Spatial Navigation, Attention, Motion Perception, Color Vision, Depth & Size Perception, Hearing & Ear Anatomy

Spatial Navigation

1. Hippocampus & Parietal Lobes

  • Hippocampus:

    • Function: Creates and stores cognitive maps of spatial environments.

    • Importance: Critical for memory of locations and navigation.

  • Parietal Lobes:

    • Function: Integrate sensory input and spatial awareness.

    • Importance: Translate spatial information into movement or attention shifts.

2. Top-Down Influence on Scene Processing

  • Definition: Prior knowledge, expectations, and goals guide focus and interpretation of scenes.

  • Example: Expecting to see a kitchen makes an individual notice a fridge faster than recognizing random shapes.

Visual Attention

1. Factors Affecting Attention

  • Stimulus Salience:

    • Definition: Brightness, color, or contrast that automatically draw attention.

  • Attentional Capture:

    • Definition: Occurs when a salient stimulus unexpectedly grabs attention (e.g., a flashing light).

2. Change Blindness & Inattentional Blindness

  • Change Blindness:

    • Definition: The failure to notice changes in a visual scene.

  • Inattentional Blindness:

    • Definition: Missing an unexpected stimulus when attention is directed elsewhere, exemplified by the Gorilla Experiment.

3. Visual Search

  • Feature Search:

    • Definition: An easy search characterized by “pop-out” for one distinct feature (e.g., color, shape).

  • Conjunctive Search:

    • Definition: A harder search that requires combining multiple features (e.g., color + shape).

  • Feature Integration Theory (Treisman):

    • Explanation: The visual system processes features separately first, and then combines them using focused attention.

4. Overt vs. Covert Attention

  • Overt Attention:

    • Definition: Shifting gaze directly to focus on a stimulus.

  • Covert Attention:

    • Definition: Attending to a stimulus without moving the eyes.

5. Selective Attention

  • Definition: Determines which stimuli are processed; can be modeled by the following:

    • Spotlight Model: Suggests attention acts like a beam focusing on specific location,

    • Bottleneck Model: Proposes that only a limited amount of information can pass through at once.

6. Divided Attention

  • Concept: Multitasking can reduce performance, as attention is a limited resource.

  • Additional Notes:

    • Practice may improve dual-task performance but does not completely eliminate performance costs.

7. Attentional Disorders

  • Hemispatial/Unilateral Neglect:

    • Definition: A neurological condition where individuals ignore one side of their visual field (often associated with right parietal damage).

  • Balint’s Syndrome:

    • Definition: Characterized by the inability to focus on individual objects.

  • Blindsight:

    • Definition: A phenomenon where individuals can respond to visual stimuli without conscious awareness.

  • ADHD:

    • Definition: A disorder characterized by difficulty in sustaining and shifting attention.

Motion Perception

1. Real vs. Apparent Motion

  • Real Motion:

    • Definition: The actual movement of objects in a space.

  • Apparent Motion:

    • Definition: The illusion of motion created between static images (foundation of movies).

  • Phi Phenomenon:

    • Explanation: The perception of continuous motion from lights flashing in succession.

2. Eye Movements

  • Saccades:

    • Definition: Quick, jerky eye movements that occur between fixation points.

  • Smooth Pursuit:

    • Definition: Continuous tracking of moving objects to maintain focus.

3. Random Dot Kinematogram

  • Definition: A visual display of dots that move randomly; shows perception of motion involving specialized motion detectors with activation of the area MT in the brain.

4. Motion Scenarios

  • Concept: The brain separates object motion from self-motion.

  • Example: Distinguishing between a car moving towards you and your own movement in the same direction.

5. Corollary Discharge Theory

  • Explanation: Involves an efference copy derived from eye movement commands that is compared with retinal motion signals.

  • Function: Aids in distinguishing self-motion from external motion in the environment.

6. Motion Detection in Retina

  • Motion-sensitive neurons respond to motion in terms of both direction and speed; these neurons are linked to ganglion cells and MT (middle temporal) cells.

7. Point-Light Walkers

  • Definition: Lights placed on joints to depict biological motion; this pattern is recognized and processed in the Superior Temporal Sulcus (STS).

