Studying the brain in 1848

1. When Phineas Gage was injured in 1848 there was no way of seeing inside a living brain.
2. All that could be recorded was what a person could still do and how they behaved afterwards.
3. Knowledge therefore depended on rare accidents, and the evidence was one person as described by those around him.
   1. That evidence is subjective and cannot be repeated, so any claim about which region did what was an informed guess.

Studying the brain in 1968

1. Sperry's split-brain work marks the next step, because living patients could be tested under experimental control.
2. Projecting a stimulus for one tenth of a second to a single visual field made it possible to question one hemisphere at a time.
3. This produced repeatable results rather than anecdotes, and it turned lateralisation from an idea into a tested claim.

Studying the brain in 1994

1. Damasio and colleagues returned to Gage's skull with modern neuroimaging and precise measurement.
2. X-rays and a three-dimensional reconstruction let them narrow the possibilities to a single best-fitting trajectory.
3. They then compared the result with 12 living patients who had damage in the same region.
   1. The original idea was vague, that a frontal injury had somehow coarsened Gage's character. The newer finding was specific, that the damage sat in the ventromedial region of both frontal lobes while the dorsolateral region was spared.
4. Later teams kept revising the picture, because Ratiu et al. (2004) and Van Horn et al. (2012) re-examined the same skull with newer imaging and disagreed about how far the damage spread.

Technology changed what was possible

1. The invention of the EEG let researchers record electrical activity through the scalp, so a living brain could be studied while it was working rather than only after death.
2. Brain scanning went further, first showing the structure of a living brain and later showing which parts were busy during a task.
3. More recently the procedures used by Damasio et al. (1994) showed technology could reach back in time, using x-rays, measurement and a three-dimensional reconstruction to study a brain that no longer existed.

What has actually changed

1. Method moved from observing rare accidents to controlled experiment and quantified reconstruction.
2. Evidence moved from the single case towards comparison groups, which improves generalisability.
3. Data became more objective, because a measurement replaces one person's description of how someone seemed.
4. Theory changed with the evidence, because localisation and lateralisation are now supported by testing rather than assumed.
5. Biological explanations of behaviour have moved towards the centre of the subject as a result.

The other side of the argument

1. The shift is a change of emphasis rather than a clean replacement, because the case study has not disappeared from the subject.
2. Sperry's conclusions still rest on 11 patients with severe epilepsy, so a newer method does not remove a generalisability problem.
3. Damasio's trajectory was still inferred from a model rather than observed, so greater precision is not the same as certainty.
4. Explaining behaviour still needs more than biology, so older approaches continue to add something.

Turning this into marks

1. Name Sperry (1968) and Damasio et al. (1994) as the evidence for the change rather than telling their stories.
2. Quote the contrast, that 1848 offered one described case while 1994 offered a measured reconstruction and 12 comparison patients.
3. The mark most often lost is the other side, so say what has stayed the same as well as what has changed.