Biological Case Studies and Experiments

HM

HM

Background: Suffered from severe epilepsy and underwent brain surgery that resections his temporal lobe.

A: To understand more about memory through an in depth look at HM’s memory probs.

M&R: can recall details from his past pre-op.

• Digit span test repeating 3 numbers —> normal digit span (5-9) 15m +

• Mirror drawing/reading —> Improved accuracy.

• MRI —> Hipporampol region (Hippocampus, amygdala, medial temporal lobe).

Maguire (MRI)

A: to investigate how the brain changes in response to high spatial navigation demands in the environment

M:  Participants: 16 London Taxi cab drivers compared to and a precisely age-matched sample of 16 normal controls

• MRI machine to measure size of structures (VBM)*

• Variables being measured: 

  • Hippocampal volume and shape (MRI)

  • Occupation (time spent as taxi driver)

R: Quasi R:  Taxi drivers had larger posterior hippocampus, but Smaller anterior hippocampus than controls

Correlation R: ↑ time spent as a taxi driver, ↑ hippocampus volume (r=0.6)

Sharot et al

A:  To investigate the qualities of memories for an emotionally significant, personally relevant and surprising event (9/11) and in particular, the activity created by these memories in the brain.

M: 

• 24 Participants who were in NYC on 9/11

•  fMRI machine: measuring brain activity

• Words on screen related to induce 2 types of memory: 

  • “Summer” (Related to holiday)- normal episodic

  • “September” ( Related to 9/11)- flashbulb

• Interviewed about these memories & asked to rate; vividness, detail, confidence, arousal of both

R:  

• Memory of 9/11 attacks showed   increased amygdala activity and decreased parahippocampal activity compared to everyday memories.

• People who were further from the attacks showed less difference in brain activity between the two types of memory, and they reported less detail about the 9/11 memory compared to those who were closer to the towers.

Kandel

A: to investigate the way Long Term Memories are formed within the brain (looking at dendritic branching)  (aggregate field vs cellular connectionist approach)

M:  Animal experiment using Aplysia sea slugs.

• Deliberately reductionist approach looking at single neurons.

• Part 1: establish that living sea slugs can form LTM using a shock conditioning task

• Part 2: Dissect the slug & extract a Sensory and motor neuron —> placed into a cell culture and encouraged to grow together.

• Electrically stimulate the sensory neuron (imitates neurons signal)

R: After a 1-2 shocks = chemical (functional) changes- neurotransmission (after a few shocks)

After repeated shocks =  anatomical change- increased neural branching prompted by proteins

 

C:  Environmental stimuli → physical changes (neuroplasticity)

• STM → forms due to temporary chemical changes

• LTM—> forms due to more permanent anatomical changes to neural networks in response to environmental cues

Greenstein

A: Longitudinal study of the link between cortical thickness and intelligence

M: studied 307 children, ages 6-19 years

Measures:

• MRI scans (most participants did 2-3 scans)

• Intelligence test (Wechsler IQ test) 

Divided participants into 3 groups based on intelligence:

• superior intelligence (IQ range 121– 149), 

• high intelligence (IQ range 109–120) 

• average intelligence (IQ range 83–108)

R:  

- More intelligent kids had:

• a more rapid (fast) and extended period of cortical thickening (neural branching), particularly in the frontal lobes

• A more rapid reduction in cortical size due to neural pruning

- No significant overall relationship between IQ and cortical thickness.

Curtis

A: Investigate people's disgust responses cross culturally

M:  Survey of volunteers (BBC TV programme) 

• 40, 000 people from 165 countries- 9 global regions

• Shown series of images to rank in levels levels 1 (least disgusting) to 5 (most disgusting). + Asked who they would be least likely to share a toothbrush with

R:  98% of ppts  found the disease related image equally or more disgusting.

• E.g. Feverish face 2x more disgusting.  

• Louse more disgusting than wasp, even though both are harmful 

Younger people & females -  higher disgust ratings on all disease related images

Universal disgust in 6/7 pairs (all 9 global regions) Cultural variation in the caterpillar/worms pairing

The more of a stranger the less people wanted to share a toothbrush  e.g. Least likely to share a toothbrush with postman (59%)

Reicher

A: To investigate the role of social identity and group membership in odor perception and preference, specifically whether individuals' perceptions of odors are influenced by their social identity and the group membership of the odor's source.

M:

• Participants were recruited and divided into two groups based on their membership in different social groups or categories.

• Each participant was exposed to a series of unlabeled T-shirts worn by members of both their in-group and an out-group.

• Participants rated the intensity, pleasantness, and familiarity of the odors emitted by the T-shirts using standardized scales.

• Participants completed measures assessing their identification with their in-group and out-group to examine the relationship between social identity and odor perception.

• Statistical analysis was conducted to compare participants' odor perception ratings between in-group and out-group sources and to assess the influence of social identity on odor perception.

R:

• In-group Favoritism: Participants consistently rated the odors emitted by T-shirts worn by members of their in-group more positively in terms of pleasantness and familiarity compared to those worn by out-group members.

• Social Identity Influence: Higher levels of identification with the in-group were associated with more favorable odor perception ratings of in-group sources and less favorable ratings of out-group sources.

• No Difference in Odor Intensity: Participants did not consistently rate the intensity of the odors differently between in-group and out-group sources.

Maguire (FMRI)

A: To investigate the relationship between cognitive thoughts in a virtual reality navigation game and brain activity using FMRI

M: 20 males, right handed London Taxi drivers, 18 years of experience

• Proc:

  • Navigate streets within Getaway video game  while being scanned with an fMRI

  • Customer destination requests are played auditorily

  • Interviewed post-driving task using video and asked to report on thoughts

R: 

• L + R Hippocampus was only functionally active in initial route planning

• L Hippocampus activated in spontaneous route planning