PS262 Chapters 4, 5 and 6

Optic Chiasm

X-shaped bundle of fibers on the underside of the brain that connects optic fibers from each eye and connect over to the other side of the brain

• they reach contralateral hemisphere of the visual cortex

Superior Colliculus

A paired structure located on the dorsal aspect of the midbrain, involved in processing visual information and coordinating eye movements.

Lateral Geniculate nucleus (LGN)

A relay center in the thalamus that processes visual information received from the retina before sending it to the visual cortex.

What’s the Thalamus’ role in visual information

it acts as a relay station for sensory information

• sensory info often makes a stop before reaching the cortex integrate and process information.

Why is the signal sent from LGN to cortex smaller than input LGN receives from retina?

LGN processes and filters incoming visual signals before transmitting them to the visual cortex

Simple Cortical Cells

cells with side by side receptive fields that respond to specific orientations of visual stimuli.

• cell responds best to bars of vertical orientation but response decreases as soon as orientation changes (little tilt)

• responds best to stationary stimuli

• have a clearly defined excitatory and inhibitory regions

• has a fixed RF

Neurons Orientation Curve

A graphical representation showing how the firing rate of a neuron varies with the orientation of a visual stimulus, indicating the preferred orientation for maximum response.

Complex Cells

respond best to bars of orientation that move in a specific direction and have larger receptive fields than simple cells.

• do not have clearly defined excitatory and inhibitory regions

• respond to motion

• responds anywhere in RF

End-Stopped Cells

fires to moving lines of a specific length or to moving corners or angles

Ganglion Cell

centre-surround RF

• responds best to small spots but responds to other stimuli

Stimulus-physiology relationship

how a specific stimulus affects neural responses

Selective Adaptation

where prolonged exposure to a specific stimulus decreases sensitivity to that stimulus, leading to a reduced neural response.

• firing rate decreases

• fire less when same stimulus reappears, making it harder to detect the stimulus

Selective Rearing

if animal is reared in an environment that only contains a certain type of stimuli, neurons willbecome tuned to those stimuli, enhancing their sensitivity and response to them.

Neural Plasticity

the ability of the brain to change and adapt in response to experience, learning, or environmental changes.

Why does selective adaptation experiment contradict selective rearing?

selective adaption says that prolonged exposure to stimuli causes a decrease in response

selective rearing says that prolonged exposure to specific stimuli causes increased sensitivity and response

• but, selective adaption is short term

• selective adaption is long term

Neural Map

a representation of sensory input that helps the brain process and integrate information from the environment.

Why are points A and B farther apart on the cortex, when they’re closer on the retina?

these points are allotted more space on the cortex than points C and D because

• A and B fall on the fovea, therefore more cortical space granted

  • higher acuity

• C and D fall on the peripheral retina, needing less space for processing

  • lower acuity

Cortical Magnification

apportioning of a large area on the cortex to the small fovea to enhance visual acuity and processing of information.

Location Columns

vertical columns in the visual cortex that respond to stimuli from specific locations in the visual field, helping to organize spatial information.

• one location column contains MANY orientation columns

Orientation Columns

group of neurons that respond to edges and bars at a specific orientation

• orientation columns are organized in a systemic fashion, gradually changing orientation

Hypercolumn

location column with all its orientations column

• will receive all types of information about all possible orientations that fall within retina and is crucial for processing visual information comprehensively.

Tiling

The arrangement of hypercolumns in the visual cortex that ensures complete coverage of the visual field, allowing for efficient processing of visual stimuli.

Ventral pathway

what pathway, responsible for object recognition and form representation.

• temporal lobe

Dorsal Pathway

where/how pathway, responsible for location recognition and spatial awareness in the visual field.

• parietal lobe

• HOW an action should be carried out

when does the receptive field of neurons increase?

when we move to higher extra-striate areas

Ablation

the removal of tissue in nervous system

Object Discrimination Task

monkey shown one object (target) and then shown 2 objects (distractor and target)

• if monkey is able to discriminate and find the target, receives reward

Location Discrimination Task

target object closer to one location than the other, monkey has to choose the location closest to target

Double Dissassoications

two people

• damage to one area causes function A to be absent but function B is present

• damage to one area causes function A to be present but function B to be absent

Patient D.F

patient suffered damage to ventral pathway

• problem in “what”/object recognition

• She was unable to recognize objects but could still interact with them, demonstrating a dissociation between object recognition and action.

