Visual Perception and Imagery

Flashcards on visual perception, the brain, and emotion identification

Dorsal Stream

A system of interconnected regions of the visual cortex involved in the perception of spatial location, beginning with the striate cortex and ending with the posterior parietal cortex.

Ventral Stream

A system of interconnected regions of visual cortex involved in the perception of form, beginning with the striate cortex and ending with the inferior temporal cortex.

Early Visual Perception Models

Early models of visual perception focused on top-down analysis and included relatively little discussion of neural implementation.

Functional Neuroimaging

functional neuroimaging allowed scientists to study what goes on in the brain during cognitive tasks

Two Visual Systems Hypothesis

Ungerleider and Mishkin proposed this in 1982

Origin of Two Visual Systems Hypothesis

experiments on monkeys in which different parts of their brain were selectively removed

Tri-Level Hypothesis of Information Processing

David Marr's framework emphasizing understanding how cognitive processes are implemented.

Computational Level

The highest, most abstract level of Marr's tri-level hypothesis focusing on the purpose of the process.

Algorithmic Level

The programming level of Marr's tri-level hypothesis specifying information-processing steps.

Implementational Level

The lowest level of Marr's tri-level hypothesis focusing on the hardware and physical realization.

Marr's Model of Visual Processing

Marr's theory of visual processing.

First stage of Marr's Model

The image projected onto the retina is analyzed in terms of the intensity of areas of light and dark

Second Stage of Marr's Model

Features in the raw primal sketch that are similar in size and orientation get grouped.

Object Constancy

recognize that an object is the same object though the image projected on our retina may change either because the object or the viewer is moving

2.5-D sketch

A representation of the object that includes its surfaces and layout, and is viewer-centered

3-D sketch

The object’s parts are described relative to one another and are linked on the basis of shared properties and axes. It solves the object constancy problem

Symmetry Axis

line that divides an object into mirror image halves

Elongation Axis

line defining direction along which main bulk or mass of a shape is distributed

First step in Human Visual System

input from the retina is conveyed via the optic nerve through the optic chiasm to the superior colliculus of the brainstem, then to the lateral geniculate nucleus (LGN) of the thalamus

second step in Human Visual System

LGN projects to area V1 or the primary visual cortex, which maps onto the striate cortex, an anatomically distinct region of the brain.

Role of area V1

Neurons in V1 (feature detectors) are sensitive to low-level features of the visual field, such as orientation and direction of movement.

Simple Cells

respond only to the presence of line segments with a particular orientation

role of area V2

Neurons in V2 process features such as complexes of edges, shape, and depth. Depth is principally determined by this

Retinal Disparity

the fact that points on objects located at different distances from the observer will fall on slightly different locations on the two retinas

Extrastriate Cortex

Region surrounding the striate cortex that processes movement, spatial frequency, retinal disparity, and color

Retinal Disparity

the basis for stereopsis or depth perception

Trichromatic Theory

explains Color perception

Color Receptors

retina has three types of color receptors (cones), each especially sensitive to one of three colors: red, green, and blue

Opponent-Process Theory

color-sensitive receptor cells respond in an opposing center-surround fashion to pairs of primary color

Opponent-Process Theory

causes color afterimages phenomenon

Ventral Pathway

information goes from V2 to V4, then to inferior temporal cortex (ITC). ITC includes specialized areas for face recognition and identification of the human body and body parts

Fusiform Face Area

specialized area for face recognition

Fusiform Body Area

specialized areas for identification of the human body and body parts

Blindsight

Rare neurological condition where people who are blind can “guess” significantly above chance the identity or location of objects

Explanation for Blindsight

Proposed explanation: second pathway of visual perception that makes a short loop through the limbic system.

Analog Code

The mental imagery debate centers on whether information is stored as this (i.e., as a pictorial representation)

Propositional Code

The mental imagery debate centers on whether information is stored as this (i.e., descriptive)

Imagery and Rotation studies

Experiments that suggested that some types of cognitive information processing involve forms of representation that are very different from how information is represented in a digital computer

Stephen Kosslyn's Imagery Study

Length of time it took to answer questions varied according to the distance of the parts from the original point of focus

Imagery and Size

People make faster judgments about the characteristics of large mental images than of small mental images; also, they take longer to travel a large mental distance, whether that’s visual or auditory

Imagery and Interference

Visual imagery may interfere with visual perception, and motor imagery with motor images.

FACS

Facial Action Coding System.

Expression of Emotions

Ekman has identified seven basic emotions that are universal

Emotional Communication

90% or more of emotional communication occurs through nonverbal channels, e.g., facial expression, gesture and voice

Display Rules

when and where it is considered appropriate to display particular emotional expressions

Facial Action Coding System

Used to identify 46 distinct muscular movements in the face

Reading Emotions

After a quick glance at someone’s photo, we have a pretty good sense of the person’s extraversion and agreeableness

Ekman

Student reading people's emotions