Exam 3- Lecture 2 Flashcards
(132 cards)
1
Q
Front: Where is the Parahippocampal Place Area (PPA) located?
A
The PPA is located in the medial temporal lobe, near the collateral sulcus and within the parahippocampal gyrus. It is involved in processing spatial scenes and places.
2
Q
What is the function of the Parahippocampal Place Area (PPA)?
A
The PPA is responsible for recognizing spatial environments, such as landscapes, buildings, and rooms. It responds more to places than to faces or individual objects.
3
Q
🧠 What is the Parahippocampal Place Area (PPA), and what does it do?
A
The PPA is a brain region specialized for processing places and spatial scenes.
It is not always in the exact same anatomical location but is typically found around the parahippocampal gyrus.
The PPA responds strongly to images of places, buildings, and spatial layouts but not as much to objects or faces.
4
Q
🧠 What kind of stimuli activate the PPA?
A
The PPA responds strongly to:
✅ Spatial environments (e.g., landscapes, cityscapes, rooms).
✅ Buildings and places (both outdoor and indoor settings).
✅ Even empty rooms, showing it is sensitive to spatial layout.
The PPA does NOT respond strongly to:
❌ Faces
❌ Hands or objects
5
Q
🧠 How do spatial environments differ from objects in PPA activation?
A
Spatial scenes activate the PPA even if they are empty (e.g., an empty room still elicits a response).
The PPA does not simply respond to objects within a scene but to the overall spatial layout.
This suggests that the PPA encodes place-based information, helping us navigate environments.
6
Q
🧠 How do researchers identify the PPA’s function using contrasts?
A
Researchers compare different types of stimuli to see what activates the PPA:
✅ Spatial scenes vs. hands/faces → PPA responds to scenes, NOT to hands/faces.
✅ Places vs. objects → PPA responds to places, NOT random objects.
✅ Empty rooms vs. cluttered rooms → PPA still responds, meaning it encodes spatial layout, not just content.
7
Q
🧠 What role does the PPA play in human cognition?
A
The PPA helps with spatial navigation and scene recognition.
It allows us to recognize landmarks, indoor spaces, and large-scale environments.
Damage to the PPA can cause topographical disorientation, making it hard to recognize familiar places.
8
Q
🧠 Why does the PPA respond strongly to empty rooms?
A
The PPA is not responding to objects in a room but to the spatial structure itself.
Even when a room is empty, the PPA still activates, showing it encodes scene layout and spatial relationships.
This proves the PPA is specialized for processing places, not just the things inside them.
9
Q
🧠 Does the PPA respond more to objects or spatial layouts?
A
Scenes with a spatial structure (e.g., rooms, landscapes) activate the PPA strongly.
Objects alone do not trigger the same response.
Even Legos arranged into a miniature 3D structure elicit a stronger response than isolated objects.
This suggests the PPA prioritizes spatial organization over individual objects.
10
Q
🧠 What happens when a room is fragmented or lacks a coherent 3D structure?
A
As long as a scene retains its overall spatial organization, the PPA still responds.
However, if a room is rearranged into a non-coherent structure, the PPA does not respond as strongly.
This proves that the PPA is tuned to coherent spatial layouts rather than just local features.
11
Q
🧠 Why does the PPA respond more to structured environments than disrupted ones?
A
The PPA detects spatial depth, orientation, and structure, not just the presence of surfaces.
A room with intact spatial coherence activates the PPA more than a scrambled version of the same room.
This suggests that the brain relies on the PPA for understanding spatial environments and navigation.
12
Q
🧠 What is the main conclusion about the PPA from these studies?
A
The PPA encodes spatial environments and place structure, not individual objects.
It is activated by real-world scenes, empty rooms, and even structured artificial spaces.
Disrupting the 3D spatial layout reduces PPA activation, proving it processes coherent place representations.
13
Q
🧠 Why is 3D spatial structure important for PPA activation?
A
The PPA is not just responding to images but to structured spatial layouts.
It is sensitive to depth, orientation, and the arrangement of space.
The stronger response to organized 3D environments suggests the PPA processes spatial navigation cues.
14
Q
🧠 What does the PPA contribute to our spatial awareness?
A
It helps us recognize places and understand spatial environments.
It encodes structural relationships between objects and scenes, forming a mental map of locations.
This supports navigation, wayfinding, and scene recognition in daily life.
15
Q
🧠 How does the brain develop spatial awareness and place recognition?
A
Early exposure to environments strengthens spatial recognition.
The brain refines spatial processing through experience and movement in different locations.
The PPA becomes more specialized as a person navigates complex places and learns landmarks.
16
Q
🧠 How does the brain translate spatial perception into real-world action?
A
Step 1: The PPA recognizes a spatial environment.
Step 2: The brain compares the scene to stored memory (familiar places).
Step 3: Other regions (e.g., hippocampus) help determine position and direction.
