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Higher Perceptual Functions
Higher Perceptual Functions
23
Psychology
12/03/2006

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Term
agnosia
Definition
Agnosia is disorder involving failure of perception.
Term
visual agnosia
Definition
Visual agnosia is limited to the visual modality.
Term
Two major fiber bundles (fasculi) which comprise most of the output from the occipital lobe.
Definition
1. the superior longitudinal fasciculus
2. the inferior longitudinal faciculus
Term
Two cortical pathways for visual perception
Definition
1. dorsal or occipito-temporal pathway
2. ventral or occipito-temporal pathway
Term
dorsal or occipito-temporal pathway
Definition
The "where" pathway. Specialized for spatial perception, for determining where an object is, and for analysing the spatial configuration between objects.
Term
ventral or occipito-temporal pathway
Definition
The "what" pathway. Specialized for object perception and recognition, for determining what it is we are looking at.
Term
What area should you lesion if you want to disrupt the "what" pathway?
Definition
The temporal lobe
Term
What area is central to spatial attention?
Definition
The parietal cortex
Term
prosopagnosia
Definition
Impaired face perception. Lesions fall along the ventral pathway.
Term
anomia
Definition
Difficulty naming objects.
Term
optic ataxia
Definition
Patients with optic ataxia can recognize objects, but they cannot use visual information to guide their actions. Associated with lesions of the parietal cortex.
Term
saccades
Definition
directed eye movements
Term
object constancy
Definition
The ability to recognize an object in countless situations.
Term
view-dependant theories
Definition
In a view-dependant theory, perception is assumed to depend on recognizing an object from a certain viewpoint. Posits that we simply need to match a stimulus to a represtntation stored in memory.
Term
view-invarient frame of reference
Definition
Recognition depends on an inferential process based on a few salient features. Sensory input defines the basic properties; the object's other properties are defined with respect to these properties.
Term
What is blindsight and why is it interesting?
Definition
Blindsight is the residual ability to localize stimuli following cortical blindness (the ability to attend to objects one is not aware of). It is interesting because those with blindsight respond to stimuli as if they can see.
Term
Describe an experiment used to describe the "what" and "where" pathways.
Definition
A double dissociation involving a landmark task and an object discrimination task. In the landmark task, food is placed in a well next to a cylinder. After the association is learned, the rule is reversed so that the food is placed in the well farthest from the cylinder. The monkey, although initially confused, eventually learns the new rule. Monkeys with temporal lobe lesions (lesions in the “what” pathway) also show eventual improvement in the reversal, however monkeys with parietal lobe lesions (“where” pathway) lesions fail to improve. In the object discrimination task, the monkey must associate food with an object. Beside each food well is an object, either a cylinder or a cube. The monkey must learn that the food is associated with the cube; whenever the cube moves to the other food well, the food move with it. The monkeys with temporal lobe lesions failed to make the connection
Term
gnostic unit
Definition
Refers to the idea that cells can signal the presence of a known stimulus.
Term
appreciative agnosia
Definition
inability to recognize objects due to perceptual problems.
Term
associative agnosia
Definition
failure of visual object recognition not due to perceptual problems.
Term
alexia
Definition
a form of acquired dyslexia
Term
Give a theoretical example of how all objects may be decomposed into a finite set of parts.
Definition
Irv Binderman’s geon theory posits that a finite set of shapes called geons, or geometric ions, comprise the perceptual alphabet for constructing object objects. Any object can be decomposed into its constituent geons. Geons are the fundamental building blocks for object recognition.
Term
Marr's theory of object recognition
Definition
A view-invarient theme which posits that a critical property for recognition is establishing the major and minor axes for object recognition. These properties will hold across different vantage points.