Exam 3

What are floaters?

Small debris in the vitreous humor that cast shadows on the retina, appearing as moving spots in vision.

Difference between rods and cones?

• Rods → low light, motion, no color

• Cones → color, detail, high acuity (fovea)

What cells do retinal ganglion cells synapse onto?

Their axons form the optic nerve, projecting to the LGN (lateral geniculate nucleus).

Lifespan of retinal cells (lens)?

Lens cells are not replaced → accumulate damage over time (aging → cataracts).

What happens at the optic chiasm?

• Nasal retina → crosses

• Temporal retina → stays ipsilateral
  👉 Ensures contralateral visual processing

What are magnocellular vs parvocellular pathways?

• Magno → motion, fast, low detail

• Parvo → color, detail, slow

What is columnar organization in V1?

Neurons are organized by orientation + eye input, forming columns that process specific visual features.

What is the binding problem?

How the brain combines features (color, shape, motion) into a single unified object perception.

What did MT (middle temporal area) show?

Cells respond to combined features like motion + direction → early feature integration.

What are the dorsal vs ventral streams?

• Dorsal → “where” (parietal)

• Ventral → “what” (temporal)

Walter Pohl’s monkey lesion experiment—setup?

• Task: object vs landmark discrimination

• Lesions: temporal vs parietal

• Delay between encoding and response

Results of Pohl’s study?

• Temporal damage → object deficits

• Parietal damage → spatial deficits
  👉 Strong evidence for what vs where pathways

What is agnosia?

Inability to recognize objects despite intact sensory function.

Apperceptive agnosia?

Cannot form a coherent percept (can’t copy or match objects).

Associative agnosia?

Can perceive object but cannot assign meaning.

What did Hannah D’Amasio show?

• Object recognition deficits depend on specific temporal lobe regions

• Faces vs animals processed in different areas

“Faces are special” finding?

• Faces processed holistically

• Objects processed by parts + whole
  👉 Suggests specialized face-processing system

What is prosopagnosia?

Inability to recognize faces (damage to fusiform face area).

Biederman’s Recognition by Components (RBC)?

Objects are built from geons (basic shapes) → recognition via parts.

Steps in RBC theory?

• Edge detection

• Parse into geons

• Match to stored representations

Template theory of recognition?

Match incoming stimulus to stored exact template
❌ Problem: too rigid, too many templates needed

Feature theory?

Objects recognized by individual features
✔ Flexible
❌ Struggles with missing/occluded features

Prototype theory?

Compare stimulus to an average representation
👉 Recognition based on similarity

Global precedence (Navon)?

We process global shape before details
👉 Big letter interferes with small letters

William James’ definition of attention?

Focus on one thing while ignoring others; includes voluntary and involuntary control.

Voluntary vs involuntary attention?

• Voluntary → controlled, goal-directed

• Involuntary → stimulus-driven

What is covert attention?

Shifting attention without eye movement.

Helmholtz experiment?

Showed attention can be shifted independently of gaze.

Posner cueing task?

Valid cue → faster RT
Invalid cue → slower RT
👉 Measures attention movement

What is inhibition of return?

Previously attended locations become harder to revisit.

Dichotic listening task?

Different messages in each ear
Participants report only attended ear

Broadbent’s filter theory?

Early selection based on physical features

Split-span task result?

Better recall ear-by-ear, not pair-by-pair
👉 Supports early filtering

Cocktail party effect?

Ability to detect meaningful stimuli (like your name) in unattended input.

Why is this a problem for Broadbent?

Suggests semantic processing happens before filtering

Treisman attenuation theory?

Unattended info is weakened, not blocked

Late selection theory?

All stimuli processed semantically; selection happens later

Stroop task significance?

Shows parallel processing + interference

EEG P1 finding?

Stronger when attention is directed to correct location

EEG N400 wave?

Reflects semantic processing (unexpected words → larger N400)

John Duncan’s finding?

Attention is object-based, not just spatial

O’Craven & Kanwisher?

Brain activity depends on attended object (faces vs houses)

Corbetta’s model?

• Frontal → control

• Parietal → spatial attention

Tipper’s negative priming?

