PY2507.6 ~ {The Frontal lobe syndrome + Agnosia & Amnesia}
neuro-anatomy of frontal lobes
FL comprise about 20/30% of cerebral cortex in humans
separated from PL by sentral sulcus and from TL by sylvian fissure
what do our frontal lobes include
motor cortex - gyrus in front of central sulcus
premotor cortex - which is immediately in front of motor cortex
prefontal cortex - all remaining cortex
motor cortex
primary motor area - involved in execution of movement and damage results in paralysis
premotor cortex
plays a crucial role in selection & direction of motor sequences - damage results in apraxia [incl Brocas area damage results in speech apraxia]
prefrontal cortex
more abstract functions in directing / controlling behaviour [EFs] has extensive, reciprocal connections with all other cortical and subcortical areas [either directly or within a few synapses]
diff areas of prefrontal cortex
dorsolateral [connections with posterior cortical areas & striatal system] + rostral/orbital + superior-medial [icl anterior cingulate, connections with other prefrontal areas & strital system] + ventro-medial [connections with limbic system]
evolution of FL
present in all mammalian species are particularly developed in primates - relative size of FL as a % of tot brain is not diff across great apes (Semedeferi et al., 2002) + relative proportion of grey & white matter are proportional across non-human primates (Schonemann et al, 2005)
sources of damage to FL
tumor, penetrating head injury, stroke, alzheimer's disease, closed head injury, systemic damage to neural circuitry involving FL [Schizophrenia, Parkinson; fronto-temporal dementias]
executive functions
mental skills needed to plan and carry out complex tasks - like the manager of your brain - help us stay organized, make decisions
dysexecutive syndrome
aka FL syndrome - someone has trouble with executive functions - occurs when brains FL are damaged - so person has difficulty with planning, decision making & complex tasks
who came up with tersm FL syndrome and dysexecutive syndrome
fls - russian neuropsychologist, Alexander Luria popularized the term relating it to difficulties with abstract thinking, prob solving and control [also introduced term executive functions
ds - Alan Baddely 1988
what broader skills are involved in executive funtions
planning + abstract reasoning + organization / coordination + inhibition + shifting [flexibility] + working memory updating [monitoring]
key skills for excuting complex tasks
planning & organization [set goals, prioritize, sequence]
flexibility [adapt to changes, shift focus]
task management [monitor multiple tasks, inhibit distractions]
social & emotional control [manage emotions and interpersonal behaviours]
FL & EF - unity
all EF are part of unified system that works toward same goal, so diff sub-functions can still be identified but they all work together to help make decisons Friedman & Miyake 2017
FL & EF - diversity
FL is large and diverse so diff parts of it control diff functions and EF don't always work the same way in diff people
stuss and collegues and their 3 separate functions of FL
EF proper - monitoring, metacog - managed by dorsolateral area + energizing - managed by superior lateral area [helps you stay motivated] + emotional/behavioural regulation - managed by ventrolateral area [helps you control emotions & behaviours]
dorsolateral prefrontal cortex function
area responsible for ef [brain's executive manager] - involved in inhibition, shifting, working memory - has strong links with posterior brain regions and basal ganglia - damage to this area leads to dysexecutive syndrome
rostral prefrontal/ orbital cortex possible roles
meta-cognition [thinking about thinking] + integration & organization [bringing diff types of info tg in coherent way] - area is tightly connected to other prefrontal areas helping coord higher level thinking & emotional regulation - associated with dysexecutive syndrome
according to Stuss & Alexander, 2007 what are the hemispheric differences of the dorsolateral prefrontal cortex
r = involved in monitoring perfomance, error detection
l = more involved in setting tasks/goals
superior-medial [which includes anterior cingulate] function
energising, involved in motivation, sustained attention & decision making - damage to the area results in apathetic syndrome - has connections with other prefrontal areas & striatal system
what happens when superior-medial is damaged
slower response speed, poor verbal fluency, not responding well to warning signals, underestimating quantities [Stuss 2011]
ventro medial function
monitioring, imulse /emotion control, behavioural control of socially appropriate behaviour , sensitivity to reward and punishment [disinhibited syndrome]
personality changes in frontal lobe patients [esp vmPFC]
leads to marked personality changes - pseudo-depression [after left frontal lesions] + pseudo-psychopathy [after right frontal lesions]
pseudo-depression symptoms
