Please enable JavaScript.
Coggle requires JavaScript to display documents.
TASK 8: Trying to make it work (Rushworth (posterior STS region (social…
TASK 8: Trying to make it work
Cisek
Traditional view
perceptual system collects sensory information to build an internal representation of objects in the external world
resulting plan is then used to generate a desired trajectory for movement
perceptual system collects sensory information to build an internal representation of objects in the external world
finally realized through muscular contraction
in a serial manner: we select ‘what to do’ before specifying ‘how to do it’
assumes modularity
NEW VIEW: affordance competition hypothesis
processes of action selection (what) + specification (how) occur simultaneously and continue even during overt performance of movements
sensory information arriving from the world is continuously used to specify several currently available potential actions, while other kinds of information are collected to select from among these the one that will be released into overt execution at a given moment
behaviour: constant competition between currently available opportunities and demands for action
behaviour = constant competition between internal representations of the potential actions (affordances)
dorsal visual system specifies actions which compete within the fronto-parietal cortex
while a variety of biasing influences are provided by prefrontal regions and the basal ganglia
VISUAL SYSTEM:
occipito-temporal ‘ventral stream’
(what) sensitive to information about the identity of objects
occipito-parietal dorsal stream
(where): sensitive to spatial information - mediates visually guided actions, maybe part of action specification system (how), represents single unique movement selected, but offers a variety of options to choose from
neural substrates of the affordance competition hypothesis (for visually guided movement)
action specification – fronto-parietal cortex – dorsal stream
visual cortex -> parietal lobe - transforming visual information into representations of potential actions
three (3) neural populations along this route
b) parietal cortex - potential actions encoded
c) premotor regions
a) encoding of potential visual targets, modulated by attentional selection
fronto-parietal system
specification of potential actions using sensory information
competition between potential actions
competition is biased by excitatory input from cortical and subcortical regions
Action Selection
distinct potential actions compete for further processing
competition is biased by input from
-basal ganglia
DLPFC - sensitive to various combinations of stimulus features + this sensitivity is always related to the particular demands of the task (task rules) - Prefrontal decisions evolve through the collection of ‘votes’ for selecting one action over others
final selected action is released into execution + causes both overt feedback through the environment + internal predictive feedback through the cerebellum
Computational model of reaching Decisions - neural network input->PPC and PFC (in parallel) - >PMd->M1-output
PROCESS
sensory information in the dorsal visual stream is used to specify the spatial parameters of several currently available potential actions in parallel
potential actions are represented simultaneously in frontal and parietal cortical regions
they compete against each other through mutual inhibition biased competition mechanism
cells with similar parameter preferences excite each other
cells with different preferences inhibit each other
competition between potential actions represented in the fronto-parietal system is biased by a variety of influences from other regions, including the basal ganglia
ACTIVITY IN THE MODEL
spatial cue causes activity in two groups of cells in PPC (each tuned to one of the targets)
Mutual excitation creates distinct peaks of activity, which compete through inhibition
topographic projections between PPC + PMd two peaks appear in PMd as well
two peaks continue to be active and compete against each other even after the targets vanish, owing to the positive feedback between layers
activity accumulates in the PFC cells selective for the particular location–colour conjunctions
colour cue -> uniform excitation to all PFC cells preferring the given colour -> causes the competition in PMd to become unbalanced -> one peak increases its activity while the other is suppressed
once the GO signal is given, activity is allowed to flow from PMd3 into M1 peak of the M1 activity = initial direction of the movement
CONCLUSION: instead of viewing the functional architecture of behaviour as serial stages of representation, we view it as a set of competing sensorimotor loops
Rushworth
social brain hypothesis (large brain = complexity of social environment)
amygdala: emotional responsiveness, link stimuli to innate behaviors and autonomic responses
posterior STS region
social cognition
probalby connected to medial frontal + ACC areas (also linked to social cognition)
determining deree to whic behavior is oriented in a social direction
ACC - Lesions:
cognitive processes, as linking of stimuli to reward outcomes remain intact
tracks the weight of interest assigned to another social agent but not that assigned to comparable nonsocial variables
disrupt the pattern of interest that macaques take in others as a function of social rank and sex
OFC:
neurons encode both information about social status + how the values of rewards change when other macaques also receive simultaneous rewards
Duncan
multiple demand network (common set of distributed brain regions that are activated during execution of a range of "cognitive" tasks)
in prefrontal and parietal cortex: inferior frontal sulcus (IFS), anterior insula (AI), pre-SMA + ACC, intraparietal sulcus (IPS)
ROLES
fluid intelligence
cognitive control
sequential mental programming = implementation of a series of smaller “programs” that have to be worked through sequentially to obtain a complex behaviour
-assembling a series of sub-tasks, each separately defined and solved
selective coding of information relevant to the current decision (lPFC – task relevant information)
rapid change of processing focus and content
PFC neurons show rapid changes in the information they code, depending on corresponding changes in how stimuli should be interpreted and responses chosen (context
New task assembly
its components must be identified, separated and assembled
ability to learn and use the multiple rules of novel, complex behaviour
closely linked to fluid intelligence
Krauzlis et al.
