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What are the 4 viewpoints for the prefrontal cortex, and what do they correspond do?
- Lateral: outer surface
- Medial: middle surface
- Superior: upper surface
- Inferior: lower surface
What did Leonore Welt study in 1888?
- More modern Phineas gage
- Described a 37-yr old man, fell from a 4th story window.
- Some months later he died from an infection.
- Autopsy found bilateral destruction of gyrus rectus and adjacent medial right inferior frontal gyrus.
- Physical recovery was swift. However after about 5 days the patient became aggressive and malicious, made bad jokes, teased other patients mercilessly and played mean tricks on hospital staff.
- After about a month his behaviour gradually improved. He knew how he had behaved and was remorseful. He could not explain what had happened to him.
- Personality change is unusual, so she examined 8 autopsied cases with personality change and found prevalent orbitofrontal damage.
- But since often OF damage can be seen without personality change, she concluded that character changes indicates OF damage, but that absence of such changes does not mean the OF region is intact.
What did Gall and Spurzheim find in 1809
- Orbital area of PFC involved in
- “memory of words” (and distinguished from a centre involved in speech articulation)
What did Bouillard argue in 1825?
- A frontal lobe lesion would be found in every patient who exhibited an “amnesia for words”.
- These views contrasted with the many clinical findings of asymptomatic patients with extensive frontal lesions.
- This led to the view held by many that from a clinical standpoint the prefrontal region was a “silent area”.
What did Ferrier (1843-1928) find?
Monkeys given PFC ablations were “whilst not absolutely demented, they had lost, to appearance, the faculty of attention and intelligent observation”
What did Bianchi (1848-1927) find?
- Monkeys & dogs with PFC lesions were:
- No longer sociable (but did groom themselves).
- Violent when frustrated
- No longer capable of “serializing and synthesizing groups of representations”
What did Franz contribute to the field of PFC research?
- (1902, 1907, 1912)
- Gave learning tasks to monkey and cats with PFC ablations. The animals learnt tasks before their operation and then were tested for retention afterwards.
- No deficit was found with unilateral PFC lesions, and the mild deficits following bilateral ablations disappeared with further training.
- Reintroduced skepticism into the field, and reinforced PFC image as a silent area
What did Jacobson do?
- Challenged the silent area view
- Monkey received punishment when making mistakes, received a frontal lobe lobotomy, no longer gave a fuck
- Gave animals a task too hard to master, and an "experimental neurosis“ was established, with the animal becoming frustrated and demotivated
- After bilateral extirpation of the frontal areas, the animal no longer had "temper tantrums" when it made mistakes, and continued training on difficult problems did not evoke an "experimental neurosis."
What did Walter Freeman do?
- Changed the name of leucotomy to lobotomy to emphasise the larger extent of damage being created
- Created a quick and easy technique using an ice pick through the eye, took only 10 minutes
- Did about 3000 of these, and got super good at it, even showing off and doing it with his left hand, cocky bastard
What is a Subcaudate Tractotomy, and what impairments might its recipients face?
- An orbitofrontal cortex lesion
- Really bad at proverbs, impaired reasoning
- Proverb: You can lead a horse to water but you can’t make it drink.
- Pre-Op: “You can show somebody what to do but you can’t make him do it”
- Post-Op: “You can try and inspire an animal but if it doesn’t want to drink it won’t”
- Proverb: People in glass houses shouldn’t throw stones
- Pre-Op: “You shouldn’t tell someone else not to do something that you do yourself”
- Post-Op: “Because they’d break the glass”
Why was the evidence from psychosurgery not given more weight?
- Where changes occurred post-op it was argued that this might be secondary to a change in the patient’s psychiatric condition.
- It would be clinically inconvenient if prefrontal lesions caused a marked cognitive disability.
- Lack of findings from animal studies.
- Lack of accepted psychometric measures specifically designed to measure impairments in the abilities supported by the PFC.
What is the most important thing (to the PFC) that Brenda Milner did, and when did she do it?
- First person to quantify deficits in cognition following frontal lobe damage
- Gave PFC damaged patients Wisconsin Card Sorting Task, where people were to sort the cards according to a set of ever changing rules
- People with PFC lesions struggled to adapt to new rules
What did Shallice look at, and when?
- Patients with frontal lobe damage sucked at the Tower of London test (see picture)
- This suggests their capacity to plan is impaired
What did Fuster do, and when?
- One of the first frontal lobe single unit recordings
- Food is placed in a randomly selected well, visible to the monkey
- A screen is lowered, obscuring vision of the well, and the 2 wells are covered
- The monkey chooses one or the other
- Some neurons in the prefrontal cortex are most active during the delay period. Perhaps their firing represents maintenance of the information over the delay period, or “working memory”.
What did Knight show, and when?
- Healthy people produce an electrical signal in the brain called a P300 when they encounter unexpected stimuli (auditory or visual.
- However he showed that people with prefrontal damage did not produce this P300 signal to novel events.
- Suggests that major features of the human frontal lobe syndrome may be explained by a physiological inability to control attention and orientation systems after prefrontal damage
What is executive function?
- In the broadest sense, the purpose of the executive system is to facilitate adaptation to novel situations
- It is thought to work by the modulation and control of more fundamental or routine cognitive skills
What is Shallice's SAS?
- Supervisory Attentional System
- Shallice & Burgess, 1996
What are the 4 components of the SAS
- Action or Cognitive Units: These are the basic skills that we have acquired through childhood and beyond, such as the ability to walk, talk, read etc. They are the “building blocks” of complex behaviour.
- Schemas: These are very well-practiced “packages” of skills, such as the ability to tie your shoelaces, do mental arithmetic etc. that you develop through childhood and beyond.
- Contention Scheduling: This is the relatively automatic selection of sets of cognitive or action units according to the context a person finds themselves in.
- Supervisory Attentional System: This is synonymous with the cognitive system that is supported by the frontal lobes. It is required when the contention scheduling process can’t come up with an appropriate response or selection. This happens in novel situations, or where a strong habitual response has to be overcome, in order to develop a new way of behaving.