Cognitive Neuroscience - Chapter 12
Stroop Task
A task invented in which a subject sees a list of words (color terms) printed in an ink color that differs from the word named. The subject is asked to name the ink colors of the words in the list and demonstrates great difficult in doing so, relative to a condition in which non-color words form the stimuli
ACC and Explore/exploit - what role does ACC play?
ACC plays a role in the exploit/explore trade-off: its activation correlates positively with the explored value and negatively with the exploit value.
An early hypothesis on the ACC function is that the ACC is part of an attentional hierarchy, playing a critical role in
An early hypothesis on the ACC function is that the ACC is part of an attentional hierarchy, playing a critical role in coordinating activity across attention systems. This system ensures that processing in other brain regions is as efficient as possible, given the current task demands. Interactions with the prefrontal cortex may select working memory buffers; interactions with the posterior cortex can amplify activity in one perceptual module over others. The interactions with the posterior cortex may be direct, or they may be mediated by connections with the prefrontal cortex
There is a huge body of evidence showing the prefrontal cortex is important for working memory:
Animal lesion studies have found that monkeys with prefrontal cortex lesions have difficulties to perform the delayed response task, but not the cue-response associative memory task. Single cell recording (in lateral PFC) also found that some neurons showed sustained activity during the delay period of the delayed response task.
Anterior -posterior axis regions are involved in...
Anterior regions are more related to more abstract representations. More posterior, more concrete motor plans. cognative decisons/branching
Working memory
As specified in Baddeley's working memory model, executive control is needed to maintain and manipulate the information in the working memory, i.e., working WITH memory.
Cognitive control
Cognitive control is "the process that allows information processing and behavior to vary adaptively from moment to moment depending on current goals, rather than remaining rigid and inflexible" http://carterlab.ucdavis.edu/research/control.php.
Cohen and colleagues proposed that the key function of the medial frontal cortex, especially the ACC, is to evaluate ____
Cohen and colleagues proposed that the key function of the medial frontal cortex, especially the ACC, is to evaluate response conflict. The reason that high attention demand and error/feedback related processes recruit the ACC may be due to the fact that these situations all involve response conflict. Consistent with this hypothesis, the incongruent condition of the flanker task and Stroop task, which triggers response conflict, all engages the ACC to a larger extent than the congruent condition of the tasks.
Decision making:
Decision making
focal injuries to the prefrontal cortex produce the following changes:
Deficits in planning complex behaviors. perseveration in responding, i.e., tendency to produce a particular response on successive trials, even when the context has changed, and the original response is no longer appropriate. They may have inhibitory control deficits or/and cannot flexibly adjust their behavior according to the changing situation. and Utilization behavior
Evidence also shows that after the ACC detects response conflict, it may signal to the ___
Evidence also shows that after the ACC detects response conflict, it may signal the lateral PFC so that the later PFC can adjust its cognitive control accordingly, e.g., pay more attention to specific aspect of the task, help to inhibit, select, or execute the action/cognition that are more consistent with the goal, etc.
Problem-solving: Tower of London task:
For example, participants will be given an initial state and asked to make movement of the balls in a specific number of step to produce the final state. We can manipulate the difficulty level (e.g., the number of steps) and record participants' errors. We can also record participants' brain activity while they are doing the task.
Different tasks can be used to probe decision making processes in animals and humans - what is choosing object task?
For example, we can train participants to learn and choose different objects associated with (1) different amounts of reward or (2) different delay of the delivery of the reward. for monkies, we will reward with water based on different choices they make For humans, the Iowa gambling task has been used to assess brain lesion patients' decision-making function. Specifically, participants will be asked to choose cards from the 4 decks. Each card is associated with either winning or losing a certain amount of money. The A and B decks provide frequent small wins and occasional large losses; the C and D decks provide frequent small losses and occasional large wins. Most people will start by preferring A and B but gradually figure out it is better to choose C and D.
Decision making: Iowa gambling task
For humans, the Iowa gambling task has been used to assess brain lesion patients' decision-making function. Specifically, participants will be asked to choose cards from the 4 decks. Each card is associated with either winning or losing a certain amount of money. The A and B decks provide frequent small wins and occasional large losses; the C and D decks provide frequent small losses and occasional large wins. Most people will start by preferring A and B but gradually figure out it is better to choose C and D.
