phineas gage study
Background to the study
In 1848, Phineas Gage was working on a railway line in the USA when an explosion caused an iron rod to be fired through his head. Although it caused serious damage to his face and the frontal lobe of his brain, Gage survived the accident and recovered quickly from his physical injuries.
However, his personality underwent a permanent change. Before the accident, Gage was described as a calm and responsible man, who was well liked. After the accident, he was irresponsible and rude – a very different person to the old Phineas Gage.
Many psychologists have used the evidence gathered from Gage’s doctor, John Harlow, to try to understand what it teaches us about the role of the frontal lobe in the brain. Gage died 12 years after his original injury following severe epilepsy as a result of the accident.
When Harlow learned of his death several years later, he requested that his body was exhumed so that he could study his skull. The skull has been kept every since in the library at Harvard University. Damasio and her colleagues were able to use this skull to further understand the damage caused to Gage’s brain using more modern methods of investigation.
Aims
In 1994, Damasio et al wanted to build a model of Gage’s skull using his actual skull as a guide, so that they could map out how the iron rod passed through his head. Using data from Gage’s skull, the researchers were able to create a 3D computer representation of the skull, including the holes made by the iron rod. This meant they were able to identify which parts of his brain were most likely to have been badly damaged in the accident.
Damasio et al wanted to discover if areas other than the frontal lobe had also been damaged. As the iron rod caused most damage around the forehead, it was assumed that the damage was mainly in the frontal lobe. Damasio et al wanted to discover if any other areas had also been damaged in the accident.
Procedure
Damasio et al began by taking pictures and measurements of the skull Phineas Gage. From the information gathered, they built a virtual 3D replica model of a skull that matched the measurements of Gage’s skull.
As the iron rod had been buried with Gage, they were able to take actual measurements of the rod, which was 3cm in diameter and 109 cm long. They compared this to the parts of the skull that were damaged in order to work out the likely path that the iron bar would have taken as it blew through his head. To do this accurately, they matched up the possible entry and exit points for the iron rod on their model.
In total, 20 different entry points and 16 different exit points were tested to try to find the most likely path taken by the rod. Once they had found the five most likely paths, Damasio et al used the virtual replica model of Gage’s brain to map out which areas would have been damaged in each case.
Results
Damasio et al found that there was likely to have been damage in both the right and left hemispheres of the frontal lobe in Gage’s brain. They were able to confidently assume that the brain damage suffered in the accident was likely to only have affected the frontal lobe, and no other areas of the brain.
The iron bar would have passed through the left eye socket and upwards through the head. This meant that there likely to have been more damage to the underlying white matter in the left hemisphere than in the right frontal lobe. The white matter is where all of the neurons pass their messages along the axon fibers. Damaging this area would have meant Gage was unable to pass neural messages in this part of his brain, making it useless.
The damage in both hemispheres seemed to be worse in the middle of the underside (ventromedial region) while the top edges (dorsolateral regions) of the frontal lobes were less likely to have been affected.
Conclusion
The researchers compared areas of Gage’s brain that were most likely to have been damaged with the reported changes in his personality after the accident. From this, they concluded that the ventromedial area of the frontal lobes seems to be important for making sensible decisions and controlling our impulses around people.
It also seems to be important for the control of emotions, as Gage found this very difficult after his accident. This evidence appears to support other findings that have been gathered from case studies of people with brain damage in similar areas. Damasio et al had evidence of 12 other patients with similar frontal lobe damage, who all showed the same problems with impulse and emotional control.
This knowledge can be used to predict the behaviour of someone who suffers brain damage in these areas in the future.
Evaluation (notice how I use a structure to answer evaluation answers ... this ensures top marks in the exam!)
One strength of Damasio et al’94 study is that the researchers were able to use modern-day technology to investigate the data from 1848, meaning the results can be given more scientific status. For example, the use of a computer model meant the evidence could actually be seen, rather than just inferred from the information gathered after the accident first happened. This is a strength because further increases the scientific understanding of the case of Phineas Gage.
Another strength of this study is that we can now make predictions about what changes to behaviour we might expect if someone has damaged their frontal lobes. For example, if a patient damaged the frontal lobe in a similar area to Gage, we can predict that they might be more impulsive and less able to control their behaviour. This is a strength because, knowing this could help the family understand what might happen and why it is happening, and it could also be useful for helping to treat the person after the brain damage.
One weakness of Damasio et al’s study is that, even though they used an exact replica of Gage’s skull, the information about how the accident happened is based on reports originally gathered over 150 years ago. For example, witnesses stated that Gage lost a 'cupful' of brain matter when he bent down to get out of the carriage when he arrived at his doctor's house. This is a weakness because the information might not be very accurate, or is simply a guess from the reports they could find, so it may not be very reliable.
Another weakness of the study is generalising the information about the case study to other people because the brain damage was unique to Gage. For example, such a specific injury is unlikely to happen in exactly the same way to someone else. This is a weakness because the information regarding Gage might not be very useful for helping us to understand what might happen to another person with frontal lobe damage.