Neuropsychology: The Acting Brain Flashcards
What is an action?
Outcome of number of cognitive processes that translates goals and intentions of individual into motor output
What is movement?
Physical act that is not necessary cognitive
Why is action computationally difficult?
-Degrees of freedom problem
-Generalized motor programs
-Sensory-motor transformation
What is the degrees of freedom problem?
Potentially infinite number of motor solutions for, say, picking up object
What are motor programs?
Generalized motor programs are stored routines of actions and action sequences that minimize problem
What is sensory-motor transformation?
Linking together position of object in retinal space with position of limbs in bodily space (proprioception)
What does a hierarchical view of action look like?
(image)
What brain regions are involved in action?
-Frontal lobes
-Parieto-frontal circuits
-Parietal lobes
-Temporal lobes
-Occipital lobes
-Subcortex: basal ganglia
-Subcortex: cerebellum
How are the frontal lobes involved in action?
Planning actions, maintaining goals, executing actions
How are the parieto-frontal circuits involved in action?
Link action with current environment
How are the parietal lobes involved in action?
Locating objects in space, sensory-motor transformation
How are the temporal lobes involved in action?
Object recognition, object knowledge
How are the occipital lobes involved in action?
Visual analysis of scene
How is the basal ganglia of the subcortex involved in action?
Modulate force and likelihood of action
How is the cerebellum of the subcortex involved in action?
Monitor action online
Which parts of the frontal lobes are involved in movement and action?
-Prefrontal cortex (medial and orbital)
-Anterior prefrontal cortex
-Ventro-lateral prefrontal cortex
-Dorso-lateral prefrontal cortex
-Frontal eye field
-Lateral premotor cortex
-Supplementary motor area (SMA, medial premotor)
-Primary motor cortex
-Anterior cingulate
(image)
How is the primary motor cortex involved in movement and action?
-Part of frontal lobes
-Executes all voluntary movements of body
-Somatotopically organized and crossed (left hemisphere is for right side of body and vice versa)
-Stimulation results in movement and lesion results is paralysis (ex: hemiplegia)
What is hemiplegia?
-Damage to 1 side of primary motor cortex in frontal lobes
-One side of body paralyzed: failure to voluntarily move (contralesional) side of body
What is tetraplegia?
-Damage to spinal cord (typically)
-Whole body paralyzed: paralysis in all limbs
How are the frontal eye fields involved in movement and action?
-Part of frontal lobes
-Involved in voluntary movement of eyes
How is the lateral premotor cortex involved in movement and action?
-Part of frontal lobes
-Prepares movement based on external contingencies
-Receives visual signals via parietal cortex
How is the medial premotor cortex involved in movement and action?
-Part of frontal lobes
-Supplementary motor area (SMA)
-Deals with spontaneous well-learned actions that don’t place strong demands on environment
-Receives strong proprioceptive signals concerning position of limbs
How is the prefrontal cortex involved in action and movement?
-Part of frontal lobes
-Involved in coordination of cognition generally (external actions and internal thoughts)
-Involved in selection, maintenance of goals and responses
-Damage: actions become inappropriate or disorganized (physical movement NOT impaired)
–>Perseveration
–>Utilization behavior
What is perseveration?
-Repeating action that is already performed and no longer relevant
-Damage to prefrontal cortex
What is utilization behavior?
-Impulsive actions on irrelevant objects in environment
-Damage to prefrontal cortex
What is automated behavior?
When actions can be performed in autopilot mode with minimal attention to action and online control
What is controlled behavior?
-When actions require interruption of ongoing behavior and setting up novel actions/cognitive procedures
-Requires intervention of executive: Supervisory attentional system (SAS)
What is the supervisory attentional system (SAS)?
-Involved in controlled behavior
-Involved in selecting which schema to use next from host of competing schemas (contention scheduling)
What are mirror neurons?
