Topic 14: Frontal Lobes Flashcards
Anatomy of the Frontal Lobes
- Constitutes 20% of neocortex
- The greatest amount of association cortex
- All regions anterior to the central sulcus
Parts of the Prefrontal Cortex
The prefrontal cortex is a large area of the brain that is located at the front of the frontal lobe. It is involved in a wide range of cognitive, emotional, and behavioral functions. The prefrontal cortex is typically divided into several subregions, including:
Dorsolateral Prefrontal Cortex (DLPFC): This region is involved in working memory, planning, decision making, and cognitive flexibility.
Ventromedial Prefrontal Cortex (VMPFC): This region is involved in emotional regulation, social cognition, and decision making. It is also important for learning and memory.
Orbitofrontal Cortex (OFC): This region is involved in decision making, emotional regulation, and social behavior. It is also important for sensory processing and reward-based learning.
Anterior Cingulate Cortex (ACC): This region is involved in attentional control, error detection, and conflict monitoring. It is also important for emotional regulation and pain perception.
Prefrontal Cortex
The prefrontal cortex is a part of the brain involved in various cognitive and emotional processes. It is divided into sub-regions, each of which has distinct connections with other brain parts.
- Receives input from the dorsomedial nucleus of the thalamus
Dorsolateral Prefrontal Cortex
The dorsolateral prefrontal cortex receives input from the dorsomedial nucleus of the thalamus and is connected to the posterior parietal and superior temporal sulcus regions of the brain. It is involved in tasks such as planning, decision making, and working memory.
- Posterior parietal & STS
Orbitofrontal Cortex
The orbitofrontal cortex receives input from all sensory modalities and the amygdala and is involved in emotional processing, reward-related decision-making, and social behaviour.
- All sensory modalities & amygdala
A Theory of Frontal-Lobe Function
Definition: a model of the brain’s frontal lobe that proposes several key functions, including planning, attention, memory, and emotion.
- Autonoetic awareness: the idea of self, awareness of self, and projecting ourselves in a future sense
- Emotion: the frontal lobe is involved in regulating emotions and responding to emotional stimuli (e.g., higher order emotional regulation, more than limbic system)
Examples:
- Planning and selecting from different options based on experience
- Ignoring distractions and maintaining focus on a task
- Remembering the sequence of events over a period of time
- Responding to internal cues, such as hunger or fatigue, as well as external and contextual cues, such as social norms and expectations
Executive Function or “Cognitive Control”
Definition: The ability to plan, make decisions, correct errors, troubleshoot, and respond appropriately in challenging or complex situations.
Examples:
Planning and prioritizing tasks for a project
Deciding on the best course of action when faced with a problem
Correcting mistakes and adjusting strategies as needed
Handling mentally demanding tasks or dangerous situations
Resisting impulses and avoiding distractions
Adapting to changing circumstances and being flexible in your approach
Related terms: Mental workload (when we are in dangerous or technically difficult situations), cognitive flexibility (i.e, opposite of perseverating, so being able to change your mind), inhibitory control, working memory, attentional control, task switching, response inhibition (e.g., resiting temptation, dieting, addiction)
Importance: Executive function is crucial for success in school, work, and daily life, as it helps individuals to make effective decisions, solve problems, and navigate complex situations.
Ventromedial Prefrontal Cortex
The ventromedial prefrontal cortex is connected to the dorsolateral prefrontal cortex, cingulate cortex, amygdala, hypothalamus, and periaqueductal gray. It is involved in processes such as emotional regulation, risk assessment, and social cognition.
Autonoetic awareness
the ability to be aware of one’s thoughts and feelings, as well as to place oneself in past and future scenarios
Wisconsin Card Sorting Test (WCST)
The Wisconsin Card Sorting Test (WCST) is a neuropsychological test that measures a person’s ability to switch their attention from one rule to another and their capacity for abstract reasoning. In this test, the participant is presented with cards and asked to sort them based on different rules such as colour, shape, or number. After a certain number of correct responses, the rule is changed without warning, and the participant must deduce the new rule and start sorting according to it.
- initially shown the row of cards
- given a card, and must sort it by a specific rule
- receive feedback “correct” or “incorrect”
- after 10 rounds, the rule will change
- frontal lobe damage results in the inability for them to change the rule and inhibit their behaviour (i.e., response inhibition, perseverating)
- similar to Stroop task
Individuals with frontal lobe damage or dysfunction, including those with certain types of dementia, schizophrenia, or traumatic brain injury, may have difficulty with the WCST. One of the most significant difficulties observed in this population is perseveration, which is the tendency to continue using the old rule even after being told that the rule has changed. Perseveration is seen as a disconnection between a person’s thoughts and actions, where the individual cannot adjust their behaviour in response to changing circumstances. The WCST is used clinically to diagnose frontal lobe damage and assess cognitive flexibility, a component of executive function.
