Phrenology and Language in the Brain

Study Notes

The brain is the most complex organ in the body, housing approximately 100 billion neurons and numerous interconnecting fibers.
The outer layer, known as the cortex or "gray matter," contains billions of neurons and acts as the decision-making center.
The cortex is responsible for processing sensory information, initiating actions, and storing memories.
A grammar system representing language knowledge is believed to reside within the gray matter.

The brain consists of two cerebral hemispheres, which are interconnected by the corpus callosum, a network of over 200 million fibers.
The left hemisphere controls the body's right side, while the right hemisphere controls the left side, exemplifying contralateral brain function.
Sensory information from one side of the body is processed by the opposite hemisphere.

Franz Joseph Gall introduced the theory of localization, suggesting that cognitive abilities are confined to specific brain areas.
Gall's theories included the controversial practice of phrenology, which connected skull bumps to personality traits and intelligence.
Despite the dismissal of phrenology, the notion of localized brain functions has been supported by modern research on aphasia and functional brain imaging.

Aphasia refers to language disorders resulting from brain damage due to illness or trauma.
In the 1860s, Paul Broca identified that language is situated primarily in the left hemisphere, particularly in Broca's area, the front lobe portion responsible for speech.
Carl Wernicke later identified another type of aphasia linked to damage in the left temporal lobe, now identified as Wernicke’s area.
Language is largely lateralized to the left hemisphere, which means specific cognitive functions are localized more in one side of the brain.

Most individuals with aphasia don’t experience total language loss; instead, specific language functions are selectively impaired based on the location of the brain damage.
This damage-deficit correlation has led to significant insights about language organization in the brain through studies involving individuals with aphasia.