Inhibitory control: Go/Nogo tasks
Go/Nogo tasks are often used to test inhibitory control processing patricipants are asked to make a response as fast as they can when they see a letter but when the letter is repeated they are not supposed to this test inhibit response because we go→go→go→ STOP We can manipulate the frequency of go vs. nogo trials to control the difficulty level of the task (more go trials will build stronger tendency of "habitual" action, which makes the inhibition more difficult. Stroop task can also be used.
Goal-directed decision vs. habitual decision or action-outcome decision vs. stimulus- response decisions.
Goal-directed (or action-outcome) decisions are based on the assessment of expected reward. Habitual (stimulus-response) decisions are NOT based on the evaluation of the expected outcome, but the direct association between stimulus and action.
ACC vs vmPFC in explore/exploit
Human neuroimaging studies (e.g., Kolling et al., 2012) also found that the ACC plays a role in the exploit/explore trade-off: its activation correlates positively with the explored value and negatively with the exploit value. It may code the value of switching to a course of action alternative to that which is taken or is the default (value-guided response selection). It facilitates the exploration of the environment for better alternatives compared to the current course of action. The vmPFC however, was found to encodes the value of chosen or attended options in comparison with unchosen or unattended options (comparing values). Similarly, another neuroimaging study found that the vmPFC activity (very often the textbook treats the vmPFC as OFC. It is better to differentiate them) is positively correlated with positive affect (green) when making a choice, whereas the ACC activity is correlated with high level of anxiety. The reason the ACC was involved in the high anxiety situation where one of two high value items needs to be selected may be that this region supports value-based selection of response. diagram
Human neuroimaging studies also found that the _____ activation was closely tied to variation in payoff, whereas activation in the striatum of the _____ was related to effort (Corxson et al., 2009).
Human neuroimaging studies also found that the OFC activation was closely tied to variation in payoff, whereas activation in the striatum of the basal ganglia was related to effort (Corxson et al., 2009).
how does the wisconsin card sorting task help studyt mental flexibility
If participants have a difficult time to switch to new rules, they will have higher perseverative errors. participants get used to the first rule, and when they get negative feedback they have to analyse the new rule some brain lesion patienst cannot switch to new rules, meaning they lack mental flexibility
The vlPFC and goal-related selection - fMRI studies with verb generation
In another fMRI study, researchers varied the demands on a filtering process during a verb generation task. In a low-filtering condition, participants were asked to name actions that go with words with fewer associated verbs (e.g., scissors). But in a high-filter condition, they need to name actions that go with words with many associated verbs (e.g., rope). Stronger activation was observed in the left vlPFC and temporal lobe regions. the high filter makes demand high The study also found the involvement of the vlPFC and temporal regions were different: The vlPFC involvement was stronger whenever a generation/selection demand was higher no matter whether the semantic information was repeated. But the temporal regions showed decreased activation when the semantic information was repeated. These results suggest that the vlPFC may help to generate and select semantic information supported by the temporal lobe. This is similar to the role of the dlPFC in working memory processing: it helps to maintain and manipulate working memory, but the WM representations may be supported by other regions.
Representation of value: the LPFC (i.e., vlPFC) was associated with the ____ control
In contrast, the LPFC (i.e., vlPFC) was associated with the degree of control, showing greater activity on trials in which a preferred but unhealthy item was refused, as compared to trials in which the item was selected. (vlPFC : selection!)
Error detection and monitoring is important for what kind of behavior?
In order to conduct goal-directed behavior to achieve our goals, we also need to monitor our behavior, or detect errors in order to correct them next time. This requires error detection or monitoring processes.
Mental flexibility: Wisconsin Card Sorting task. - Basics
In this task, participants will learn how to sort (i.e., match) the cards according to a specific rule, e.g., based on color, using the feedback given by the examiner. During the task, the rule will be changed, discreetly from one criterion to another (e.g., from color to shape to number). Participants have to shift sets accordingly and sort the cording based on the new rule.
Inhibitory control
Inhibitory control: the process that is used to inhibit or stop habitual responses, or prepotent responses so that a more well- planned goal directed response can be possible.
