Frontal Lobes Flashcards
Statistics of the frontal lobes
- 1/3 of the brain
- 20% of the brain’s oxygen
Frontal lobe maturation
Development comes in bursts all the way into one’s 20s. Due to the lateness of the development, the loves are individualised and specialised - environment influences development
Why are the frontal lobes historically considered silent?
Damage to the frontal lobes doesn’t present in an obvious way, the way that damage to other areas does. Speech, motor functions etc. remain intact.
What did Walter Freeman do in 1936?
Performed the first lobotomy
Define lobotomy
Psychosurgical procedure: severe the PFC and underlying structures, or destroy frontal cortical tissue.
Motivation for a lobotomy
It uncoupled the brain’s emotional centres from the seat of the intellect
Clinical reasoning behind silence of the lobes
The everyday behaviour was in tact. Namely, memory and intelligence. By this reasoning, FL lesions are asymptomatic
Changed view on the role of frontal lobes
With the advancing of testing tools, we can see that lesions:
- disrupt normal cognition
- produce a number of severe problems
Phineas Gage’s role
He was the first evidence that damage may be problematic, his personality changed and he became inappropriate in his behaviour
Modern understanding of frontal lobes
They act as conductors, guiding, directing, integrating and monitoring goal-directed behaviour
Interconnectedness of the frontal lobes
They are vastly interconnected, within and between hemispheres, as well as maintaining reciprocal connections across the brain. Consequently, frontal lobe deficits effects cross domains
Why do we take the syndrome approach to frontal lobe damage?
It’s a complex region, focusing on executive functions is difficult. It’s easy to look at certain regularities of frontal lobe pathology.
Two distinct anatomical and functional systems of the frontal lobes
- Dorsolateral
2. Ventral mesial (orbitofrontal/basal/medial)
Two sections of the ventral mesial system
- Ventral/orbitofrontal regions
2. Medial regions, including the anterior cingulate
Five parallel frontal-subcortical circuits
- Skeletomotor
- Oculomotor
- Orbitofrontal region
- Dorsolateral PF region
- Anterior cingulate
Neurological structure of the circuits
They all project from the frontal lobes to the basal ganglia, it’s a reciprocal projection. Each circuit returns via a specific thalamus nucleus
The three circuits most often implicated in neuropsychological and neuropsychiatric disorders
- Dorsolateral PF circuit: executive dysfunction
- Orbitofrontal circuit: personality change
- Anterior cingulate circuit: apathy
Primary functions of the dorsolateral prefrontal circuit
- provision of structure and strategy for problem solving
- cognitive flexibility
Damage to the DLPFC
Disordered thinking and executive functions
Effects of disordered thinking
- patients appear dull and concrete
- pseudo-depression
- difficulty with anticipation or planning
- difficulty focusing and sustaining attention and generating hypotheses
- difficulty with maintaining and shifting in task demands
- problems with abstraction, complexity and problem-solving
- generativity problems
Other words for the orbitofrontal circuit
Ventral-mesial (includes the anterior cingulate) or basal
Important functions of the orbitofrontal circuit (3)
- mediation of emotional and social responses
- significant anatomic correlates with sensory and limbic regions
- inhibition processes specific to emotional and social behaviour
Result of damage to the orbitofrontal circuit
Behavioural disinhibition and prominent emotional lability (exaggerated changes in mood)
Symptoms of damage to the orbitofrontal circuit (6)
- Lack of judgement and social tact
- Inappropriate jocularity (playfulness etc.)
- Decreased impulse inhibition (sexual remarks, gestures etc.)
- Irritable, quickly angered, little remorse
- Distracted
- Increased motor activity
Environmental dependency syndrome (cause and symptom)
- large/bilateral lesions
- action is emitted without voluntary intent, due to lack of inhibition.
- external stimuli directly trigger thought or action
Stereotypical behaviour in OFC damage
- echopraxia
- utilisation behaviour (inability to inhibit a response to an object or environment)
- over elaborated speech
What does the anterior cingulate consist of and what does it do?
- large neural substrate with widely distributed interconnections, both cortical and subcortical
- cognitive and motivational processing
- supports overlapping functions
- volitional movement
- initiation of behaviour (suppressing inappropriate and initiating appropriate)
Bilateral damage to the anterior cingulate region
- Akinetic mutism
2. Abulia
Commentary on the most important role of the frontal lobes
Affective responsiveness, social and moral development and higher order conscious states, like self awareness and theory of mind. It makes us human.
The four developmentally sensitive executive functioning domains
- Attention controls
- Information processing
- Cognitive flexibility
- Goal setting
Attention controls
Selective and sustained attention, inhibitory control, mo itorong of executed plans
Information processing
Fluency, efficiency and speed of output
Cognitive flexibility
Set shifting, developing alternative strategies, dividing attention
Goal setting
Planning, organising, strategic problem-solving
Difference between damage to the PFC and the rest of the brain
It escalates, the problems worsen with development, there’s little hope for recovery and effects can be delayed
Prominent deficits of damage to PFC (4)
- Problem solving and reduced planning
- Inappropriate social skills
- Lack of empathy and remorse
- Poor self awareness
Early PFC damage in three regions
- Dorsolateral: visuospatial and attentional deficits
- Mesial frontal: loss of initiation and motivation
- Ventral: deficits in self regulation, emotions and executive function
EF of empathy
Cognitive flexibility
EF of identity formation
Impulse control, integration of feedback, info synthesis and self monitoring
EF of moral maturity
Symbolic thinking, considering possibilities, anticipation, cost benefit analysis
EF of vocational maturity
Planning, timing, decision making and goal orientation