- After 10 correct trials: change the rule
- Patients who perseverate cannot switch behaviour to fit with new rules.
- Even continue when they “know” they are not following the new rule.
- Disconnection between thought and action.
Environmental Dependency Syndrome
Environmental Dependency Syndrome (EDS) is a neurological condition in which an individual tends to act in a manner that is heavily influenced by external cues and stimuli in their immediate environment. This can lead to behaviours such as touching objects in their surroundings, rearranging items, or imitating the movements of others. Individuals with EDS may also have difficulty ignoring or resisting environmental cues and may experience a loss of sense of agency or control over their own actions.
- EDS can be caused by damage to the brain’s frontal and other regions, such as the parietal and temporal lobes.
- Environmental cues” trigger perseveration
- Also relates to pre-morbid functioning
- Cannot inhibit responses – Free will? stuck in perseveration
- E.g., in the image, the interior designer began decorating; the woman was a homemaker and began doing chores
Novelty & Prefrontal Regions: Oddball Task
Frontal Lobe:
- Important for detecting and focusing on novel items in the environment
- Damage can impair this ability to focus on extremely novel items
- Novel elicits P3a. The frontal lobe has a higher activation of this in the brain, and we need to adjust our attention to these things.
- P3a decreases after prefrontal cortex damage
Experiment:
Frequent = high pitch 78% of the time
Rare = low pitch 20% of the time
Novel = car horn, sneeze, etc. 2% of the time, very unique
The P3a is most strongly elicited by rare or unexpected stimuli that require attentional processing and orienting responses. The exact characteristics of the stimuli can vary depending on the experimental paradigm and task used to elicit the ERP.
- you do not see p3a activate for the frequent condition
ERPs and PFC:
- ERPs (event-related potentials) can measure brain responses to novel stimuli
- P3a is an ERP component typically elicited by novel or unexpected stimuli that require attentional processing and orienting responses; we see activation after they see something novel
- PFC (prefrontal cortex) is involved in attentional processing and orienting responses
Examples of stimuli that can activate P3a:
- Sudden or unexpected changes in the environment
- Novel or unfamiliar stimuli
- Emotionally salient stimuli
- Stimuli that require a shift in attention or a response
Sequencing: Recency Judgment Task
During the task, the individual is presented with a series of items (e.g. numbers or letters) and is asked to remember the sequence in which they were presented. The individual is then presented with a new item and asked to judge whether it was presented before or after a target item that was presented earlier in the sequence.
The task is designed to measure several cognitive processes, including working memory, attention, and the ability to sequence and organize information.
- focus on temporal memory
- Passive task; participants are not told explicitly to list what they have seen
Recognition trials: will be asked, “Which of these two things have you seen?”
- Temporal damage – poor recognition (explicit LTM memory)
- HM (i.e., temporal, hippocampus damage) may struggle with the recognition task
Recency trials: “Which one have you seen most recently?”
- Prefrontal damage – poor recency, even when they can do the recognition trial; this relies on the short-term working store
Hemispheric differences; differences between visual (right hemisphere) and verbal (left hemisphere damage, causes impairments)
- LH damage: issues with verbal recency
- RH damage: nonverbal (pictorial)
Six-item Self-ordered Pointing Task
The task is when the participant is presented with an array of six stimuli (e.g., pictures or shapes) on the screen. They are asked to touch each stimulus in a specific order without repeating any stimulus. They point, are given a new card, and are asked to point again without repeating.
- Point to different items on each sheet (active)
- MTL (Medial temporal lobe damage - hippocampal damage) patients can do the task; if they do the task fast enough, they can rely on their STM
- PFC damage disrupts performance because they can’t access their STM and have a difficult time remembering what they have just recently pointed to
LH: both verbal & nonverbal versions; affects both because more strategy is involved. Ppl may use verbal strategies when completing this task.
RH: only nonverbal
Demands memory (WM) & organized strategy (verbal?) -
Tower of London Task
The Tower of London task is a neuropsychological test of planning and problem-solving skills. It requires the participant to rearrange a set of coloured balls or disks on three pegs to match a goal configuration, with specific rules for how many moves are allowed and how the pieces can be moved. The task is timed and becomes progressively more difficult with each new problem. The Tower of London task is often used to assess frontal lobe function and executive functioning in clinical and research settings.
