Frontal Lobes

Primary Motor Cortex (M1)

• controls movement force and direction

• Cells project to subcortical motor structures

  • Basal ganglia, red nucleus, spinal cord, etc.

Premotor cortex

• areas 6, 8, and 44

• Influences movements directly through corticospinal projections or indirectly to M1

• divides into dorsal, ventral and inferior frontal gyrus (Broca’s area)

Dorsal premotor cortex (PMd)

• areas 6 and 8

• Receives projections from parietal regions 5, 7, 40, 43

• Receives projections from DLPFC

Ventral premotor cortex (PMv)

• inferior area 6

• Contains mirror neurons

• Receives projections from DLPFC

Prefrontal cortex divisions

• dorsolateral prefrontal cortex

• Orbitofrontal cortex

• Ventromedial prefrontal cortex

• Anterior cingulate cortex

Dorsolateral prefrontal cortex (DLPFC)

• reciprocal connections with the posterior parietal areas and STS

• Connections also project to

  • Cingulate cortex, basal ganglia, superior colliculus

Orbitofrontal cortex (OFC)

• Main afferent from temporal lobe

  • STS, visual regions of inferotemporal cortex, subcortical amygdala

• Inputs from amygdala, S2, gustatory cortex in insula

• Projects to amygdala and hypothalamus

Ventromedial prefrontal cortex

• broadmann’s 11 and 13

• Receives cortical connections from the DLPFC, cingulate cortex and medial temporal cortex

• Projects to amygdala, hypothalamus and periaqueductal gray

• Links with emotional behaviour

Anterior cingulate cortex

Bidirectional connections with motor, premotor, prefrontal cortex and insula

Functions of Premotor cortex

• selects movements to be executed

• Choose behaviour in response to external cues

• Controls cognitive processes so that appropriate movements are selected at the correct time

Internal cues

• temporal memory (working memory)

• Memory for what has just happened (DLPFC)

External cues

• feedback about rewarding properties of stimuli

• Orbital frontal cortex- learning by association

• Injuries cause difficulty inhibiting behaviour directed to external stimuli

Context cues

• behaviour is context dependent

• Orbitofrontal area for social interactions

  • People with lesions make social gaffes

Autonoetic awareness

• self knowledge

• Binds together the awareness of oneself as a continuous entity through time

• Impairment causes deficit in self regulation

Connectome

• comprehensive map of structural connections of the nervous sytem

• Eg. Default and Salience networks

Default network

active while participants are resting, also when thinking of one’s past, future or mind wandering

Salience network

• most active when a behavioural change is needed

• Correlated activity in the ACC, supplemental motor cortex and anterior insula

Crystallized intelligence

• general knowledge

• Vocabulary

• Ability to reason using words and numbers

Fluid intelligence

• reason and solve novel problems

• Independent of any knowledge from the past

• Activation in DLPFC and medial PFC

Theory of frontal lobe function

• able to plan and select relevant activities

• Selective attention

• Memory of what you have already done

• Responds to internal, external and context cues

Symptoms of frontal lobe lesions

• Disturbances of motor function

• Disturbances of olfactory processing

• Different thinking

• Loss of behavioural spontaneity

Disturbances of motor function

• loss of ability for fine movements, speed and strength

• Loss of movement programming

• Changes in voluntary gaze

• Speech problems

Disturbances of olfactory processing

Impairments in discriminating between different odours although the ability to detect odours is still intact

Loss of behavioural spontaneity

• decreased verbal fluency and loss of spontaneous speech

• Decreased design fluency to right orbitofrontal lesion

• Impaired strategy formation

Environmental control of behaviour

• Orbitofrontal damage causes patients to take more risks

• Loss of self regulation

• Unable to associate hand posture with colour

Symptoms of frontal lobe lesions

• temporal memory

• Spatial deficits

• Impaired social and sexual behaviour

Temporal memory

• memory of what just happened, where and when

• Impaired in tasks related to such judgements

Spatial deficits

DLPFC damage impairs short term memory for the location of events and selections of behaviour with respect to location

Pseudodepression

• lesions of the left frontal lobe

• Outward apathy, indifference, loss of initiative

• Reduced sexual interest, no verbal output

Pseudopsychopathy

• lesions of the right frontal lobe

• Immature behaviour, lack of tact and restraint

• Promiscuous sexual behaviour

• Lack of social graces

Phineas Gage

• tamping iron passes through his brain and survived

• Damage to left medial prefrontal cortex

• He swore, bad temper and inappropriate behaviour

Disorders affecting frontal lobe

• schizophrenia

• Parkinson’s

• Korsakoff’s syndrome

Tower of Hanoi and Tower of London

• test planning function

• Damage to left or right prefrontal cortex impairs performance

Asymmetry of frontal Lobe function

• left hemisphere for language and encoding memories

• Right hemisphere for non verbal movements, facial expression and retrieving memories