Cog Neuro - Txb C6 Object Recognition (6.3, 6.7)

what are the three types of visual agnosia

1. apperceptive

2. integrative

3. associative

apperceptive visual agnosia?

problem seeing the shape

patients may be able to recognize an object from a typical viewpoint, but it if it is in a different view point or distorted with shadows, recognition deteriorates

• they have acuity, colour vision, and brightness discrimination intact, but cannot verbally recognize objects based on limited stimulus information like a line drawing

• impaired object constancy

object constancy

ability to understand that even though something is moving or, the object is not changing. Ex. if a car is going off in the distance, we can discern that the car is staying the same size

integrative visual agnosia

problem combining parts into wholes

can identify parts of an objects, but not recognize that the parts make up a coherent whole

ex. can identify a door, window, or walls, but not a house

• cannot identify an object it there is overlap. ex. a chair covered by a table, cannot identify the chair unless they see the entire chair

associative visual agnosia

problem linking perception to meaning

perception occurs without recognition; inability to access conceptual knowledge from visual input

ex. can see a house and draw a house but cannot tell its a house or describe what a house is for

ex. can be shown a picture of a mice and dog and asked which is bigger, cannot do it, but when told that they are a mouse and a dog, he knows which is bigger verbally

prosopagnosia

term used to describe an impairment in face recognition

where is the most common area where patients with prosopagnosia have lesions?

ventral pathway, especially regions associated with face perception such as the FFA and are usually bilateral due to 2 strokes involved with the Posterior Cerebral Artery

developmental prosopagnosia (DP)

people with no known history of brain injury that have deficits in face perception and in particular the ability to recognize faces.

due to gene mutation presumably arising from impaired information transmission between the FFA and other face-processing regions

can people with developmental prosopagnosia (DP) identify an intact face from a scrambled face?

no, the FFA activation patters from these individuals could not distinguish between intact and scrambled faces

what is the link between autism spectrum disorder (ASD) and face recognition

reduced connectivity between the FFA and other core and extended face-processing regions. 

observed hypoactivity in response to faces

fewer neurons and less neuronal density in the fusiform gyrus layers

have lower facial recognition maybe because they don’t look at faces for a long time

acquired dyslexia

loss of reading ability

visual word form area

area of the left fusiform gyrus important for recognizing written words and letter strings and turning them into meaningful language 

holistic processing

perceptual analysis that emphasized the overall shape of an object.

important for face recognition to analyze peoples facial features to identify them

can you have typical object recognition but have prosopagnosia and dyslexia at the same time

what happens if the analysis-by-parts system is damaged but the holistic system is ok or visa versa

object recognition can still occur, but will be suboptimal because its relying on the other system to take over

what is the analysis-by parts system

a form of perceptual analysis that emphasizes the component parts of an object

ex. recognizing someone’s nose alone

important for reading

Individuals with developmental prosopagnosia typically have _____ activation patterns of the FFA, but _____ connectivity with other face-processing regions.

normal; decreased