MEDI 258 Info Processing Part 1 PDF

Example of information processing… Dr Eugene Poh, MEDI 258 1 MEDI 258 - Pre-programmed reactions Info processing in the Motor System Q1. What are the stages of IP in the motor system? Q2. How do we know that the motor system processes information in stages? Dr Eugene Poh, MEDI 258 2 St...

Example of information processing… Dr Eugene Poh, MEDI 258 1 MEDI 258 - Pre-programmed reactions Info processing in the Motor System Q1. What are the stages of IP in the motor system? Q2. How do we know that the motor system processes information in stages? Dr Eugene Poh, MEDI 258 2 Stages of info processing in the motor system Discrete stages of information processing are: 1) Stimulus identification, 2) Response selection, 3) Response programming Whatever the environmental conditions, processing occurs in stages... Dr Eugene Poh, MEDI 258 3 Stage 1- Stimulus ID Representation of environmental information 1. Performer determines if information (stimulus) is presented and how to identify it 2. Analysis of stimuli (various sources: visual, tactile, auditory, proprioceptive, olfaction, etc. 3. ‘Assemble’ components of dimension (edges/colours, direction, speed) Dr Eugene Poh, MEDI 258 Stage 2 - Response selection Stage involves translation of inputs (from sensory modalities) to movement outputs 1. Performer must decide what response should be 2. Is response needed? - selects appropriate response (e.g. catch, pass, etc.) Dr Eugene Poh, MEDI 258 5 Stage 3 - Response programming Mechanisms retrieve and organize plan of action to control movement and signals to muscles with correct timing, force, etc. Task = organize motor system to produce desired movement Lower level mechanisms (brainstem, spinal cord) Dr Eugene Poh, MEDI 258  How can we test RT experimentally? Reaction time (RT) and movement time (MT) measurements Warning Signal ‘Go’ Signal Initiation of response Termination of response Foreperiod Reaction Time Movement Time Time Dr Eugene Poh, MEDI 258 7  Components of reaction time EMG Recording Pre-motor Time Motor Time Go Initiation of Observable Signal muscle Movement activity Dr Eugene Poh, MEDI 258 8 Reaction Time (RT) How long it takes to prepare and initiate a movement from stimulus onset. Used to identify: 1. Identify the environmental context used in preparing a response 2. How quickly individual can initiate response 3. Assess the capabilities of a person to anticipate a required action and determine when to initiate it. Is independent of movement time (MT) Dr Eugene Poh, MEDI 258 9  Types of reaction time paradigms SIMPLE RT CHOICE RT DISCRIMINATION RT Stimulus light(s) Response key(s) Finger Index Index Middle Ring Index Dr Eugene Poh, MEDI 258 Factors influencing RT / Decision making 1) Number of stimulus-response (SR) alternatives Presentation of different stimuli (lights, etc…) which require different responses = choice RT Each trial begins with warning, followed by an interval of random length RT = measure of time required to detect stimulus, decide which response and initiate movement As # of stimulus-response pairs increases, time required to respond to them (choice RT) increases (slower movements) Dr Eugene Poh, MEDI 258 Factors influencing RT / Decision making (Hick’s Law) Shortest RT found when only 1 stimulus and 1 response Longer responses result from greater number of SR alternatives = Hick’s Law See Fig, RT increases as # of alternatives increases from 1 to 2 E.g., RT of 190 ms with 1 S-R pair increases to >300ms for 2 SR pairs As # of S-R responses gets bigger, RT gets longer, but increase gets smaller and smaller Dr Eugene Poh, MEDI 258 12 Speed of reaction time also affects accuracy of movement Time required for a movement changes as distance to be moved increases How does the resulting speed of a movement affects its accuracy? As early as 1899, Woodworth showed that as performers increased length and speed of line-drawing, their accuracy diminished Paul Fitts (1954) added to this by establishing Fitt’s Law: the first mathematical interpretation of this speed-accuracy trade-off Dr Eugene Poh, MEDI 258 13 Speed-Accuracy trade-offs for rapid, continuous movements Dr Eugene Poh, MEDI 258 14 Speed-Accuracy trade-off for rapid, continuous movements Fitts asked subjects to tap between 2 targets for a number of seconds As width of targets increased, MT’s were faster than for narrower targets As visual feedback is probably used to ‘home in’ on target, Fitt’s law describes the integration of open and closed loop control processes (ballistic and more decelerating control to target) What could be the causes of accuracy deficits with speed? Dr Eugene Poh, MEDI 258 15  Speed-Accuracy trade-off for rapid, continuous movements How does accuracy change as movement time and distance change? Experiment: Aiming movements using a pointer to a target. Subject is asked to move with a specific MT and is given feedback about errors Main results: All movements