lecture 13: cognitive control and the frontal lobes Flashcards
Cognitive Control
mental abilities that involve
planning, controlling, and regulating the flow of information processing
Goal-Oriented Behavior
interacting with the
world in a purposeful manner
Cognitive Control has Wide Ranging Implications: name 2
“Cognitive control underlies our striking technological achievements over an equally striking range of domains, from agriculture and housing to medicine, transportation, communication and large-scale
economies. ”
David Rand & Jonathan Cohen, Behavioral Scientist, 2017
what part of the brain plays a role in cognitive control and goal-oriented behavior
Prefrontal cortex: includes all of the areas in front of the primary and secondary
motor areas. We will focus mainly on lateral PFC.
John Fulton
Performed experiment in which he removed
most of the frontal lobes in two
chimpanzees.
Their behavior changed dramatically –
previously wild/uncontrollable; now calm,
‘tamed’.
Presented results at 1935 World Congress of
Neurology in London.
Egas Moniz
Attended Fulton’s 1935 talk in
London and wondered whether similar
approach might work in human
psychiatric patients.
Severed white matter connections
between frontal lobe and thalamus
(key relay station) in 20 psychiatric
patients, mainly psychotic and severely
depressed. In 1936 paper, reported that
symptoms improved.
Attended Freeman’s 1935 talk in
London and wondered whether similar
approach might work in human
psychiatric patients.
Severed white matter connections
Between prefrontal cortex and thalamus
(key relay station) in 20 psychiatric
patients, mainly psychotic and severely
depressed. In 1936 paper, reported that
symptoms improved.
Apparently not in all cases – was shot
and paralyzed in 1939 by angry patient
who had received frontal lobe operation.
Moniz received Nobel Prize in 1949 for
this discovery.
Walter Freeman
Had attended Fulton’s talk and read
Moniz’s 1936 paper.
Extended and popularized Moniz’s
procedure, called it frontal or transorbital
lobotomy
Came up with a quicker and simpler
method of performing operation:
“ice-pick lobotomy
Frontal Lobotomy
A lobotomy is a type of brain surgery that became popular in the 1930s as a treatment for mental health conditions such as schizophrenia. It involves severing the connection between the frontal lobe and thalamus
Problems with Frontal Lobotomy
Very limited effectiveness: roughly 1/3 improved, 1/3 unchanged, 1/3 got worse
Consistently produced undesirable side effects in patients: “They are described by the nurses and the doctors, over and over, as dull, apathetic, listless,
without drive or initiative, flat, lethargic, placid and
unconcerned, childlike, docile, needing pushing,
passive, lacking in spontaneity, without aim or purpose, preoccupied and dependent.”
Hoffman (1949, New England J. of Medicine)
Began by lobotomizing severely mentally ill patients who were otherwise untreatable, but became more widespread and applied to adults with less severe forms of depression and children with behavior problems (like howard)
working memory
Working memory is a multi-component system which proposes that short-term memory (STM) is a collection of multiple stores which actively process different types of STM includes the central executive, visuospatial sketchpad, phonological loop, and episodic buffer
Dual task test- Baddeley and Hitch (1974) set out to test the hypothesis that the short-term store also functioned as a working memory. They did so by requiring participants to perform reasoning, comprehension or learning tasks at the same time as they were holding in STM between 0 and 8 digits for immediate recall
Lateral PFC Role in Working
Memory
Temporary activation of a limited amount of information over a brief time span; rapidly accessible, frequently updated, & used for higher cognitive processes.
Human delayed response task:
*Intact & scrambled faces presented.
*Try to hold the intact faces in WM across delay.
*Number of intact faces varied across trials.
*After delay, probe presented and participant
decides whether it was in previously presented set.
non lesion monkey delayed response task:
Prefrontal neurons can show sustained activity during delayed- response tasks. Each line represents a single trial. The cue indicated the location of the reward. The monkey was trained to withhold the response until a “Go” signal (arrows) appeared. Each vertical tick represents an action potential. This cell did not
respond during the cue interval. Rather, its activity increased when the cue was turned off.
