EXP 3202 Sensation and Perception AKA THE MOST BULLSHIT CLASS EVER Study Guide for Exam 2 ESSAY QUESTIONS WILL BE 1 THE SYNAPSE QUESTION 2 ONE OF THE BELOW QUESTIONS WILL BE AN ESSAY QUESTION DIAGRAM BE ABLE TO DRAW A SYNAPSE AND PARTS OF A NEURON LABELING EXPLANATION DON T KNOW WHAT THOUGH Lecture study questions 1 Compare a neuron to neuron synapse to a hair cell to neuron synapse Draw a typical synapse If an action potential reaches the terminal of the presynaptic cell what sequence of events happens to result in a synaptic potential in the postsynaptic cell be sure to use proper terms and the proper sequence of events Draw a typical hair cell What happens when the stereocilia are deflected and then what sequence of events happens to result in an action potential being sent to the brain Neuron to neuron Voltage gated calcium channels open up at terminal Important step o Happens for any synapse o Calcium goes in and vesicles release neurotransmitter into gap Some bind to particular receptor on post synaptic cell Chemical interaction between the recepter and neurotransmitter opens up ligand gated channel Ions go through the membrane o Less negative in new cell because of the positive ions that come in o Channels are key Proteins embedded in membrane What opens them and what ions og through Is how they are classified o Ligand gates and neurotransimitter recepter are synonomas They are o Channels only let certain ions through but can onl do that if they are one big unit opened Hair cell o Potassium coming in because of the high concentration o That depolarization doesn t start action potential because no voltage gated channels Opened by mechanical activity by being opened o Depolarization enough to open voltage gated calcum channels and calcium goes in neurotransimitter is release o Then biding to receptor open gate let sodium in if enough goes in you get action potential same as with neuron Can hear better in the ear that is covered when doing bone conduction theory because outside noise is not affecting the sound 2 What is a cochlear implant and how does it work What principle of cochlear function neural coding does it taking advantage of tonotopic organization Used for profound hearing loss when hearing aid wont work Cochlear implant comes from basic understanding of cochlea o Hair cells are damaged but the auditory nerve fibers are still there but cant activate them o Brain doesn t care how auditory nerve is stimulated but if it is you will hear sound doctrine of specific nerve energy o Electrically stimulate nerve fibers Coils of electrodes placed inside cochlea o Different electrodes can stimulate different places so different frequencies are perceived tonotopic organization labeled line coding Hearing aid Electrode array in cochlea Coil up into the cochlea with places to stimulate along the way o Receiver under skin with wire to implant o Transmitter worn outside provides commands to activate electrodes Why have little tube go into ear o Microphone placed in ear canal so you get to filter out sound through pinna still Very successful telephone o Many patients can go from profound deafness to talking on the 3 What is tinnitus What are some of the causes of tinnitus What evidence suggests that some forms of tinnitus are not generated by the ear What does tinnitus tell us about how perception relates to physical changes in the world around us Tinnitus is common disorder o Perception of sound in the absence of an acoustic stimulus Ringing in the ears after a concert but some people have it as a chronic condition could cause depression o 10 15 of all adults o Cause multiple noise induced some drugs aspirin aging related to hearing loss but not necessarily produced by damaged ear per se can have tinnitus even when auditory nerve is cut o antidepressents used if its driving people crazy o its just central activity in the tinnitus patients if brain is ative then perception it doesn t need to be started by sound MEG overlaid on MRI scan of subject with unilateral tinnititus o Leading hypo loss of inhibition in the central auditory pathway Excess of activity debate of where gets started o For most people this is transient and it comes and goes o Many returning vets will have this who were exposed to loud noises More common because more people have noise induced hearing o Just activity in the brain it really doesn t have to be from outside loss today Neural coding What info is available o Action potentials simple yes or no event cant vary in size All or none o Location of activity o Rate of activity how fast are they happening o Pattern of activity 4 How is information about sound frequency coded in the brain How is information about the intensity of a sound coded in the brain Frequency Coding In an Auditory nerve fiber we get a tuning curve the threshold to get action potential started in a particular neuron as we vary the frequency Lower frequency need higher intensity to get action potential So Brain knows which frequencies are in the sound by which neurons are Tonotopic frequency map organization o Systematic arrangement of what the best frequency for those cells active are o Combination of where frequency and how much intensity neural activity codes what the sound is That s going to tell you whats in a sound Intensity rate of action potentials related to intensity of stimulus o rate intensity functions How many spikes per second As increase intensity of sound individual neuron will have started to give action potential tart go at faster rate until reach saturation point o A neuron cannot code the whole intensity range but different neurons might code different parts of the range Intensity Coding 5 What are the cues that we use for determining where a sound is located Which one works best for high frequency sounds and which works best for low frequency sounds Where does coding of interaural time differences begin in the brain What is meant by phase locking and why is it important for coding time differences What is sound localization o Two ears are better than one Cues Interaural time difference ITD o Works best for low frequency sounds Interaural intensity difference IID between ears o Works best for high frequency sounds Together We mostly use ITD at low frequencies IID at high frequencies and both for middle frequencies o Cochlear nucleus and auditory nerve superior olivary complex first place to get info from both ears ITD for coding interaural time differences timing must
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