Step 4: The motor system uses this spatial map to guide movement and navigation.
17
Q
A
17
Q
🧠 How does expertise influence spatial recognition?
A
Architects, urban planners, and navigators develop highly refined spatial expertise.
Training in complex spatial tasks strengthens the PPA’s ability to process and remember environments.
This suggests that spatial expertise is not just innate but can be developed through experience.
18
Q
🧠 How does expertise in spatial recognition develop?
A
Experience and training refine spatial perception over time.
People who navigate complex environments regularly (e.g., pilots, architects) develop stronger PPA activation.
This suggests that spatial processing can be improved through repeated exposure and learning.
19
Q
🧠 How does the brain encode spatial environments?
A
The PPA processes places holistically, capturing 3D structures and spatial layouts.
It encodes geometrical relationships, like depth and positioning.
The hippocampus and other areas integrate this to form cognitive maps for navigation.
20
Q
🧠 Does the brain encode places based on the observer’s viewpoint?
A
Viewpoint-Specific Encoding: The scene is stored as seen from a specific angle.
Viewpoint-Invariant Encoding: The brain generalizes spatial features, making it easier to recognize places from new angles.
The PPA likely encodes both but leans toward viewpoint-invariant processing.
21
Q
🧠 How does the brain encode spatial information beyond direct sensory input?
A
The brain doesn’t just store images of places—it encodes abstract spatial structures.
This allows us to navigate places even when they change (e.g., a familiar street with construction).
This suggests that spatial cognition is more about understanding geometrical structures than just memorizing views.
22
Q
🧠 Why does the brain prioritize 3D spatial structure?
A
The PPA and other spatial processing areas respond to the layout and depth of spaces, not just individual objects.
The brain encodes geometric relationships, allowing us to understand how spaces are organized.
This supports navigation, spatial memory, and scene recognition.
23
Q
🧠 How does the PPA contribute to spatial awareness?
A
The PPA extracts key spatial information from an environment.
It helps us understand depth, barriers, and pathways.
This processing is crucial for wayfinding, remembering places, and constructing cognitive maps.
24
🧠 How does the brain encode and store information about spatial environments?
1️⃣ Visual input provides depth, edges, and object relationships.
2️⃣ The PPA processes the overall layout rather than individual objects.
3️⃣ The hippocampus links the scene to memory, creating a spatial map.
4️⃣ Parietal regions integrate movement, allowing navigation based on the encoded space.
25
🧠 Does the brain store spatial data from a fixed perspective or in an abstract way?
Viewpoint-Specific Encoding: The environment is stored as seen from a particular angle.
Viewpoint-Invariant Encoding: The brain encodes the core geometric features so we recognize spaces from different perspectives.
Research suggests both exist, but the PPA leans toward viewpoint-invariant processing, helping with flexible navigation.
26
🧠 How does expertise affect spatial processing?
Training and experience refine the brain’s ability to process spatial data.
Experts in architecture, navigation, or virtual simulations develop enhanced PPA responses.
This shows that spatial perception is both innate and trainable.
27
Does the brain encode spatial environments based on a specific viewpoint or abstractly?
Viewpoint-Specific Encoding: The environment is stored relative to the observer's position.
Viewpoint-Invariant Encoding: The brain encodes abstract spatial structures, allowing recognition from different angles.
Findings suggest that while viewpoint matters, the brain also encodes generalized spatial relationships for flexibility in navigation.
28
🧠 Is spatial encoding only about recognition, or does it also guide movement?
Spatial representation is not just for recognition but also for action planning.
The brain uses spatial data to guide movement, helping with tasks like navigating a room or reaching for objects.
This suggests that spatial encoding is functional, integrating both perception and motor planning.
29
🧠 What happens when the same spatial scene is shown twice in a row?
If a scene remains unchanged, the brain shows a reduced response (adaptation).
If something in the scene changes (e.g., objects move), the response remains high, indicating new processing.
This proves that the brain actively detects and updates spatial changes rather than passively storing scenes.
30
🧠 Does the brain respond more to object changes or scene changes?
Changing objects in a scene still causes adaptation, suggesting that objects are less critical than layout.
Changing the spatial layout (scene change) leads to higher brain activation, meaning the brain prioritizes spatial structure over objects.
The Parahippocampal Place Area (PPA) is more sensitive to scene changes than object changes.
31
🧠 What did studies reveal about how the brain processes spatial environments?
The brain encodes scenes holistically, not just as collections of objects.
Changes in scene layout trigger stronger responses than object changes.
Spatial processing is both viewpoint-specific and viewpoint-invariant, balancing immediate perspective with general spatial understanding.
32
Front: What does the Parahippocampal Place Area (PPA) respond to the most?
The PPA is most sensitive to viewpoint changes in a scene, meaning it detects alterations in spatial perspective more than changes in objects or specific places.
33
How does the PPA compare to the FFA and LO in sensitivity to viewpoint changes?
