Transcript M&E and the Frontal Lobes

The Frontal lobes
Executive functions and Impulse
control
MOTIVATION/EMOTION and
the FRONTAL LOBES
Remember that the thalamus projects to both the amygdala
….and to sensory cortex areas.. Where it is eventually processed
by the frontal lobes
The Dual Process theory
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1. sensory event via sense mode pathways to THALAMUS
2. From Thalamus to Amygdala ( fast)
3. from Thalamus to cortex/Frontal lobes (slower)
4. Amygdala triggers “ automatic affective responses
5. Amygdala input to frontal lobes inhibits rational
thought …..And may produce “cognitive bias
• 6. Frontal lobes project to Amygdala and may suppress
affective impulses
The amygdala also projects to the frontal lobes
mainly to the “Prefrontal cortex” …the frontal
cortical areas found anterior to the 2nd and primary
motor areas
The Amygdala also projects to the Anterior
Cingulate cortex (ACC) of the frontal
lobes…(sometimes referred to as the “limbic lobe” )
The frontal lobes also project to
amygdala
EVIDENCE
Cortex Dampens Subcortical Affect
• sham rage—occurs following removal of the cerebral
cortex from experimental animals..
• In Cats:
– lashing of the tail, vigorous arching of the back, clawing and attempts to
– bite, and autonomic responses. It is called sham rage because unlike
– genuine rage ( or predatory aggression)
the rage occurs spontaneously or can be triggered by
mild tactile or other non-noxious stimuli.
Evidence that the frontal lobes
Regulate Subcortical Affective
impulses
• Phineas Gage• Emotional lability
emotional outbursts
• irrationality
(Deficits in emotional
Impusle control)
Prefrontal lobotomy
The effects of this
procedure varied
considerably
Early treatment
Perhaps due to differences in procedure- two
general syndromes associated with frontal
lobotomy (as well as naturally incurred frontal lobe damage)
-Pseudopsychopathy- (indicates loss of regulatory functions)
• Immature impulsive behavior, aggressive outbursts,
Inappropriate jocular affect , Poor judgment and
insight , coarse language, promiscuity, general loss
of social skills, euphoria, Emotional lability,
Distractibility (see Phineas Gage, orbito-frontal cortex; see
fronto-temporal dementia )
Pseudodepression – (loss of M&E influences of PFC)
– Apathy, indifference, loss of initiative, loss of
libido (see ventromedial ACC)
Confabulation
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Patients with severe frontal lobe lesions tend to fabricate quick, impulsive answers
to questions. Some responses may be quite fanciful and imaginative. The patient
cannot inhibit a response in order to check its validity. This tendency to fabricate an
answer is called confabulation.
• Confabulation and Reduplication Syndrome
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Patients with severe frontal lobe lesions tend to fabricate quick, impulsive answers
to questions. Some responses may be quite fanciful and imaginative. The patient
cannot inhibit a response in order to check its validity. For example, when asked,
"How did you get to the hospital?", the patient may respond with an imaginative
tale that has very little relationship to the truth. This tendency to fabricate an answer
is called confabulation. It is most common among patients with basal forebrain
lesions and among patients with additional impairment of memory ability.
Another syndrome that is similar to confabulation is reduplication. Here, the patient
with a frontal lobe lesion confabulates that the current environment, usually the
hospital, is actually another place that is similar to the current setting but has a
different name and location. The patient may even claim that the current hospital is
a university dormitory or an apartment building. The confabulated place is always
somewhere else and it is usually familiar to the patient, such as the hospital in the
patient's home town. The patient will often maintain this confabulation even when
confronted with salient, contradictory information.
Frontal Lobe Damage- Misc..
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Frontal lobe stroke
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Frontotemporal dementia
Frontal lobe
Seizures
Seizures 2
 A seizure is usually defined as a sudden alteration of behavior due to a temporary change in the
electrical functioning of the brain, in particular the outside rim of the brain called the cortex. Below
you will find some of the symptoms people with epilepsy may experience before, during and after a
seizure. Seizures can take on many different forms and seizures affect different people in different
ways. It is not implied that every person with seizures will experience every symptom described
below.
