Rd
Banich & Compton (2011) Cognitive Neuroscience, 3 Ed. Wadsworth Cengage.
nd
Jamie Ward (2010). Student’s Guide to Cognitive Neuroscience, 2
Ed. Psychology Press
nd
M Gazzaniga, R Ivry & G Mangun (2002) Cognitive Neuroscience 2 Ed. Norton
How do we recognise objects of different sizes, orientations or
configurations as the same thing?
Parallel processing: Different areas of the brain are responsible for different aspects of
perception.
Dorsal is responsible for “where”, whereas ventral is responsible for “what”, ie ventral parts
of the brain have receptive fields.
The ventral visual-processing stream consists of the areas of the occipital, occipito-
temporal, and temporal regions that are devoted to processing visual stimuli. Certain
characteristics of cells in these areas seem to be especially adaptive for object recognition.
In other words, areas in the posterior region have more simple functions, but as we travel to
the anterior region of the brain the processing become more complex and the receptive fields
become larger. A large receptive field is necessary to allow for objects to be recognized
regardless of its size.
Important points to remember:
• The ventral-visual processing stream allows us to differentiate colour. (Figure-ground
separation)
• Is located in the occipital, occipito-tempral and temporal regions of the brain
• Posterior – simple ; anterior- complex
Deficits in object recognition:
Visual agnosia is an inability to recognize objects within the visual modality that cannot be
explained by other causes such as memory or general mental decline. It is modality specific,
meaning that it manifests in only one of the senses; in this case it is visual. The word
“agnosia” means “without knowledge”. There are two main times of agnosia, namely
Apperceptive and Associative agnosia. They differ in that apperceptive agnosia is the
inability to “see” a given object. They fail to match shapes and colours and fail to see things
as a whole. They also fail at line orientation so battle to distinguish words as a whole. They
therefore battle to copy whole images or patterns and they cannot give meaning to it. Damage
to the occipital lobe is associated with this type of agnosia. Whereas associative agnosia; the
patient can quite easily copy and identify images. However, they would be unable to draw the
same image from memory. They are able to recognize an object in front of them, however the
key thing here is that they cannot attach semantic meaning to it. For example, they may
identify and copy a picture of an anchor, but when shown it later would be unable to recall its
context.
Differences between the Agnosias:
• Apperceptive Agnosia
• Diffuse occipital damage
• Cannot put stimuli together into meaningful image
Banich & Compton (2011) Cognitive Neuroscience, 3 Ed. Wadsworth Cengage.
nd
Jamie Ward (2010). Student’s Guide to Cognitive Neuroscience, 2
Ed. Psychology Press
nd
M Gazzaniga, R Ivry & G Mangun (2002) Cognitive Neuroscience 2 Ed. Norton
How do we recognise objects of different sizes, orientations or
configurations as the same thing?
Parallel processing: Different areas of the brain are responsible for different aspects of
perception.
Dorsal is responsible for “where”, whereas ventral is responsible for “what”, ie ventral parts
of the brain have receptive fields.
The ventral visual-processing stream consists of the areas of the occipital, occipito-
temporal, and temporal regions that are devoted to processing visual stimuli. Certain
characteristics of cells in these areas seem to be especially adaptive for object recognition.
In other words, areas in the posterior region have more simple functions, but as we travel to
the anterior region of the brain the processing become more complex and the receptive fields
become larger. A large receptive field is necessary to allow for objects to be recognized
regardless of its size.
Important points to remember:
• The ventral-visual processing stream allows us to differentiate colour. (Figure-ground
separation)
• Is located in the occipital, occipito-tempral and temporal regions of the brain
• Posterior – simple ; anterior- complex
Deficits in object recognition:
Visual agnosia is an inability to recognize objects within the visual modality that cannot be
explained by other causes such as memory or general mental decline. It is modality specific,
meaning that it manifests in only one of the senses; in this case it is visual. The word
“agnosia” means “without knowledge”. There are two main times of agnosia, namely
Apperceptive and Associative agnosia. They differ in that apperceptive agnosia is the
inability to “see” a given object. They fail to match shapes and colours and fail to see things
as a whole. They also fail at line orientation so battle to distinguish words as a whole. They
therefore battle to copy whole images or patterns and they cannot give meaning to it. Damage
to the occipital lobe is associated with this type of agnosia. Whereas associative agnosia; the
patient can quite easily copy and identify images. However, they would be unable to draw the
same image from memory. They are able to recognize an object in front of them, however the
key thing here is that they cannot attach semantic meaning to it. For example, they may
identify and copy a picture of an anchor, but when shown it later would be unable to recall its
context.
Differences between the Agnosias:
• Apperceptive Agnosia
• Diffuse occipital damage
• Cannot put stimuli together into meaningful image