The PPA shows the highest signal change in response to viewpoint changes, whereas the FFA (Fusiform Face Area) and LO (Lateral Occipital Complex) are less sensitive to these changes.
34
Front: What types of changes were tested in the study shown in the image?
Back: The study tested no change, object change, viewpoint change, and place change to analyze how the PPA, FFA, and LO respond to different scene modifications.
35
Front: What does the image suggest about PPA’s role in scene perception?
Back: The PPA is viewpoint-sensitive, meaning it plays a role in recognizing and differentiating spatial layouts based on perspective shifts.
36
What happens when the viewpoint of a scene changes but the layout stays the same?
If only the viewpoint changes, the brain does not show strong adaptation.
This suggests that the brain treats different viewpoints as distinct spatial experiences.
This differs from object perception, where recognition often remains stable across viewpoints.
37
oes the Parahippocampal Place Area (PPA) treat viewpoint changes as different scenes?
The PPA does not fully adapt when the viewpoint shifts, meaning it encodes spatial layout relative to the observer.
If only objects change but the layout remains the same, the PPA still shows adaptation.
This suggests that the PPA prioritizes spatial structure over viewpoint consistency.
38
🧠 What type of scene manipulation causes the greatest neural activation in the PPA?
structure) causes the highest activation.
Changing the viewpoint of the same scene causes moderate activation, meaning the brain treats it as somewhat different.
Changing only objects within the scene results in lower activation, showing that spatial structure is more critical.
39
🧠 Does the PPA store spatial scenes from a specific viewpoint or in an abstract way?
Viewpoint-Specific Encoding: If the scene is stored with reference to a specific angle, a viewpoint shift will cause strong activation.
Viewpoint-Invariant Encoding: If the brain encodes abstract spatial features, viewpoint shifts should have minimal impact.
Findings suggest a mix of both, with some sensitivity to viewpoint but stronger sensitivity to spatial layout.
40
🧠 Why does the brain need both viewpoint-specific and viewpoint-invariant spatial encoding?
Viewpoint-Specific Processing helps us orient ourselves in real-time and understand scenes relative to our current position.
Viewpoint-Invariant Processing allows us to recognize places from different angles and form mental maps for navigation.
The PPA balances both processes, helping with both immediate perception and long-term spatial memory.
41
🧠 How does changing the viewpoint affect spatial encoding?
If two viewpoints of the same scene are presented, the brain does not fully adapt, meaning it recognizes them as different perspectives.
This suggests that the brain encodes some spatial information relative to the observer's position.
However, the brain still relies on spatial structure and context for recognition, not just viewpoint.
42
🧠 Why do spatial environments evoke stronger contextual associations than individual objects?
Scenes (e.g., libraries, hotels, museums) are tied to rich contextual associations.
Seeing a library may activate thoughts of books, desks, quiet spaces, etc.
In contrast, seeing an individual object (e.g., a chair) does not necessarily trigger a strong web of associations.
43
🧠 How do contextual associations help us recognize and understand places?
The brain groups related elements when encoding spatial environments.
Seeing a museum scene may activate memories of art, sculptures, and history.
This contextual linking allows us to predict and navigate unfamiliar spaces based on past experiences.
44
🧠 What is the difference between strong and weak contextual associations?
Strong contextual associations: Objects or places that are frequently experienced together (e.g., a blackboard in a classroom).
Weak contextual associations: Objects that are less consistently tied to a particular context (e.g., a generic chair).
The PPA responds more strongly to objects with strong contextual ties to places.
45
🧠 How does context influence the way we process objects and scenes?
The brain processes objects differently depending on their environment.
A couch in a living room makes immediate sense, but a couch in a forest creates cognitive dissonance.
This suggests that scene context shapes how we interpret objects, influencing recognition and memory.
46
🧠 How does the brain process objects with strong vs. weak contextual associations?
Strongly associated objects activate a widespread network of brain regions, including the Parahippocampal Place Area (PPA).
Weakly associated objects do not trigger as strong a response, suggesting that context matters in object recognition.
This suggests the PPA is not just for spatial layout but also integrates contextual meaning.
47
🧠 Does the PPA only process spatial environments, or does it also respond to objects?
While primarily a spatial processing region, the PPA also responds to objects that have strong contextual ties to places.
Example: A cash register activates the PPA strongly because it is tied to store environments.
This shows that place recognition is influenced by both spatial structure and familiar objects.
48
🧠 Why do some objects elicit stronger neural responses in the PPA than others?
Objects that are highly tied to specific places (e.g., an altar in a church) activate both spatial and contextual processing areas.
The brain integrates objects into their expected spatial layouts, reinforcing scene recognition and navigation.
This explains why familiar objects help us identify and categorize places quickly.
49
🧠 Why is it difficult to define the exact function of a brain region like the PPA?
Brain regions rarely have single, isolated functions; they interact with multiple cognitive systems.