looks like clinical depression but isn't caused by a mood disorder. - apathy + indiff to surroundings + lack of emotional expression + low sexual interest + minimal speech
pseudo-psychopathy symptoms
resembles psychopathic or antisoccial behaviour but stems from brain damage - Phineas Gage - immature, inappropriate behaviour + poor impulse control & judgement + socially inapproriate or offensive remarks + promiscuous sexual behaviour + increased physical activity + lack of social awareness or remorse
how are frontal lobes special for EFs
they [FL] mediate goal oriented behaviour vs automatic processing + supervisory attentional system + not site of specific capacities contribute to intellectual capacity & operate in context of integrated networks
lesion in frontal lobes and behavioural symptoms
deficits in control + deficits in abstract and conceptual thinking + deficits in temporal sequencing [remembering the order of events]
psychological inertia [deficits in control of action]
patients poor at starting an action or behaviour but once engaged in it they have great difficulties shifting or stopping it - tendency to repeat the same action is often referred to as perserveration
inertia
tendecy for a body in motion [or rest] to stay in motion [or rest] unless acted on by an outside force
what does psych inertia lead to
difficulty breaking established associations [lack of flexibility] + prob in stopping everyday actions + prob in clinical tests [verbal fluency + Wisconsin Card Sorting test]
why does psych inertia disrupt goal-oriented behaviour
lack of flexibility + difficulties in response to novelty
enviro dependency syndrome
lesion in FL causes behaviour to be controlled by the sensory stimuli present in enviro [rather than goals or social expectations]
enviro dependency syndrome symptoms
distractibility + utilization behaviour + impulsivity / imitative behaviour
what does enviro ds lead to
disrupts goal-oriented behaviour becuase carrying out sideline tasks disrupts completion of target tasks - difficulty inhibiting inappropriate responses + probs in everyday life [stopping habitual but unwanted behaviours] + probs in clinical tests [stroop test]
why do deficits in abstract thinking & cog monitoring disrupt goal-oriented behaviour
difficulties formulating plans and strategies + difficulties evaluating when success is reached
why do probs of sequencing disrupt goal-oriented behaviour disrupt goal-oriented behaviour
difficulties in assessing order in which tasks must be carried out + difficulties keeping track of where one is in a sequence of actions [what has been done and what needs doing]
what tests can be used to assess executive functions
Winconsing Card Sorting Test + Verbal fluency + Stroop task + Trial making task + Cog Estimation test
batteries testing EF
Delis-Kapan Executive Function System [D-KEFS; Delis, Kaplan and Cramer, 2001] = trial making test + verbal fluency test + design fluency test, colour-word inference test + sorting test + 20 questions test + word context test, proverb test, tower test
ecological tests of EF
Six Element Test [hospital] + Multiple Errands test [shopping center] + Cooking tasks
amnesia
generalised memory loss that involves either storing or retrieving info
2 types of amnesia
retrograde = retriving is deficit
anterograde = encoding & storage is deificit
point of damage for amnesias
r = extends froma few hours to a few days before damage
a = can resolve after a few days or weeks or be permanent depending on severit of damage
causes of amnesia
head trauma + electroconvulsive therapy + alcoholism-thiamine deficiency [mainly encoding deficit for these 3] + carbon-monoxide poisoning + herpes simplex encephalitis + degenerative brain diseases
the diencephalon [thalamus]
d= made up of smaller parts, extends from brain stem to cerebrum and surrounds third ventricle, a relay station for all sensory info[besides smell], 4/5 made up by thalamus[paired oval masses of grey matter containing nuclei] allowing crude perceptions [other parts = hypothalamus, epithalamus and subthalamus]
hippocampus
horeshoe shaped sheet of neurons located within temporal lobes & adjacent too amygdala - strongly implicated in consolidation and retrieval of memories
behavioural defining symptoms of amnesia
not representation-specific [in contrast with cortical impairments] + involve storage of info [in contrast with STM deficits that involve what is simultaneously in our consciousness
what are the brain regions involved in amnesia vs STM deficits
a - involves subcortical structures [diencephalon & hippocampal system]
stm - involve specific cortical regions depending on type of memory affected
depending on type of memory affected which cortical regions involved in stm deficits
phonological = left temporo-parietal
lexical-semantic = left fronto-teporal
visuo-spatial = right temporo-parietal
how do amnesia and stm deficits differ in type of memeory affected
a = affects ltm, ability to form new memories anterograde amnesia
stm = affect stm, working memory, specific to a type of representation [like verbal or spatial info]
