perc mid 2

Area V1: The primary visual cortex located in the occipital lobe, the first cortical area to receive visual input from the LGN.

Binocular Rivalry: When different images are presented to each eye, resulting in the perception alternating between the two images.

Bottom-up Processing: Sensory information processing that starts with the receptors and moves to the brain without the influence of prior knowledge or expectations.

Change Blindness: Failure to notice a visible change in a scene, often due to attention not being focused on the change.

Cognitive Load: The amount of mental effort being used in the working memory.

Complex Cells: Neurons in the visual cortex that respond best to moving bars of light of a specific orientation.

Conjunction Search: A type of visual search where a target is identified based on a combination of features, requiring focused attention.

Corollary Discharge Theory: A theory that explains how the brain distinguishes between eye movement and motion in the visual scene; it involves a copy of motor signals sent to the brain.

Cortical Magnification: The disproportionate representation of the fovea (the central part of the retina) in the visual cortex.

Covert Attention: Shifting attention without moving the eyes.

Dorsal Stream: The "where/how" stream of visual processing, which travels from V1 to the parietal lobe and is responsible for processing spatial information and directing actions.

End-Stopped Cells: Neurons in the visual cortex that respond best to moving lines of a specific length or to corners or angles.

Extrastriate Body Area (EBA): An area in the brain that responds specifically to images of bodies.

Feature Integration Theory (FIT): Anne Treisman’s theory which proposes that we perceive objects in two stages: a preattentive stage, where features are processed separately, and a focused attention stage, where features are bound together.

Feature Search: A type of visual search where a target is identified by a single, distinct feature.

Feature Detectors: Neurons in the visual cortex that respond to specific features of stimuli, such as orientation or movement.

Figure-Ground Segregation: The process of distinguishing objects (figures) from their backgrounds (ground).

Fovea: The central part of the retina that has the highest visual acuity.

Fusiform Face Area (FFA): An area in the brain that responds specifically to faces.

Geons: Geometric components, such as cylinders, cubes, and pyramids, that make up objects according to Recognition by Components (RBC) theory.

Gestalt Approach: A psychological approach that emphasizes that perception of a whole is more than the sum of its parts, and it highlights how our perception is organized.

Good Continuation: The Gestalt principle that we tend to perceive lines as continuing in their established direction rather than abruptly changing direction.

Illusory Conjunctions: The mistaken combination of features during the preattentive stage, e.g., perceiving a red square when you actually saw a red circle and a blue square.

Inattentional Blindness: The failure to notice an obvious stimulus that is within sight when one is focusing attention on something else.

Inverse Projection Problem: The fact that the image on the retina is ambiguous and can be caused by many different objects.

Lateral Geniculate Nucleus (LGN): A part of the thalamus that receives visual signals from the retina and relays them to the visual cortex.

Likelihood Principle: The idea that we perceive objects based on what is most likely to have caused the retinal image.

Multivoxel Pattern Analysis (MVPA): A technique for analyzing patterns of brain activation across multiple voxels to predict the stimulus being observed.

Ocular Dominance Columns: Columns in the visual cortex that respond preferentially to one eye or the other.

Oblique Effect: The tendency for people to perceive horizontal and vertical lines more clearly than slanted lines.

Orientation Columns: Columns in the visual cortex that respond to lines of a specific orientation.

Overt Attention: Shifting attention by moving the eyes.

Parahippocampal Place Area (PPA): An area in the brain that responds specifically to scenes and spatial layouts.

Preattentive Stage: The first stage of Feature Integration Theory, where features are processed separately before attention binds them.

Predictive Coding: The brain constantly generating predictions about sensory input. When sensory input matches, no errors occur, but mismatches cause prediction errors that update future predictions.

Prägnanz: The Gestalt principle that perception seeks the simplest, most stable structure.

Proximity: The Gestalt principle that elements close together are perceived as grouped.

Receptive Field: The area of the retina that, when stimulated, affects the firing rate of a given neuron.

Recognition by Components (RBC) Theory: A theory that objects are recognized based on the combination of geons (geometric ions) that constitute them.