The vlPFC and inhibitory control: Knight & Grabowecky experiment
Knight & Grabowecky (1995) asked patients with different brain lesions to listen to tones (auditory stimuli) and measured their brain responses using ERP.
Lateral prefrontal cortex is where in brain?
Lateral prefrontal cortex is just anterior to the premotor or motor cortex. These regions should be more related to planning, controlling actions, attention, etc. directly related to action/plans/waht to do
Model-based vs. model-free decision making
Model-based means the agent has an internal representation of some aspect of the world and uses this model to evaluate different actions. For example, a cognitive map would be a model of the spatial layout of the world, enabling us to choose an alternative path if we found the road blocked. This is similar to goal-directed decisions. something like our model/idea of the outside world Model-free means we only have an input-output mapping, which is similar to stimulus-response decisions.
Lateral-medial are involved in...
More medial regions are related to processing of information that is more related to self, emotion, reward, internal stimuli, etc (hot). Lateral regions are more related to "cold" information (not related to self, emotion, etc.).
Neuroimaging studies have also show that when a simple rule (simple stimulus- response mapping) is maintained in working memory, the ______ are involved. But when the rule becomes more complex (more stimulus-response mappings), more _____ regions in the PFC will be involved.
Neuroimaging studies have also show that when a simple rule (simple stimulus- response mapping) is maintained in working memory, the ventral PFC(prefrontal cortex) and premotor cortex are involved. But when the rule becomes more complex (more stimulus-response mappings), more anterior regions in the PFC will be involved. more anterior is responsible for abstract Together with other evidence, it has been proposed that more anterior regions along the rostro-caudal axis of the frontal cortex support rule learning at higher levels of abstraction.
One region in the thalamus, the dorsal posterior part of the thalamus, called habenula, may be one of the regions that convey the _____ information to the midbrain dopamine system.
One region in the thalamus, the dorsal posterior part of the thalamus, called habenula, may be one of the regions that convey the value information to the midbrain dopamine system.
Originally scientists thought of dopamine as the neural correlate of reward or pleasure (liking), but currently its activity has been conceptualized as
Originally scientists thought of dopamine as the neural correlate of reward or pleasure (liking), but currently its activity has been conceptualized as the expectancy of reward (i.e., wanting) and plays an important role in decision making and reward-based (reinforced) learning. Research has also shown that the activation of dopaminergic neurons reflects prediction errors, i.e., the difference between the reward received vs. expected.
Prefrontal cortex and cognitive control - How do we know a connection is there>?
Our early understanding of the functions of the prefrontal cortex and how it is related to cognitive control came from brain lesion patients. Phineas Gage is one of the most famous early cases, which we have talked about in the Emotion chapter. After his injury in the prefrontal cortex, "Gage is no longer Gage". His personality changed, his social behavior changed, ...
How do we or our brain compute value and processes rewards? - primary vs secondary reinforcers
Primary reinforcers: the rewards such as food, water, or sex, that have a direct benefit for survival fitness. Secondary reinforcers: The rewards such as money, status, aesthetics, that have no intrinsic value themselves, but become rewarding through their association with other forms of reinforcement.
ventral-dorsal axises are involved in...
Regions that are more ventral are more likely to paly a role in What related to executive processing. Regions that are more dorsal are more related to "how".
Similarly, another neuroimaging research found that the LPFC was associated with the ___ of reward, whereas the delay between the time of the action and the payoff was correlated with activity in the ____
Similarly, another neuroimaging research found that the LPFC was associated with the probability of reward, whereas the delay between the time of the action and the payoff was correlated with activity in the medial PFC and other regions.
Evidence showing the prefrontal cortex is important for working memory
Single cell recording also found that some neurons seem to specifically maintain information related to objects ("what" information), some for location "where" information, and some for both, i.e., 'what-where'. The results indicate that cells in the lateral PFC exhibit task-specific selectivity, i.e., supporting the exact information in working memory. Human neuroimaging studies (e.g., fMRI) also found the activation in the dorsal lateral PFC increased with working memory load (e.g., more faces need to be kept in working memory). it seems the lateral prefrontal cortex might work with the posterior perceptual region to maintain working memory Similar activation pattern was found in the posterior perceptual regions, i.e., the fusiform face area. oIt suggests that the lateral PFC may help to sustain representations of task goals/stimuli by working in concert with other brain regions. dorsal prefrontal cortex cannot represent face stimuli itself but it can help maintain info in other regions To what extent the PFC itself represents the information or supports other regions to represent the information is still in debate.
