rather than on the sensory stimulation itself. This perspective was first described in detail by the German physicist Hermann von Helmholtz in 1867, who referred to it as “unconscious inference.”

Question 39

Direct perception

Answer 39

A theoretical approach to perception that holds that the sensory stimuli be used to guide behavior in an action/perception loop. This view is often associated with the American psychologist, James J. Gibson, who did important work on behaviors such as locomotion.

Question 40

The Ambiguity of the Sensory Stimulus

Answer 40

The sensory data in the body are used as evidence to infer the external conditions in the environment outside the body. Our entire notion of an external world, filled with objects and other people, laid out in 3D space, is a construct of the brain, based on the available sensory evidence. This sensory “evidence” is highly ambiguous, any sensory stimulus is consistent with many possible distal stimuli.

Question 41

Illusions

Answer 41

The ambiguous nature of sensory stimuli can be seen very clearly in the case of illusions, the rare examples where our brain consistently makes the wrong guess. Illusions can be interesting because they reveal the underlying assumptions that the brain makes during perception

Question 42

Why are we subject to illusions?

Answer 42

Our perceptual brain is more concerned with the properties of an object that remain stable across variable conditions, a fundamental property of the constructive perception model. You want your black backpack to look black whether you are indoors or outdoors. If we just measure the light currently bouncing off of it, this will vary wildly across conditions. But if we figure out its reflectance, this will not change based on the lighting conditions.

Question 43

Bi-stable (stimulus)

Answer 43

Property of a stimulus that has alternating stable perceptual interpretations. Ex. seeing a 3D cube. This bi-stability actually depends on the fact that your brain must guess the third dimension from two-dimensional images.

Question 44

Top-down processing

Answer 44

Perceptual processing that leverages stimulus or category specific knowledge.

Question 45

Bottom-up processing

Answer 45

Perceptual processing that is applied generally too all stimuli and does not depend on specific knowledge of the stimulus or its category.

Question 46

Phonemic restoration effect

Answer 46

A perceptual phenomenon in which missing sounds are “filled in” by the brain based on knowledge of language. The “filling in” of the missing sounds behind other noises are based on a top-down guess, on your expectations due to your knowledge about the English language and how it sounds.

Question 47

Image segmentation

Answer 47

While the retinal image is a continuous array of measurements, your brain may want to know how to divide up the image into different objects and regions. It depends on a combination of bottom-up and top-down processes.

Question 48

Figure-ground assignment

Answer 48

The determination of which side of a boundary contains the shape versus the background. Convexity refers to the general bias to assign figure or ground such that the assigned figure has a shape in which more of the contour is protruding outward (convex, such as your fingers) rather than inward (concave, such as the region between your fingers). This is because, in the real world, objects tend to have more convex shapes than concave ones. There is also bias towards symmetrical figures.

Question 49

Visual grouping

Answer 49

The perception of discrete visual elements as forming a larger pattern or whole. It was first described by the Gestalt school of psychology over a hundred years ago. he Gestaltists identified a number of grouping cues, which they referred to as “laws”, like similarity, proximity, etc. Again, like figure-ground cues, the Gestalt grouping cues may also be seen as reflecting a type of inference based on commonly observed properties of objects.

Question 50

Depth perception

Answer 50

Depth information is important not only in order to figure out how far an object is away from you in order to interact with it but also for the purposes of determining the shape of an object, which may be critical for recognition.

Question 51

Binocular disparity

Answer 51

The fact that the image of the world falling on each of the two eyes is different. The amount of disparity between the two eyes changes as a function of how far away an object is in depth from the point you are fixating on.

Question 52

Stereopsis

Answer 52

The use of binocular disparity (the fact that image falling in the two eyes is different) in perceiving depth.

Question 53

Recognition

Answer 53

Matching some incoming stimulus to a stored representation in memory.

Question 54

Template model

Answer 54

A simple model of recognition that depends on directly matching an incoming image to an image of an object or category in order to determine whether they reach some threshold of similarity. However, it turns out that template models are failures when trying to recognize objects in the real world. This is because every time that you view an object, the image it produces on your retina is different due to external factors such as changes in depth, lighting, and viewpoint.

Question 55

Identification

Answer 55

A form of recognition that consists of determining whether a given image corresponds to a specific individual object or individual.

Question 56

Classification

Answer 56

A form of recognition that consists of determining whether a given image corresponds to a class or category.

Question 57

Contextual Factors in Recognition

Answer 57

The context in which an object appears can sometimes contain valuable information that can help you to recognize it. This contextual information is another form of top-down processing: using our past experience to make inferences about the current sensory information.

Question 58

Irving Biederman (1972) studies on recognition

Answer 58

Biederman sought to determine whether context can facilitate object recognition. He compared accuracy in a fast recognition task when objects appeared in their appropriate context as opposed to when they were shown in the wrong context and found that appearing in the correct context led to better and faster accuracy in identifying the target object.

Question 59

Scene schema

Answer 59

A learned representation of which objects tend to appear in specific kinds of scenes.