-Single neurons that respond to observed as well as self-enacted actions
-Basis of learning via imitation and possibly understanding action and intentions of others
-Found in frontal and parietal lobes: supplementary motor area, inferior frontal gyrus, premotor cortex and inferior parietal lobe
-Important for action comprehension and imitation
(image)
How are the parietal lobes involved in movement and action?
-Object-based action
-Tool use
How is are the parietal lobes involved in object-based action?
-Where/how route starts in visual cortex and transforms into what-route while travelling into parietal lobes
-Lesions in what route: visual form agnosia
-Lesions to where/how route: optic ataxia
(image)
What is visual agnosia?
-Lesion in what-route of movement and action
-Difficulties matching orientation of objects
-Able to use objects or put objects in right orientation
What is optic ataxia?
-Lesion in where/how route of movement and action
-Hand posture problem: holding hand wrong
-Misreaching: hand misreaches slit wrong
-Inability to use vision to accurately guide action, without basic deficits in visual discrimination or voluntary movement per se
How are the parietal lobes involved in tool use?
-Humans developed huge variety of tools associated with specific actions and functions: due to walking upright and changes in environment and hand anatomy
-Lesions: associative agnosia
-Affordances needed to use objects
–>Where/how route: computes affordances between structure and potential functions
–>Affordances not always enough
-Lesions: ideomotor apraxia
(image)
What is associative agnosia?
-Lesion in parietal lobes
-Unable to recognize or comprehend familiar objects
-Use of tools usually good
What is ideomotor apraxia?
-Lesion in parietal lobes
-Inability to produce appropriate gestures to object, word, command, etc.
-Problems with tools: chooses wrong tool and/or uses tool wrong
-Problems with pantomiming
What is the role of the subcortex in movement and action?
Two different (important loops)
-Cerebellar loop: timing and trajectory of action
-Basal ganglia loop
(image)
What are characteristics of the cerebellar loop of the subcortex in movement and action?
-Timing and trajectory of action
-Involved in coordination of movement
-Uses visual feedback to update motor program
-Cerebellar lesions: tremulous movements and problems with motor learning, fine motor control and posture
What are characteristics of the basal ganglia loop of the subcortex in movement and action?
-Different pathways
–>Direct: accelerator, more movements when active
–>Indirect: brakes, less movements when active
-Initiates and executes internally generated movements
-Links one action to next
-Modifies activity in frontal motor structure to influence probability of movement
-Lesions: hypokinetic disorders (too few movements) or hyperkinetic disorders (too much movements)
-Both involve cortex and thalamus
Which hypokinetic disorders of the basal ganglia are there?
Parkinson’s disease
Which hyperkinetic disorders of the basal ganglia are there?
-Huntington’s disease
-Tourette’s syndrome
What is Parkinson’s disease?
-Form of hypokinetic disorder of basal ganglia
–>Problem with connection between substantia nigra to basal ganglia
-Symptoms: akinesia (lack of spontaneous movement), bradykinesia (slowness of movement), decay of movement sequences (walking degenerates to shuffle), failure to scale muscle activity to movement amplitude, failure to weld several movement components into single action plan, rigidity and tremor when stationary
-“Treatments” to lessen symptoms
–>Administering dopaminergic drugs to compensate
–>Deep brain stimulation and pacemaker to subthalamic nucleus and globus pallidus in basal ganglia
(image)
What is Huntington’s disease?
-Form of hyperkinetic disorder of basal ganglia
-Genetic, degenerative disorder
-Excessive movement: dance-like flailing limbs (chorea) and contorted postures
-Indirect pathway (brake) affected: depletion of inhibitory neurons
What is Tourette’s syndrome?
-Form of hyperkinetic disorder
-Excessive and repetitive actions
–>Motor tics
–>Vocalizations: echolalia (repeating someone’s words), palilalia (repeating own words) and coprolalia (production of obscenities)
-Activation in direct pathway correlated with tic severity
-Deep brain stimulation possible, but doesn’t always work
