Lecture 18 - Higher function 2: Regulation of behaviour by the prefrontal cortex Flashcards
Prefontal cortex
Major difference between higher primates which includes humans and other animals
Largest in humans
Prefrontal cortex has subtle roles in
Subtle roles in
Working memory
Region we are actively behaving in due to the information in it being current
Planning, judgement
Including interpersonal relationships
Behavioural regulation
Emotional regulation
Phineas Gage
Phineas Gage: Accidental prefrontal lobotomy, Vermont,1848.
Subtle changes in personality: “Gage was no longer Gage” - his whole nature as a human had been changed
Before: competent, responsible, prudent, popular
After: fitful, irreverent, profane, vagrant
Who gave rise to the main functions of the prefrontal cortex?
Phineas Gage
Functions of the prefrontal cortex
Personality
Executive functions:
Planning
Moral judgement
Emotional control
Prefrontal lobotomy
“Therapeutic” prefrontal lobotomy
Rapid “outpatient” procedure
Cut fibres connecting PFC with rest of brain (disrupt the prefrontal cortex)
Became a treatment craze in the 1940’s
Used to reduce violent, antisocial, agitated, and just “troublesome” behaviour, as well as depression
Little evidence for any benefit overall Many bad side effects on personality and emotional life
Declarative memory
Memory for things that can be described in words
Episodic (snapshots of life events, experiences). Allows imagining the future.
Semantic (words and their meanings, people, faces, things, concepts – in categories)
Declarative memory STM to LTM
STM - Hippocampus and other temporal lobe structures
to
LTM - many areas of the association cortex
Procedural memory
Memory for how to do things
Widely stored in regions of the brain that are involved in doing what we just had to do)
In the long term it is stored in parts of the brain involved in motor control
Procedural memory STM to LTM
STM - widely distributed
to
LTM - basal nuclei, cerebellum, premotor cortex
Consolidation
transition from STM to LTM
Short term memory also called
working memory
Short term memory
Continued activity in brain circuits. If activity is interrupted, memory is lost.
Does not involve long term changes in synapse etc.
Long term memory
More permanent changes in brain function &/or structure
Probably involves long term changes in strength of specific synapses (“long term potentiation”, LTP)
(LTP) Requires the post synaptic cell to be generating action potential for there to be Ca2+ entry in the presynaptic terminal for there to be some coincidence/close matching in time which involved Ca2+ post synaptic entry through NMDA receptors s it is the strengthening of the synapse that is the consequence of the calcium that enters during repeated activity
LTM and long term potentiation
Probably involves long term changes in strength of specific synapses (“long term potentiation”, LTP)
(LTP) Requires the post synaptic cell to be generating action potential for there to be Ca2+ entry in the presynaptic terminal for there to be some coincidence/close matching in time which involved Ca2+ post synaptic entry through NMDA receptors s it is the strengthening of the synapse that is the consequence of the calcium that enters during repeated activity
Where are the memories stored in the brain?
no single memory storage area
Memories are distributed among brain areas involved in processing the information
Transfer of working to LTM is enhanced by
High emotional impact
High can enhance it
Importance for survival (one-trial learning can occur)
Repetition (recency important)
Primacy effect
Processing, forming new combinations, linkage to existing knowledge
If you can make network of ideas and associate them together then paint a bigger picture for yourself then by making these lints in the memory then all of these memories collectively become much more effective and more likely to be retained long term
Involves hippocampus
Damage reduces ability to form new memories
Consolidation involves the hippocampus
Clive Wearing
Had to be in care
Life was stalled as he could not remember anything due to hippocampus damage
Hippocampus plays a role in
memory
H.M.
Unable to form any new declarative memories from now on
Anterograde amnesia: Unable to form new declarative memory.
Memory of prior events intact (No/more limited retrograde amnesia)
HM’s procedural memory also intact.
Language
Involves both word knowledge (vocabulary) and structure knowledge (grammar)
Language functions concentrated in left hemisphere in 90% of people, including left- handers
Main areas identified by problems commonly suffered by stroke patients
Language areas of the brain
Broca’s area = Involved in “constructing” language Most obvious in output (fluency)
Assembling sentences that mean something
Unilateral in most people… does only one side of the brain speak?
Wernicke’s area= Involved in processing language “meaning”… Both input & output (comprehension)
Undestanding what we hear and speaking in a comprehensive way
Language areas of the brain - ______ in most people
unilateral
Broca’s area
frontal lobe
Broca’s area = Involved in “constructing” language Most obvious in output (fluency)
Assembling sentences that mean something
Wernicke’s area
Temporal lobe
Wernicke’s area= Involved in processing language “meaning”… Both input & output (comprehension)
Undestanding what we hear and speaking in a comprehensive way
Corpus callosum
joints the two halves of the brain
Interconnecting fibres between the two hemispheres, dense white matter fibre band
In some cases of very extreme and untreatable epilepsy particularly in childhood then the seizure may originate in one side of the brain which is damaged/poorly developed in some way and then spread to the other side and in extreme cases the side of the brain that is generating the seizure is generally irretrievable and so its functionality is not there so the solution in some patients is to just cut the corpus callosum which prevents the seizures from brain propagated through the brain
If shown in the RVF (left hemisphere) can say what it is, if show in the LVF of split brain patient then they can identify images of the same object but not say what the object is
Left brain
Analytical
Verbal
Right brain
Intuitive
Involved in how things feel, to do with the nature of things
Space perception (maps)
Music
Primitive language ability, but gives context
More in a poetic way than a grammatical way as in it is about the deeper meaning of language
Split brain - two minds?
Patients appear entirely normal, report no odd experience
If you ask a person if they feel any differently after surgery then they say they do not feel any differently but this is because only one hand of the brain can speak and it is not aware that it is missing all this subconscious input that would normally be getting and feeding into the broader network that would be driving their behaviour
Conflict plays out in patients brain and this disconnection results in 2 independently but fully functioning personalities
There are uncrossed and crossed pathways deeper in the brainstem that are still intact so can still coordinate bipedal movement because the corpus callosum is not necessarily depriving one side of the brain from any access of spinal motor circuits on the other side
