Week 13 - Behavioral Neuroscience
Week 13 - Behavioral Neuroscience PSYC 4183-001
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This 8 page Class Notes was uploaded by Celine Notetaker on Saturday April 23, 2016. The Class Notes belongs to PSYC 4183-001 at University of Arkansas taught by Nathan Parks in Spring 2015. Since its upload, it has received 29 views. For similar materials see Behavioral Neuroscience in Psychlogy at University of Arkansas.
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Date Created: 04/23/16
Week 13 – Behavioral Neuroscience Example Question: The ossicles are: A. Bones B. Membranes C. Mechanoreceptors Answer: A. Bones Example Question: A frequency of 20,000 HZ would maximally displace what part of the basilar membrane? Answer: Base (receives high frequencies) Example question: Fill in this pathway: CochleaCochlear Nuclei SO ? ? A1 Answer: Inferior Colliculus Thalamus (MGN) Example Question: True or False. Each superior olive receives input from both the left and right ear. Answer: True Hearing (continued) The Stimulus The Sensory Apparatus Neural Pathways Cortical Representations Sound is localized in three ways: 1. Interaural time difference: Difference of arrival time of sound between the two ears -Occurs in the superior olive 2. Interaural Intensity differences: Difference in sound intensity between the two ears in the horizontal plane -Occurs in the superior olive 3. Pinnae Cues: Performs spectral filtering to identify sound patterns allows localization in the Vertical plane **After passing through the superiorolive the spatial information feeds into the Inferior colliculus which contains a complete map of auditory Space Cortical Representations Primary Auditory cortex = A1= the core Tonotopic/Cochleotopic organization: Orderly layout of frequency along A1 o Anterior A1 = Apex of cochlea low frequency representations (500 Hz) o Posterior A1= Base of cochlea High frequency representation (16,000 Hz) Has SOME Cortical magnification where there is a bit more tissue devoted to representing mid=frequencies A1 Neural Response Properties FrequencySelectivity:Thefrequencythatthecellpreferswillstimulatethatcellmorethan other frequencies Spatial Selectivity: The location of the sound in space will stimulate a cell more in its preferred location than in any other location Has Columnar organization (to an extent) o Frequency Columns o Summation Columns and Suppression columns Provides info about depth in space Summation = columns of cells that are MAXIMALLY responsive to sound from both ears Suppression = responsive to sound in one ear vs. the other Information feed of A1 A1 info belt Parabelt - Belt: Surrounds the A1 - Parabelt: Surrounds the belt *From A1, the information separates into “what” and “where” streams towards the prefrontal cortex Where Stream Infogoingthroughtheparietalcortextendstobespatially related What Stream Info going through T2/T3 tends to be Complex characteristic identifiers - Detects Auditory “objects” A voice o your ability to recognize frequency, timbre, and signaturepatterns iswhatallowsyoutoidentifyavoice’suniqueness HOWEVER, Wernicke’s area: Critical for language comprehension & understanding speech this argues that not EVERYTHING object oriented goes ventrally/anteriorly in the pathway Critical Thinking Question: How will hearing be affected with bilateral damage to the inferior colliculus? Answer: You would become deaf. This will prevent the auditory information from completing its pathway to the cortex which makes one essentially deaf. Critical Thinking Question: How will hearing be affected with damage to the left A1? Answer: You would not become deaf. This is because after the superior olive, the auditory pathway will receive information from both ears on each side of the brain AKA binaural representation. So losing the Left A1 would not cause a complete loss of hearing on either the right of left side of auditory space so you would still have your hearing. Critical Thinking Question: How would bilateral damage to the most posterior portions of A1 affect hearing? Answer: You would be unable to hear high frequencies. This is because bilateral damage to Posterior A1 takes out the reception of information from the base of the cochlea in both ears. Base of cochlea = responds to high frequencies. Motor System Neural Pathways Cortical Representations o M1 o PMA/SMA o Basal ganglia o Cerebellum Neural Pathways Posterior Parietal cortex/ Brodman area 7 – visually guided movements o Also contributes to the planning of motor output Prefrontal cortex – Goal directed behaviors o Contributes to motor output that helps you achieve that goal Descending Pathways - Activity within all descending pathways is modulated by cortical motor areas Lateral Pathways : axons traveling down the lateral side of the spinal cord - Involved in voluntary movement of the disal musculature - under direct cortical control - Largest concentration of cell bodies for these pathways are located in the Primary motor cortex 1. Corticospinal tract : 1 cell body, 1 axon that goes all the way down to the motor neurons in the spinal cord a. Motor neurons = cell bodies in the ventral root of the spinal cord b. Completely contralateral (stroke in the left motor cortex paralysis on the right side) c. If you suffer a stroke in this pathway it is possible to have the pathway rerouted to the red nucleus of the midbrain to continue through the rubrospinal tract (via plasticity) i. Damage could potentially cause paralysis but if the rubrospinal tract is still intact then you could