 Seizures have a beginning, middle, and end
 When an individual is aware of the beginning, it may be thought of as a warning or aura. On the other
hand, an individual may not be aware of the beginning and therefore have no warning.
 Sometimes, the warning or aura is not followed by any other symptoms. It may be considered a
simple partial seizure by the doctor.
 The middle of the seizure may take several different forms. For people who have warnings, the aura
may simply continue or it may turn into a complex partial seizure or a convulsion. For those who do
not have a warning, the seizure may continue as a complex partial seizure or it may evolve into a
convulsion.
 The end to a seizure represents a transition from the seizure back to the individual’s normal state.
This period is referred to as the “post-ictal period” (an ictus is a seizure) and signifies the recovery
period for the brain. It may last from seconds to minutes to hours, depending on several factors
including which part(s) of the brain were affected by the seizure and whether the individual was on
anti-seizure medication. If a person has a complex partial seizure or a convulsion, their level of
awareness gradually improves during the post-ictal period, much like a person waking up from
anesthesia after an operation. There are other symptoms that occur during the post-ictal period and are
detailed below.
Frontal Lobe Syndromes
Frontal lobe epileptic seizures
• likely to involve brief episodes of screaming,
bicycling movements, or even movements
suggestive of sexual activity.
FL epilepsy inter-ictal characteristics
• hebephrenic characteristics (i.e. emotional
withdrawal and blunted effect).
Executive effects of Frontal Lobe
Damage
-difficulty formulating common rules and goals.
if a rule or goal is given to the patient there is great difficulty in using it to
guide behavior. ..perhaps related to social motivations/perseveration
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Actions are motivated by immediate
impulses…
gratification of simple
Relates to circumstantiality
• dissociation between the discriminative and affective
aspects of pain. When stuck with a pin, such a patient reports that it hurts, but
it doesn't bother him.
“Executive Functions”
particularly affected by damage to dorsal parts of the ACC
EXECUTIVE FUNCTIONS
Frontal Lobes and Emotion
The Anterior Cingulate Cortex (esp
ventromedial) may be critical in frontal
generation of emotion
The Anterior Cingulate
Frontal Lobes and Emotion- The Anterior
Cingulate Cortex
• neuroimaging studies have implicated the. the dorsal ACC has been considered
critical for cognitive and motor control (Posner and DiGirolamo, 1998 ).
-whereas the the ventral ACC has been implicated intransient mood changes (Mayberg et al., 1999 ).
depression and anxiety disorders (Mayberg et al., 2000 ; Brody et al., 2001 )
perception of pain (Rainville et al., 1997 ).
• lesion of the ventral ACC - patients have been described as apathetic and
unconcerned when significant events occur, such as making mistakes
(Eslinger and Damasio, 1985 ; Rylander, 1947 ).
Ventromedial frontal cortex
lesion of the ventral ACC
• - patients described as apathetic and
unconcerned when significant events
occur, such as making mistakes (Eslinger
and Damasio, 1985 ; Rylander, 1947 )…like
pseudodepression
ACC- and Self-reflection
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Moran et. al.
subjects judged the personal relevance of personality characteristics that were
either favorable (e.g., "honest") or unfavorable (e.g., "lazy"), they
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found
that distinct neural circuits in adjacent regions of the
prefrontal cortex subserve cognitive and emotional
aspects of self-reflection.
When material is judged to be self-relevant, the emotional valence of
the material was associated with activity in the ventral
anterior cingulate.
The Frontal Poles
(OrbitoFrontal cortex)
The Frontal Poles/ORIBITO-FRONTAL CORTEX
The frontopolar cortex (FPC), the most anterior part of the frontal lobes,
The FPC
long-term mental plans
Generation of new, possibly more rewarding, behavioral or cognitive
sequences.
These areas have interconnections with the amygdala and hypothalamus.