Single cell recording studies and dopamine - What happened when animals did/did not receive CS?
Single cell recording studies using Pavlovian conditioning method supported the prediction error theory. When an animal receives positive US (unconditioned stimuli), the dopamine neural activity in the VTA become stronger (suddenly receiving reward- positive prediction error). After CS is paired with US, the CS starts to trigger dopamine activity. This is because when CS appears, the animal will have a positive prediction error (expecting something good, without consuming it yet). Learning will occur -learning the associations. When the animal receives what it expects, no dopamine activity (because no expectation error). No new learning will occur. When the animal did not receive what it expected to receive, dopamine activity will be depressed. Extinction will occur.
Patients with OFC lesions showed abnormal temporal discounting compared to patients with lesions outside the OFC (orbital frontal cortex) or healthy controls. Specifically, OFC patients were...
Specifically, OFC patients were not willing to wait longer for a larger reward, for which, for example, normal controls would. This indicates the OFC and vmPFC is important for supporting value processing and related decision making. (different value with different time delay lets us study this)
Studies also found that disturbing the vlPFC primarily disrupted participants' ability to ignore ____
Studies also found that disturbing the vlPFC primarily disrupted participants' ability to ignore irrelevant stimuli (i.e., disrupted inhibition)
Temporal discounting
Temporal discounting is the observation that the value of a reward is reduced when we have to wait to receive that reward. ex, 10$ now worse than 10 later? better? Patients with OFC lesions showed abnormal temporal discounting compared to patients with lesions outside the OFC (orbital frontal cortex) or healthy controls. Specifically, OFC patients were not willing to wait longer for a larger reward, for which, for example, normal controls would. This indicates the OFC and vmPFC is important for supporting value processing and related decision making. different value with different time delay lets us study this Diagram
Recent literature calls for differentiation of the ACC from MCC - Why?
The ACC (stronger connection with basic lymbic system) and MCC have different connectivity, respond to different tasks, and likely have different functions.
The ACC has been proposed to a crucial component of a
The ACC has been proposed to a crucial component of a monitoring system. Neuroimaging studies found that this region showed stronger activity when the monitoring demand is high in different tasks. It also plays a role in error detection, conflict monitoring, attention control, resolving response conflict, etc. Anatomically, this region has many subregions that connect with different other brain regions, which makes the ACC in a key position to influence decision making, goal directed behavior, and motor control.
The ACC was also found to evaluate effort associated with a
The ACC was also found to evaluate effort associated with a behavioral choice, as mentioned earlier in the exploit/explore trade-off processing. However, although neuroimaging studies have found the ACC is involved in many aspect of cognitive control, deficits in these aspects of executive function were not found human lesions studies. Therefore, the specific function of the ACC is still under intensive investigation and debate. congruent
The anterior cingulate cortex, what is it?
The anterior cingulate cortex, i.e., the anterior portion of the cingulate cortex, is part of the medial prefrontal cortex. But it has different cytoarchitectonic structures and belongs to the limbic system. Therefore, very often this region is discussed separately from other PFC regions.
The dopamine release is the result, not the cause of learning - What does this mean?
The dopamine neurons may code informational consequences of prediction and learning, and then do something with the information. The dopamine system also plays a key role responding to salient stimulus or event. The dopamine system only mediates the ""wanting" component of reward processing, not "liking" or "learning". Reducing dopamine will reduce "wanting", which has significant implications in the current thinking of addiction.
The lateral prefrontal cortex may also help us to select or filter...
The lateral prefrontal cortex may also help us to select or filter information related to the current goal For example, studies have found that vlPFC is involved in fluency tasks, in which participants need to generate words semantically associated with a cue word. found regions involved in sementaic tasks
The medial PFC, i.e., the OFC, vmPFC and ACC, receives stronger ____ input compared to the lateral PFC, so does the ventral striatum (ventral part of the basal ganglia)
The medial PFC, i.e., the OFC, vmPFC and ACC, receives stronger dopamine input compared to the lateral PFC, so does the ventral striatum (ventral part of the basal ganglia)
The more anterior a region is, the further it is separated from the _
The more anterior a region is, the further it is separated from the motor regions. Then, it may process more abstract cognitive/action representations.