The PPA was originally thought to process only spatial layout, but research shows it also responds to objects with strong contextual associations.
Cognitive scientists must disentangle overlapping functions by carefully designing experiments to separate spatial, object, and contextual processing.
50
🧠 Why is it difficult to fully define the role of the PPA?
The PPA responds to multiple aspects of spatial environments, making it hard to isolate one function.
It processes both spatial layout and contextually relevant objects.
Researchers must carefully design experiments to separate spatial encoding from object-based associations.
51
🧠 Does the PPA only encode spatial layout, or does it also process context?
Back:
Some parts of the PPA are more focused on spatial structure, while others encode associations between objects and places.
This means the PPA does not just store maps of locations but also processes meaning tied to environments.
The interaction between spatial structure and contextual meaning helps in scene recognition and navigation.
52
🧠 Why do some studies show different results for PPA function?
me experiments suggest the PPA is purely spatial, while others show it processes objects relevant to places.
These variations may be due to differences in study design, stimuli, and task demands.
The best conclusion is that the PPA integrates multiple aspects of spatial cognition rather than having a single function.
53
🧠 What are researchers still trying to understand about the PPA?
Whether the PPA is strictly a spatial processing region or an area integrating spatial and object-context relationships.
How different subregions of the PPA contribute to scene recognition and navigation.
How experience and expertise (e.g., architects vs. non-experts) influence PPA activation.
54
🧠 What are frames of reference, and why are they important in spatial cognition?
Frames of reference are the perspectives the brain uses to interpret spatial information.
They help us understand where objects are relative to ourselves and the environment.
Different tasks require different types of spatial representations (e.g., navigating a city vs. reaching for an object).
55
🧠 What types of spatial information do we use in daily life?
1️⃣ Local spatial awareness (e.g., where objects are in a room).
2️⃣ Object location relative to our body (e.g., reaching for a cup).
3️⃣ Large-scale navigation (e.g., finding a route to another building).
4️⃣ Fixation points (e.g., tracking where words are on a screen while reading).
Each requires a different frame of reference to process effectively.
56
🧠 What are the two primary frames of reference for spatial processing?
Egocentric frame of reference:
Represents locations relative to oneself (e.g., "the phone is to my right").
Important for reaching, grasping, and personal navigation.
Allocentric frame of reference:
Represents locations independent of the observer (e.g., "the coffee shop is next to the bookstore").
Crucial for maps, large-scale navigation, and remembering landmarks.
57
🧠 How does the brain apply different frames of reference to spatial tasks?
The parietal cortex helps process egocentric (self-based) spatial awareness.
The hippocampus is crucial for allocentric (map-based) navigation.
The brain switches between these frames depending on the task, like reaching for an object vs. planning a walking route.
58
🧠 Why does the brain rely on multiple spatial reference frames instead of just one?
Different tasks require different perspectives (e.g., grabbing a coffee vs. navigating a campus).
Egocentric frames are fast and action-oriented, useful for immediate interactions.
Allocentric frames allow for long-term spatial memory and flexible navigation.
The brain's ability to switch between them is essential for efficient movement and spatial reasoning.
59
🧠 What is a frame of reference, and why is it important?
A frame of reference is the coordinate system the brain uses to understand and navigate space.
It defines how we locate objects, places, and directions relative to a reference point.
Different tasks require different reference frames, depending on whether we are navigating, reaching for objects, or describing locations.
59
🧠 Why is a reference point necessary when representing spatial information?
Spatial information is meaningless without a reference point (e.g., "The classroom is on the left" → Left of what?).
Reference points anchor spatial representations, allowing for clear directionality.
The brain chooses different reference points based on the context (e.g., personal viewpoint vs. map-based navigation).
60
🧠 What are the three main types of frames of reference in spatial cognition?
Egocentric Frame of Reference:
Spatial information is centered around the observer.
Example: "The book is to my right."
2️⃣ Allocentric Frame of Reference:
Spatial information is encoded relative to external landmarks.
Example: "The library is next to the café."
3️⃣ Intrinsic Frame of Reference:
Spatial relations are defined relative to an object itself.
Example: "The handle is on the left side of the door."
61
🧠 How do different frames of reference help us navigate?
Egocentric navigation helps us move through space from our current position (e.g., "Turn left at the intersection").
Allocentric navigation allows us to use maps and landmarks (e.g., "The library is two blocks east of the park").
The brain switches between these frames depending on the task, environment, and prior experience.
62
🧠 How does the brain decide which spatial frame of reference to use?
For immediate action (grabbing an object), the brain uses an egocentric reference.
For long-term navigation (remembering a city layout), it switches to an allocentric reference.
The brain flexibly shifts between frames depending on whether the focus is self-centered movement or object-based spatial relationships.
63
What is the representation of location?
Are relative to some reference points, are in the same frame or reference.
64
🧠 What are the three main frames of reference in spatial cognition?
