Lecture 5-Higher Visual Processing Flashcards
What are the critical features of the Primary Visual Cortex?
The critical features of the Primary Visual Cortex include three major vertically-oriented systems: orientation columns, blobs in upper layers concerned with color, and ocular dominance columns.
What are orientation columns?
Orientation columns consist of neurons that respond selectively to light bars oriented in particular directions.
What are blobs in the Primary Visual Cortex concerned with?
Blobs in the upper layers of the Primary Visual Cortex are concerned with processing color information.
What are ocular dominance columns?
Ocular dominance columns receive inputs from one eye or the other, contributing to depth perception and visual processing.
How are units in the Primary Visual Cortex organized?
Units in the Primary Visual Cortex are organized into hypercolumns, representing small areas of the visual field.
What are the critical functions of the Primary Visual Cortex?
- It represents every part of the visual field with line segments (edges) in all orientations, which is important for recognizing shapes.
- It combines the visual input from both eyes through ocular dominance coloumns, which helps with depth perception.
What is the role of the P pathways in the primary visual cortex?
P pathway essential for:
1. colour vision
2. high spatial frequency sensitivity (fine form discrimination)
3. low temporal frequency sensitivity (detecting slow changes in visual stimuli)
What is the role of the M pathways in the primary visual cortex?
Lower spatial (larger features or patterns in an imag) and higher temporal frequency (faster changes or movements in visual stimuli)
What are the two perspectives in visual processing proposed by Ungerleider and Mishkin?
Ungerleider and Mishkin proposed the “What” and “Where” perspectives, suggesting that object recognition relies on visual information processed in the inferior temporal cortex (IT), while spatial perception depends on information processed in the posterior parietal cortex (PP).
What were the observations from studies on monkeys with lesions in IT and PP?
Monkeys with lesions in the inferior temporal cortex (IT) showed deficiencies in perceiving objects, while those with lesions in the posterior parietal cortex (PP) were deficient in perceiving spatial relations between objects.
What theory was proposed by Livingstone and Hubel regarding the “What” and “Where” perspectives?
Livingstone and Hubel theorized that the “What” and “Where” visual processing streams are direct extensions of the Magnocellular (M) and Parvocellular (P) pathways, respectively.
Which cortical regions are associated with the perception of faces and location in the ‘What’ and ‘Where’ pathways?
The ventral temporal cortex is associated with face recognition (‘What’), and the dorsolateral cortex is associated with location (‘Where’).
What perspective on visual processing is proposed by Goodale and Milner? (Vision in action perspective)
Propose perspective emphasizing vision in action, suggesting that visual processing streams evolved to transform incoming visual information for different purposes: perception or action.
What are examples of cortically-based visual disorders involving upstream visual deficits?
Examples include achromatopsia (deficts in color perception), and akinetopsia (involving deficits in motion perception)
What are examples of cortically-based visual disorders involving downstream visual deficits in the ventral stream?
Examples include apperceptive agnosia (unable to recognize objects) and associative agnosia (Difficulty linking objects with their meaning)
What is visual agnosia and what is it caused by?
The inability to recognize objects; results from damage to secondary visual areas, usually along ventral visual stream.
What are two basic types of agonisa?
- Apperceptive: Difficulty perceiving and discriminating objects
- Associative: Difficulty linking perceived objects with their meaning or significance.
What is the focus of the ventral visual processing system according to Goodale and Milner?
The ventral system encodes enduring object characteristics, essential for long-term object recognition and significance (What).
What role does the dorsal visual stream play in visual processing according to Goodale and Milner?
The dorsal visual stream is tuned to visually guided actions, processing moment-to-moment changes to mediate the control of goal-directed actions (Where).
What is Apperceptive Agnosia?
Apperceptive Agnosia is characterized by the inability to form a perceptual understanding of objects, despite intact sensory functions (You have trouble even seeing or understanding what the object is, so recognizing its purpose becomes difficult)
What are the key features of Apperceptive Agnosia?
Individuals with Apperceptive Agnosia can describe basic features of objects but struggle to integrate these features for recognition, copying, or matching of simple shapes.
What brain damage is associated with Apperceptive Agnosia?
Apperceptive Agnosia is associated with bilateral damage to the lateral occipital lobes.
What is associative agnosia?
involves the inability to recognize objects despite intact perception. (You see the object clearly but can’t remember what it is or what it’s used for.)
What abilities are preserved in individuals with Associative Agnosia? (2)
- Individuals with Associative Agnosia can copy objects and match simple, similar-looking objects.
- They can also define what an object is based on a label, indicating that it’s not a language or memory problem.