attention - arises as a byproduct of circuits centered on the basal ganglia involved in value-based decison making (attention as an effect, not a cause)
Attention as a
regulator
of sensory representations
Attention as a causal agent = exerts its effects on the sensory data processing
filter-like property of attention limits but does not fully exclude basic features from further elaboration
curating of sensory data may occur either early or late in sensory processing
by actively filtering the representation of sensory signals, cortical attention mechanisms control which data is then available to drive perception, action, and memory
evidence
neurons in sensory areas modulate their firing depending on how attention is allocated
this effect occurs both early and late in processing
central principle for achieving the filtering of sensory data: competition for representation within the neocortex
competition is believed to be regulated by feedback signals from later stages of processing (frontal and parietal cortex) - provide ‘priority’ signals that bias competition for representation in sensory cortex
Attention as an
effect
of interpreting sensory (and other) data
attention as an effect = attention arises as a functional consequence of circuits centered on the basal ganglia involved in value-based motor and non-motor decision making
KEY FEATURES
A) current state estimation
subject must consider several possible estimates of the state
these different estimates could be generated by differentially weighting the possible inputs
involves the input nuclei of the basal ganglia, especially the striatum
striatum: guide reinforcement learnin, learned associations between a particular state + set of actions with the highest expected values, establish a decision policy that guides the subject’s behavior
B) Competition
between possible interpretations of the current state by the basal ganglia
but determines which estimate of the ‘state’ provides the best match to the current sensory data, prior knowledge + internal status of the subject
dominant estimate of the state then determines which decision policy is followed
C) Attention
can be explained by this competition between possible states
different sensory inputs contribute unequally to different states
filter-like properties of attention result from the particular weights applied to the sensory and non-sensory inputs that define the current state
shifts of attention = transitions from one dominant state to the next
EVIDENCE
The SC (superior colliculus) regulates attention but not through the visual cortex
SC: role in controlling orienting movements of the eyes and head
necessary for the control of spatial attention
STUDY: When activity in the SC is locally and reversibly suppressed, animals have difficulty performing attention tasks for stimuli placed in the affected part of the visual field
the enhanced responses of sensory neurons to attended stimuli were preserved during SC inactivation
if attention operates by regulating how sensory signals are represented in the neocortex, some aspect of cortical activity should have changed to cause the deficits in attention performance
Subcortical routes lead to the basal ganglia: SC -> thalamus ->striatum-
many of the anatomical routes out of the SC to other sensorymotor structures lead to the basal ganglia
a conserved circuit motif for attention
basal ganglia play a crucial role in value- based decision making in all vertebrates in mammals: basal ganglia receive most of their inputs from neocortex. In mammals: basal ganglia receive most of their inputs from neocortex. Neocortex is important for attention: process of extracting salient features has been outsourced