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Neurological damage: agnosia, prosopagnosia and the prefrontal cortex
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Damage to particular parts of the brain can cause very specific problems. Studying these helps psychologists understand what each area does.
Visual agnosia
Visual agnosia: the inability to recognise a visual stimulus (such as an object) despite being able to see it and describe it.
Symptoms: eyesight works, but the person cannot identify everyday objects by sight; they may describe the shape and colour of a key but not know it is a key; they can often recognise the object by touch, sound or smell; some cannot copy or match drawings, while others can copy an object but still not name it.
It is usually caused by damage to the occipital and temporal lobes (for example by a stroke).
Symptoms: eyesight works, but the person cannot identify everyday objects by sight; they may describe the shape and colour of a key but not know it is a key; they can often recognise the object by touch, sound or smell; some cannot copy or match drawings, while others can copy an object but still not name it.
It is usually caused by damage to the occipital and temporal lobes (for example by a stroke).
Prosopagnosia
Prosopagnosia ('face blindness'): the inability to recognise the faces of familiar people, while other visual processing and intellectual abilities remain intact.
Symptoms: cannot recognise family, friends or even their own face in a mirror; recognises people instead by their voice, hair, clothes or walk; may avoid social situations.
It can be acquired through brain damage (often to an area of the temporal lobe called the fusiform gyrus) or be present from birth (developmental).
Symptoms: cannot recognise family, friends or even their own face in a mirror; recognises people instead by their voice, hair, clothes or walk; may avoid social situations.
It can be acquired through brain damage (often to an area of the temporal lobe called the fusiform gyrus) or be present from birth (developmental).
Damage to the prefrontal cortex
The prefrontal cortex is at the very front of the frontal lobe. It is involved in planning, decision-making, controlling impulses and social behaviour.
Effects of damage: impulsive behaviour; poor decision-making and planning; emotional blunting (reduced emotional response); outbursts of anger; socially inappropriate behaviour; changes in personality.
The famous case of Phineas Gage shows this.
Effects of damage: impulsive behaviour; poor decision-making and planning; emotional blunting (reduced emotional response); outbursts of anger; socially inappropriate behaviour; changes in personality.
The famous case of Phineas Gage shows this.
Ali can describe a picture of a cup as 'white, round, with a loop on the side' but cannot say what it is. When handed the cup, he says 'a cup' at once. What condition is this?
- He can see and describe the object.
- He cannot recognise it by sight, but can by touch.
Answer: Visual agnosia.
Visual agnosia is being unable to recognise objects by sight despite seeing them. Prosopagnosia is being unable to recognise familiar faces. Damage to the prefrontal cortex can cause impulsivity, poor decisions, emotional blunting and personality change, as with Phineas Gage.
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