- Three pegs; 3, 2, 1 ball
- Assess strategies used to sequence action
- Left Hemisphere-PFC damage has trouble: LH is involved in goal-directed planning and strategy (imaging data – activation in PFC in NI)
- Efficiency, effectiveness
Advance Information Paradigm
Task A: the top R is correct when you rotate it clockwise, and the patient must identify if the R is in the normal or backward groups.
Task B: Give them a cue before every trial, and then they only have to match it instead of having to do a mental rotation
- looking at reaction time and if they got it right.
- Frontal Lobe patients can do it just as well as controls in Task A
- Frontal lobe patients have difficulty using advanced information in Task B (i.e., cannot employ advanced info for strategy formation; Ppl with frontal lobe damage do not improve when given the cue)
- Alternative hypothesis: cannot maintain the image in working memory
- Alternative hypothesis: Perseveration
Error Related Negativity (ERN) - the Go-NoGo Oddball Task
Response inhibition task = Go-NoGo Oddball task
- Example: 80/100 trials are green lights where you push the button. Once the red light comes on, you need to inhibit yourself
- “Blunder Blip” ERP when we make a mistake
- Hypothesis that the inhibition is generated in the ACC (anterior cingulate cortex)
- Definitely believe there are interactions between PFC and inhibition: With lesions in the PFC, you get that ERN response on both correct and incorrect responses
Condition A: do it as fast as possible, SPEED
- Even when you get incorrect, there is some difference; your frontal lobe is more worried about the “fast strategy,” not an “accurate strategy.”
Condition C: told to get it perfect so you get a cash reward; errors are important, do not make them
- Blue line spikes when a person makes a mistake; they should have inhibited their response
If the ERN tells you you made a mistake, imagine what it does when you get that ERN response on both correct and incorrect responses.
Brain no longer distinguishes between correct and incorrect responses; you feel like you are doing everything wrong.
Response Inhibition
Determine what role the ACC has in response inhibition.
- fMRI = location; using the Go-NoGo Task
- Data in the image shows all correct responses (response inhibition - inhibiting the response when necessary
- ACC: we see high levels of activation for both the Go and the NoGo trials - can think of this like it is flagging and prep for the frontal
- LH/RH Inferior frontal: high levels of activation for the NoGo, so inhibition - when we need the inhibition, we see frontal lobe activation
Emotion: ACC
Believed that various regions of the ACC can be involved in emotional processing, and some regions are involved in higher cognitive processing – the interface between emotion & cognition.
- Ventral/Lower ACC (emotion) vs. Dorsal/Upper ACC (cognition)
- Reciprocal deactivation: if one is more active than the other, it inhibits the other
- Clinical Depression is correlated with low dorsal activation (CBT can help get the cognitive thought involved)
- ACC is involved in pain processing (in image): as you increase the pain intensity of the signal, the ACC increases = how we respond to pain emotionally
- Lesions in the anterior portion of the ACC to help with ppl experiencing pain, they still feel the pain but they are not bothered by it
PFC & Depression
Looking at patients with damage (e.g., frontal lobe, and then anywhere else) and comparing the effects to the effects of clinical depression.
- Left hemisphere lesions = higher levels of depression if towards the frontal lobe, not so much at the back of the brain
- Right hemisphere lesions = lower levels of depression if towards the frontal lobe, much much more at the back of the brain
Valence-Arousal Model of Emotion
According to this model, emotions can be described based on two primary dimensions: valence and arousal.
Valence is the degree of positive or negative feeling associated with an emotion. Pleasant or enjoyable emotions, such as happiness or contentment, are considered to have a positive valence. Conversely, unpleasant or uncomfortable emotions, such as sadness or anger, are considered to have a negative valence.
Arousal refers to the level of physiological activation associated with an emotion. Emotions that are highly arousing, such as fear or excitement, are considered to have a high level of arousal. In contrast, less arousing emotions, such as calm or relaxation, are considered to have a low level of arousal.
The Valence-Arousal Model of Emotion suggests that emotional experiences can be plotted on a two-dimensional graph with valence on the vertical axis and arousal on the horizontal axis. This creates four quadrants that represent different emotional states: high arousal positive valence (e.g., excitement), high arousal negative valence (e.g., anger), low arousal positive valence (e.g., contentment), and low arousal negative valence (e.g., sadness).
