Conditioning and Learning Motor Learning October 7 8 2013 John M Ackroff 2013 Voluntary Movements Require Perception of target Awareness of location of movable body part Ability to aim movement of body part Ability to detect errors and re adjust use feedback Ability to use feedback to control movement of body part John M Ackroff 2013 Overview of Motor System Parietal cortex Premotor and supplementary motor Planning cortex Execution Motor cortex and basal ganglia and body movement Cerebellum and nervous system program John M Ackroff 2013 Cortical Motor System John M Ackroff 2013 Motor Somatosensory Maps John M Ackroff 2013 Planning Motor learning occurs because the final posture of a successful movement is stored in memory When the target again appears in the same location the posture is retrieved and becomes the plan that is programmed and executed The retrieval of stored postures reduces the amount of computation necessary for fast accurate action John M Ackroff 2013 Planning An Action Parietal cortex Neurons respond to both visual and tactual Input used in activating and selecting inputs among plans Premotor and supplementary motor cortex Activation and selection of plans mirror neurons respond when the same action is performed or observed John M Ackroff 2013 Planning a grasp Figure 2 5 Four steps in planning a grasping action Representations of grasping hand postures are retrieved from memory top panel The hand posture providing the closest fit to the target is selected second panel Representations of arm extensions are retrieved from memory third panel The arm extension providing the best fit with the grasp posture and its location is selected bottom panel John M Ackroff 2013 Characteristics of Motor Plans Complex patterns of movements can be built up hierarchically by combining posture plans Advantage of large program speed Though exact repetition is the key to learning what is learned is very abstract This makes tool use possible John M Ackroff 2013 Execution Motor subsystems Locomotion Motor cortex Manipulation Motor cortex Vocalization Broca s area Visual Fixation and tracking Frontal eye fields John M Ackroff 2013 Motor Programming the Cerebellum Smooth accurate movements require that many different muscles throughout the body must contract or relax in a precisely timed sequence Determining this sequence requires a huge number of computations These computations are performed by the Cerebellum which constructs the motor program John M Ackroff 2013 Cerebellum A motor program produces smooth movements by specifying a precisely timed sequence of muscle contractions Vestibulocerebellum contains reflexes for maintaining balance and coordinating eye movements vestibular ocular reflex if you shake your head u can still read a paper but if you move your hand up and down with the paper it is harder to read Spinocerebellum neocerebellum turn motor plans into motor programs John M Ackroff 2013 Hemispheric Coordination One side of brain is responsible for coordinating movements on both sides of the body Messages sent via the corpus collosum connects left and right cortex John M Ackroff 2013 Corpus Collosum John M Ackroff 2013 Execution Motor production control systems Movements may be made voluntarily under perceptual guidance e g catching through the parietal cortex Movements may be generated internally e g speaking through the basal ganglia Movements may be activated by a central pattern generator e g walking in the brain stem John M Ackroff 2013 How Perceptually Guided Limb Movements are Made Proprioceptive feedback loops Short loop Directly from Rapid approximate Long loop Goes through Slower detailed Multiple levels of control involving brain stem cerebellum basal ganglia and cortex John M Ackroff 2013 Feedback visual and kinesthetic inputs provide redundant sources of feedback for guidance John M Ackroff 2013 Perseveration As the result of aging or injury control through inhibition of action sequences weakens and perseverations result These are extra repetitions of a response John M Ackroff 2013 Test for Perseveration John M Ackroff 2013 Motor Learning Occurs through the accumulation of plans John M Ackroff 2013 Stages of Motor Skill Learning Cognitive New activity requires many small motor plans Constant attention required Associative Some attention still required to control multiple independent sequences Autonomous A single motor program for the entire action Attention freed to perform other activities John M Ackroff 2013 Practice and speed in cigar making Each point is the average cycle time over one week s production for one operator The ordinate is the total production by the operator since beginning work After Crossman 1959 John M Ackroff 2013 Question In order to learn to type how much time should you spend practicing every day recruited people and taught them how to type John M Ackroff 2013 Learning for four training schedules hours x day hour x day John M Ackroff 2013 Retention Function John M Ackroff 2013 Characteristics of Motor Skill Learning The learning curve is a power function Complex patterns of movements can be built up hierarchically by combining posture plans Advantage of large program speed Disadvantage inflexibility There is no asymptote There is always improvement with practice There is no forgetting Though exact repetition is the key to learning what is learned is very abstract John M Ackroff 2013 Autonomous vs Automatic An action under the control of a plan stored in memory is autonomous It does not require computation so other mental actions requiring computation may be carried on at the same time e g tying your shoes An autonomous action that is initiated by a perceptual input e g hitting a baseball is called automatic Normal activity relies on both autonomous and automatic actions John M Ackroff 2013 Characteristics of Retention Function Long term retention appears to be a function of number of days of practice rather than number of hours of practice So distributed learning produces better retention than massed learning Perhaps forgetting does not occur for routine activities John M Ackroff 2013 Summary of Motor Control The motor control system is heterarchical Contains both Hierarchical control Parallel operations A motor plan specifies the body posture location of limb and location to which limb is to be moved A motor plan specifies the sequence in which muscles must contract to execute the plan John M Ackroff 2013