Visual Perception disorders

Firstly it is important to understand how we gather visual information. 

Our eyes make Saccades- These are rapid eye movements, from left to right, they are quick simultaneous movements of both eyes in the same direction and happen 2 to 3 times every second. 

There are a number of different visual perception disorders.

The most well known being Agnosias, Visual Agnosias, Object Agnosia and Prosopagnosia.

There are two main functions that can be negatively effected by disorders, these are

Object perception- What is it? and Spatial Perception- Where is it?

Agnosias - is a loss of ability to recognize objects, persons, sounds, shapes, or smells. However the specific sense is not defective nor is there any significant memory loss, it is a fault within the connections of the brain.

Visual Agnosias Is the inabilty of the brain to make sense of the world, often characterised by the inability to recognise others faces and well known objects.

Object Agnosia  is the inability of the brain to make sense of or make use of some part of otherwise normal visual stimulus and is typified by the inability to recognize familiar objects, sufferers however have no problem recognising faces.

Prosopagnosias- Also known as faceblindness and facial agnosia: Patients cannot consciously recognize familiar faces, sometimes even including their own, they therefore tend to rely on peripheral cues such as an individuals hair colour or voice. They can however still recognise basic objects.

Akinetopsia -Also known as motion blindness, is an extremely rare neuropsychological disorder in which a patient cannot perceive motion in their visual field, despite being able to see stationary objects without issue.

Research from people who suffer from these visual perception disorders, suggests that objects and faces may be processed in separate perceptual mechanisms/ Brain areas.

Seperate areas of the brain have been identified using FMRI scans

- FFA has been shown to become more active during face viewing whereas another area 

- PPA becomes more active during object recognition.

Moore and Armstrong found that the FEF (Frontal eye field) plays a central role in directing spatial attention.