Localization of Function in the Brain

IB Psychology

Levels of Analysis

Neuroplasticity

What is brain localization?

This is where one section of the brain is responsible for a specific function.

This is the Classic Localizationist View. Three Key Examples of this “classical view” are:

– Broca’s Area– Wernicke’s Area– Split Brain

Broca’s Area

Damage to any one of several cortical areas can cause aphasia.

In 1865, Paul Broca reported that after damage to a specific area of the left frontal lobe a person would struggle to speak words while still being able to sing familiar songs and comprehend speech.

Wernicke’s Area

In 1874, Carl Wernicke discovered that after damage to a specific area of the left temporal lobe people could speak only meaningless words.

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Localization Research

Broca’s and Wenicke’s research gave the first proof of brain localization…

That specific areas of the brain provided specific functions.

Split-Brain Research

Criticism of Classic Localization Studies Studied on small number of participants. Participants are often “different” before

they started. Not done on the general population.

Modern Viewpoint

The brain is not as localized as once believed.

Neuroplasticity allows the brain to adapt.

Multiple brain areas coordinate to complete cognitive functioning.

Modern Localization Research: Bilingualism Hull and Vaid (2006) Studied Bilingualism

Past Research on Bilingualism

Left hemisphere was dominant for language processing, the right hemisphere supported the process more than was originally believed.

Case studies on language loss and recovery in bilingual aphasics led research to believe that multiple languages might be localized in different brain areas.

Past Research on Bilingualism

The age that someone acquires a second language and their level of proficiency might affect the pattern of left hemisphere dominance.

Past Research on Bilingualism

Hull and Vaid (2006) 4 Hypotheses

1. Second Language Hypothesis- bilinguals use more of the right brain.

2. Balanced Bilingual Hypothesis- proficient bilinguals are more right-brain lateralized than monolinguals.

3. Age of second language hypothesis- the closer in time two languages are acquired, the more similar the brain localization.

4. Stage of Second Language hypothesis- early stages of learning a second language depends largely on contextual cues which are located in the right hemisphere.

A meta-analysis was conducted. 23 studies 1234 normal monolingual and bilingual

participants. AIM: Under what conditions did a

second language affect brain development.

Hull and Vaid (2006)

Studied the following three variables:– Experience (monolinguals or bilinguals)– Proficiency– Age acquiring the second language (before

or after age 6).

Hull and Vaid (2006)

Key Findings– Early Experience KEY variable.

Hull and Vaid (2006)

Monolinguals and Bilinguals who acquired their second language after 6 showed the most left hemisphere dominance.

Supports the age of second language hypothesis.

Key Findings

Early bilinguals were bilateral. Supports the second language

hypothesis.

No significant hemispheric localization differences between the proficient and non-proficient bilinguals.

Key Findings

The left hemisphere is not as dominant for language as once thought.

Bilateralism does occur. More research is needed on normal

brains to examine this further.