The motor system Flashcards
explain the behavioural appraoch to studying actions
A) Behavioural: Use video or electronic recording equipment -allows one to record the position of body parts in space and time
Can measure speed, accuracy and kinematics (velocity, acceleration, etc.)
Strengths: Allows us to systematically investigate the output of the action system
Weaknesses: Cannot tell us anything about the brain
evaluate and explain Muscle Physiology (electromyography)
Muscle Physiology (electromyography): can record activity of individual muscles or muscle fibers during action
Strengths: Allows an understanding of how muscles operate
Weaknesses: Also does not directly tell us anything about the brain
evaluate and explain Neurophysiology
Neurophysiology: Implant electrodes in brain and record activity of individual neurons
Can take a record of a number of neurons and measure their activity in real time
Strengths: Allows for excellent spatial and temporal resolution
Weaknesses: cannot examine more than a miniscule percentage of the neurons at any one time
monkeys aren’t humans
outline Neuroimaging
) Neuroimaging: Put a subject in a brain scanner and measure blood flow while they perform a task
More blood flow = more brain activity
Strengths: Allows for a direct measure of activity in the human brain
-has good spatial and fairly good temporal (at least for fMRI) resolution
Weaknesses: Many action processes take less than 2-4 seconds
-hard to make many movements in a scanner environment
Outline and evaluate Neuropsychology
Neuropsychology: examine the consequences of brain damage in humans or animals
If damage to one area is linked to a behavioural deficit, then can infer that area is necessary for that function
Strengths: Allows one to examine consequences of (in humans) naturally-occurring brain damage -can be used to show what areas are most important for a particular function
Weaknesses: Cannot (in humans and often not in animals) place lesions where you want them and the size you want them -lesions often have effects on neurons far from the lesion site
Outline and Evaluate TMS
Transcranial Magnetic Stimulation (TMS): temporarily disrupt brain activity in healthy humans (or animals) using a high-powered magnetic coil
-as with neuropsychology, infer function from effects of TMS
Strengths: A lot more ethical than giving people brain damage -can more or less precisely define the area of disruption and the time of disruption
Weaknesses: not all areas can be tested, must be on the surface of the brain -must be very careful not to give the participant a seizure!
Outline and evaluate Computational Modelling
Computational Modeling: devise mathematical models of how actions might be carried out by a set of neurons
Strengths: Approaches the question of brain function from a synthetic rather than analytical perspective
Weakness: Does not address how brain actually works
Outline and Evaluate event-related potentials
) Event-related potentials: record electrical activity from the scalp
Strengths: Very good temporal resolution
Weakness: Poor spatial resolution- what are you actually recording?
what are the two factors that effect The unfolding of movement kinematics
The unfolding of movement kinematics varies systematically with two factors:
1) the characteristics of the target
2) the relation between the target and the hand
E.g. grip aperture increases with increasing size ., grasping a fragile object leads to an extended deceleration phase Smaller targets lead to lower peak velocity and longer movement times
what information does reaching and grabbing rely on?
Reaching (arm) and grasping (hand) rely on different information:
Reaching relies on extrinsic object properties
e.g., distance, position, velocity
Grasping relies on intrinsic object properties
e.g., size, shape, weight
what info does percieving and action rely on
Milner & Goodale (1995) argued that perception and action rely on different parts of the brain
Perception and action said to use different visual information
what are the two visual streams
eyes --> LGN--> V1--> Dorsal(SPL) and ventral (IT) Ungerleider and Mishkin (1983) SPL deals with localization IT deals with identification Milner & Goodale (1995) SPL = action IT is perception
what is the differences between perception and actino
‘Perception’ involves identifying objects on the basis of
comparisons between what is seen and stored memories
‘Action’ involves moment-to-moment computations of a
target’s relation to the body
outline how perception and action rely on two different retina streams
A fast magnocellular (M) channel that relays information about motion and orientation
A slow parvocellular (P) channel that relays information about form and color
The ventral stream largely contains P type cells
The dorsal stream contains both M and P cells
Perception should be affected by such things as color and form that are coded in P cells
Action should be more sensitive to such things as motion and orientation that are coded in M cells
Brain activity in the ventral and dorsal stream should be associated with perception and action, respectively
what are the predictions made by perception Vs Action info
Contextual information (coded in the ventral stream) should affect perceptions but not actions
Thus, visual illusions should have small or null effects on actions