Prefrontal cortex and long-term recency/source
memory: Evidence from neuropsychology and
neuroimaging
Recency memory is thought to depend on the ability
to segregate and organize information (to a greater extent than simple old/new recognition), and therefore might be affected by prefrontal damage.
Tested in patients with parts of prefrontal cortex removed for relief of epilepsy (lobectomy).
Recency memory
is thought to depend on the ability
to segregate and organize information (to a greater extent than simple old/new recognition), and therefore might be affected by prefrontal damage.
Tested in patients with parts of prefrontal cortex removed for relief of epilepsy (lobectomy).
Recency memory test
Subjects were presented with a series of cards, each one showing a pair of objects. On
test cards, the objects were flanked by question marks, and the subject had to indicate
which object was seen most recently. In the recency test, both objects on the test cards
had been seen previously. In the item recognition test, only one object had appeared
previously
Recency deficits observed only in those patients
with lesions to
dorsolateral prefrontal cortex
Source Memory (aka Source Monitoring
Recalling the source of information or the context in which the information was learned – e.g., a friend, at a party, the Internet, etc.
Patients with prefrontal damage can learn novel or fictitious facts normally, but have great difficulty remembering which of two experimenters told them the facts or even that the information was acquired earlier during the study phase of the experiment
Neuroimaging data have implicated specific PFC regions in cognitive control processes that
are especially important for source memory, such as monitoring and evaluationare especially important for source memory, such as monitoring and evaluation
Studies with monkeys and humans indicate that prefrontal cortex is important for
working memory/delayed response task and that prefrontal neurons show sustained activity across delay
Neuropsychological and neuroimaging studies implicate mainly lateral prefrontal regions in
recency memory and source memory, which
demand cognitive control during retrieval
The Think /No-Think Paradigm
In the classical TNT paradigm participants are instructed to think or not to think of a target item that has previously been associated with a cue. For instance, individuals learn that the words ordeal and roach are associated and are then instructed to recall the target (roach) when exposed to the cue (ordeal). At the same time, for certain cues they are instructed to inhibit memory retrieval of the associated target word by preventing its content from entering consciousness (Anderson and Levy, 2009). Additional targets not presented during the TNT serve as baseline. Results revealed reduced recall for “no-think” targets compared to “think” or “baseline” targets.
what were they trying to prove with the think no think paradigm?
avoiding a Memory Makes it
Harder to Recall
think no think paradigm FMRI Expt: Procedure
In the classical TNT paradigm participants are instructed to think or not to think of a target item that has previously been associated with a cue. For instance, individuals learn that the words ordeal and roach are associated and are then instructed to recall the target (roach) when exposed to the cue (ordeal). At the same time, for certain cues they are instructed to inhibit memory retrieval of the associated target word by preventing its content from entering consciousness (Anderson and Levy, 2009). Additional targets not presented during the TNT serve as baseline. Results revealed reduced recall for “no-think” targets compared to “think” or “baseline” targets.
Memory Impairment is Cue Independent
GABA
Using fMRI and magnetic resonance spectroscopy, Schmitz et al. (2017) showed that a higher resting concentration of GABA in the
hippocampus is associated with greater ability to suppress “no think” items, and with stronger coupling between the hippocampus and
prefrontal cortex during attempted suppressions an inhibitory neurotransmitter.
Patients with PTSD are plagued by intrusive memories of traumatic experiences, which could reflect impaired cognitive control. Can they suppress memories in the think/no-think paradigm?
they seem to have difficulties with suppression
2015 Paris Terrorist Attacks
130 people killed, deadliest peacetime attacks in French history
130 people killed, deadliest peacetime attacks in French history. Mary et al. (2020, Science) used the think/no-think paradigm and fMRI to study 102 people exposed to the attacks, 55 PTSD+ and 47 PTSD-, and 73 people who were not exposed to the attacks.
Types of exposure:
directly targeted; witnessed attack; first responders/police; close relative of deceased victim
Non-exposed: were not in Paris during the attacks
“Inhibitory control models predict that memory suppression will generate more negative coupling between frontally mediated
control processes and memory regions
PTSD- and non-exposed groups showed decreased coupling between control and
memory regions during suppression attempts, whereas the PTSD+ group did not,
and these differences were related to impaired memory suppression in the
PTSD+ group.