Egocentric Frame of Reference:
Location is represented relative to the self.
Example: "The phone is to my right."
2️⃣ Allocentric Frame of Reference:
Location is represented relative to external landmarks.
Example: "The coffee shop is next to the library."
3️⃣ Intrinsic Frame of Reference:
Location is defined relative to an object itself.
Example: "The handle is on the left side of the door."
65
🧠 What is the egocentric frame of reference?
Spatial information is centered around the observer.
Used for reaching, grasping, and self-centered navigation.
Example: "The book is behind me."
Primarily processed in the parietal cortex, which tracks body-relative spatial locations.
66
🧠 What is the allocentric frame of reference?
Spatial information is based on external landmarks rather than the observer’s position.
Used for map-based navigation and remembering places.
Example: "The museum is north of the park."
The hippocampus plays a key role in allocentric spatial processing
67
🧠 What is the intrinsic frame of reference?
Objects define their own spatial relationships.
Used to describe part-to-part relations.
Example: "The clock is on the front of the building."
Important for object manipulation and spatial reasoni
68
🧠 Why does the brain switch between different spatial frames of reference?
Egocentric frames are used for short-term actions (e.g., reaching for an object).
Allocentric frames help with long-term navigation and map reading.
Intrinsic frames allow us to understand object parts and orientations.
The brain dynamically shifts between these frames depending on the task.
69
🧠 Which brain regions are responsible for processing different frames of reference?
Egocentric processing → Parietal cortex (tracks objects relative to the body).
Allocentric processing → Hippocampus (encodes spatial maps and relationships).
Intrinsic processing → Occipital and temporal regions (object-centered representations).
Understanding brain activity patterns helps researchers identify spatial processing disorders.
70
🧠 What is a spatial field, and how does it relate to vision?
A spatial field refers to how visual and spatial information is organized and processed in relation to a reference point.
In vision, it helps define where objects are located relative to the observer's viewpoint.
Different parts of the visual field correspond to specific locations on the retina.
71
🧠 How does the brain determine the location of an object in space?
The brain maps objects relative to the observer using egocentric (self-centered) frames of reference.
Allocentric representations help in scene perception and navigation.
The visual field provides location cues that are processed relative to the retina and eye movement.
72
🧠 What does it mean for a location to be defined in the visual field?
Objects are positioned relative to where they appear on the retina.
A given location in the visual field is mapped consistently, even if eye movement changes.
This allows for stable perception of objects despite head or eye movement.
73
🧠 How does the retina contribute to spatial representation?
The retina encodes spatial positions of objects by mapping them to specific locations.
Each retinal cell corresponds to a fixed location in the visual field.
Even if the eyes move, the visual system maintains consistent spatial awareness.
74
🧠 Why does the brain need to represent spatial information in a structured way?
Helps us locate and track moving objects in space.
Enables depth perception and scene organization.
Supports navigation and object interaction by providing a stable reference for spatial awareness.
75
🧠 What are spatial receptive fields, and how do they relate to vision?
A spatial receptive field refers to the area of the visual field that a neuron or group of neurons respond to.
These fields track objects relative to fixation points.
They help determine where something is in space relative to where we are looking.
76
🧠 How are spatial receptive fields mapped in the brain?
Receptive fields are defined relative to fixation points (where the eyes are focused).
They shift dynamically as the eyes move, allowing for continuous tracking of objects.
Studies in monkeys and humans show that receptive fields are tied to spatial attention and precision movements.
77
🧠 Why is fixation important for spatial perception?
Fixation provides a stable reference point for mapping visual space.
Spatial fields shift relative to fixation rather than absolute positions.
This helps in tracking moving objects and maintaining a stable visual world.
78
🧠 How do spatial receptive fields adjust when we shift our gaze?
When we move our eyes, the receptive fields shift to maintain spatial awareness.
This process is called retinotopic mapping, where the brain updates spatial information dynamically.
Even if the screen or environment remains the same, the reference point changes with gaze shifts.
79
🧠 Why are spatial receptive fields essential for visual processing?
They help the brain track objects as they move.
They allow us to fixate on a point while maintaining spatial awareness.
They enable accurate perception of spatial relationships even when our eyes shift positions
80
🧠 Why is a reference point important in spatial perception?
A reference point anchors spatial perception, allowing us to determine where objects are located relative to our focus.
In vision, fixation acts as the primary reference point, helping the brain map objects based on where we are looking.
Neurons encode spatial information relative to fixation, ensuring accurate eye movements and visual tracking.
81
🧠 How do neurons encode spatial location in vision?
eurons in the retina and visual cortex respond to specific regions of the visual field.
These responses are organized relative to fixation, meaning spatial perception is centered around where we are looking.
The brain processes incomplete visual input and fills in gaps to create a stable perception of space.
82
🧠 Why is fixation crucial for spatial encoding?
Fixation provides a stable reference for organizing visual space.