The Frontal Poles/ORIBITO-FRONTAL CORTEX
counterfactual processing/ Regret?
Counterfactual processing -The consequence of a decision/behavior can lead
to feelings such as: satisfaction, relief, or regret… evaluation of the potential
outcomes of alternative decisions.
Testing the role of the orbito-frontal cortex in counterfactual reactionsa simple gambling task was used- subject’s choices were categorized in terms
of their anticipated and actual emotional impact.
Normal subjects reported emotional responses consistent with counterfactual thinking;
they chose to minimize future regret and learned from their emotional experience. (also
associated with increased activity in the orbito-frontal regions)
Patients with orbitofrontal
cortical lesions, however, did not
report regret or anticipate negative consequences of their choices.
Damage to the orbito-frontal cortex?
May partially account for the pseudopsychopathic syndrome
• “Like pseudopsychopathy”-Emotional disturbance most
often results from lesion of the orbital frontal areas.
• superficial emotional expression like laughing, crying etc
in situations inappropriate to the emotion. The patient
usually has no awareness that their emotional response is
incorrect or extreme.
VON ECONOMO NEURONS
When we interact with another person we create a mental model of how that persons thinks and
feels. We are likely to have initial, quick intuitions about the person, which are then followed by
slower, more reasoned judgments.
Both intuition and deliberation are influenced
by emotional value judgments.
Von Economo neurons (VENs) are a recently evolved cell type which may be involved in the fast
intuitive assessment of complex situations.
We propose that the VENs relay an output of
fronto-insular and anterior cingulate cortex to the parts of frontal and temporal cortex associated
with deliberative judgments. The VENs emerge mainly after birth and increase in number until
age 4 yrs.
VENs
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ACC are activated when subjects view an image of a loved one compared with that of an
acquaintance, suggesting that there might be an involvement of these structures in bonding
[15].
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areas are also active when subjects experience guilt, embarrassment and engage in deception
[26–28].
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ACC are also active in humor (Watson and Allman,unpublished fMRI data),
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trust, empathy, and the discrimination
of the mental states of others [25,29,30].
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VENs probably serve to relay output of the processing within ACC
to other brain structures.
Other interesting links to frontal
lobe functions
• Cotard’s syndrome
• Mirror Neurons
DRUG CRAVING
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An important factor that contributes to drug-seeking in addicted individuals
is the dopamine input pathways that arise from midbrain structures such as
the VTA
• Dopamine and the frontal lobes
Amygdala and the frontal lobes
• Amygdala stimulation can have a direct effect on personality including
increasing social withdrawl and defensiveness (Cain, 1992) as well as
increasing sensitivity to dopamine. PTSD
• These amygdala dopamine neurons project to frontal lobes and are
believed to play an inhibitory role on neocortical information processing
(Stevens, 1992), which in turn is important in selective attention.
• The limbic/emotional brain generally refers to amygdala, hippocampal
formation, hypothalamus, thalamus, and nearby “paralimbic” cortex, such
as the anterior cingulate cortex, orbitofrontal cortex insula, and temporal
poles
• Given the role of aberrant, intrusive, emotional memory in PTSD
symptomatology, the limbic brain defines an obvious target of
investigation; however, evidence linking these structures to specific PTSD
symptoms is just emerging.
PTSD Brain Activity
Frontal lobes and Pain
• There is the well-known suppression of pain sensations that occurs as
an everyday event, but is more prominent during military battles. A
person may be wounded seriously and not be aware of it, or he may
suppress being aware of it during concentration on some other activity.
Whether this sort of suppression is of cerebral cortical origin is
unknown, but it could be.
• prefrontal lobotomy or lobectomy, results in a dissociation between
the discriminative and affective aspects of pain. When stuck with a pin,
such a patient reports that it hurts, but it doesn't bother him.
FRONTAL CORTEX
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Empirical studies suggests that broadly speaking,
preferences, drives and choices are respectively processed in the ventral,
medial and lateral sector of the frontal lobes [1].