Week 5 Topic 1 - Cerebral cortex and mental health Flashcards
How do we know that the frontal cortex is important for executive functions?
There are at least three sorts of evidence,
- neuroimaging [fMRI studies show prefrontal regions are active when volunteers engage in tasks, like those you just
tried, the Wisconsin card sorting test, the Tower of Hanoi, the Stroop task, and the N-back task.] - neuropsychological cases of acquired frontal lobe damage
- Neurodevelopmental disorders
When are the frontal regions most involved?
Frontal regions seem to be particularly important when we’re learning new skills. Once
a skill is well established, fMRI studies show less frontal involvement. So to respond flexibly to our
environment, frontal regions are essential. This is illustrated in a study by Hampshire, et al., 2015.
See how the activation in the frontal regions decreases across the blocks of an inhibition task as the
volunteers become more practised at the test.
What happens when previously healthy people
have a head injury or a stroke that damages their frontal lobes?
They typically show impairments in
judgement and decision-making.
What are some psychiatric and neurodevelopmental conditions that are associated with impairments
in executive functions and frontal lobe integrity?
Autism spectrum disorder,
schizophrenia,
bipolar disorder, and
major depression have all been linked to executive function deficits.
What is ASD and how does it present?
Autism spectrum disorder, or ASD, is a neurodevelopmental condition characterised by impaired
social and communicative development, with rigid and repetitive behaviours and interests.
Children
and adults with ASD show impairment in executive functions, particularly on planning tasks, like the
Tower of Hanoi, and set-shifting, like the Wisconsin card sorting test. Most children and adults with
ASD dislike change and have a strong preference for narrow routines and repetition.
This is thought
to reflect impairments in frontal functions that are necessary for adaptive response to change and
novelty.
What are social and communication problems that define ASD thought to be a result of?
The problems are thought to result
from an impairment in recognising what others are thinking, so-called “theory of mind.”
Because
people with ASD find it hard to recognise what others might think or mean, they are often confused
by social situations and struggle with communication.
Think how confusing it would be to be told to
“paint the child next to you” if you couldn’t guess what the teacher meant.
How can theory of mind be tested?
Theory of mind can be tested with a variety of tasks. (recall the short triangle animation)
What does the small triangle want? What is the big triangle trying to do? Let’s look at some more
examples.
Using animations like these, or static cartoons or written stories that also cause healthy volunteers
to think about other people’s thoughts, fMRI studies show activation of medial prefrontal cortex, as
well as temporal poles and superior temporal sulcus. People with ASD often simply see triangles
moving around and don’t attribute thoughts to them. Asked what was going on in the animations, they
might say the red one moved right and then the blue one turned 90 degrees. The brain activity of
volunteers with ASD doing theory of mind tests is also different, even when they can answer the test
questions correctly.
What are top-down effects and how do they relate to ASD?
Reduced top-down effects have also been suggested to be important in understanding autism.
Remember how seeing the picture of the face helped you see the blobs as a face? People with
ASD don’t show that strong top-down effect, especially when they’re looking at faces versus other
objects.
What’s the difference between the brains of acquired frontal lobe patients and people with ASD?
Unlike acquired frontal lobe patients, people with ASD do not have circumscribed lesions. Instead, it
seems the connectivity of different brain regions is atypical.
What happens when frontal lobes are impaired and what is the effect on executive functions?
Acquired or developmental abnormalities in these regions impair
the ability to respond flexibly to novel situations. Because of the importance of these functions,
frontal involvement is hypothesized to underlie many psychiatric and neurodevelopmental symptoms.
What is the Wisconsin Card Sorting Test?
In 1948, Grant and Berg published their now very famous Wisconsin Card Sorting Test. It is a test of
cognitive reasoning. In the Wisconsin Cart Sort Test, you have to classify cards according to different
criteria. You have three ways to classify a card, and the only feedback you get is whether you are
doing it correctly or not. Cards can be classified according to the colour of its symbols, the shape of
the symbols, or the number of the shapes on each card.
Let’s watch as someone plays the game. Our player chooses blue squares first. She’s lucky, because
the first rule needs her to classify the cards by colour. She continues to follow the colour rule. Then
suddenly the rule changes.
Our player now has to decide on which rule to try out. She can choose either shape or number. She
chooses number, and again, she is lucky. As you will notice later when you try the game yourself, after
the rule changes, you are prone to making more mistakes. The task measures how well people can
adapt to the changing rules.
What is the Tower of Hanoi?
The Tower of Hanoi was designed to test your cognitive abilities. The rules of the game are
straightforward. You are presented with three pegs and a number of discs stacked up on one of the
pegs in order of size, with the biggest disc at the bottom. Your task is to transfer the whole tower
onto a different peg disc by disc, but you are not ever allowed to place the larger disc onto a smaller
one.
To do this task, you have to think ahead several moves to make the best decisions. The task tests
your ability to plan. Let’s watch as someone plays the game.
What’s the Stroop task?
In this task, you are presented with a number of coloured shapes and are then asked to name the
colours as fast as you can from left to right. Once you have completed this task, you are given a
similar list. But this time, you are not presented with shapes but rather with coloured words. The
trick is that the actual word red, for example, is not necessarily coloured red but blue or some other
colour. You are then asked to name the colourYou will notice that it is much harder to get the colour right when reading the words, because the
printed word distracts you. Reading is automatic, and it takes effort to suppress the meaning it
generates. So the Stroop task measures inhibitory control.
What is the N-back test?
Used as an assessment in cognitive neuroscience to measure
attention and working memory. In the task, you are asked to look at a sequence of objects. In the
two-back test, you are asked to respond when you see an object repeated after a sequence of two
images have been displayed. In a three-back test, you have to wait until you see the same image after
a sequence of three images have been displayed, and so on.
Let’s have a look at someone playing the two-back game. The sequence starts, and when our player
notices that the fish appears again after the pencil, she clicks. And the same happens when she sees
the image of the cheese repeated.
The game will get harder as the player has to hold longer intervals in mind. Recalling three-back
is harder than two, and so on. The n-back game tests working memory. That’s the ability to hold
information in mind while you manipulate it.
What are the three traditional divisions of the cortex?
The cortex can be divided into 1. primary sensory and motor areas, 2. secondary sensorimotor areas, and 3. association cortices.
