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EXECUTIVE FUNCTIONS (Executive deficit theories of cognitive aging Goal…
EXECUTIVE FUNCTIONS
EFs are multifaceted control processes that
regulate thought and behavior
A family of general-purpose mechanisms
Critical to other higher cognitive abilities
including planning, reasoning, long-term memory, decision making, and problem solving
Mediated mainly by
prefrontal cortex
, the
parietal
lobes, and
subcortical
regions, including the
thalamus
,
basal ganglia
,
limbic system
,
mid-brain
, and the
cerebellum
Test used for EF
• Wisconsin card sorting test (WCST)
• N-back
• Trail making test B
• Stroop Task
• Stop signal
• AX-CPT
Miyake's model
inhibition
switching
updating
They are related but independent
age related deficit in all of these factors
Working Memory
Complex tasks require that information are stored and
manipulated in a short-term storage system
Older adults have a reduction in WM storage capacity
This lead to deficits in several cognitive tasks but tasks that seem to tap into the function of WM capacity show minimal effect of age
it is not just the reduction in the storage capacity,
But rather an interaction of storage and control mechanisms
Age deficits in complex WM span tasks seem to mainly reflect a decline in executive control, rather than a decline in storage capacity
Executive deficit theories of cognitive aging
Goal manteinance deficit
Inhibitory Deficit Theory (Hasher & Zacks)
Frontal Lobe Hypothesis of Cognitive Aging
Goal Maintenance Deficit (Braver & West)
Goal Maintenance Deficit
deficits in executive control =
which consists of the internal representation, maintenance, and updating of goal information in the service of exerting control over thoughts and behavior
executive control tasks rely on internal representations of tasks-set goals
Critical role of the lateral PFC in executive control processes
Critical role of the dopamine (DA) in executive control processes
DA modulates PFC function by regulating the way that goal representations are maintained and updated DA regulates the access of afferent inputs to lateral PFC
Lateral PFC:
exerts a top-down control on posterior and subcortical brain systems engaged in task-specific processing based on actively maintained goal representations
It's important in maintain in mind goals of the task and to transform goal representations into plan to respond to upcoming stimulus
required when multiple conflicting responses are activated but some are irrelevant
clarifies the relationship between
attention
,
working memory and inhibition
, and the
role of lateral PFC
in these domains: in situations of behavioral inhibition (stroop) top-down control may have a suppressive effect
Stroop
multiple perceptual dimensions that compete for attention
tendency to make an inappropriate response
Age-related
declines in lateral PFC and dopamine function
result in a specific impairment in the ability of older adults to actively represent and maintain goal information over time
Goal e Working memory
age effects on WM can be explained by the older adults’
reduced ability to maintain goal representations in working memory
Increased susceptibility to interference
declines in the ability to control the focus of attention within working memory
memory impairments occurring in task condition that require the binding of arbitrary stimulus features together in working memory
Susceptibility to interference
Proactive interf: previous stored info interfere with processing e tretrieval
Retroactive interf: interfering info is presented successively
minimizing proactive interference: better performance
Decline in the ability to control the focus of attention within working memory
short-term memory zone is very close to the conceptualization of actively maintaining goal representations within the goal maintenance account
O have a decline in refreshing and updating the focus of attention, in switching between the processing of no more relevant items and now relevant items
Binding deficit hypothesis
a disruption in the ability to bind together the various elements of a representation within working memory
memory tasks with retrieve of item based on a conjunction of more features show age-related deficit
Decline in left anterior hippocampus and right rostral prefrontal cortex
Inhibition of responses
inhibit irrelevant, inappropriate, but dominant or prepotent responses
Stroop task
This interference effect accelerates in an exponential fashion from the sixth to eighth decades
Antisaccade task
Difficulty in suppression of an automatic tendency to attentionally orient towards abrupt visual cues
Task management
difficulties in managing and coordinating multiple task demands
studies with task switching
no ages differences in
SWITCHING COST
Only differences in
MIXING COST
if there's a preparatory interval Y e O are facilitated but switching cost is greater in old
O unable to use info to appropriately select the current relevant task and deselect the irrilevant task
Lateral anterior PREFRONTAL CORTEX (PFC) plays a key role in maintaining task goals active in mind
in task switching blocks activation of Lateral PFC, which resulted associated with mixing costs
in O REDUCED activation of lateral PFC during task-switching blocks
Goal manteinance theory explain
WM
ep memory
prospective memory
inhibition of responses
task management
Paradigm AX-CPT:
Respond to an X following and A
errors in BX
errors in AY
O errors in BX, Y in AY
age related deficit in contextual info
in Y activation of lateral PFC: successful in BX inhibition but AY facilitation
impairment in the use of context info in O are caused by changes in lateral PFC
Temporal dynamic of Ex control
Dual mechanism of control DMC
proactive control
= active manteinance of goal representation and anticipatory preparatory attention
reactive control
= stimulus-driven reactivation of goal information in situation where such info is critical to avoid inappropriate performance
Older adults may have a
reduced tendency to use proactive control
, but a relatively spared or even enhanced
tendency to engage in reactive control
Ex control is more then a process
more areas:
left e right DLPFC activation,
inferior medial PFC monitoring,
superior medial PFC inhibition
Error/Performance monitoring
ERN error-related negativity
: a specific ERP brain wave sensible to error monitoring and detection
electrophysiological signal associated with
ACC
monitoring process, occurring
100ms
after an errors is made
activated not only for errors made, but also for response conflict
ACC provides a signal to
PFC
about the correction of behavior
It requires high
degree of cognitive control
lateral
PFC
can adjust the actions based in ACC signals
amplitude of ERN is attenuated in O
reduction in the magnitude of
dopamine-mediated error feedback signal from the basal ganglia to the anterior cingulate
DECLINE IN DOPAMINE ACC-PFC MONITORING SYSTEM
Somatic marker theory
Affective bodily signals can bias our decision
ventromedial regions of PFC
no age related effects in task used for vmPFC, aging effects on dlPFC
O show slower learning curves from negative feedback (errors) and higher tolerance to risk
O better control their emotions than Y and there's a reduced impact of negative info of memory and attention
even if vmPFC regions are not impaired, O show some deficits in affective-directed tasks due to deficit in dlPFC
Anterior PFC is involved in Ex processes related to integration of higher-order goal info actively maintained in WM
age differences in reasoning, high order thinking, planning, integration (aPFC dependent)