Task 8 - Trying to make it work

The action selection (what to do) and action specification (how to do it) happen in serial succession.

1. Brain first collects sensory information to build a representation of the environment
2. this information is combined with information about goals, needs, desires and memories of past experiences (cognition) which are used to select an action plan.
3. The plan is then further specified and executed.

This approach relies on the view that neural processes can be distinguished into three classes:

1. Perceptual systems: Take sensory information and construct internal representations of the world.

2. Cognitive systems: Representations and past experiences build up knowledge to make decisions about the environment.

3. Action systems: Decisions are implemented through planning and execution of movement

Action selection and specification happen in parallel (simultaneously)

- The brain and its attention systems do not build a detailed, complete picture of the environment, but instead, sensory information is processed in an action-dependent fashion.

- Different stimuli may afford different actions, which then compete early on and result in a set of preliminary action plans appropriate to the current circumstances from which one can choose

• Not all possible action are turned into action plans
• Selective attention can eliminate certain actions early on and reduce the number of action plans

1. The “attention” square encodes potential visual targets, modulated by attention selection.
2. The “parietal cortex” square encodes potential actions.
3. Activity occurs in the premotor cortex

Attention acts as an early filter and selects only the most promising action plans, which are then represented in the parietal cortex (number of actions decreases the further away from V1 or

the deeper into the dorsal stream), which in turn leads to premotor cortex activity

May be involved in representations of the environment, due to which it might be involved in specificationof potential actions.

→Lateral Intraparietal Cortex (LIP) specifies potential saccade targets (salience map).

→Medial Intraparietal Cortex (MIP) specifies possible directions for reaching.

- The dorsal system does not just specify the final selected action, but multiple currently afforded actions.

- Selective attention is guided by the frontal cortex

- parietal cortex is strongly connected to frontal motor areas.

→LIP connects to FEF (object selection), MIP connects to PMd/M1 (movement specification) and Anterior Intraparietal area (AIP) connects to PMv.

- Fronto-parietal loops relate to different aspects of movement

In each of the involved areas, different movement preferences mutually inhibit one another and compete with one another until one is singled out (= action selection)

• Basal ganglia favours certain actions over others, based on decision factors.
• LIP activity correlates with sensory and motor variables, but also with decision variables (e.g. expected utility, subjective desirability).
• DLPFC may be another candidate involved in resolving competition; it is sensitive to task demands and makes decisions through votes for certain options (ballot box model)

Initially thought to be responsible for object recognition.

→According to the affordance competition model, this function may have evolved from stimulus detection involved in action selection

Two parallel processing pathways

1. Occipito-temporal ventral stream: Involved in identity of objects (“what”).

2. Occipito-parietal dorsal stream: Involved in spatial information (“where”).

→This dorsal stream diverges into several sub-streams specialized toward the needs of different kinds of actions.

→Involved in mediating various visually guided actions.

>>So it does not build a unified representation of the world.

>>LIP cells: Involved in eye movements (dorso-ventral)/ saccades, Connected to FEF.

>>MIP cells: Involved in hand movements (dorso-dorsal)/ directions of reaching -> Connected to PMd and M1.

→May be part of a system for action specification; processing visual info to specify potential actions.

→Attentional modulation: Some info is enhanced or suppressed.

→Parietal representation of the external space becomes increasingly sparse as one moves away from the striate cortex.

→Only the most promising targets for movements are represented in the parietal cortex

-A set of loops spanning over the central sulcus, each processing information related to different aspects of movement.

-There isa competition between potential outcomes.

-There is mutual inhibition for cells with different preferences.

-The competition is biased by excitatory input from a variety of sources (e.g. basal ganglia and DLPFC

There is little cross talk between the dorso-dorsal & dorsal-ventro pathway whereas in Cisek's model there is integrated, parallel brain functioning where particular structures are not only for specific functions and a lot of interplay.

Similarities:

• Both models propose the enhancement of one action, a feedback loop that re-evaluates action consequences, filtering, biasing of basal ganglia and PFC.
• Both models focus on functional differences.

Differences:

-Seriality (Binkofsky) vs parallelism (Cisek); different brain areas may be implicated

No rigid temporal sequence in which decisions appear in the fronto-parietal system.

Each cell population in the network is proposed to involve competitive interactions, and biasing influences can modulate this competition in different places.

Since cortico–cortical connections are bidirectional, if a decision begins to emerge in one region, then it will propagate outward to other regions

Attention is meaningful toward considering a goal.

→Attention is goal-related, and a way to achieve a goal is the intermediate process of attention.

-The traditional view regards attention as a filter, but Krauzlis explains why the brain should filter its inputs to begin with.

→The attentional filter is required to isolate relevant stimuli for obtaining a goal or desired goal-state

-The occipito-parietal “dorsal” stream:

→Involved in spatial information, and mediation of visually guided movements.

→LIP is involved in gaze control, functions as a body centred reference frame, and oculomotor system connection.

→MIP is involved in arm reaching, functions as a hand centred reference frame, and is connected to the frontal PreMC.

→Increases influence of attentional modulation (enhancement + suppression)

Representations become sparser along the dorsal stream, away from the striate cortex.

→Only the most important targets make it all the way to the parietal cortex.