are the deficits pervasive or specific in amnesia vs stm impairment
a = pervasive - impacts memory broadly, across many types of content + stm = specific - only affect certain modalities [verbal, semantic, spatial] depending on location of brain damage
what are the real world consequences of amnesia vs stm deificits
a - very debilitating, severely limits the ability to learn new info navigate daily life or form personal continuity
stm - more limited in impact, though they can still impair specific functions like remembering instructions, tracking conversations, or spatial navigation, depending on type
example of an amnesic patient [patient HM] (Scoville & Milner, 1957)
in his mid 20s underwent bilateral resection of medial portions of TL, with partial removal of hippocause & amygdala on each side = profound anterograde amnesia [retro am a few years before surgery] -
patient HM characteristics & symptoms
normal though processes = can carry convo, play a game, solve puzzel + normal stm + difficulties with episodic memeory & semantic memory [couldn't acquiew new words, facts, faces, routes, political & geo info] + difficulties in carrying out complex behaviour & social interactions
what LTM function is spared in amnesia
non-declarative [implicit] memory types like skill learning and priming are often preserved
what are examples of skill learning tasks that amnesic patients can still perform?
motor pursuit task + mirror drawing or mirror reading + puzzle solving (e.g., Tower of Hanoi) + learning to play new piano pieces
what is priming and how is it affected by amnesia
p = unconscious memory effect where previous exposure to a stimulus improves performance later, often preserved in amnesia
what is paired and impaired in amnesia
amnesia impairs declarative memory (facts and events) due to damage to hippocampus/medial TL, but non-declarative memory (skills, priming, conditioning) is spared because it relies on other brain systems like the basal ganglia, cerebellum, and neocortex
declarative vs procedural memory
d = facts, specific items, conscious recall, depends on hippocampus, impaired in amnesia
p = skills and habits, unconscious [learned through practice], depends on basal ganglia and cerebellum, spared in amnesia
memory can be subdivided into which 2 types
explicit [conscious events]
implicit [unconscious, not available for verbal report]
what are the characteristics of amnesic patiets having a selective prob with implicit memory
poor in tasks which require explicit remembering: recall, recognition, cued recall + good in taks which don't require explicit remembering: lexical decision, stem completion, fragment completion [using cue, say 1st word that comes to mind]
amnesic patients and their perfomance on cued recall & fragment completion
normal for fc - complete the word previously seen word more often then experience by chance
poor for cr (Graf, Shire & Mandler, 1985)
fragment completion task
tests whether participants use contextual cues [from word pairs studied earlier] to influence how they complete word fragments [healthy vs amnesic patients]
results from fragmentation task
healthy = more likely to complete fragments with og studied word if og piring is preserved
amnesic = don't show context effects whether og pair is present or not [suggesting deficit in item-context binding]
memory in amnesia based on fragment-completion task
amnesia may spare basic priming, but impairs ability to link info with context, pointing to role of hippocampus in relational memory.
what are the 2 componenets of declarative memory
[source] episodic memory - capacity for acquisition and retention of knowledge about personally experienced events and their temporal relations
semantic memory - memory for decontextualized facts
procedural knowledge
subset of episodic knowledge - motor & perceptual skills, habits, identification of words and objects
long term memory systems - Squire (1986)
explicit [declarative] - episodic + semantic
implicit [nondeclarative] - procedural + priming + classical conditioning
Agatha Christie and her episode of amnesia
dec 3, 1926 [36 yearsold at that time] drove towards surrey and her vehicle was found abandoned with fur coat & driving licence left after 11 days of 1000 policemen and 15000 volunteers searching for her found her in hotel in Harrogate where she was registered under the name of husband's lover [she suffered from a case of amnesia]
psychogenic amnesia
caused by psch trauma & distress [may be triggered by brain damage] - common in soldiers during war - you want to block out your whole past so you forget everything that concerns you [esp identity] - can remeber new info but not retrograde info
mirror drawing
participants trace a shape by watching their hand only through a mirror testing procedural memory and motor learning - shows that pm is preserved even in people with amnesia [they can learn motor sskills through prctice even though they don't remember doing task] showing separate memory system from declarative memory