Retinotopic Map: The organization of the visual cortex where nearby points on the retina are represented by neighboring neurons in the cortex.

Saccades: Rapid eye movements between fixations.

Saliency Map: A visual map showing which regions of a scene are most visually distinct, often driving initial attention.

Scene Schema: Mental representations of what is typical in a particular scene.

Selective Adaptation: A decrease in the firing rate of neurons after prolonged exposure to a specific stimulus.

Selective Rearing: An experimental procedure where an animal is raised in an environment with only specific visual features.

Semantic Regularities: Characteristics tied to activities that commonly happen in different scenes.

Simple Cells: Neurons in the visual cortex that respond best to a bar of light of a particular orientation in a specific location.

Spatial Frequencies: The rate at which a pattern changes from black to white across space.

Structuralism: An approach to psychology that emphasizes the idea that perceptions are combinations of sensations.

Top-down Processing: Information processing guided by prior knowledge, expectations, or goals.

Ventral Stream: The "what" pathway, which travels from V1 to the temporal lobe and is responsible for object recognition.

Visual Perception: A Comprehensive Study Guide

Quiz

Answer each question in 2-3 sentences.

1. What is the function of the Lateral Geniculate Nucleus (LGN), and how is it organized?

2. Describe the difference between simple, complex, and end-stopped cells in the visual cortex (V1).

3. Explain the concept of retinotopic mapping and cortical magnification in the visual cortex.

4. What are the "what" and "where/how" streams of visual processing, and what are their primary functions?

5. Describe the Gestalt approach to perceptual organization and give two examples of Gestalt principles.

6. Explain the concept of figure-ground segregation, including the characteristics of figures and ground.

7. How does the activity of V1 neurons relate to Gestalt grouping principles?

8. Describe the concept of inattentional blindness and explain why attention is necessary for perception.

9. What is the feature integration theory, and how does it explain illusory conjunctions?

10. Explain how the corollary discharge theory helps stabilize our perception during eye movements.

Quiz Answer Key

1. The LGN is the first stop between the retina and the cortex, and it serves as a relay station for visual information. It is organized into six retinotopic maps, with neighboring locations corresponding to neighboring locations on the retina, and it is also divided into parvo and magno layers for processing different information.

2. Simple cells in V1 respond best to bars of light of a particular orientation, whereas complex cells respond best to moving bars of light of a particular orientation. End-stopped cells respond best to a moving line of a specific length, or a moving corner or angle.

3. Retinotopic mapping refers to the organization of the visual cortex where each location corresponds to a location on the retina. Cortical magnification is the disproportionate representation of the fovea, a small area of the retina, by a large area of the cortex, which reflects its importance for detailed vision.

4. The "what" stream, or ventral pathway, goes from V1 to the temporal lobe and is responsible for identifying objects. The "where/how" stream, or dorsal pathway, goes from V1 to the parietal lobe and is responsible for determining object location and how to act on objects.

5. The Gestalt approach emphasizes that perception of a whole stimulus is more than the sum of its parts, and it highlights how our perception is organized based on grouping principles like similarity and proximity. These principles describe how we organize small parts of an image into larger groups.

6. Figure-ground segregation is the process of distinguishing objects (figures) from their backgrounds (ground), with figures seen as more “thing-like,” memorable, and owning the contours, while the ground is perceived as the unformed material that extends behind the figure.

7. V1 neurons respond to specific features within their receptive fields, but their activity can be influenced by stimuli outside of their receptive fields, especially when those outside stimuli are part of a larger group following Gestalt principles like similarity or good continuation.

8. Inattentional blindness is the failure to notice a visible, unexpected object because attention is focused elsewhere. Attention is necessary because our visual system has a limited capacity for processing information, requiring us to selectively attend to inputs.

9. The feature integration theory proposes that perception involves a preattentive stage where features are processed independently, followed by a focused attention stage where features are bound together. Illusory conjunctions occur when, during the preattentive stage, features are incorrectly combined when attention is divided.

10. The corollary discharge theory helps maintain a stable perception during eye movements by sending a copy of the motor signal to the comparator which, combined with image displacement on the retina, cancels the perception of movement in the scene.