Functions of The Frontal Lobes

• Frontal lobe functions


  Damage to the frontal eye fields does not affect a person's ability to make saccades (reflex saccades are unaffected), but it does affect their ability to produce saccades voluntarily
• Damage to frontal motor areas


  Effects of damage to the supplementary motor area (SMA) and the role of frontal motor areas in initiation and planning of voluntary action
• Supplementary motor area (SMA)


  • There is one SMA in left hemisphere and one in the right
• Unilateral damage to SMA


  • Symptomatology associated with the contralateral upper limb
  • No abnormal experiences of ownership: patient knows that the limb is their own limb
  • No abnormal perceptual/sensory experiences: tactile and kinesthetic sensation and perception are normal
  • Abnormal action execution: limb seems to act autonomously (no intention), performing actions appropriate for the environment
• Anarchic Hand Syndrome


  Unilateral damage to SMA where the movements of one hand are apparently directed towards a goal and are smoothly executed, yet are unintended
• Alien Hand Syndrome


  Unilateral damage to SMA accompanied by delusions of ownership
• Bilateral damage to SMA


  • Symptom called utilization behaviour
  • Spontaneous performance of object-appropriate actions when the person sees an object (regardless of time, context or ownership)
• Unlike Anarchic Hand Syndrome, Utilization Behaviour patients do not experience the behaviour as unwanted or unwilled and often do not realize that it is inappropriate (self-deception?)
• Organization of voluntary action


  • AHS and UB well-learned, voluntary behaviours that are directed at external objects (use-type behaviours) have a kind of reflexive (S-R) structure that is normally regulated by volitional (intentional) processes
  • Voluntary decision to act means releasing a circuit from inhibition
• Given that we can mime and perform actions based on memory (rather than current stimulation), there must also be excitatory connections to the response production circuits
• Learning established the S-R structure in subcortical mechanisms: development of automaticity involved a transfer of command generation from cortical to subcortical circuits, but this has turned out to be an oversimplification
• Frontal cortex


  Volition and cognitive control do require cortical circuits, but acquired automatic behaviour involves both cortical and subcortical circuits
• Case of Phineas Gage


  • Gage worked as a railway excavation crew foreman and was involved in blasting routes for railways
  • His accident occurred in 1848 when he was 25
  • He was using a tamping iron 1.1 metres long and 3.2 cm in diameter when the charge accidently ignited, projecting the iron through his head
• Phineas Gage's injuries


  • Loss of virtually all the prefrontal cortex of the left hemisphere, minor damage to the right probably (but extent unclear)
  • Both the superior region and the inferior regions
• Gage survived for 12 years, but ultimately died from complications arising from the injuries sustained
• Effects of Phineas Gage's injuries


  • His memory and language (comprehension and speech) were preserved
  • His personality was altered - he became fitful, irreverent, indulging at times in the grossest profanity, manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously (holding firm to an opinion or course of action) obstinate (stubborn), yet capricious/ vacillating (fickle, inconstant, ambivalent, irresolute)
• These characteristics stood in stark contrast to what is reported about Gage from before the accident: he was viewed by his employers as a shrewd and smart in business, conscientious and efficient, mild-mannered and highly respected by the men in his crew
• Lobotomy


  • Grey matter not destroyed (allegedly): operation cuts through the fibres of the white matter
  • Severs connections to and from the prefrontal cortex
• Transorbital lobotomy


  A method for performing the lobotomy operation that could be done in the patient's home, developed in Italy and the USA soon after WWII
• What tissue was actually destroyed was difficult to control as the practitioner can't see what's they're doing and all brains are slightly different - some grey matter would be lesioned, how much was impossible to determine at the time
• Given the point of entry, the tool would have penetrated the orbitofrontal cortex, but the extent of the damage produced was uncontrolled and unknowable
• Impairments and psychological effects of lobotomy


  • Significant 'personality' changes: patients typically became withdrawn, inactive, rather docile and compliant
  • Depressed patients reported being less depressed, anxious patients reported feeling less anxious and fearful
  • Excessive or inappropriate emotions were reduced or eliminated - indeed all emotional experience was reduced or eliminated (though not necessarily emotional behaviour)
• Lobotomy was a scandal of epic proportions - it is basically a method that permits control, it doesn't help the patient (yet elements of the medical profession still defend it)
• One of Moniz's lobotomized patients shot him in the spine and he spent the rest of his life in a wheel chair. After Freeman killed one patient too many with the ice-pick during an operation, he lost his medical license (about 5% of his patients died as a result of the procedure - more than 100 people)
• Impairments from frontal damage


  • Ability to control 'impulses' and to control the urge to satisfy desires
  • Ability to plan a course of action to achieve an overall goal
  • Ability to hold information in working memory and retrieve task-relevant information into working memory
  • Ability to maintain concentration when carrying out extended tasks
• Threat, Fear and Emotion


  • Responses to threat and danger: freeze, flight or fight
  • Autonomic responses mediated by the sympathetic branch of the autonomic nervous system
  • Increased heart rate, respiratory rate, sweating, pupil dilation, etc.
  • Hormonal responses controlled by the hypothalamus
• Components of emotional response


  • Skeletomotor component (motor behaviours such as fight or flight responses)
  • Physiological component (autonomic and hormonal responses)
  • Experiential, subjective component or 'feeling'