Goal-selection: in another neuroimaging study (Dux et al., 2009), participant were asked to intensively practice a visual-manual task (e.g., press one of two buttons to indicate the position of a stimulus) and an auditory-vocal task (e.g., say different sounds to different auditory stimuli) task. They practiced the two separately (single task) and together (multitasking). practice tasks either simultaniously or just a single one. Results were...
The researchers found that the connectivity between the vlPFC (ventral lateral prefrontal cortex) with the sensory and motor regions related to each task remained strong and task specific before and after the training, indicating that the vlPFC may help to select the response based on the stimuli.
goal related selection: Dux et al., 2009) More interestingly, before the training when participants did the two tasks together (i.e., the multitasking condition), the vlPFC was engaged in a longer time period compared to the single task condition; however, after the training, this region showed the same level of engagement (in terms of time length) in the single and multitask condition. results were
The results suggest that with practice, the involvement of the vlPFC may become more efficient in helping switching between the two tasks.
How do we or our brain compute value and processes rewards? - Value and what factors give value
The value (or our overall preference) we assign to a specific stimulus or event can be affected by different factors. For example: Payoff, i.e., what kind of reward do the options offer Probability, i.e., how likely are you to attain the reward Effort or cost: how much it will cost or how much effort you need to make to obtain the reward? Temporal discounting: the longer we need to wait to get the reward, the more effort is needed or the more discount the reward will have. Context: this factors involves external things, like the time of day, or internal things, such as whether you are hungry or tired, etc.
The ventral striatum also plays an important role in
The ventral striatum also plays an important role in value processing or decision making. For example, neuroimaging research has found that prediction error also predicts brain activity in the ventral striatum. (not only dopamine system) The ventral striatum is involved in motivations. Therefore, value/reward (and punishment), dopamine activity, and motivations are closely related. We need to take actions based on the value of the stimuli or events.
The ventral tegmental area in the midbrain contains _ neurons
The ventral tegmental area in the midbrain contains dopamine neurons which send input to the limbic system (mesolimbic pathway) and other regions in the neocortex (mesocortical pathway).
The vlPFC not only plays a role in inhibiting mental representations but also
The vlPFC not only plays a role in inhibiting mental representations but also inhibiting actions! In addition to the Go/nogo task, another task called stop signal task has also been widely used to examine inhibitory control function. There are both go and stop trials in this task. For go trials, participants need to press a button as fast as possible after seeing a go signal. In stop trials, after the go signal is given, while participants are starting to make a button press, a stop signal will be given, and participants have to inhibit or abort the already prepared action.
Working memory: n this delayed response task, a monkey is shown that food is associated with a specific location. What happens next?
Then there is a short delay during which the animal cannot see the food well, and researchers will cover the food well. Then the monkey needs to find the food well. In this task, the monkey need to hold the information of where the food is during the delay, until they are allowed to find it. delayed response is a working memory task queue is long term memory task
Dorsolateral prefrontal cortex and working memory
There is a huge body of evidence showing the prefrontal cortex is important for working memory: Animal lesion studies have found that monkeys with prefrontal cortex lesions have difficulties to perform the delayed response task, but not the cue-response associative memory task. Single cell recording (in lateral PFC) also found that some neurons showed sustained activity during the delay period of the delayed response task.
Therefore, the vmPFC and OFC plays a key role in
Therefore, the vmPFC and OFC plays a key role in the representation of value.
vlPFC may help to generate and select _ information
These results suggest that the vlPFC may help to generate and select semantic information supported by the temporal lobe. This is similar to the role of the dlPFC in working memory processing: it helps to maintain and manipulate working memory, but the WM representations may be supported by other regions.
To investigate how the brain represents the different aspect or dimension of values, Kennerley et al (2009) used multiple electrodes to record from cells in three regions: the anterior cingulate (ACC), the lateral PFC, and the orbitofrontal cortex (OFC). They found that all the three regions included...