-Attention is an early mechanism for action selection, it works as a filter for sensory input.

→It is a central principle of filtering.

>>There is competition for representation in the neocortex.

>>There is enhanced representation of some stimuli at the expense of others

According to the classical view, attention serves as a bottleneck/filter which aids in prioritizing certain stimuli, as our cognitive resources are limited.

→Attention helps by biasing perception to task relevant stimuli.

-The dorsal attention system (top-down):

→Fronto-parietal circuits are involved in goal oriented spatial attention allocation.

→Helps create priority maps.

→Stimulus priority is set through the attentional loop (FEF represents motor goals, IPS represents task relevant stimuli).

→There is a trade off; task irrelevant stimuli receive less attention and may be ignored.

-But this only explains top-down attention.

sensory input, prior knowledge and an internal state are the input,

leading to a state estimation (which state estimate matches best with the input), leading to a weighting of sensory input, and eventually a decision policy.

→Attention here is an effect rather than a cause, a by-product of value-based decision making centred around the basal ganglia.

→This framework explains learning: Weights are not innate but are learned (through dopamine)

Sensory input of several stimuli occur, which couples with prior knowledge and internal status of the individual to form input to the basal ganglia.

-Circuits in the basal ganglia (motivation, cognition, motor loop

, ballot box model; voting for current state estimation) operate in conjunction to resolve the competition between current state estimates.

-Weights are assigned to sensory and non-sensory inputs that best define the current state.

→Filtered attention occurs (focusing on the preferred product in the store).

-Output of the basal ganglia is sent to decision policies

In the supermarket decising between pineapple and banana:

Priority maps: LIP makes a priority map based on the memory that you have already eaten bananas all week

Superior colliculus (SC) is involved in making you realize that the bananas are very ripe already, so you would be unable to keep them for a few days. On the other hand, the pineapple is not fully ripe

yet, so it won’t go bad if you take it home to eat it over the weekend.

Frontal cortex: Makes you realize that you generally prefer the taste of pineapple anyway.

→You eventually pick the pineapple

State:

-The current condition of a subject in its environment; a mixture of learned associations between inputs, outputs, and prior knowledge.

→Each state is a template for a particular situation and dictates what the relevant stimuli, actions and rules are.

→Decides what to attend.

→Involves interpreting various information: Features of the external world and internal status of the subject (prior knowledge, current needs, ...).

Basal ganglia:

-Involved in the competition between possible interpretations of the current state.

-Learns associations between a state and a set of actions with the highest expected value (reward).

-Receives information from many different areas and weights those inputs according to the current state.

-If attention shifts, one’s state changes

Cisek:

While sensory information is collected in parallel fashion, different actions compete for further processing, and the collected sensory info biases the competition until a single response “wins”.

→Constant competition between affordances (internal representations of potential actions).

→Fronto-parietal network is involved in this competition.

Krauzlis:

Conditions in the environment and the state of the animal decide about the best fitting interpretations of the current state in the basal ganglia.

→Each state differs in weights, and the best-matching template wins the competition

Cisek:

PFC and basal ganglia have a biasing influence.

→Fronto-parietal networks are modulated by a decision variable (salience, attention).

→The biasing inputs influence the competition.

→Basal ganglia and PFC are involved in action selection.

Krauzlis:

Priority signals stem from feedback signals from later processing stages in frontal and parietal cortex and superior colliculus.

→This biases competition

→A shift in attention is triggered by changes in the environment, which leads to transitions in the state

Cisek:

Many actions are eliminated by selective attention mechanisms due to limited sensory processing.

→Only currently available actions are specified.

→Only the most promising possible actions reach the parietal cortex.

→The decision on what to attend is based on feedback-loops.

Krauzlis:

Attention is an effect rather than a causal agent.

→Attention is the consequence of value-based decision-making in the basal ganglia.

→The strength of the contribution to the current state decides how much attention is paid to processing particular sensory inputs and types of knowledge

Cisek:

Highlights the primacy of goals in action selection, proposing that goals bias the competition among action possibilities.

Krauzlis:

While not directly discussing the primacy of goals, this article emphasizes that attention is modulated by goals and intentions, suggesting that attentional mechanisms are effects of goal-directed behavior.

Cisek:

Suggests a more integrated view.

→Perception, cognition and action should be regarded as integrated and are not believed to happen serially.

>>Instead, sensory info is processed in a parallel way.

Krauzlis:

Criticizes the traditional view of attention as a filter.

→Instead, attention is an effect/by-product rather than a causal mechanism

Cisek:

PFC should not be seen as only being concerned with new cognitive functions.

→Instead PFC can be interpreted similarly to how subcortical structures are interpreted, in terms of interactive behaviour.

Krauzlis:

Challenges the view that neocortex is necessary for attention.

→Instead, connections between basal ganglia and PFC are important.

Cisek:

Action specification and action selection must be performed constantly

and simultaneously to attain continuous interactive behaviour.

→Many different actions are simultaneously prepared to be able to switch plans in case that environmental circumstances change.

→The dorsal stream is implicated in action specification.

Krauzlis:

Focuses on defining the state of the environment and the individual (similar to Cisek’s action specification).

→Basal ganglia (particularly striatum) are involved in sate estimatio