c BBB - Chapter 10: The acting brain

Degrees of freedom problem

There are potentially an infinite number of motor solutions for acting on an object.

Motor programs

Stored routines that specify certain motor parameters of an action (e.g., the relative timing of strokes).

Somatosensorial

A cluster of perceptual processes that relate to the skin and body, and include touch, pain, thermal sensation and limb position.

Proprioception

Knowledge of the position of the limbs in space.

Sensorimotor transformation

Linking together perceptual knowledge of objects in space and knowledge of the position of one’s body to enable objects to be acted on.

Homunculus problem

The problem of explaining volitional acts without assuming a cognitive process that is itself volitional (“a man within a man”).

Primary motor cortex

Responsible for execution of voluntary movements of the body.

Hemiplegia

Damage to one side of the primary motor cortex results in a failure to voluntarily move the other side of the body.

Population vector

The sum of the preferred tunings of neurons multiplied by their firing rates.

Premotor cortex

The lateral area is important for linking action with visual objects in the environment; the medial area is known as the supplementary motor area and deals with self-generated actions.

Supplementary motor area (SMA)

Deals with well-learned actions, particularly action sequences that do not place strong demands on monitoring the environment.

Perseveration

Repeating an action that has already been performed and is no longer relevant.

Utilization behaviour

Impulsively acting on irrelevant objects in the environment.

Schema

An organized set of stored information (e.g., of familiar action routines).

Contention scheduling

The mechanism that selects one particular schema to be enacted from a host of competing schemas.

Sense of agency

The subjective feeling that voluntary actions are owned and controlled by the actor.

Forward model

A representation of the motor command (a so-called efference copy) is used to predict the sensory consequences of an action.

Intentional binding

The phenomenon that voluntary actions and their sensory consequences appear closer together in time than they really are.

Imitation

The ability to reproduce the behaviour of another through observation.

Mirror neuron

A neuron that responds to goal-directed actions performed by oneself or by others.

Optic ataxia

An inability to use vision to accurately guide action, without basic deficits in visual discrimination or voluntary movement per se.

Parietal reach region (PRR)

A part of the Occipitoparietal cortex that responds, in particular, to reaching movements.

Anterior intraparietal area (AIP)

A part of the intraparietal sulcus that responds, in particular, to manipulable shapes or 3D objects (from vision or touch).

Ventral intraparietal area (VIP)

A part of the intraparietal sulcus that responds to objects close to the body and in body-centred (as opposed to gaze-centred) coordinates.

Phantom limb

The feeling that an amputated limb is still present.

Tool

An object that affords certain actions for specific goals.

Affordances

Structural properties of objects imply certain usages.

Ideomotor apraxia

An inability to produce appropriate gestures given an object, word or command.

Parkinson’s disease

A disease associated with the basal ganglia and characterized by a lack of self-initiated movement.

Hypokinetic

A reduction in movement.

Hyperkinetic

An increase in movement.

Huntington’s disease

A genetic disorder affecting the basal ganglia and associated with excessive movement.

Tourette’s syndrome

A neuropsychiatric disorder with an onset in childhood characterized by the presence of motor and/or vocal tics.

Action

the outcome of a number of cognitive processes that translate the goals and intentions of an individual into a motor output

Movement

a physical act that is not necessarily cognitive (e.g. reflexes)

Frontal lobes (with action)

planning actions, maintaining goals, executing actions

Parieto-frontal circuits (with action)

link action with current environment

Parietal lobes (with action)

locating objects in space, sensorimotor transformation

Temporal lobes (with action)

object recognition, object knowledge

Occipital lobes (with action)

visual analysis of scene

Subcortex (e.g. basal ganglia) (with action)

modulate force and likelihood of action

Subcortex (e.g. cerebellum) (with action)

monitor action online

Action is difficult because

there are degrees of freedom, motor programs, and sensorimotor transformation

Primary motor cortex (action)

executes all voluntary movements of the body

Frontal eye field (action)

voluntary movement of eyes

Left hemisphere (action)

right side of body

Medial Premotor cortex (SMA)

Deals with spontaneous well-learned actions that don’t place strong demands on the environment

Prefrontal cortex (action)

Involved in coordination of cognition generally (both external actions and internal thoughts) And selection and maintenance of goals and responses

Perseveration (action)

repeating an action that has already been performed and is no longer relevant

Utilization behaviour

impulsive actions on irrelevant objects in the environment

associative agnosia

unable to recognize or comprehend familiar objects

Dorsal route

affordances

Cerebellar loop

involved in coordination of movement, may update the motor program online using visual feedback

Basal ganglia loop

Important for initiation and execution of internally generated movement and linking one action to the next

Parietal reach region (PRR)

A region of occipitoparietal cortex particularly involved in reaching movements.

Anterior intraparietal area (AIP)

A region of the intraparietal sulcus that responds strongly to manipulable objects and object shape.

Ventral intraparietal area (VIP)

A region of the intraparietal sulcus that represents objects near the body in body-centred coordinates.

Object + Manual action

Pantomime

Manual action + action

Imitation

Verbal naming + object

Object naming

Verbal naming + Action

Action naming

Efference copy

A copy of a motor command that is used by the forward model to predict the sensory consequences of an action.

Supervisory Attentional System (SAS)

A control system that intervenes when routine schema selection is insufficient, particularly in novel or difficult situations.

Automatic action selection

Selection of actions through contention scheduling without requiring conscious executive control.

Controlled action selection

Selection of actions requiring intervention by the Supervisory Attentional System.

Body-centred coordinates

A spatial coding system in which object locations are represented relative to the body.

Gaze-centred coordinates

A spatial coding system in which object locations are represented relative to the direction of gaze.

Pantomime

Producing an action gesture without the actual object being present

Double dissociation between vision and action

Evidence that object perception and object-directed action can be independently impaired.

Online motor control

Continuous updating of movement during execution using sensory feedback.