Perception Chapter 10: The Visual System: Cortical Processing and Object Perception

Optic Radiation

Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex.

Monocular

Depth cues, such as interposition and linear perspective, available to either eye alone.

Pop-Out Phenomena

Exists when our attention is drawn to a stimulus that stands out as different from others

Contralateral

On the opposite side of the body.

Ipsilateral

On the same side of the body

Pretectum

Part of the midbrain that controls the size of the pupil and certain types of eye movements

Saccades

Quirk, jerky movements of the eyes as they jump from one fixation to another in the reading of continuous text

Retinotopic Organization

adjacent parts of retina project to adjacent parts of LGN. aka adjacent in visual field, adjacent in retina. things next to each other in real world, then next to each other in retina then brain.

Area 17

primary visual area

Circadian Rhythms

24-hour biological cycles found in humans and many other species

Thalamus

A Subcortical structure that relays and filters information from the senses and transmits the information to the cerebral cortex.

Suprachiasmatic Nucleus (SCN)

A cluster of neurons in the hypothalamus in the brain that governs the timing of circadian rhythms

Ocular Dominance

A column in the visual cortex that contains neurons that respond best to stimulation from a specific eye and not the other.

Ocular Dominance Columns

A column in the visual cortex that contains neurons that respond best to stimulation from a specific eye and not the other.

Blindsight

A condition in which a person can respond to a visual stimulus without consciously experiencing it

Orientation Tuning Curve

A function relating the firing rate of a neuron to the orientation of the stimulus

Melatonin

A hormone manufactured by the pineal gland that produces sleepiness.

Optical Imaging

A method for visualizing brain activity in which near-infrared light is passed through the scalp and skull.

Pulvinar

A part of the thalamus that integrates somesthetic, visual, and auditory input

Gestalt Psychology

A psychological approach that emphasizes that we often perceive the whole rather than the sum of the parts

Heuristics

A simple thinking strategy that often allows us to make judgment and solve problems efficiently; usually speedier, but more error-prone than algorithms

Feature Integration Theory (FIT)

An approach to object perception developed by Anne Treisman that proposes that object perception occurs in a sequence of stages in which features are first analyzed and then combined to result in perception of an object.

Fusiform Face Area (FFA)

An area in the inferior temporal lobe believed to participate in the recognition of familiar faces, especially in the right hemisphere

Structuralism

An early school of psychology that used introspection to explore the elemental structure of the human mind.

Visual Cortex

Area of the brain responsible for the initial conscious registration of visual information; the designation of electric (nerve) impulses from the retina

Subcortical Structures

Areas of the forebrain housed under the cerebral cortex near the very center of the brain

Lateral Geniculate Nucleus

Component of the thalamus that processes visual information from the eyes and sends this information to the primary and secondary visual cortex.

Edinger-Westphal Nucleus

Controls the activity of the ciliary muscle of the eye is controlled in the midbrain

Superior Colliculus

Controls visual reflexes- appears as bumps on the brainstem

Geons

Different three dimensional shapes that combine to form three dimensional patterns

Law of Good Continuation

From Gestalt Psychology, it is the tendency for elements appearing to follow in the same direction (such as a straight line or a simple curve) to be grouped together.

Functional Architecture

How the brain is organized to serve the functions it performs.

Agnosia

Impairments in perceptual recognition.

Hypercolumn

In the striate cortex, unit proposed by Hubel and Wiesel that combines location, orientation, and ocular dominance columns that serve a specific area on the retina. Each hypercolumn contains a single location column (since it responds to stimuli presented to a particular place o

Temporal Pole

Lesions here cause loss of recognition of famous scenes, loss of memory for events and loss of person related knowledge

Superior Temporal Sulcus (STS)

Neurons here increase firing rate when a monkey looks at photographs of another monkey or human gazing in a particular direction

Orientation Selectivity

Neurons in V1 that respond best to an elongated bar of light moving across their receptive field, greatest response to a particular angle that bar lies at.

Directional Tuning Curve

Neurons vote most strong for a particular kind of movement (left, right, up, down etc.) if votes for left movement most, moves left etc, direction of movement determined by averaging the votes

Subjective Contours

Perceived contours that do not exist physically.We tend to complete figures that have gaps in them by perceiving a contour as continuing along its original path.

Optic Chiasm

Point behind the eyes in the brain where the two optic nerves merge and the axon fibers from the nasal retina of each eye cross to the opposite side

Straite Cortex

Primary visual cortex (V1)

Form Primitives

Simple structural units that are used to create more complex form representations

Midget cells

Small cells found in the ganglion that receive input from a small amount of receptors. They respond to changes in color, but not much in contrast unless it is very apparent. Receive SMALL input and are involved in sustained transmission.

Visual Association Area

Surrounds the primary visual cortex and covers much of the occipital lobe; uses past visual experiences to interpret visual stimuli (color, form, and movement); complex processing involves entire posterior half of the hemisphere

Dorsal Coritcal Stream

Terminates in the parietal lobe and is involved with processing the object's spatial location relative to the viewer

Ventral Cortical Stream

Terminates to the temporal lobe and is involved with object identification and recognition

Law of Similarity

The Gestalt principle that we tend to group similar objects together in our perceptions.

Law of Common Fate

The Gestalt principle that we tend to group similar objects together that share a common motion or destination

Retinal Fields

The areas on the retina upon which the signal is received.

Image Raster

The distribution of light in a point-wise manner across an area, such as the retina, a computer monitor or television

Area V1

The part of the occipital lobe that contains the primary visual cortex

Figure-Ground Segregation

The perceptual organization of the visual field into a figure (object of central interest) and a ground (less important background).

Binding Problem

The problem confronted by the brain of recombining the elements of a stimulus, given the fact that these elements are initially analyzed separately by different neural systems.

Geniculocortical Pathway

The retrolenticular portion of the internal capsule continues posteriorly as the optic radiation. Part of it (Meyer's Loop) swings down into the temporal lobe as it projects to the occipital cortex.

Recognition-by-components (RBC)

The theory that asserts that we perceive and categorize objects in our environment by breaking them down into component parts and then matching the components and the way they are arranged against similar 'sketches' stored in memory.

Inferior Temporal Cortex (Area ITs)

This area responds to identifiable objects: ability to ignore changes in size, direction,

Orientation Columns

Vertical columns of neurons in V1, all of which respond to stimuli (e.g., bars, edges) oriented at the same angle. adjacent columns contain all possible orientations.

Ice-Cube Model

a 3-D model of area V1 where ocular dominance and orientation columns run perpendicular to each other

Parvocellular Neurons

cells with small cell bodies and small receptive fields; mostly in or near the fovea; detect visual details and color

Extrastriate Areas

cortical areas that lie beyond the striate cortex (area V1). many of these areas in the parietal and temporal lobes have been shown to process different aspects of visual functions

Magnocellular Neurons

large cell bodes; large receptive fields; throughout the retina; not color sensitive; respond to movement and broad outlines of shape

Parasol Cells

large cells found in the ganglion that receive a large amount of input from many receptors. They respond to low-contrast stimuli. Are concerned with visual perception, motion, and coarse outlines; works at speed at expense of detail.

Geometric Ions

simple geometric figures such as cubes, cylinders, and pyramids, that can be combined to create all other shapes. An early (and crucial) step in some models of object recognition is determining which geons are present

Cytochrome Oxidase Blobs

the central region of a module of the primary visual cortex, revealed by a stain for cytochrome oxidase; contains wavelength-sensitive neurons; part of the parvocellular system

Directional Selectivity

the preference of a neuron for a visual stimulus moving along a particular direction in comparison to all other possible directions.