  • couldn’t complete static orientation task

  • could complete the orientation matching task.

    • could determine HOW an action should be carried out, (dorsal pathway intact)

Inferotemporal Cortex

area of temporal lobe involved in object recognition and facial processing.

• increase in RF size

• responds to complex stimuli instead of simple stimuli like lines

Medial Temporal Lobe

Important for memoryand learning, involved in forming new memories and spatial navigation.

• parahippocampal cortex

• entorhinal cortex

• amygdala

• hippocampus

Patient H.M

hippocampus on both sides of brain removed

• eliminated his seizures but also

• the ability to form and store any new memories

• resulted in anterograde amnesia, affecting declarative memory.

• did not affect retrograde memory

Contextual Modulation

stimulating outside the receptive field that influences the response of neurons in the receptive field. It plays a role in enhancing or suppressing sensory processing.

Perceptual Organization

The process by which the brain organizes sensory information into meaningful patterns and structures, allowing for the recognition of objects and scenes.

• 3 lines, 1 in RF

  • causes most firing

Why are computers bad at perception?

due to their inability to process sensory information in a way that mimics human perception, which relies on context, experience, and nuanced understanding of the environment.

Viewpoint Invariance

ability to recognize objects seen from different viewpoints and perspectives, allowing for consistent identification regardless of orientation or angle.

perceptual organization

process by which elements in a person’s visual field become perceptually grouped and segregated to create perception

grouping

elements of a visual scene are put together into coherent units and objects

segregation

process of separating one are or object from another

• seeing two building as separate from one another

Structuralism

the idea that we understand what we see by breaking it down into basic sensory elements

• colour, shape, brightness

Gestalt’s Approach

suggesting that the whole is different from the sum of its parts, emphasizing patterns and configurations in perception.

• argues the structuralism approach

Apparent Movement

the perception of motion where none exists, often seen in visual illusions

• stock ticker in new york

  • letters and numbers seem to be moving smoothly across the scene, are created by hundreds of small lights flashing on and off

Illusory Contours

perceived edges that do not physically exist

Principles of Perceptual Organization

determine how elements in a scene become grouped together

Good continuation

is a principle stating that elements that follow a smooth path are perceived as belonging together, leading to the perception of a continuous line or shape.

Principle of Good figure/Simplicity

is a principle that suggests we perceive objects in the simplest form possible, leading to the organization of visual elements into a coherent whole.

Principle of Similarity

is a principle stating that elements that are similar in color, shape, or size are perceived as belonging together in a group.

Principle of Proximity

is a principle stating that elements that are close to each other are perceived as being related or part of the same group.

Principle of Common Fate

is a principle stating that elements moving in the same direction or at the same rate are perceived as a group.

• flock of hundreds of birds flying, that flock is seen as a unit

Principle of Common Region

is a principle stating that elements enclosed within a boundary or region are perceived as a group, regardless of their proximity or similarity.

Principle of Uniform Connectedness

is a principle stating that elements that are visually connected by uniform visual properties are perceived as a single group.

Figure-Ground Segregation

is the perceptual ability to distinguish an object (figure) from its background (ground)

Figural-Cues

are visual signals that guide the perception of figures and their relationships to their backgrounds, aiding in figure-ground segregation.

Recognition by Components (RBC) Theory

states that

• objects are compromised of individual geometric components called geons that combine in various ways to form complex shapes, allowing for object recognition despite changes in viewpoint.

Gist of a Scene

refers to the overall meaning of a scene, processed rapidly

Persistence of Vision

where an image lingers for 250ms after it has been presented

Masking stimulus

a visual stimulus to disrupt the process of persistence of vision

Global Image Features

aspects of a visual scene that provide a summary of its overall appearance, such as color, edges, and spatial arrangement.

• help perceive quicker

Degree of Naturalness

refers to how closely a visual scene resembles real-world environments, influencing viewer perception and interpretation.

Degree of Openness

refers to the extent to which a visual scene includes open spaces or areas without obstruction, impacting the perception of depth and distance.

Degree of Roughness

refers to the texture and irregularity of surfaces in a visual scene, affecting how viewers interpret the scene's complexity and realism.

Degree of Expansion

refers to the perceived amount of space or area that is visually represented in a scene, influencing how viewers gauge the scale and openness of the environment.