Ignored items become harder to process later

What is language?

A system of symbols used to communicate ideas and transmit knowledge.

What is a phoneme?

Smallest sound unit that changes meaning.

What is a morpheme?

Smallest unit of meaning.

What is syntax?

Rules for arranging words into sentences

What is semantics?

Meaning of words.

What is orthography?

How words are visually represented (spelling).

What is the internal lexicon?

Mental dictionary of words in long-term memory.

Levels of the lexicon?

• Conceptual

• Grammatical

• Word-form

How many words does an adult know?

~50,000 words

Meyer & Schvaneveldt experiment?

• Lexical decision task

• Faster responses for related word pairs

What does this show?

Evidence for spreading activation

What is spreading activation?

Activation spreads between related concepts in memory.

PDP (Parallel Distributed Processing)?

• Many simple units interact

• Info processed in parallel

Key PDP assumptions?

• Units

• Activation

• Excitatory + inhibitory connections

Content addressability?

Memory can be accessed by any feature

Graceful degradation?

Partial damage → partial function remains

Default assignment?

Activated properties spread to similar items

Spontaneous generalization?

Similar items activate similarly

Hierarchical network model?

• Concepts organized in hierarchy

• Cognitive economy

• Distance affects response time

Problem with hierarchical model?

Cannot explain false or flexible relationships

Collins & Loftus model?

• Network with flexible links

• Activation spreads
  👉 More realistic

Fan effect?

More associations → slower retrieval

Broca’s area function?

Speech production

Wernicke’s area function?

Language comprehension

Conduction aphasia?

Cannot repeat words (connection issue)

Broca’s patient Tan?

Could only say “tan” → speech production deficit

Wernicke’s aphasia?

Fluent but meaningless speech

Anomia?

Difficulty naming objects

Lichtheim-Geschwind model?

• Broca → production

• Wernicke → comprehension

• Arcuate fasciculus → connection

Daneman & Carpenter experiment?

Reading span task → measures working memory + comprehension

Balint’s syndrome?

Cannot attend to multiple objects

Fan effect?

More associations → slower recall

EEG flanker task finding?

Shows interference from nearby stimuli

What is the fovea and why is it important?

Central retina region with highest cone density → best visual acuity and color vision

What happens if light hits the optic disc?

No photoreceptors → creates the blind spot

What is the function of the LGN?

Relay station between retina and V1; maintains separate magno/parvo pathways

Why are magnocellular pathways important for attention?

Fast processing → supports motion detection and rapid attentional shifts

Why are parvocellular pathways important for object recognition?

High detail + color → supports fine feature discrimination

What is viewpoint invariance?

Ability to recognize objects from different angles
👉 Problem for template theory

What is the “non-accidental properties” idea in RBC?

Features like edges/parallel lines remain constant across viewpoints → help identify geons

What happens when geons are removed from an object?

Recognition becomes much harder
👉 Shows geons are critical for object perception

What is edge detection in object recognition?

Early stage where visual system identifies boundaries and contours

What is the difference between posterior vs anterior ventral stream?

• Posterior → visual discrimination

• Anterior → object memory

Why is feature theory limited?

Cannot easily explain recognition when features are missing or ambiguous

Why is prototype theory useful?

Explains category learning and generalization

What is the word superiority effect?

Letters are recognized better within words than alone
👉 Shows top-down processing

What is endogenous attention?

Internally driven, voluntary attention

What is exogenous attention?

Stimulus-driven, automatic attention capture

Why is attention considered limited capacity?

Only a certain amount of information can be processed at once

What is the “spotlight model” of attention?

Attention focuses on a region like a spotlight, enhancing processing there

What is the difference between spatial vs object-based attention?

• Spatial → location-based

• Object → entire object selected

What did EEG studies show about reflexive attention?

Early sensory components (like P1) are enhanced at attended locations

What happens at long cue-target intervals in attention tasks?

Inhibition of return → slower responses at cued location

Why is attention necessary for feature binding?

Without attention, features may be incorrectly combined (illusory conjunctions)

What are illusory conjunctions?

Incorrect combinations of features due to lack of attention

What is selective attention?

Ability to focus on relevant stimuli while ignoring others