Audition Lecture Notes PDF

Audition X.Liu PSYC 5130 Perceiving Pitch Rate Coding Neurons fire in synchrony with the movement of the basilar membrane Lower frequencies are detected by rate coding X.Liu PSYC 5130 Perceiving Pitch Rate Coding Neurons fire in synchrony with the movement of the basilar membrane Lower frequencies a...

Audition X.Liu PSYC 5130 Perceiving Pitch Rate Coding Neurons fire in synchrony with the movement of the basilar membrane Lower frequencies are detected by rate coding X.Liu PSYC 5130 Perceiving Pitch Rate Coding Neurons fire in synchrony with the movement of the basilar membrane Lower frequencies are detected by rate coding X.Liu PSYC 5130 Place Coding X.Liu PSYC 5130 Tonotopic Mapping in the Cochlea X.Liu PSYC 5130 Perception of Pitch Cochlear Implants Devices that utilize place and rate coding of pitch in the cochlea to enhance hearing Restore hearing caused by damage to hair cells X.Liu PSYC 5130 Perceiving Loudness Loudness Louder sounds produce more intense vibrations of the eardrum and ossicles Cochlear nerve alters rate of firing action potentials Loudness of low-frequency sounds is signaled by the number of axons arising from the neurons in the basilar membrane X.Liu PSYC 5130 Perception of Pitch and Loudness for High-, Moderate- and Low-Frequency Sounds Frequency Perception of Pitch Perception of Loudness High-frequency sounds Place coding; firing by hair cells at location of basilar membrane that is active Determined by rate of action potentials from hair cells Moderate-frequency sounds Place coding; firing by hair cells at location of basilar membrane that is active Determined by rate of action potentials from hair cells Low-frequency sounds Rate coding; hair cells at apical end of basilar membrane fire in synchrony with frequency of sound wave Determined by number of active hair cells This table summarizes how pitch and loudness are represented by the activity of hair cells in the cochlea. X.Liu PSYC 5130 Control of Movement (by the brain) X.Liu PSYC 5130 Sensory System EPSP IPSP Resting Potential & Action Potential Synaptic Transmission X.Liu PSYC 5130 Neurotransmitter Drug Effects Motor System Movement Goal-directed, voluntary movement depends on… –knowledge of where the body is in space –where it intends to go –the selection of a plan to get it there And…once a plan is selected, it must be held in memory until an appropriate time –carrying out X.Liu PSYC 5130 Neurosurgeon: Wilder Penfield X.Liu PSYC 5130 Primary Motor Cortex Weak electrical stimulation of Primary Motor Cortex (M1) produced twitching in muscles on contralateral (opposite) side of body. X.Liu PSYC 5130 Motor Cortex and the Motor Homunculus Stimulation of various regions of the primary motor cortex causes movement in muscles of various parts of the body. X.Liu PSYC 5130 How is Movement Coded in M1? For a long time… –It was thought that M1 possessed a detailed mapping of individual muscle movement –such that the activity of a single M1 neuron would lead to certain activity of a single set of motor neurons and activate a specific muscle or group of muscles However, the new view focuses on the impact of populations of neurons –Encoding the force and direction of a movement… X.Liu PSYC 5130 Some experimental evidence Monkeys trained to move a joystick toward a small light whose position varied randomly around a circle. X.Liu PSYC 5130 Monkey Joystick Performance The M1 cells fired most vigorously during movement in one particular preferred direction …But also discharged during movements that varied +/45 degrees from the preferred direction Pretty coarse directional tuning But, monkeys were VERY accurate in their movements… How can the brain be less accurate than behavior? X.Liu PSYC 5130 AP Firing Rate of M1 Neuron X.Liu PSYC 5130 Predicting Movement from a Population of Neurons Each cluster shows direction vectors for many M1 neurons during movement in each of the directions Sum across them to get population vector (red arrow) This predicts movement direction! X.Liu PSYC 5130 Predicting Movement from a Population of Neurons Each cluster shows direction vectors for many M1 neurons during movement in each of the directions Sum across them to get population vector (red arrow) This predicts movement direction! X.Liu