Lecture 19: Lateral Frontal Lobe Flashcards
Frontal lobe regions (label regions with the red arrows)
Know them in the lateral, medial and prefrontal cortex.
Functions of the frontal lobe
- voluntary movements (which are movements you control) of the opposite side of your body
- sequencing of complex or multistep movements, such as getting dressed or making a cup of tea
- speech and language production in the dominant frontal lobe (opposite your dominant hand)
- attention and concentration
- working memory, which involves processing recently acquired information
- reasoning and judgment
- organization and planning
- problem-solving
- regulation of emotions and mood, including reading the emotions of others personality expression
- motivation, including evaluating rewards, pleasure, and happiness
- impulse control
- controlling social behaviors
Possible results to lesions in the frontal lobe
- loss of movement, either partial (paresis) or complete (paralysis), on the opposite side of the body
- difficulty performing tasks that require a sequence of movements
- trouble with speech or language (aphasia)
- poor planning or organization
- persistence with one behavior, way of thinking, or set of rules related with intelligence
- difficulties with higher order functions like reasoning, problem-solving, and judgment
- problems with maintaining attention or concentration
- decreases in motivation
- mood swings
- impaired ability to initiate activities or interactions
- drastic changes in personality or behavior, which can include apathy, irritability, and inappropriate social behaviour
- poor impulse control or lack of inhibition
The prefrontal cortex
• The prefrontal cortex has been hypothesized to be proportionally largest in humans (although see Semendeferi et al., 2002 Nature Neuroscience on this subject). This has caused researchers to suggest that it is the seat of intelligence or even consciousness … (one of the main hypothesis is that consciousness could be located in the prefrontal cortex)
• But other areas of our brain – parietal lobes, temporal lobes - have expanded as well! If you look at other species.
• For instance, monkeys do not have a middle temporal gyrus or a fusiform gyrus. The homologous cortex is likely within the sulci and expanded over evolution.
• The prefrontal cortex is one of the last regions of the brain to mature during human development. Another argument for its role in inhibition of behaviors. When we are born all of the neural maturation is kind of complete (not really new neurons will form) but some of the synapses will grow, the myelinazation of the axons will also increase (myelin sheath). therefore, there is development of the brain during the early years.
• Evolution is there for a reason, it is there for us to have all the neural resources in order to express thinking and all of our consciousness.
• At four years old, we have expansion of our synapses and then there is elimination of our synapses that we do not use (connections no longer used).
•However, myelination continues growing with age.
• Depending on what you are learning when you are young, you develop some part of your cognitive abilities. Ex: play the piano since you are four, more connections with all the regions associated with your training.
- Prefrontal cortex continues to evolve until we are in our mid 20s - so in terms of functions they are not fully developed until we are in our mid 20s.
The link between the prefrontal cortex and intelligence
• Donald Hebb tested patients of Dr. Penfield with resection of PFC and they performed well on standard IQ tests. In fact, IQ often went up post surgery!
The prefrontal cortex is fully activated when your are in unfamiliar situations or environments. It needs to make new connections because it is things you have never seen. So intelligence is not only how you perform when you do an exam. It is how you behave in unknown situations, how you are able to solve problems you have never seen (ability tobe creative,flexible)
• Patient K.M. (mentioned in Milner, Corkin, and Teuber article) had both anterior PFC removed due to epilepsy. This patient performed normally on IQ tests…
• But what do these tests really involve? At least in the 1950’s: reading tasks, spatial tasks, math questions…not testing the frontal lobes directly.
• Wilder Penfield performed several cases of frontal resection (usually unilateral):
• “a lack of capacity for planned administration”
• “the loss of power of initiative”
• The case of Phineas Gage
• Injured working on railway, 1800’s
• Damage to orbitofrontal and ventromedial frontal cortex (the left PFC). His personality and behaviour were completely changed. After 2 years, he recovered his personality came back.
• Conclusion was that the frontal lobes deal with “personality” or “inhibition of behaviour”.
• But what is really going in in the frontal lobes? We need to figure out the specifics…
• Other cases of unilateral lesions showed that it affected the capacity for planned administration and initiative.
