Neuropsychology

From previous posts, we've learned that it's possible to define parts of the brain that specialize in specific tasks. But what happens if one of these parts is damaged? Is that ability compromised or enhanced? The branch of psychology that deals with linking brain damage to the loss of abilities is called neuropsychology.

Let's start by defining the types of damage the brain can suffer:
- Trauma: A mechanical blow to the head that affects the brain.
- Stroke: When a part of the brain is deprived of oxygen, causing it to 'shut down.'
- Degeneration: Impairment due to a pathological condition.
What are the consequences of these damages? Let's explore a few.

There's an area of the brain called the inferotemporal cortex. To locate it, place your hands on your temples and extend towards your ears. Damage in this area results in a disorder called agnosia, which can be translated as 'inability to recognize.' A person with agnosia can use an object properly, but might not be able to name it (associative visual agnosia) or draw it (apperceptive visual agnosia).

Damage to the right inferior parietal lobe (a bit tricky to pinpoint) causes a disorder known as neglect. Neglect is the inability to shift attention to the left. What does that mean? If you give a plate of pasta to someone with neglect, they might only eat the right side because they can't pay attention to what's coming from the left.

Another disorder caused by selective damage is apraxia, which stands for 'inability to do something.' It can be divided into ideational apraxia (damage to the angular gyrus) and ideomotor apraxia (damage to the supramarginal gyrus). A person with ideational apraxia doesn't know what to do with an object. Give them a coffee pot, and even if they recognize it, they won't know how to use it.

Someone with ideomotor apraxia knows what to do but doesn't know how to do it. If you ask them, 'Can you wave goodbye?' they can imagine the correct sequence of movements (raise the arm and move the hand), but they can't execute it. Additionally, if you greet them, they respond to the greeting. In other words, if you ask them, they can't do it, but if it's implicit from the situation, they can. This peculiar behavior is called automatic-voluntary dissociation.

A final disorder that starts with an 'A' is aphasia. Aphasias are language disorders divided into non-fluent and fluent aphasias. In non-fluent aphasias (e.g., caused by damage to Broca's area), the person speaks slowly and with great effort. In fluent aphasias (e.g., caused by damage to Wernicke's area), the person speaks at an appropriate speed but replaces so many words that what they say is often incomprehensible. They also have difficulty understanding others' speech.

Sources:
- Kandel, E. (2000) - Principles of neural science.

Do you know anyone with agnosia, apraxia, or aphasia? What's their story? What kind of damage did they experience?

If you'd like me to describe a psychology topic in my own words, please write it in the comments.