PSYC 5130 Predicting Movement from a Population of Neurons Each cluster shows direction vectors for many M1 neurons during movement in each of the directions Sum across them to get population vector (red arrow) This predicts movement direction! X.Liu PSYC 5130 X.Liu PSYC 5130 https://www.youtube.com/watch?feature=o embed&v=wxIgdOlT2cY X.Liu PSYC 5130 Movement by Vote much of M1 is active for every movement The activity of each cell represents a single vote for a particular direction of movement votes vary in their strength –How many APs the direction of movement is determined by a tally and averaging of the votes registered by each cell in the population X.Liu PSYC 5130 A Consequence... The larger the population of neurons…the finer the possible control So, we would expect the hands and face to have finer motor control This is the case... X.Liu PSYC 5130 More than M1 READY, SET, GO X.Liu PSYC 5130 Planning and Initiating Movements: PMA & SMA Supplementary Motor Area and Premotor Cortex Especially important to control of movement Supplementary motor area (SMA) is located on the medial surface of the brain Premotor cortex (PMA) is located mostly on the lateral surface of the brain X.Liu PSYC 5130 PMA & SMA X.Liu PSYC 5130 Some Evidence for This… PET to monitor changes in patterns of cortical activation that accompany voluntary movements in humans Ss asked to perform a series of finger movements from memory. The following areas showed increased blood flow: – SMA, PMA and M1 X.Liu PSYC 5130 Some Evidence for This… BUT… –when Ss were asked only to rehearse the movement mentally without actually moving the finger, PMA, SMA, remained active, but M1 did not. –So, PMA/SMA seem to be more active in planning, with M1 more active in carrying out this plan. X.Liu PSYC 5130 Electrophysiological Evidence Neurons in SMA/PMA –typically increase their rate of action potentials about 1 second before the execution of a hand or wrist movement –This is consistent with their proposed role in planning movement X.Liu PSYC 5130 Delay = Ready Monkey! Instruction Stimulus = Get Set Monkey! Tells him which movement he will need to make (e.g. left arm) Variable delay until Trigger Stimulus Trigger Stimulus = Go Monkey! Reward if correct X.Liu PSYC 5130 Delay = Ready Monkey! Instruction Stimulus = Get Set Monkey! Trigger Stimulus = Go Monkey! PMA neuron continues to fire AP until the movement is initiated X.Liu PSYC 5130 Standing on the mound The decision to throw a curve ball has been made Batter walks away from the mound to clean his cleats, “psyche out” the competition The pitcher stands and waits X.Liu PSYC 5130 Standing on the mound The decision to throw a curve ball has been made Batter walks away from the mound to clean his cleats, psych out the competition The pitcher stands and waits The pitcher is Ready, SET A select population of neurons in PMA and SMA are firing away in anticipation to throw the curve ball. What’s needed is an internal GO signal X.Liu PSYC 5130 The “Go” What is responsible for the internal go? Basal Ganglia –Major complexity –Only beginning to be appreciated –Many circuits, only some motor –Cognitive, learning, memory X.Liu PSYC 5130 X.Liu PSYC 5130 X.Liu PSYC 5130 https://www.youtube.com/watch?start=183 &feature=oembed&v=JBuAFWKWxDQ X.Liu PSYC 5130 X.Liu PSYC 5130 Basal Ganglia Direct Pathway = Go Signal Indirect Pathway = No Go Signal Hyperdirect pathway = STOP! X.Liu PSYC 5130 When Something is Wrong X We watch a movie! We watch two movies! X.Liu PSYC 5130 https://www.youtube.com/watch?start=369 &feature=oembed&v=dKQXDve6WiE X.Liu PSYC 5130 Parkinson’s Disease Symptoms –Bradykinesia - Slowness of movement –Akinesia - Difficulty initiating willed movement –Increased muscle tone – Rigidity –Tremors of hands and jaw that are prominent at rest (often disappear w/ willed movement) X.Liu PSYC 5130 Parkinson’s Disease X X.Liu PSYC 5130 Comparison of Healthy Brain and Brain with Parkinson’s Disease Showing Loss of Substantia Nigra X.Liu PSYC 5130 Huntington's disease X X.Liu PSYC 5130 Summary of BG BG may facilitate movement by focusing activity from widespread regions of cortex onto motor areas Importantly, the BG also serve as a FILTER that keeps inappropriate movements from begin expressed X.Liu PSYC 5130