They found that all the three regions included cells that responded selectively to a particular dimension, as well as cells that responded to multiple dimensions. But they also found many cells in the ACC responded to all 3 dimensions, meaning that they are important for supporting all aspects of value processing. The LPFC cells, however, usually encoded just a single decision variable, with a preference for probability. The OFC cells had a bias to be tuned to payoff, reflecting the amount of reward associated with each stimulus item.
The vlPFC and inhibitory control: Knight & Grabowecky experiment: what did they find?
They found that compared to healthy controls, patients with the prefrontal lobe lesions showed stronger response in the auditory cortex, suggesting the signal is less inhibited. Importantly, when asked to only pay attention to the tones in one ear and ignore those in the other ear, they found that the attended and unattended signal did not trigger different brain response in the auditory cortex contralateral to the lesion side. This suggests that the inhibitory effect supported by prefrontal cortex is affected by the brain lesion.
value representations: To test which brain region plays a key role in deciding the transition from exploit to explore, Hayden and colleagues trained monkeys to do exploit/explore trade-off task. Specifically, after fixation, two eccentric targets, a large gray and a small blue rectangle, appear. Monkey chooses one of two targets by shifting gaze to it. Choice of blue rectangle (stay in patch) yields a short delay (0.4 s, handling time) and reward whose value diminishes per trial. Choice of gray rectangle (leave patch) yields no reward and a long delay (travel time) and resets the value of the blue rectangle. They found the ACC (anterior cingulate) activity signaled...
They found the ACC (anterior cingulate) activity signaled the transition from exploit to explore! When the ACC neuronal firing rate reach the threshold earlier, the monkey will leave the current option earlier!
Aron and Poldrack (2006) - Stop signal task - what did it show?
Using stop signal task, Aron and Poldrack (2006) found that patients with lesion of the right inferior frontal were slow to abort a planned response.
Dorsolateral prefrontal cortex with working memory. Using the n-back working memory task...
Using the n-back working memory task, neuroimaging studies also found that activation in the lateral PFC increase as n- back task difficulty is increased. In n-back tasks, the working memory information not only needs to be maintained in each trial but also be updated constantly. The results also suggest that this brain region is crucial for working memory manipulation or operation, not static maintenance.
Using the n-back working memory task, neuroimaging studies also found that the dorsolateral PFC network...
Using the n-back working memory task, neuroimaging studies also found that the dorsolateral PFC network expands, showing marked connectivity with parietal, temporal, and visual regions, which reinforces the idea that the PFC may work with other regions to support working memory processing current thinking is the dorsolateral sends out a signal to other regions which support more detail
Utilization behavior:
Utilization behavior: an extreme dependency on prototypical use of an object without regard for its use in a specific context. Patients' behavior, instead of goal-driven, becomes stimulus driven. ex, seeing a hammer might make them want to use it, more impulsive They may become impulsive, distractible, or apathetic, or disregard social conventions. Disruption of working memory/might have working memory problem
Studies also found that the inhibitory GABA neurons in the midbrain control the activity of the
VTA dopamine neurons. It is likely that the cortical limbic system (e.g., amygdala or hypothalamus) sends value related information to the GABA inhibitory neurons to control the dopamine release (see figure 12.17 in the textbook).
Value, emotion, and motivation are closely related and involve...
Value, emotion, and motivation are closely related and involve the big limbic system, including some PFC regions (e.g., vmPFC, OFC, ACC) and the midbrain dopamine system.
Ventral tegmental area (VTA) sends _ to many brain regions
Ventral tegmental area (VTA) sends dopamine to many brain regions,
Ventral tegmental area (VTA) sends dopamine to many brain regions, including
Ventral tegmental area (VTA) sends dopamine to many brain regions, including the prefrontal cortex, cingulate gyrus, ventral striatum, etc. supporting "wanting" behavior.
Exploit vs Explore - What does this mean?
Very often the situation in which we need to make a decision is ever evolving and dynamic. We may need to constantly evaluate whether we should stay with the same choice or it is time to explore new possibilities for a better outcome (For some people, finding a job or partner can be a good example ☺). In decision making science or behavioral ecology, especially related to foraging behavior (finding food or other valuable resources), "exploit" refers to the behavior that continues to accept or take advantages of familiar options with known or diminishing reward, and "explore" refers to trying unfamiliar options for unknown rewards (can be larger or smaller or none). Very often we need to deal with the explore/exploit trade-off.
