lecture 14: History of localisation of function

Question 1

Rene Descartes debate (early 1600s)

Answer 1

Two key findings:
- recognised that the brain was symmetrical and every structure on left side was on the right side as well
- recognised that we don’t see two of everything, so he searched for a structure for which there was just one and that structure must unite everything
–> pineal gland, a pea sized structure between the two hemispheres

Question 2

Gall and Spurzheim debate (early 1800s)

Answer 2

Phrenolgogy:
- pseudoscience in which bumps and depressions on the skull were associated the with well-developed and under-developed behaviours
- one of the first attempts at localisation of function
Faculties:
- many odd “behaviours” were mapped onto the brain

Question 3

limitations/ challenges to Phrenology

Answer 3

• bumps and depressions on the outer skull do not map onto bumps and depressions on the brain
• in fact, bumps and depressions on the outer skull bear no resemblance to bumps and depressions on the inner skull, which is for the most part smooth
• but phrenology fails mainly because people are not willing to accept the fact that there is localisation function in the brain

Question 4

Paul Broca (1861) findings

Answer 4

Patient: Tan, has a severe language problem and is only able to say “tan”
–> tan comes under the care of Paul Broca
–> tan passes away under brocas care
Findings:
- Broca removes Tan’s brain and notices a large lesion in the left frontal area (now known as Broca’s area)
- broca localises language to the left frontal lobe
- broca’s aphasia is a difficulty with language output

Question 5

Karl Wernicke (1873) findings

Answer 5

• notices a severe language problem in his patient
• patients output is normal but comprehension seems impaired
• upon his patients death, Wernicke removed the brain and notices a lesion in the left temporal lobe
• Wernicke’s finding challenge the notion of localisation of function

Question 6

Do Wernicke’s findings really challenge the notion of localisation of function?

Answer 6

Double dissociation
- Brocas Aphasia is a difficulty with the motor output of language. comprehension is fine
- Wernicke’s aphasia is a difficulty with comprehension of language. motor output is fine

Question 7

double dissociation

Answer 7

to describe a situation in which two related mental functions or processes are shown to operate independently of each other

Question 8

frtisch and hitzig (1870) findings

Answer 8

• noticed that stimulation of a strip of cortex (motor cortex) caused contralateral movement of body parts
• very organised topography suggests localisation of function and ..
• the brain is an electrical structure

Question 9

current views

Answer 9

• the brain is modular
• within each sensory module there is further detailed localisation of function