How do characterize the prefrontal cortex by cytoarchitecture
• Homologous cytoarchitectonic areas established in human and macaque monkey (Petrides and Pandya, 1994)
• As you move anterior to the precentral gyrus, layer IV starts to emerge.
• The “prefrontal cortex” is often defined as everything in the frontal lobes that is typical granular cortex.
• Remember, area 44 is dysgranular. Sometimes interpreted as a transition area… sometimes included in the prefrontal cortex, sometimes not
Brodmann areas of lateral frontal lobe that must know and what regions they are
Role of the main Brodmann areas in the lateral frontal regions
The lateral frontal regions is not about stable information/ it is not about what we already know. It is about how we can perform in unknown situations. Therefore, we need the connections between the areas to be really performant.
• BA9,enables our emotional intelligence, engaging the psychosocial domain. Understand how to behave right socially
• BA47, enables our practical intelligence, engaging the material domain (how can we solve a problem when we are in front of objects)
• BA46 (or BA46-9/46), enables our abstract intelligence, engaging the hypothetical domain (hypothetical domain: how we can think about abstract things).
• BA10, enables our temporal intelligence, engaging in planning within any of the other three domains. Connects all three domains.
Area 47 is connected to area 22 (wernickes area), area 44 (brodmann area). Associated with the conceptualization of the material domain. Associated with the orbital cortex.
Area 46 is connected to the dorsal stream, to our notion of space/where we are, what time it is = space and time. Allows us to understand intangible phenomenon/abstract phenomenon. it is connected to area 9 and area 47.
All of these regions are connected to area 10. Area 10 can guide the interactions between these regions and allow planification (conceptualization of future). This is called temporal intelligence = making links between different events in our life.
**you dont need to know all the areas connected just understand the logic of it
LAateral frontal lobe disorders
Dysexecutive syndrome
• Problems with “Executive processing” = attention regulation + Procedural Regulation + Emotional regulation. Frontal lobe is really associated with all of the functions that are not really concrete (more abstract). It has an impact at one moment in time, needs to be processed at this time point.
• Age can affect executive functions - when we are young we don’t have a lot of these abilities. Executive function decreases with age (elderly people).
• Executive processes are associated with going and grasping new information. Handling information in a dynamic way.
• Lesions are extensive – rarely localized (unless we have specific removal of one area):
• Surgery (epilepsy)
• Head injury
• Cerebrovascular disease (stroke)
• Tumors
• Alzheimer’s disease
• Frontotemporal dementia.
• Patients perform adequately on the traditional tests measuring intelligence, perception, and static short-term memory
What are the side effects of Dysexecutive syndrome?
• Struggle organizing everyday activities:
• Poor problem solving (concrete and rigid)
• Poor organizational strategies (distraction, disorganization, cannot multi-task, cannot plan, lack of flexibility in behavior = if you already learn something, you are not able to learn something)
• Impaired set-shifting, perseveration, and impersistence (hard to change their Mind)
• Memory may be disrupted – Reduced working memory, encoding/retrieval strategies, and temporal organization (order). Retrieval improved with recognition cues. Impairments of familiarity and recency but not of recollection.
• Apathy and psychomotor slowing. Poor motivation/Abulia
• Decreased emotional range. May appear uncaring or emotionally unresponsive
A hypothesis for why as people get older they become more rigid and less flexible is that their connections become stronger. The brain is less plastic as we get older.
How do we test for executive processing - assessing frontal lobe function?
Tests for assessing frontal lobe function – tests of “executive processing”:
• Tests involving flexibility - changing response tendencies based on feedback (e.g., the Wisconsin Card Sorting Task)
• Tests of divergent thinking (e.g., verbal fluency tests)
• Temporal ordering tasks/ Recency discrimination tasks
• The self-ordered pointing task
• Conditional associative learning tasks
• Tasks of active memory retrieval
The Wisconsin card Sorting Task
It is about being able to chose a card. You have 4 cards in front of you and one card that is handed to you. Everyone can see that the 4 cards are different, there is a variation in forms ( 1 variable = different shapes, 2 variable = different colours, 3 variable = different numbers).
