Lecture 1: Intro to Sensort Systems

Question 1

Brain Info

Answer 1

• 100 billion neurons (each neuron is directly connected to about 7000 other neurons and 100-500 trillion synapses)
• glial cells (-500 billion to 1 trillion)
• Each neuron is also covered by thousands of receptors

Question 2

The challenge of understanding the sensory systems

Answer 2

• the sensory info we get is so ambiguous
• different lines in the world, same projection on the retina

Question 3

The challenge of understanding the sensory systems pt 2

Answer 3

• Your brain actively constructs your sensory experience (everything you see is actively constructed - color, shading, texture, motion, shape)
• The “internal model of the world” is built by innate rules combined with your own experiences including your memories, emotions, logic, and beliefs

Question 4

Foreground effects

Answer 4

• Refer to the brain’s ability to focus on and prioritize specific stimuli from the environment
• These stimuli stand out due to their relevance, intensity, novelty, or importance
  Example: When you hear your name in a noisy room, your brain elevates this auditory signal above the background noise, allowing you to recognize and respond it. (this process is associated with selective attention, where the brain actively filters and enhances certain sensory inputs)

Question 5

Background Effects

Answer 5

• involve the sensory system’s handling of the less prominent, surround stimuli that provide context but are not the main focus of attention
• These stimuli form a backdrop against which the foreground stimuli are perceived
  Example: While reading a book in a cafe, you might not notice the hum of conversation around you, but this ambient noise creates the auditory context in which the primary activity (reading) occurs

Background processing allows the brain to maintain situational awareness and adapt to changes in the environment without being overwhelmed by all sensory inputs

Question 6

Interaction between foreground and background

Answer 6

• The brain constantly toggles between foreground and background processing to create a coherent perception of the environment
• Sensory inputs that initially form part of the background can become foreground stimuli if they change in a way that attracts attention, similarly foreground stimuli can fall back into the background once they become familiar or less relevant

Question 7

Shephard Elephant

Answer 7

• An image depicts an elephant with legs that appear to be in impossible positions (challenges the viewer’s ability to correctly interpret the spatial relationships in the picture)

Question 8

Pattern recognition

Answer 8

Our brains are wired to recognize patterns and familiar shapes (when faces with conflicting visual information, the brain attempts to resolve the inconsistency based on learned patterns)

Question 9

Perceptual ambiguity

Answer 9

The illusion (sheps elephant) underscores how the brain deals with ambiguous information. When sensory inputs are ambiguous, the brain may struggle to form a coherent interpretation, resulting in perceptual anomalies

Question 10

Contextual Interpretation

Answer 10

the context in which we see objects greatly influences our perception. In shephard’s elephant, the unusual arrangement of the legs creates a context that disrupts normal interpretation processes
- This contextual processing allows for more accurate perception in varied lighting condition and environments

Question 11

Illusory contours

Answer 11

• Are perceived edges without a physical gradient or boundary in the stimulus.
• They demonstrate how the brain interprets visual information to create coherent perceptions, even when actual physical edges are absent
• Occur when the visual system perceived edges or shapes that are not explicitly present in the stimulus.

Question 12

Visual Cortex processing

Answer 12

• The primary visual cortex (V1) and higher level areas such as V2 play significant roles in generating illusory contours
• Neurons in these areas respond to edges and contrasts, even when they are implied rather than directly visible
• Process the size of objects by integrating retinal image size with contextual cures about distance (this helps the brain maintain a consistent perception of object size despite the changes in distance)

Question 13

Gestalt Principles

Answer 13

• are crucial for the perception of illusory contours
• The brain tends to fill in missing information for form whole shapes, promoting a sense of completeness and continuity

Question 14

Top Down processing

Answer 14

• Higher cognitive processes, based on prior knowledge and expectation, influence the perception of illusory contours.
• The brain uses contextual information and past experiences to infer the presence of edges and shapes that make sense in the given visual scene

Question 15

Edge Detection

Answer 15

• a fundamental process in vision, helping the brain define object boundaries
• Illusory contours show that the brain can perceive edges without direct sensory input, relying on contextual cues

Question 16

Perceptual Filling in

Answer 16

• The brains ability to “fill-in” gapes in sensory information ensures a continuous and coherent perception of the environment
  -this is crucial for navigating and understanding our surroundings

Question 17

Simultaneous Contrasts

Answer 17

• When a color or shade appears different depending on the colors or shades surrounding it
  Example: A grey square might look lighter when placed on a dark background and darker when placed on a light background

Question 18

Lateral Inhibition

Answer 18

• where neurons in the retina inhibit the activity of neighboring neurons. This process enhances the contract at edges, making borders more distinct influencing the perceived brightness and color of adjacent areas

Question 19

Relative Perception

Answer 19

• Perception of color and brightness is relative rather than absolute
• The brain constantly compares visual information from different parts of the visual field to make sense of what it sees

Question 20

Adaptation and Calibration

Answer 20

• the visual system adapts to different lighting conditions and calibrates perceptions to maintain consistent and accurate interpretation of the environment

Question 21

Relative size

Answer 21

• a perceptual phenomenon in which the size of an object is interpreted based on its size in relation to other objets in the visual field (plays a crucial role in depth perception and spatial understanding)

The illusion
- Objects that are assumed to be of the same size can appear larger or smaller depending on their surroundings
Example:
If 2 idenical objects are placed at different distances from the viewer, the one that is farther away will project a smaller image on the retina, but the brain interprets this correctly as the same size considering the context and known distance

Question 22

Retinal image

Answer 22

• The retina captures a 2 dimensional image of the 3 dimensional world. Objects farther away from the viewer cast a smaller image on the retina than closer objects of the same size

Question 23

Depth Cues

Answer 23

• The brain uses varuous depth cures, such as linear perspective, texture gradient, and occlusion, to assess the relative size of objects
• These cures help the visual system infer the actual size of objects regardless of their retinal image size

Question 24

Size Constancy

Answer 24

• The brain maintains a perception of constant size for familiar objects, even when their distance from the viewer changes, ensuring a stable and predictable perception of the environment

Question 25

Spatial Awareness

Answer 25

Relative size contributes to spatial awareness by helping the brain map out the relationships and distances between various objects in the visual field