Case studies

H.M Milner (Intro)

Localization is the theory that specific parts of the brain have specific functions that are related to specific behaviors. One example of localization is the role of the hippocampus in memory formation as seen in the case study of HM. HM had surgery to stop his epileptic seizures by removing his hippocampus, and as a result was not able to recall his recent past, or form new episodic memories.

H.M Milner (Aim)

to study the biological reasons for anterograde amnesia in the patient HM

H.M Milner (Participants)

Henry Molaison

H.M Milner (Procedures)

Milner used many different strategies (like triangulation)
- psychometric testing: IQ testing was given to HM
- direct observation of his behavior
- interviews with both HM and his family members
- cognitive testing: memory recall tests and learning tasks (reverse mirror drawing)
- MRI to determine extent of damage to the brain

H.M Milner (Results)

HM could not acquire new episodic knowledge (memory of events) and he could not acquire new semantic knowledge (general knowledge about the world). this suggests that the brain structures that were removed from his brain are important for long-term explicit memory. HM had a capacity for working memory since he was able to carry out a normal conversation. Memories in the form of motor skills (procedural memory) were well maintained.

H.M Milner (Con)

After an MRI scan of HM's brain was performed in 1992 and 2003 by Corkin, the extensive damage to the temporal lobe (including the hippocampus) explains the problem of transferring short-term memory to long-term memory as this is the area where the neurotransmitter acetylcholine is believed to play an important role in learning and the formation of expicit memories.

H.M Milner (Outro)

The removal of HM’s hippocampus explains the inability of HM to form new episodic memories. Through this study, Milner determined that the hippocampus is responsible for the consolidation of episodic and semantic memories from short-term to long-term memory.

Troster and Beatty (Aim)

To evaluate how acetylcholine impacts retrieval and formation of memory.

Troster and Beatty (Procedure)

Troster and Beatty used the acetylcholine (neurotransmitter) antagonist scopolamine in order to determine the effects of acetylcholine on memory. There were three groups within this experiment, a group that was injected with saline, one that was injected with .5 mg and .8 milligrams of scopolamine. Each participant performed a free-recall test of 14 words (7 low and 7 high imagery), a recall of celebrities faces, and a recall test for locations in a fictional state.

Troster and Beatty (Participants)

13 men aged 31 to 59, with a mean age of 39.2.

Troster and Beatty (Findings)

Scopolamine injections indicated worse performances in the new map test and word recall test, but not the celebrity face test. This indicates that acetylcholine is important in STM, but not long term memory.

Troster and Beatty (Pros)

Placebo condition, informed consent, true experiment (causation), Reductionist

Troster and Beatty (Cons)

Artificial task, ethical considerations

Split Brain Theory (Sperry & Gazzaniga) (Aim)

The aim of this study was to test the theory of lateralisation and investigate how the two hemispheres of the brain function independently when the corpus callosum, which connects them, is severed.

Split Brain Theory (Sperry & Gazzaniga) (Method)

Quasi-experiment in a laboratory with an independent measures design. The independent variable was whether the individual had a split-brain or not. The dependent variable was the individual's performance on visual and tactile tasks.

Split Brain Theory (Sperry & Gazzaniga) (Procedure)

Visual Tasks
1. Sperry asked the participants to sit in a chair and look at 2 visual boards.
2. He asked them to focus on the dot in the middle of the board.
3. He flashed words on both sides of the dot.
4. He asked the participant to read the word out loud.
5. He recorded the data from the response from the experiment.
6. Repeated the same order for the next participant

Tactile Tasks
1. Sperry sat the participant down and asked them to put their hands under the tachistoscope.
2. He placed objects in the right and left hand one at a time.
3. He asked them to describe the objects.
4. From their response, he recorded the data.
5. Repeated the same order for the next participant.

Split Brain Theory (Sperry & Gazzaniga) (Results)

Participants would only recognise stimuli if the stimuli were presented again to the same visual field. If participants were shown stimuli in the right visual field, but then shown the same stimuli to the left visual field, they would claim to have not seen it before. Information presented to the right visual field (left hemisphere) could be described in speech and writing (with the right hand). If the same information is presented to the left visual field (right hemisphere), the participant insisted he either did not see anything and could not describe it in speech or writing.