Hierarchically ordered executive system
Posterior-to-Posterior-to-
anterior gradient
‘Branching’ equivalent to maintaining
multiple goals over time
Cognitive Control of Goal-Directed Behavior
Attaining complex goals involves multiple component processes that depend on prefrontal cortex
Filtering tasks
Verb generation task (come up with one verb semantically associated to noun) for nouns associated with many actions (high filtering) or few (low
filtering).
Patients with prefrontal lesions are more impaired in the high filtering than low filtering condition, and prefrontal regions in healthy participants show increased activity in high filtering vs. low filtering condition.
Prefrontal Lesions Severely Impair Performance on
Everyday Tasks Requiring Complex Goal-Directed Behavior
(Shallice & Burgess, 1991)
Multiple Errands Task
(Shallice & Burgess, 1991)
explain what the task is and the difference between a healthy patient and one with prefrontal damage
Requires participants to carry out a variety of errands in a real-world environment.
Given list of items to purchase (e.g., loaf of bread), different types of information to collect (e.g, exchange rate for a particular currency), and related types of errands that can be accomplished in everyday (or virtual) setting. Told to spend as little money as possible and take as little time as possible
without ‘undue’ rushing
Not a memory test – patients have the list, have to figure out where to go and how to accomplish tasks.
Frontal Lobotomies
- Performed on psychiatric patients to alleviate symptoms
- Patients became much calmer
Horrible side effects due to problems with cognitive control
and goal directed actions
* Lack of drive or initiative,
* Lethargic
* without aim or purpose
* Etc.
Working memory and the prefrontal cortex
Associative memory task:
Learn the relationship between a picture and food
(no information is kept in mind over the delay)
Details:
Visual cue images on the cards & the location of the food was always associated
with one visual cue. Requires the monkey to just remember which cue image
was associated with a reward
Key Finding:
Lateral prefrontal damage: monkey can still do the task
Working memory and the prefrontal cortex
Monkey experiment: lateral prefrontal cortex is necessary for
working memory
* What happens within lateral prefrontal cortex when
information is maintained?
Presented with a series of faces, asked to hold in mind for
later judgment
* Manipulation: vary the number of faces to hold in mind (vary
WM load)
- Vary the number of faces to hold in mind (vary WM load) to
test which brain regions are involved in WM
Lateral prefrontal cortex is more engaged when holding more items in mind
(=involved in working memory)
Same pattern of results in monkeys:
* Direct recordings from lateral prefrontal cortex: sustained
activity while holding information in mind
testing recency memory
- View a series of pictures over time, then judge which one was
more recent
Frontal damage patients (green) are worse at identifying which
items were seen most recently
Recency deficits observed only in those patients
with lesions to dorsolateral prefrontal cortex
(area 46), either in left or right hemisphere
how to cognitively control goal-directed behavior:
1) Identify goals and subgoals
2) Select relevant and filter out irrelevant
information
3) Link subgoals into a plan of action
4) Switch from one task to another once you
have completed one of the subgoals
** Attaining complex goals depends on
multiple component processes that depend
on the prefrontal cortex!
1) Wisconsin card sorting task
- Assesses switching from one task to another. Specifically, switching rules/policy
halfway through
Patients sort cards based on shape, color or number
* They must figure out the rule and update how they sort the
cards when the rule changes
* Results:
* Patients with lateral PFC damage are impaired and repeat the same
sorting response even when it’s no longer appropriate =
perseveration
2) Filtering tasks
- Select relevant, and filter out irrelevant, information
- Participants sort between competing bits of information
- Participants come up with one verb that is associated with
the presented noun (verb generation task) - (dog – walking, chewing, petting)
- Some nouns are associated with many actions (which
requires high filtering) - E.g. rope
- Some nouns are associated with few actions (which requires
low filtering) - E.g. kite
3) Task switching
- Assesses switching from one task to another
- Approach: Every 2 trials, task goal is cued by color
- Assessment of task switching ability: compare response
times between switch and non-switch trials - ‘switch cost’ = how much slower responses on switch trials are
compared to non-switch trials
Results: Prefrontal patients show greater RT (i.e., greater switching cost!)
only in the color condition because it requires more working memory
