9. Motor System Flashcards
What are the 8 methods of studying actions?
Behavioural, Musclephysiology, Neurophysiology, Neuroimaging, Neuropsychology, TMS, Computational modelling and event-related potentials
Describe the method of studying actions through behavioural studies
Use of video or electronic recording equipment to record the position of body parts in space and time (can measure speed, accuracy and kinematics)
What are the strengths of behavioural studies?
Allows us to systematically investigate the output of the action system
What are the weaknesses of behavioural studies?
Cannot tell us anything about the brain
Describe the method of muscle physiology (electromyography) to study actions
Can record activity of individual muscles or muscle fibres during action
What are the strengths of muscle physiology?
Allows an understanding of how muscles operate
What are the weaknesses of muscle physiology?
Does not directly tell us anything about the brain
Describe how neurophysiology can be used to study actions
Implants electrodes in brain and records the activity of individual neurons, can take a record of a number of neurons and measure their activity in real time
What are the strengths of neurophysiology?
Allows for excellent spatial and temporal resolution
What are the weaknesses of neurophysiology?
Cannot examine more than a minuscule percentage of the neurons at any one time
We rely on monkey’s for this research and can only draw inferences from this
Describe the technique of neuroimaging (fMRI) to study actions?
Put a subject in a brain scanner and measure blood flow while they perform a task
More blood flow = more brain activity (as working neurons require more energy for brain activity)
What are the strengths of neuroimaging?
Allows for a direct measure of activity in the human brain
Has good spatial and fairly good temporal resolution
What are the weaknesses of neuroimaging?
Many APs take less than 2-4 seconds (blood does not flow instantaneously to active neurons)
Hard to make many movements in a scanner environment
Describe the method of neuropsychology to study actions
Examine the consequence of brain damage in humans or animals, if damage is linked to behavioural deficits, then we can infer that area is necessary for that function
What are the strengths of neuropsychology?
Allows us to examine the consequences of brain damage and can be used to show which areas are most important for which functions
What are the weaknesses of neuropsychology?
Cannot place lesions wherever we want
Lesions often have effects on neurons far from the lesion site
Describe the process of Transcranial Magnetic Stimulation to study actions?
Temporarily disrupt brain activity using a high-powered magnetic coil
What are the strengths of TMS?
More ethical
What are the weaknesses of TMS?
Not all areas can be tested
Must be very careful not to cause seizures
Can’t test deeper areas of the brain as the magnetic field cannot penetrate that far
Describe the process of computational modelling in terms of studying actions
Devise mathematical models of how actions might be carried out by a set of neurons
What are the strengths of computational modelling?
Approaches the question of brain function from a synthetic rather than an analytical perspective
What are the weaknesses of computational modelling?
Does not address how the brain actually works
Describe the method of event-related potentials in studying actions
Record electrical activity from the scalp
What are the strengths of event related potentials?
Very good temporal resolution
What are the weaknesses of event-related potentials?
Poor spatial resolution
Can’t know exactly where the electrode is measuring as it covers a vast area of the brain
The unfolding of movement kinematics varies systematically with two factors, what are they?
- The characteristics of the target
2. The relation between the target and the hand
What information does reaching and grasping rely on (and give examples for each)?
Reaching = extrinsic object properties (e.g. distance, position, velocity) Grasping = intrinsic object properties (e.g. size, shape and weight)
What did Milner & Goodale (1995) argue in terms of perception and action?
That they rely on different parts of the brain
Identification and localisation are known as what?
Identification = what Localisation = where
What does ‘perception’ involve?
Identifying objects on the basis of comparisons between what is seen and stored memories
What does ‘action’ involve?
Moment-to-moment computations of a target’s relation to the body (e.g. is the hand big enough to pick up the object and can it get to the object in the appropriate shape)
What are the two types of channels which receives input from the retina?
A fast magnocellular (M) channel relays info about motion and orientation
A slow parvocellular (P) channel relays info about form and colour
The ventral stream largely contains what type of cells?
P
The dorsal stream contains what type of cells?
Both M and P
Perception should be affected by what (which is coded by which cells?)?
Colour and form
Coded by P cells
Actions should be more sensitive to what things (which are coded in what cells?)?
Motion and orientation
Coded in M cells
Brain activity in the ventral and dorsal stream should be associated with what?
Perception and action
Contextual info should affect ___ but not ___
Perceptions
Actions
Visual illusions should have ___ or ___ effects on actions
Small or null
What are the positives of the perception-action model?
It is simple and straightforward
It accommodates a fair amount of behavioural and neurological data
It makes several predictions
What are the negatives of the perception-action model?
It is too simple and too straightforward
It cannot explain the subtleties of much data (e.g. why things happen sometimes but not others)
What are the 3 main points of the planning vs control theory of action?
- Actions involve ‘planning’ and ‘on-line control’
- Planning uses a motor program (a set of stored muscle commands called up from memory) to plan and initiate movement
- On-line control uses visual and proprioceptive feedback to guide hand in flight
Planning tends to be slow and involves much… (planning-control model)
Visual/cognitive info
On-line control is fast and relies on… (planning-control model)
Simple info
What are the two features of planning?
Subjects to some conscious influence
Involves a medial visual stream
What are the two features of control?
Immune to conscious influence
Involves the dorsal stream
What are the 2 predictions of a planning-control model?
Planning will be affected by cognitive factors such as illusions and semantics
Activity related to planning and control will follow a inferior-superior gradient in the parietal lobes
Describe the evidence for a planning-control model
Illusions do have larger effects early in a movement than later
Words can affect the portions of an action, but not the later portions
Describe the evidence for which language influenced planning vs control
‘Large-object’ words led to a larger grip aperture early in a movement than ‘small-object’ words
Prefrontal activity precedes an action by how much?
Several hundred ms
Premotor activity precedes an action by how much?
200-300 ms
Primary motor activity goes on throughout what?
The action
Activity in the frontal lobes follows a caudal-rostral gradient from what to what?
Planning to execution
Reaching involves the caudal part of which lobes?
The superior parietal lobes (known as ‘parietal reach region)
Grasping involves which brain area?
The anterior intraparietal sulcus
Eye movements involve which brain area?
The lateral intraparietal region
Planning movements involves which brain areas?
The areas of the inferior parietal lobule
On-line control involves areas of which lobe?
The superior parietal lobe
When is the basal ganglia active during movements?
Before and during
What does the cerebellum appear to be linked to?
Timing of actions and on-line adjustments
The basal ganglia and cerebellum also encode what?
Actions
Neurons in ventral premotor cortex appear to represent what and respond to what?
Actions
They respond both to the action carried out by the monkey and a similar action carried out by the experimenter
Neurons in the superior temporal sulcus appear to code what motion?
Biological
Neurons in ventral PMS appear to represent what?
Actions
Neurons in the superior temporal sulcus appear to encode what?
Biological motion
What does PET work by doing?
Intravenous injection of radioactive isotope that is taken up in the blood
fMRI works by measuring what?
Blood flow
PET studies showed what in humans (in comparison to monkey’s)?
Actions related to similar areas as found in monkey brain
Why is it more complicated to compare the parietal lobes of humans vs monkey?
Due to evolutionary changes