potentially recover 2. Rubrospinal tract: Smaller, originates in the red nucleus in the membrane a. Completely Contralateral b. Damage of this tract in monkeys caused temporary deficits in motor movements but you can recover this tract is thought to have a role in movements for early development (i.e.crawling) Ventromedial pathways - Receives inputs from the Primary motor cortex - Involved in the control of posture and locomotion Allows you to keep the tone of musculature and balance - You don’t have to actively think about this control its how you stay standing or sitting upright without thinking about contracting/tensing your muscles 1. Colliculospinal tract: Projects into all the other pathways (listed below + rubrospinal tract) 2. Vestibulospinal tract: Corrects when your head suddenly accelerates AKA you lose balance/fall in a direction a. Coordinates information to keep you uprught 3. Pontine reticulospinal tract 4. Medullary reticulospinal tract a. Subserves orientation (automated) Cortical Motor Representations Plan it in PMA/SMA execute it with M1 M1 receives additional info from Basal Ganglia and Cerevellum M1 Primary Motor Cortex = M1 - Provides majority of descending fibers in the corticospinal tract o Placing an electrode on the M1 and stimulating it will send a signal down the corticospinal tract o Damage can lead to partial or full paralysis - Cell bodies in M1 have axons that descend all the way down the spinal cord o Sometimes thought of as an extension of the spinal cord in terms of function - Last stage before you can actually contract musculature Organization - CONTRALATERAL - Somatotopic organization: Neighboring regions of M1 control the musculature of neighboring parts of the body o EX: Neurons that move your thumb will be found next to the neurons that move your forefinger - Cortical Magnification: Larger portions of the M1 is devoted to the more dexterous parts of the body o Large portion goes to face and fingers lips and tongue = highly dexterous as it produces language Encoding - Neurons in M1 encode for 2 aspects of movement: o Direction o Force - There is a distribution of preffered output in the neurons of M1 o They are TUNED for a direction but that only means the neuron will fire the most for that direction, but it does not move only in that single direction - The only way to accurately predict the exact movement that will occur by stimulation is by looking at a whole population of cells that are stimulated o The Average vector of response in the population of cells will determine the direction of movement *This knowledge has helped in the creation of neural prosthetics/robotic arms (prosthetics controlled by the brain) PMA/SMA - Planning movement, complex sequences of distal musculature in particular - PMA and SMA represent different muscle groups Damage - Damage to just the PMA/SMA does not cause paralysis - Creates more difficulty in planning and executing motor actions Monkey experiment: Instructing a monkey to press a button - When there’s no instruction there is a baseline firing rate in the monkeys brain - When a monkey is given an instruction the PMA starts firing rapidly o This means that there is a motor plan o Instruction stimulus turns on - When the monkey moves according to those instructions the SMA starts firing rapidly o Trigger stimulus comes on o Instruction stimulus turns off Mirror Neurons – can be found in the PMA o Fires when a particular movement is performed AND when the monkey sees a similar action being performed by someone else (i.e. the human trainer) o Thought to represent learning through imitation (monkey see, monkey do) - Visually observing what someone else is doing converting that into a program of how it was done and translating it to your own body and then executing that same action. Basal Ganglia - Involved in the selection and initiation of voluntary movements - Receives widespread inputs from the cortex, process that information, then feed it back into PMA/SMA through the thalamus (Ventral Lateral Nucleus) - This cycle of info. proccessing through the basal ganglia is referred to as the cortico-basal ganglia motor loop Cerebellum - The cerebellum is involved in timing and coordinating sequences of movements - Forms another motor loop with cortex, the corticocerebellar motor loop, which mediates the coordination of movement sequences. - Broad cortical inputs feed into the cerebellum then project back into M1 via the VL nucleus of the thalamus. Learning & Memory Cellular Mechanisms of Learning Neural Circuitry of memory Cellular Mechanisms of Learning Eye Blink Conditioning = Neural model of Classical conditioning (think Pavlov’s dog) - Puffing air at the eye is met with a reflexive blink response - By pairing a tone with the puff of air you can create a synapse between the neuron in the auditory system (of that tone) to the neuron that causes you to blink o Eventually you could cause that person to blink reflexively to that tone even without that puff of air THEREFORE, The strengthening of a synapse = learning Hebb’s Rule: A synapse is strengthened by the simultaneous activation of presynaptic and postsynaptic neurons o Cells that fire together, wire together Long Term Potentiation (LTP): A long-lasting enhancement of the effectiveness of synaptic transmission o AKA the post-synaptic graded potential is bigger than what it was before represents learning o LTP = mechanism that strengthens synapse - Post synaptic glutamate receptors are the key to LTP o Glutamate receptors NMDA: AMPA
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