IB Psych: Localisation - biological approach to behaviour

Definition of localisation of function

The theory that certain areas of the brain are responsible for certain psychological functions

Definition of weak localisation

The idea that one brain area may be responsible for a function, but not exclusively, and other area may also take over the function

Definition of Strict localisation

The idea that a specific brain area is responsible for a specific function (direct correspondence), and that all functions can be clearly mapped onto the brain

Definition of widely distributed functions

Functions that cannot be localised anywhere in the brain (there is no specific brain area responsible)

Explain the theory of relative localisation

It believes that some functions are more localised than others, some are strictly localised, others are widely distributed, while some are relatively localised to multiple areas.

In the theory of relative loalisation, several brain areas are responsible for the same function but one of these areas is dominant, as well as this localisation is not static, brain areas can respecialise due to neuroplasticity

What study supports the theory of relative localisation

Maguire et al (2000) and HM Milner (1966)

Maguire et al links to localisation of function by demonstrating how the hippocampus is involved in spatial memory and navigation. The study found that London taxi drivers who rely heavily on spatial navigation had significantly more grey matter in the posterior hippocampus compared to non-taxi drivers. This supports the idea that spatial memory is strictly localised to the posterior hippocampus.

Maguire also highlights that localisation of function is relative, as redistribution of grey matter from the anterior to the posterior hippocampus in taxi drivers suggests that brain areas can adapt and respecalise due to neuroplasticity

What is the aim of HM (Milner, 1966)

To investigate the role of the hippocampus in memory formation and understand the effects of the removal of the medial temporal lobe on memory processes

What is the method and who was the participant of HM (Milner, 1966)

Milner conducted a longitudinal case study of HM, using method triangulation (included psychometric testing like IQ tests, cognitive testing like memory recall tasks and reverse mirror drawing and later MRI scans to determine extent of brain damage)

Participant: HM was a male patient who underwent experimental surgery to remove parts of his medial temporal lobe including hippocampus to treat severe epilepsy.

What were the findings of HM (Miler 1966)

• HM showed severe anterograde amnesia: he could not form new episodic or semantic long‑term memories, and forgot everyday events and new people shortly after meeting them.

What was the conclusion of Broca

Broca’s area is responsible for the production of articulate speech, as Broca made the correlational understanding that damage to Broca’s area must have caused the lack of articulate speech because all other abilities were still intact, while the rest of the brain were undamaged.

What is the aim of maguire et al

To investigate how the brain structure of London taxi drivers is different from the average brain

What was the method and who were the participants of Maguire et al

Method: Quasi-experiment (comparison of two pre-existing groups) correlational study in the part where driving experience was correlated with grey matter volume. MRI was used to measure the variables.

Participants: 16 right-handed male taxi drivers. The average experience as a taxi driver was 14.3 years for taxi driver group

50 healthy right-handed malesubjects who did not drive a taxi

What was the procedure of Maguire et al

MRI scans were compared between drivers and non-drivers.

Researchers also correlated the number of years of taxi driving experience with results of the MRI scans

What are the results of Maguire et al

Taxi drivers had increased grey matter volume in the posterior hippocampus, compared to the control group subjects. On the other hand, control subjects had increased grey matter volume in the anterior hippocampus.

A correlation was observed between the number of years of taxi driving experience and grey matter volume in the hippocampus: the longer they drove a taxi, the larger the volume of their posterior hippocampus. The opposite was true for the anterior hippocampus (smaller as the taxi driving experience increased)

This means that redistribution of grey matter occurred in the hippocampus of taxi drivers, from the anterior to the posterior

What is the conclusion of maguire et al

Redistribution of grey matter in the hippocampus occurs in taxi drivers in response to gaining navigational experience (from the anterior hippocampus to the posterior hippocampus)

the posterior hippocampus is involved in using previously learned spatial information, while the anterior hippocampus is known to be responsible for learning new spatial information

What was the evaluation of Maguire et al

Strengths:

• No researcher bias - Brain scans were coded so that analysis could be done blindly (researchers did not know which brain scan belonged to which participant to avoid researcher bias)

• No ethical implications, MRI does not pose any health risks to participants and all gave consent.

• Nature vs nurture debate support for nurture: some believed that those with larger hippocampi might be more spatially talented and thus chose to be taxi drivers, however disproven by the correlation between size of the hippocampus and number of years driving. (driving experience affects brain size)

Weaknesses:

• The study was a quasi-experiment, so no cause-and-effect relationship can be established, researchers couldn’t manipulate the independent variable

• Some sampling bias as all participants were male, however majority of london taxi drivers are male, but may make it slightly more difficult to generalise the findings