What does mass action refer to?
The idea that a greater amount of damaged area will lead to a greater deficit
What are some methods for studying how the brain works?
- the lesion method
2. the general approach
Describe the lesion method. How does it work? Which participants can be included in research?
The lesion method assumes that damage to a certain brain region can help us infer the function of that region by observing the resulting deficit
- this, however, does not allow us to extrapolate on how this brain area mediates a function; it simply tells us that it does
- participants who have experienced some sort of brain trauma are all possible candidates for research, as well as animals who have had their brains damaged manually
What is double-dissociation?
This tries to show that damage to area A impairs function X but not Y, and damage to area B impairs function Y but not X
What might double-dissociation suggest?
That different modules are independent and depend on different regions of brain tissue
What is telegraphic speech?
A trait that is sometimes observed in patients with Broca’s aphasia - sentences are stripped down to the bare minimum to convey a message
Describe the general approach?
It is a comprehensive, broad assessment of cognitive function to determine what further tests need to be done
What is the MoCA?
The Montreal Cognitive Assessment
- it is a screening tool for mild cognitive impairment, which can indicate the future development of Alzheimer’s Disease
What did patient HM contribute to our knowledge of how the brain works?
HM underwent a hippocampal surgery and then it was observed that they had severe memory deficits - they could not remember significant life events such as the death of a parent, and they were unable to form new memories
- this is an example of how the lesion method can help us understand the functionality of the brain
Since HM, what have we learned in addition to memory concerning the hippocampus?
Damage to the left hippocampus causes verbal deficits and damage to the right hippocampus leads to non-verbal and spatial deficits
When do we use single-case studies?
We use single cases to narrow down assumed function, as well as to perform screening tests
When do we use group studies?
When we notice a pattern of behaviour in people who have similar types of brain damage to similar areas
What is a major con of using single-case studies?
The results are not generalizable to the population
What are some cons with using group studies?
The size and severity of the lesion, as well as individual differences could have an impact on the resulting behaviour
What is the critical window?
The stage at which a brain function stops developing
What are some examples of variability in types of brain damage?
- head trauma: did it penetrate or was it due to impact?
- tumours: did the surgeon damage other areas when it was removed? Did the tumour put pressure on other brain regions?
- neurodegenerative disorders, surgical lesions, carbon monoxide poisoning, stroke, etc…
What is a stroke caused by?
Blockage in one of the cerebral arteries
What are the three cerebral arteries? Where do they supply blood to?
- anterior cerebral artery - affects medial brain
- middle cerebral artery - affects everywhere
- posterior cerebral artery
What are the benefits of using human subjects over animals?
Hypotheses are generated from single cases of humans, and we are able to test these hypotheses with group studies
Why might we want to use animal models instead? What can be a con of using them over humans?
Animals have highly selective regions, but we are unable to examine uniquely human abilities
What are some limitations of the lesion method?
- acute vs. chronic effects
- sparing of function - when the damage occurs in the patient’s life can influence the effect of the lesion
- location and amount of damage is very variable
- etiology (how it happened) impacts the result
- premorbid ability (what they were able to do before)
- cognitive reserve (people who have a higher education level protect themselves in a way more so than people with less education)
- observation of function is indirect (there can be many other brain areas that participate in the function, or alternate brain areas due to reorganization of function
What is the give and take between the lesion method and neuro imaging?
Neuro imaging can tell us the area, but not its critical function, and the lesion method can tell us a critical function, but not exactly where
What does CT/CAT scan stand for?
Computerized Tomography and Computerized Axial Tomography
When were CT and CAT scans first made available?
in the 1970s