Regularities in Environment

are predictable patterns or structures found in the visual environment that help individuals interpret and navigate their surroundings effectively.

physical regularities

regularly occurring physical properties of environment

• more verticals and horizontals in environment compared to angled

• all trees are vertical

  • thus, people have no difficulty perceiving horizontals and verticals

light-from-above assumption

we usually assume light is coming from above since sunlight and any other light comes from above

semantic regularities

meaning of the scene

• an office contains a desk, computer and chair

scene schema

mental knowledge of what to expect in a familiar setting

Unconscious Inference

A theory suggesting that our perception of the world is influenced by past experiences and expectations, allowing us to interpret sensory information automatically.

Retinal Ambiguity

image projected onto the retina is ambiguous, many different objects could create the same retinal pattern

• most people perceive a blue rectangle overlapping the red one, but the retinal image could also be created by a 6-sided red figure

Likelihood Principle

we perceive the most probable object that could have caused the retinal stimulation

• brains automatically resolve ambiguity by choosing most likely interpretation based on past

Probabilistic approach to perception

A framework suggesting that perception is based on the likelihood of various interpretations of sensory input, influenced by prior knowledge and experiences.

• example

  • Step 1 (Prior): Maria believes that colds and heartburn are common, but lung disease is rare. 

  • Step 2 (Likelihood): She observes her friend Charles coughing. Coughing is associated with colds and lung disease, but not heartburn. 

  • Step 3 (Conclusion): Combining prior knowledge with new evidence, Maria concludes that Charles most likely has a cold. 

   

prior probablity

persons initial belief about how likely an outcome is based on experience

likelihood

the extent to which new sensory evidence supports a particular interpretation

Lateral Occipital Complex

active when

• person views any object, animal, face, house or tool

not active when

• person views texture or object with parts scrambled

Fusiform Face Area FFA

an area of the brain that is specifically involved in the recognition of faces and is activated when viewing faces compared to other objects.

• in the fusiform gyrus on the underside of the brain, directly below IT cortex

Prosopagnosia

difficulty of recognizing faces of familiar people

• can’t recognize faces of family, friends or even themselves in the mirror

due to damage to FFA

Amygdala’s function in Facial processing

involved in emotional responses and recognition of facial expressions, particularly fear and social signals.

Frontal Lobe’s function in Facial Processing

evaluation of attractiveness

Superior Temporal Sulcus function in facial processing

involved in processing dynamic aspects of faces, such as gaze direction and facial movements.

Extrastraiate Body Cortex (EBA)

activated by pictures of bodies and parts of bodies

• not activated by anything else, including faces

Parahippocampal Place Area (PPA)

specialized for processing scenes and places, responding to images of landscapes and buildings.

spatial layout hypothesis

suggests that the PPA responds to surface geometry and spatial relationships in visual scenes.

• scenes elicit larger responses than buildings

• building elicit larger responses than objects

Expertise Hypothesis

idea that our expertise in perceiving faces and large response in the FFA to faces can be explained by the fact that we are experts in perceiving faces

• the FFA is not solely for facial recognition, but an area that activates to things we are experts about

Attention

the process of selectively focusing on specific stimuli while ignoring others, influencing perception and cognitive resources.

Overt Attention

move your eyes from one place to another to focus on a particular object or location

Covert Attention

Not moving eyes, instead, looking at one thing while paying attention to something different

Dichotic listening

refers to presenting different stimuli to left and right ear

Shadowing

a technique used in dichotic listening where a participant repeats one message while ignoring another.

Cocktail Party Effect

the ability to focus on a single conversation in a noisy environment, while filtering out other sounds.

Broadbent’s flow diagram

is a model illustrating how information is processed in the brain, emphasizing selective attention and the filtering of stimuli.

Spatial Attention

attention to specific location

Precueing Experiment

A method used to study spatial attention, where participants are cued to pay attention to a specific location before a target is presented

Illusory Conjunction

combination of features that are perceived when stimuli contain several features are presented briefly, where attention is difficult

• red square and blue triangle

• participant may confuse it for red triangle

Feature Integration Theory

how individual features of an object are combined to create a unified perception of that object, suggesting that attention is required for accurate feature binding.

• pre attentive stage

• focused attention stage

Pre-attentive stage

features of objects are analyzed rapidly and unconciously and independently of one another

Focused Attention Stage

attention is involved and conscious perception occurs, which involves binding (combining features)

Visual Search

the process of locating a specific object among distractors in a visual field.

Feature Search

looking for a target with a single feature

• look for horizontal line amongst verticals