The vlPFC and inhibitory control - why does it matter?
Very often, if not always, we need to inhibit unwanted thoughts and behaviors so that we can select the ones that are consistent with our goals. Therefore, inhibitory control is one of the most important executive functions we need for our goal-directed behavior.
What Controls Cognitive Control?
We can use these variety of executive functioning tasks to test brain lesion patients or animals, or measure their brain activity when they are doing the task, to figure out which brain regions play an important role in supporting these processes. A huge body of literature shows that it is the prefrontal cortex (PFC) that plays a key role in our executive functions.
vLPFC Impact on inhibition
When the vlPFC activity is disturbed, inhibition control will also be affected. For example, Zanto et al (2011) asked participants to attend to either color or motion of a visual stimulus while stimulated participants' vlPFC, they found that not only participants' behavioral performance (i.e., accuracy on color recognition) became worse, the simultaneously recorded brain activity measured by ERP (P100 component) also showed reduced attention modulation, i.e., the advantage of attended stimuli over unattended stimuli was reduced. reduced because The p100 was larger for the ignored stimuli after rTMS. So, the inhibition on ignored stimuli was reduced because of the disturbance of the vlPFC by the rTMS.
ACC: Error Detection
When using EEG/ERP method, scientists have found specific ERP components that reflect the error- or feedback-related processing, called error-related negativity (ERN) and feedback- related negativity (FRN). These components was found from the electrodes located in the frontal medial part of the scalp and likely generated from the ACC. (Gehring lab at UM) The ACC was also involved when we need to effortfully monitor our performance. E.g., in the stroop task, we have to monitor whether we indeed name the ink of the color words, not the words themselves. Using ERN measure, scientists also found that the ACC is also more active when we receive unexpected feedback, not just when making errors
hen we are expecting some reward and have not received it yet, we have a
When we are expecting some reward and have not received it yet, we have a positive prediction error, this will yield a positive dopamine activity (wanting).
Where is the prediction information in the dopamine system (VTA in the midbrain) coming from?
Where is the prediction information in the dopamine system (VTA in the midbrain) coming from?
prefrontal cortex, plays a key role in supporting executive functions like
Working memory Inhibitory control Planning Decision making Performance/conflict monitoring Information updating Multitasking ...
Cognitive control It is very complex, relying on many different types of executive functions. E.g., when we try to execute goal-directed behaviors, we may need to:
`maintain the goal, or goal-related stimuli/context information in mind (working memory) pay attention to different stimuli or aspects of the goal/context (attention control) be able to inhibit behaviors/thoughts/emotion incompatible with the goal (inhibitory control). make plans regarding how to achieve our goals (planning, strategy use) make decisions when we have different options/plans (decision making) monitor our behavior or performance to make sure it is consistent with our goals (monitoring, conflict resolution). be flexible: changing behavior/plan/attention/decision when necessary (flexibility) follow rules or make rules, related ideas, retrieve memories ...
patients with lesion of the right inferior frontal were slow to
abort a planned response.
Stroop task and error detection - how does it help us study?
and many other tasks, can be also used to examine the neural mechanisms of error detection, response monitoring, or post-error adjustment.
Functional divisions of the prefrontal cortex:Medial Prefrontal cortex:
anterior cingulate cortex (ACC)
In general, the frontal lobe, especially the prefrontal cortex, plays a key role in supporting
cognitive control, or executive functions,
Because cognitive control, supported by the prefrontal cortex, is very important for goal- directed behavior, lesions in this brain area can
disrupt different aspects of normal cognition, emotion, and behavior and produce an array of problems in real-world situations.
Functional divisions of the prefrontal cortex: Lateral Prefrontal cortex:
dorsal lateral prefrontal cortex (dlPFC) and ventral lateral prefrontal cortex (vlPFC)
Functional divisions of the prefrontal cortex:Medial Prefrontal cortex:
dorsal medial and ventral medial prefrontal cortex (dmPFC and vmPFC).
Working memory: Delayed response tasks, for example, monkey task
food well showed/covered, monkey has to choose where the food is delayed response task, where the monkey has to remember where the food is he has to maintain working memory!
