Hoofdstuk 10 Flashcards
Degrees of Freedom problem
infinite number of motor solutions for acting on an object
Motor Programs
stored routinges that specify certain motor parameters of an audience (e.g. relative timing of strokes)
- they may code general aspects of the movement (e.g. timing of different components) rather than the actual means of performing the movement (the joints and musclles)
Somatosensation
a cluster of perceptual proceses that relate to skin and body (thermal sensation, touch, pain, 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 (also: remapping)
Homunculus sProblem
There is no “I” in the brain that makes all kinds of action decisions
Frontal Lobe
1/3 of cortical area. Moving posterior to anterior = function becomes less specific to movement and action
Primary Motor Cortex - initiates voluntary movement
Premotor Regions - online coordination of movements
Prefrontal Regions - plan and select actions according to goals
Somatotopically Organized
different regions of the primary motor cortex represent different regions 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
FEF = Frontal Eye Fields
Brodmanns area 8 - separate region of the frontal lobes
Eye Movement is primarily guided by external senses (vision and hearing)
where as skeletal - based movements rely on proprioceptive information concerning the position of the limbs (somatosensory cortex)
Premotor Cortex
Area immediately in front of (lateral) the priamry motor cortex
- linking acion with visual objects in the environment; the medial area is known as the supllementary motor area and deals with well learned actions (ones that don’t place strong demand on monitoring the environment)
- the lateral premotor cortex recceives signals via the parietal cortex (dorsal route in vision), whereas the medial premotor cortex (SMA) receives strong proprioceptive signals concerning the current position of the limbs
Prefrontal regions lie anteriorly to the premotor regions
and are principally involved in planning and higher aspects of the control of action
Preserveration
repeating an action that has already been performed and is no longer relevant
Utilization Behavior
impulsively acting on irrrelevant objects
SAS Model (Norman and Shallice)
Supervisory Attentional System
Contention Scheduling
- the mechanism that selects one particular schema to be enacted from a host of competing schemas (form of motor attention)
- competition between schemas is key part of this model
Decision to act
is directly determined by the activation levels of schemas
Sense of Agency
subjective feeling that voluntary actions are owned and controlled by the actor
Forward Model
a representation of the motor command (efference copy) is used to predict the sensory consequences of an action (links together action intention and action outcome)
Changes (predictions) in visual input environment
may arise via interactions between frontally based action systems and structures such as the cerebellum and superior colliculus (for sensory consequences of eye movement)
Intentional Binding
voluntary actions and their sensory consequences appear closer in time
Mirror Neuron
responds to goal-directeed action performed by oneself or by others
- ventral premotor cortex (Area F5) responds both during performance and the observation of the same action
- tuned to precise actions that are goal directed
“What” Route
Ventral Stream from occipital to temporal
“Where” Route
Dorsal Stream from occipital to parietal
Optic Ataxia
- Damage to occipitoparietal junction
- unable to accurately reach toward objects under visual guidance
PRR Parietal Reach Region
part of the occipito parietal cortex that responds to reading movements
- Neurons effectively code the distance and direction needed to move a hand from its current visually perceived location to another endpoint
Sensorimotor Transformation
the dorsal stream that transforms visually based information into motor based actions
Hand Movement = Reaching
Eye movement = Saccade
Area LIP (lateral Intraparietal)
neurons in this region effectively code the distance and direction needed to move the eyes from the current location to a visual stimulus in its receptive field
LIP/PRR
Preferred direction ddepends on locaation of sensory information
Primary Motor Cortex : movement direction alone
Grasping may require greater processing of object-based properties than reaching or pointing
- Reaching PRR (occipitoparietal region)
- Grasping AIP (anterior intraparietal area) + premotor cortex
- responds to manipulate shapes of 3D objects (from vision or touch)
- connections to motor regions of frontal lobe (premotor area and FEF) + infero temporal cortex of the visual ventral stream which is involved in object recognition
VIP Ventral Intraparietal Area
- part of the intraparietal sulcus that responds to objects close to the body and in body-centered (as opposed to gaze-centered) coordinates
- head + hand centered neurons
Tools, repesented in the brain at several levels
1) stored visual by visual ventral stream
2) semantic representation - medial and anterior temporal lobes
3) volumetric represenntation - visual + motoric for grasping (AIP in Parietal Lobes)
4) motor-based component-gestures- left inferior parietal lobe
Affordances
structural properties of objects imply certain usages
Ideomotor Apraxia
inability to produce appropriate gestures given an objecct, word or command
Object-based actions
reside predominantly in the left hemisphere
The Basal Ganglia
regulate action via a balaance of action-promoting and action-inhibiting pathways and are particularly involved in self-generated actions (prepared in the supplementary motor area). Parkinson + huntington are disruptions of this balance
Hyperkinetic (increase in movement)
Hypokinetic (reduction in movement)
Cerebellar loop
involved in coordination of movements
- Basal Ganglia Loop - 5 loops consisting of excitatory and inhibitory pathways
- direct route that promotes action (increases activity in cortex)
- indirect route that inhibits action (decreases activity in cortex)