- When the cards are given to you and you see the four cards, and then you have your card, you don‘t know what rule you have to follow. The task is to associate the card that you have with another one based on a rule (the rule is based on the three variables). You could follow the rule associated with the number, colour or suit. At the start of the test, you will not know which rule to follow and will make a mistake but this will help you realize that is not the rule to follow and you will switch to another rule.
•Requires alteration of behavior based on external feedback
• Requires:
• cognitive flexibility of behavior
• ability to disengage and switch categories despite previous response tendencies
Meta-analysis of 3 tasks. What regions activated with which tasks (WCST, Task switching and go/no-go)?
1, WCST (green)
2, task switching (red)
3, go/no-go (blue)
4, WCST and task switching (yellow)
5, WCST and go/no-go (cyan) 6, task switching and go/no-go (violet)
7, WCST and task switching and go/no-go (white).
Yellow = general lateral frontal lobe, activating more the left hemisphere
The WCST and frontal lobe dysfunctions
Photo: meta analysis study. Looked at patients with lesions and that performed different neuropsychological tests. They called this the test of cognitive control because the pre frontal cortex (lateral frontal lobe) is associated with our cognitive control. They used various tests:
- TMT: measure executive response switching
- Wisconsin task
- Stroop: inhibit our lecture of the words and name the colours
- Cowa: measures creativity, verbal fluency, thinking
*In blue, is the different slices they took to analyze the different tests. In this image, we can see the regions that are important for patients to perform these tasks. To determine this, they looked at patients with lesions in those regions and determined that they had poor performance in these tasks.
From these tasks, they concluded:
Important diagnostic tool for frontal lobe dysfunctions
• Lateral PFC damage
• Exhibit perseverative errors (they
“persevere”)
• Mental inflexibility.
• No disengagement.
• Cognitive control
• More impairment after left dorsolateral PFC* than right
• Verbal feedback? Verbal categories?
• *Involves LARGE lesions in DLPFC. No specific cyto area
- If we wanted to test more of these functions in the right hemisphere. We would be using visual stimuli (abstract stimuli) to not recruit the semantic system.
- It’s hard to do matching tasks for animals because our prefrontal cortex is more evolved .
- its not about one region, it is about the connectivity between the regions.
What is divergent thinking? What is convergent thinking?
Convergent thinking: being able to think as usual, like we already learned to think. Usually, there is a problem in front of us and there is one correct answer, so it is easy to get this answer. Convergent thinking is not sensitive to frontal lobe damages. It is usually associated with a well-defined problem that we are used to solving. We have a specific number of items, ideas and we are able to go in one pathway. We are able to select the best idea to solve the problem and then conclude have a simple correct answer. Converges to one specific solution. Not able to be creative and flexible.
Divergent thinking: Associated with problem that is more open-ended and that maybe has multiple solutions. Many different responses can be produced to the same question.
Different ways to look at divergent thinking - test for divergent thinking?
You do not need to learn all of this.
*Adaptation to variable environment is important because it is the ability to integrate intellectual and creative abilities to introduce change, innovation or improvement over what exists. Nice definition of divergent thinking.
What is a way to test creativity or innovative thinking?
The Torrance test: start with some shape, do a drawing starting with the shape given/ only using those shapes. Way to test creativity.
Tests:
• Innovative thinking
• Novel ideas
• New connections between existing ideas
• Divergent thinking: open-ended; large number of potential “solutions”
When looking at people doing the Torrance test, what do you observe?
We will see that high creative individuals will have increased activity, connectivity so an increased network of the lateral prefrontal cortex. It is more connected to the dorsal part of the brain.
In high creative network, the prefrontal lobe is connected to other regions.
In low creative network, they will have more connectivity in the more sensorial systems, so the parietal and the temporal lobes.
What is problem solving?
Problem solving is about identifying a problem, defining and conceptualizating the problem, developing strategies to solve the problem , organizing knowledge about the problem… dont need to remember all of that.
Mainly the lateral prefrontal cortex that is associated with problem solving.