When we shift our gaze, spatial information is updated dynamically to maintain perception.
Fixation-based encoding allows for precise eye movements and object tracking.
83
🧠 How does the brain know where an object is relative to fixation?
Neurons encode object positions based on their location in the visual field relative to the fovea.
If fixation changes, the neural map updates automatically.
This system allows us to read, track moving objects, and shift attention smoothly.
84
🧠 Why is vision organized around a centered frame of reference?
Retinotopic mapping ensures that visual information is centered around fixation.
This organization allows the brain to guide eye movements accurately.
It supports efficient attention shifts, helping us focus on important details in our environment.
85
🧠 What does it mean that V1 neurons use a retino-centric frame of reference?
V1 neurons map visual input based on retinal position.
Objects that stimulate the same spot on the retina activate the same V1 neurons.
If fixation shifts, the same objects in the world will activate different V1 neurons.
This means the brain’s visual representation updates dynamically with eye movements.
86
🧠 What is the reference frame for V1 neurons?
V1 neurons use a retino-centric frame of reference, meaning they encode location relative to the retina.
They represent objects in terms of direction (right/left, above/below) and distance from fixation.
When fixation shifts, the same object activates different V1 neurons.
This system helps maintain spatial accuracy in visual processing.
87
🧠 How does fixation affect spatial perception and object representation?
Fixation anchors spatial processing, meaning visual input is mapped relative to the point of focus.
When you move your eyes, the fixation point shifts, but the world remains the same.
Objects are remapped to different neurons in V1 depending on their new position relative to fixation.
88
🧠 How does the brain process visual input contralaterally?
Each hemisphere processes the opposite side of the visual field.
Right visual field → Left V1 activation, Left visual field → Right V1 activation.
Objects in the periphery activate neurons farther from the fovea, while central vision maps to the fovea region in V1.
89
🧠 What happens to visual representation when you shift fixation?
The stimulus remains in the same place in the world but activates different neurons in V1.
The visual system remaps objects dynamically to keep track of spatial relationships.
This allows us to scan a scene while maintaining stable perception.
90
🧠 Why does the brain use retinotopic mapping for spatial organization?
Retinotopic mapping means neurons encode spatial positions relative to the retina.
This system allows for precise tracking of moving objects.
It ensures seamless transitions when the eyes shift focus without disrupting perception.
91
🧠 What is the difference between relative and absolute spatial location in vision?
Relative location: Objects are coded based on fixation (e.g., "to the left of my focus").
Absolute location: Objects are coded based on external world coordinates (e.g., "next to the building").
The brain prioritizes relative location for fast and efficient eye movement coordination.
92
🧠 How do V1 neurons activate based on fixation?
V1 neurons encode visual information relative to fixation.
Objects in the left visual field activate the right V1, and vice versa.
Objects in the upper visual field activate the lower part of V1, and vice versa.
If fixation shifts, the same object will activate different neurons.
Example: In the image, the red square in the upper left visual field is processed in the lower right portion of V1.
92
🧠 What is cortical blindness, and how does it occur?
Cortical blindness results from damage to V1 in the occipital lobe.
The retina and optic nerve remain intact, but visual signals cannot be processed.
The area of blindness corresponds to the damaged hemisphere’s visual field representation (e.g., left V1 damage causes right visual field blindness)
93
🧠 What happens to vision when V1 is damaged?
Damage to left V1 → blindness in the right visual field.
Damage to right V1 → blindness in the left visual field.
Vision loss follows a retinotopic map, meaning only the affected area of the visual field is lost.
94
🧠 Why can a patient with cortical blindness sometimes see objects by shifting fixation?
ortical blindness is fixed to a location in the visual field, NOT the eye.
If a patient moves their eyes, the object may shift to an undamaged area of V1.
This allows them to "see" objects that were previously in the blind spot.
95
🧠 How does a retino-centric frame of reference explain cortical blindness?
V1 neurons encode vision relative to fixation.
A damaged V1 region permanently removes visual input from its mapped area, causing blindness in that portion of the field.
Moving the eyes shifts fixation, allowing undamaged neurons to process new parts of the scene.
96
🧠 What does it mean that vision follows a retino-centric frame of reference?
Vision is mapped relative to fixation, meaning neurons encode locations based on where the eyes are looking.
If a part of V1 is damaged, the corresponding visual field area is permanently lost, even if the eyes move.
Moving the eyes shifts what is visible, allowing unaffected neurons to process new parts of the scene.Vision is mapped relative to fixation, meaning neurons encode locations based on where the eyes are looking.
If a part of V1 is damaged, the corresponding visual field area is permanently lost, even if the eyes move.
Moving the eyes shifts what is visible, allowing unaffected neurons to process new parts of the scene.
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🧠 Do people with cortical blindness realize they are blind in part of their visual field?
Many do not immediately notice their blind spot because they assume they can see everything.