Working memory: DMS task (delay-match-to-sample (DMS) task) - What is it
here 2 choices are shown, and monkey needs to choose the one they saw before/choose the one they did not see they must need to maintain some sort of working memory to experiment, we can change the variables in order to see results(adding variables, show interferences to hurt working memory
the prefrontal cortex has extensive connections with _ by utilizing _
just understand, don't memorize just remember, the prefrontal cortex has extensive connections with almost all other regions! connects with a lot of other lobes with white matter
Research has found that when animals approach a reward, the neural activity in the habenula decreases, but the
midbrain dopamine neurons show increased activity (and vice versa).
Working memory: n-back task
n-back task is more often used for studying human working memory. In this task, , responses are required only when a stimulus matches one shown n trials earlier. The contents of working memory must be manipulated constantly in this task because the target is updated on each trial. something like the card trial, where participants need to say if a card they've been shown was just shown 1 back (1 time ago) or 2 back (2 times ago) We can manipulate the load and delay using different "n" value. again changing the number of times we need to go back
When we are expecting some reward but did not get it, there is a
negative prediction error, dopamine activity will be inhibited (aversive)
When we are expecting some reward and get the expected reward, we have a
no prediction error, no dopamine activity (neutral).
Functional divisions of the prefrontal cortex: Ventral/orbital Prefrontal cortex:
orbital frontal cortex (OFC)
Working memiry test: Delayed match/nonmatch-to-sample task
participants are asked to match sample/which one they have not seen, tested working memory
successful or failed stop trials both produce a strong response in the
right inferior frontal gyrus (vlPFC). In contrast, the vlPFC is silent on go trials. The study also found that in the failed stop trial the primary motor cortex showed strong activity at the beginning of the trial, indicating a strong readiness for a movement, which cannot be inhibited by the signal from the vlPFC. The subthalamic nucleus also plays a role inhibiting movement -indirect pathway is inhibitory! When patients with Parkinson's receive deep brain stimulation to improve their symptom, they start to have deficit in inhibitory control!
Research has revealed different groups of dopamine neurons in the midbrain that respond to either
salience neurons will fure reguardless of the response stimulus valece neurons will fire less when given bad reward and more when given good rewards
Humans have well-developed prefrontal cortex!
some scientists think this prefrontal cortex is what gives us so much cognitive control
ventral is more
stimulus-driven, bottom-up/firing/inhibiting
the vlPFC is more important for inhibiting ____
task-irrelevant information.
It has been found (Feredoes, et al 2011) that stimulating the dlPFC (dorsal) during the delay period of a working memory task led to an increased response in
task-relevant brain areas when distractors were presented during the delay. For example, when we have to focus on face images and ignore house images, if our dlPFC activity is disturbed/stimulated, we can process the faces better and our fusiform face area in the posterior part of the brain may show stronger activation. So, it is likely that the dlPFC is more important for maintaining task relevant information, consistent with its role in supporting working memory.
Representation of value: `Human neuroimaging studies also found the OFC (more of the vmPFC) activation is associated with ___ preference
taste preference, regardless of whether the item was healthy
Mental flexibility
the ability to rapidly switch from one cognitive task to another
The prefrontal cortex usually refers to
the part of the frontal lobe that is anterior to the primary motor (or sometimes premotor) cortex. it is what controls cognitive control!
different factors may affect how we, or other animals, assign values to specific object or event, such as
the payoff itself, the probability, or effort of obtaining it.
Go/Nogo task and error detection - ho can we use it?
they may make a response to the Nogo trials for which they are supposed to withhold their response, or they may withhold a response to a Go trial. WE CAN LOOK AT participants brain responses in response to the mistake We can then analyze brain activity corresponding to the moment participants just made a mistake.
dorsal is more
top down/working memory
3 axises in the prefrontal cortex for organization are
ventral-dorsal, Anterior -posterior, Lateral-medial
vlPFC may become more efficient in helping ______ with tasks.
vlPFC may become more efficient in helping switching between the two tasks.
vlPFC may help to select the ____ based on the stimuli.
vlPFC may help to select the response based on the stimuli.
Working memory: Delayed-match-to-sample or delayed-nonmatch-to-sample task, are often used to test
working memory maintenance.We can manipulate the length of the delay, the load of the task (how many wells), or add interference ...