8. Brain Regions Involved in Motion Processing

  • V1: Initial processing of motion signals.

  • MT (V5): Responsible for processing direction and speed of motion.

  • MST: Involved in complex motion perception, such as expansion and rotation.

  • Superior Colliculus: Coordinates eye movements and orienting responses.

  • STS: Processes social and biological motion, including gestures and walking movements.

9. Akinetopsia

  • Definition: A condition resulting in motion blindness due to damage in the MT area, leading to the perception of the world as a set of frozen frames.

Color Vision

1. Light & Reflectance

  • Visible Spectrum: Ranges roughly from 400 to 700 nm in wavelength.

  • Spectral Reflectance: The tendency of an object to reflect certain wavelengths of light.

2. Color Properties

  • Wavelength: Determines the hue of the color.

  • Amplitude: Relates to the brightness of the color.

  • Purity: Refers to the saturation of the color.

3. Color Circle vs. Color Solid

  • Circle: Represents relationships among hues and saturation.

  • Solid: Represents the relationship among hue, saturation, and brightness.

4. Hue Cancellation Experiments

  • Purpose: Provide evidence for opponent color processes such as red–green and blue–yellow.

5. Types of Cones

  • S Cones: Short wavelength cones, sensitive to blue light.

  • M Cones: Medium wavelength cones, sensitive to green light.

  • L Cones: Long wavelength cones, sensitive to red light.

6. Principle of Univariance

  • Definition: States that one type of cone alone cannot signal color; color vision necessitates comparisons between multiple cone types.

7. Theories of Color Vision

  • Trichromatic Theory (Young–Helmholtz): Explains that color perception arises from the combination responses of three cone types.

  • Opponent Process Theory (Hering): Suggests that opposing color pairs account for effects like afterimages and color contrast.

  • Integrated View: Assuming trichromatic processing at the receptor level and opponent processing at the neural level.

8. Color Deficiencies

  • Monochromacy: Condition where only one or no type of cone is present.

  • Dichromacy: Condition involving two cone types.

  • Cortical Achromatopsia: Result of brain damage leading to total color perception loss.

  • Note: The term “color deficiency” is more accurate as many who are “color blind” still perceive some colors.

Depth & Size Perception

1. Cue Approach

  • Explanation: Depth perception is derived from various types of cues:

    • Oculomotor Cues: Feedback from eye muscles (e.g., accommodation and convergence).

    • Monocular Cues: Cues available to one eye (e.g., occlusion, perspective, shading).

    • Binocular Cues: Cues derived from the disparity between images seen by both eyes.

2. Stereograms & Correspondence Problem

  • Description: Random dot stereograms demonstrate depth perception through disparity alone.

  • Process: The brain matches corresponding points from each retina to solve for depth perception.

3. Size-Distance Invariance

  • Definition: Perceived size is dependent on both the actual retinal image and available distance cues.

4. Size & Shape Constancy

  • Explanation: The brain uses contextual depth cues to maintain a consistent perception of size or shape despite changes to the retinal input.

5. Illusions

  • Müller-Lyer Illusion: Arrows attached to lines distort the perceived length of the lines.

  • Ponzo Illusion: Converging lines create depth cues that affect the perceived size.

  • Ames Room: A manipulated geometry creates distortion in perceived size constancy.

Hearing & Ear Anatomy

1. Sound Basics

  • Definition: Sound arises from pressure changes in air, characterized by phases of compression and rarefaction.

  • Physical Properties:

    • Frequency: Corresponds to pitch.

    • Amplitude: Related to loudness.

    • Timbre: Refers to sound quality.

2. Human Hearing Range

  • Range: Generally between 20 Hz and 20,000 Hz.

3. Ear Anatomy

  • Outer Ear: Comprises the pinna, auditory canal, and tympanic membrane.

  • Middle Ear: Contains the ossicles (malleus, incus, stapes) and the eustachian tube.

  • Inner Ear: Begins at the oval window, proceeds to the cochlea, basilar membrane, organ of Corti, and ends at the auditory nerve.

4. Auditory Pathway

  • Pathway: Auditory nerve → Brainstem → Inferior colliculus → Thalamus (medial geniculate nucleus, MGN) → Primary auditory cortex (A1).