This is sometimes referred to as visual spatial neglect or lack of visual awareness.
The brain may compensate by "filling in" missing details, making the blindness less obvious.
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🧠 What happens in higher-level vision when part of the visual field is lost?
Some patients experience visual neglect, where they are unaware of missing parts of their vision.
The brain processes everything it sees but may fail to register certain areas as "missing".
Reference frames matter: The brain may interpret vision relative to body position or object-centered frames.
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🧠 How does the brain use different reference frames in vision?
Egocentric (Body-Centered): Objects are mapped relative to the body, meaning left and right are defined from the person's perspective.
Object-Centered: The brain processes objects relative to themselves, meaning one side of an object is always "left" even if the person moves.
Vision loss may be relative to a specific reference frame, affecting how a patient perceives objects.
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🧠 What are the two types of spatial neglect in vision?
Egocentric Neglect:
Deficit is relative to the person's body (e.g., left side of space is ignored).
Common in right parietal lesions, leading to left visual field neglect.
Object-Centered Neglect:
Deficit is relative to the object itself, regardless of body position.
Example: A person may ignore the left side of an object even if it is in their right visual field.
Linked to right temporal and inferior occipital damage.
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🧠 How does object-centered neglect affect perception?
Patients ignore one side of an object, even when they can move their eyes freely.
The deficit is not tied to their overall visual field but to how objects are processed.
Example: When drawing a clock, they might only draw the right half, even if the whole clock is in view.
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🧠 How does contralateral processing relate to spatial neglect?
The right hemisphere processes the left visual field and vice versa.
Damage to the right hemisphere (parietal/temporal) can cause left-side neglect.
Neglect may be egocentric (left side of space) or object-centered (left side of objects).
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🧠 Can patients with spatial neglect compensate by moving their eyes?
No, moving the eyes does not help in object-centered neglect.
The missing side of the object remains unseen, even when fixating on it.
This suggests the brain fails to register part of the object, not just ignore its location in space.
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🧠 What symptoms are common with right hemisphere lesions?
Left-side neglect (egocentric or object-centered).
Impaired scene reproduction (only drawing right-side details).
Failure to detect objects in the left visual field despite normal eye movements.
Difficulty integrating the full visual scene, even with active scanning.
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🧠 Who is Patient CS, and what neurological condition do they have?
Patient CS: 66-year-old, right-handed.
Condition: Right temporal/parietal hemorrhage due to drug overdose.
Possible Symptoms:
Left-side neglect (difficulty perceiving the left visual field).
Spatial processing deficits (trouble navigating or recognizing objects in space).
Object-centered neglect (ignoring the left side of objects).
Impaired attention and awareness of surroundings.
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🧠 What is the difference between object-centered neglect and egocentric neglect?
Egocentric Neglect → Patients ignore the left side of their entire visual field, relative to their body.
Object-Centered Neglect → Patients ignore the left side of individual objects, even if they appear in the right visual field.
Caused by right parietal or temporal lobe damage.
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🧠 What happens when a patient with visual neglect performs a line cancellation task?
Task: Patients are asked to cross out all lines on a page.
Findings:
Patients with left-side neglect will only cross out lines on the right.
They fail to perceive the left-side lines, even though their eyes can move freely.
This confirms spatial awareness deficits rather than vision loss
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🧠 Why doesn’t moving the eyes help patients with visual neglect?
Unlike blindness, the visual system is intact—the brain just fails to process certain parts of the scene.
Shifting gaze does not restore awareness of the neglected space.
The deficit is in higher-order processing, not the eyes or retina.
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🧠 Do patients with neglect realize they are missing parts of the scene?
No, they often believe they are seeing everything.
The brain fills in missing information, making it feel like nothing is wrong.
This illusion of completeness makes the condition more difficult to recognize.
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🧠 What causes patients to be unaware of missing visual information?
Damage to right temporal/parietal regions disrupts higher-level visual processing.
Even though visual input reaches the brain, conscious awareness of one side is lost.
This shows that perceiving something and being aware of it are separate processes.
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🧠 What are the key findings from the case study of Patient CS?
Not cortical blindness → V1 is intact, meaning the eyes and basic visual processing are functional.
Deficit persists despite eye movements, showing that the problem is not in the retina or early vision.
Attentional deficit due to a parietal lobe lesion → Suggests an issue with higher-order visual attention, not basic sight.
Viewer-centered neglect → The "left" side is defined relative to the viewer, not the visual scene or objects.
Critical Evidence:
Neglect persists even when the eyes move.
The problem is in how attention is allocated, not in detecting stimuli.
Is not like color blindness.
They may have a sense that something is not. right
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Do patients with visual neglect have any awareness that they are missing parts of a scene?
Sometimes, patients show signs of partial awareness, like trying to balance a drawing.
Example: Drawing a flower but adding too many petals on one side, as if compensating.
They may sense that something is missing but cannot consciously perceive the missing part.