Split Brain Theory (Sperry & Gazzaniga) (Conclusion)

People with split brains have two separate visual inner worlds, each with its own train of visual images. Split-brain patients have a lack of cross-integration where the second hemisphere does not know what the first hemisphere has been doing. Split-brain patients seem to have two independent streams of consciousness, each with its own memories, perceptions and impulses i.e. two minds in one body.

Split Brain Theory (Sperry & Gazzaniga) (Evaluation)

Strengths: This study was able to locate the relative localization of each visual information received.

Limitations: Low ecological validity as this study investigated such a unique condition, the sample size was extremely small. On top of this, the samples were not all equal, varying in gender, age, as well as the time for which they have had a split brain.

Rosenzweig, Bennet, and Diamond (1972) (Aim)

To investigate whether environmental factors such as a rich or an impoverished environment affect development of neurons in the cerebral cortex.

Rosenzweig, Bennet, and Diamond (1972) (Methods)

- Rats were placed in either an enriched environment (EC) or an impoverished condition (IC).
- EC: 10-12 rats in a cage provided with different stimulus objects to explore and play with. This group also received maze training.
- IC: each rat in an individual cage (isolation and no stimulation).
- The rats typically spent 30 to 60 days in their respective environments before they were killed so the researchers could study changes in brain anatomy.

Rosenzweig, Bennet, and Diamond (1972) (Results)

- The anatomy of the brain was different for rats in the EC and the IC.
- The brains of EC rats had increased thickness and higher weight of the cortex. EC rats had developed more acetylcholine receptors in the cerebral cortex (important neurotransmitter in learning and memory).

Rosenzweig, Bennet, and Diamond (1972) (Conclusion)

- The research challenged the belief that brain weight cannot change. This was an important finding
- Follow-up of this research indicated that just 2 hours a day in an enriched environment produced the same plastic changes in the brain as in rats that had been constantly in the EC condition. This shows that the brain can change and adapt to new situations.
- Since brain plasticity is assumed to follow the same pattern in animals and humans the implications of the study are that the human brain will also be affected by environmental factors such as intellectual and social stimulation

Rosenzweig, Bennet, and Diamond (1972) (Strengths and Weaknesses)

S- The experiment was a rigorously controlled laboratory experiment so it was possible to establish a cause-effect relationship.

W- The experiment used animal models and therefore it may be difficult to generalize to humans unless research with humans provides the same results
- Rats were sacrificed

Baumgartner et al (2008) (AIM)

To see if increased levels of oxytocin would affect levels of trust

Baumgartner et al (2008) (Methods)

- The participants played a trust game used by economists and neuroscientists to study social interaction. The "investor" (player 1) receives a sum of money and must decide whether to keep it or share it with a "trustee" (player 2). If the sum is shared the sum is tripled. Then player 2 must decide if this sum should be shared (trust) or kept (violation of trust).
- fMRI scans were carried out on 49 participants. They received either oxytocin or placebo via a nasal spray.
- Participants played against different trustees in the trust game and against a computer in a risk game. In 50% of the games their trust was broken. They received feedback on this from the experimenters during the games.

Baumgartner et al (2008) (Results)

- Participants in the placebo group were likely to show less trust after feedback on betrayal. They invested less. Participants in the oxytocin group continued to invest at similar rates after receiving feedback on a breach of trust.
- The fMRI scans showed decreases in responses in the amygdala and the caudate nucleus. The amygdala is involved in emotional processing and has many oxytocin receptors. The caudate nucleus is associated with learning and memory and plays a role in reward-related responses and learning to trust.

Baumgartner et al (2008) (Con)

Increased levels of oxytocin can correlate to increased levels of trust

Baumgartner et al (2008) (Strengths and Weaknesses)

s- Oxytocin could explain why people are able to restore trust and forgive in long-term relationships

w- Scanner research is merely mapping brain activity but nothing definite can be said about what it really means at this point in science.
- Giving oxytocin like this in an experiment may not reflect natural physiological processes. The function of oxytocin is very complex and it is too simplistic to say that it is "the trust hormone"