Prefrontal Cortex and Executive Function Flashcards
What brain region plays a central executive role?
PFC
What kind of processing is automatic behaviour produced by?
Bottom-up
A reflex is where you act before making a conscious decision to do so thus perception of thoughts leading up to the decision is false
Classical view of sensory processing
behaviourist
Brain does not create meaning
Perception is a ‘bottom-up’ process
Early, reflex decisions are fast but can ‘short-circuit’ potentially adaptive responses
Sequential stages reconstruct features to represent objects
Neural representation will show similar changes as you progress up the
processing hierarchy
The world is created de novo again and again
Open to behaviour ‘stalling’ when presented with ambiguous input cues
activating more than one internal representation
Problems with the bottom up strategy
Inflexible and potentially maladaptive
Top-down processing
Main task of cognition being the guidance of intrinsic goal-directed & rewarded behaviour (latter are learnt through experience)
Successful outcome then relates not to the accurate representation of the world but rather the generation of appropriate actions
Internal brain states should conform to ‘action-oriented pointers’ (not object representations) – deals with ambiguous input through access to internal states and intentions, knowledge of immediate and future goals and memory of past successes.
For cognitive control, systems must have:
Access to information from many brain systems
Ability to encode the goal-relevant relationships between them
Flexibility through learning (‘complex learning’)
Capacity to deal with gaps in time between events/cues/actions (working memory) – and ‘pause/resume’ to allow new, more vital processes
In cognitive control, systems must be able to select:
Which sensory, motor and memory processes are active at any given moment (cognitive resource allocation)
Why is it important in cognitive control to be able to select which processes are active at any given moment?
Limited number of controlled behaviours that can be active simultaneously (in contrast to automatic behaviours)
Why is finite allocation of resources to a small number of tasks inefficient?
Trade-off between information processing and depth of analysis allows elaborate analysis of a situation
Allows individuals to stay ‘on track’ – processing irrelevant information increases chance of distraction – attention = control.
What does the meaning og top down/ bottom up depend on?
Experimental context: Anatomical Cognitive Contextual Dynamic (anatomical hierarchy not an absolute requirement)
Stephen Grossberg’s active brain model
Feedback has a role in focusing selective attention to important elements of the environment
Adaptive filtering of inputs
Predictive signals for expected (learned) patterns (priors)
Compare actual vs expected, amplify match, inhibit mismatch
Divisions of the primate PFC
Dorsolateral, ventrolateral and orbital sub-regions - but these represent at least 18 distinct areas (Brodman)
Anatomy of the primate PFC
Areas forward of motor cortex (Brodmann 4 and 6) are considered prefrontal
PFC = Brodmann areas 8-13, 44-47
Can also be defined as the region of cortex supplied by the mediodorsal nucleus of the thalamus (n.b. This does not apply to rodents)
The PFC is connected directly to every distinct functional unit of the brain
Connectivity of the PFC (the great integrator)
diagram
Sensory – most PFC regions have inputs from 2+ sensory association/multimodal regions
Motor – Area 46 may be particularly important for motor output. Connections to premotor planning regions (e.g., supplementary motor area) as well as striatum
“Limbic” – Direct and indirect (via thalamus) connection to hippocampus/MTL, amygdala and hypothalamus.
Anatomically, PFC is well placed to synthesise internal and external information to provide complex behaviour
SWRs
Sharp-wave ripples are fast (short duration) oscillation sequences that can be seen ‘riding’ on sharp waves in hippocampus. Groups of pyramidal cells fire during SWRs