This suggests some residual processing in the brain, even if the patient is unaware.
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🧠 Why do patients with neglect sometimes show "guessing" behaviors?
Some unconscious processing of the full scene may still occur.
Patients might intuitively sense the missing portion but cannot explicitly perceive it.
They compensate by overfilling the visible side, indicating a vague awareness.
This behavior suggests the brain receives some information but does not fully process it.
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🧠 If neglect patients sometimes "sense" missing details, does that mean they are perceiving everything?
No, but they may retain some unconscious visual processing.
They cannot actively focus on the missing part, but their behavior suggests some residual input.
Some theories suggest low-level visual areas detect stimuli, but higher-order processing fails.
This explains why they sometimes correct or adjust their actions without full awareness.
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What is this case Patient NG?
79 year old, female
left parietal/temporal lesion.
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🧠 What is object-centered neglect?
A condition where a patient neglects one side of an object, regardless of their own viewpoint.
Caused by parietal-temporal lesions, usually in the right hemisphere.
Example: When drawing a clock, the patient only fills in numbers on one side of the clock face.
Differs from viewer-centered neglect, which is based on the patient’s body perspective rather than the object itself.
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🧠 What is the difference between viewer-centered and object-centered neglect?
Viewer-Centered Neglect:
Patient neglects one side relative to their body (e.g., always ignores the left side of space).
Example: Only eating food from one half of a plate.
Object-Centered Neglect:
Patient neglects one side of individual objects, regardless of their orientation.
Example: When copying a picture, they only draw one side of each object, even i
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🧠 How does object-centered neglect influence what patients "see"?
Patients may see the full scene relative to their body, but fail to perceive the missing side of objects.
Example: They see a full table of objects but only process one side of each item.
This shows the brain encodes spatial relationships using different reference frames (viewer-based vs. object-based).
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🧠 What brain damage leads to object-centered neglect?
Typically results from damage to the right parietal-temporal cortex.
Affects how objects are represented in space, independent of the viewer’s position.
Patients fail to perceive one side of objects, even when rotated or repositioned.
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is their multiple variations of it?
yes, it can be one whole side or be only one side of the extremity.
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🧠 What is an object-centered (allocentric) frame of reference?
Locations are defined relative to an object’s right and left side, rather than the viewer's perspective.
Example: If an object is flipped, its right and left sides remain the same in an object-centered reference frame.
Important for perceiving spatial relationships independent of the observer’s position.
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🧠 What is object-centered neglect?
condition where patients fail to process or perceive stimuli on the contra-lesional side of objects, regardless of eye position or object location.
Caused by damage to the right parietal-temporal cortex.
Example:
If a patient has right hemisphere damage, they ignore the left side of objects, even if those objects move.
When copying a drawing, they only reproduce one side of each object, not the whole scene
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🧠 How is object-centered neglect different from viewer-centered neglect?
Back:
Viewer-Centered Neglect: Patients neglect one side of space relative to their body (e.g., always ignoring the left half of their environment).
Object-Centered Neglect: Patients neglect one side of each individual object, no matter where the object is placed.
Example:
Viewer-centered neglect: If a clock is on the left side of the room, the patient ignores it entirely.
Object-centered neglect: The patient sees the clock but only recognizes the numbers on one side of it.
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🧠 How does neglect affect mental imagery?
Patients with viewer-centered neglect can have impairments in mental imagery, similar to their visual perception deficits.
When asked to describe a familiar scene (like their hometown), they only recall the right side of the scene.
If they imagine turning around, they now describe the previously neglected side while ignoring the opposite side.
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🧠 How does changing perspective affect recall in neglect patients?
Neglect patients store a full 3D spatial map of a familiar place.
However, they only access information on the right side relative to their body's position.
When mentally shifting their viewpoint, they recall new details but still neglect the left side relative to their new orientation.
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🧠 What does this mental imagery experiment tell us about spatial memory?
Spatial knowledge is stored independently of viewpoint but is retrieved based on current perspective.
The neglect is not due to memory loss—patients have the full scene in memory but fail to access certain parts based on their reference frame.
Suggests that spatial neglect affects both perception and mental imagery.
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🧠 What is a retino-centered frame of reference?
Defines object location relative to fixation (where the eyes are focused).
Used by LGN and V1 in the visual system.
Function: Guides eye movements to track and focus on stimuli.
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🧠 What is a viewer-centered frame of reference?
Defines object location relative to the observer (their body position).
Associated with the inferior parietal lobe (IPL).
Also called ego-centric reference.
Function: Guides reaching, grasping, and body-centered movements.
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🧠 What is an object-centered frame of reference?
Defines object parts relative to the object’s own structure, independent of viewer position.
Associated with the superior temporal lobe.
Function: Supports object recognition despite changes in orientation, location, and viewpoint.
Also helps guide interactions with object parts (e.g., reaching for a specific handle on an object).
