2/09/12-2/11/16 Psychobiology Lecture Notes
2/09/12-2/11/16 Psychobiology Lecture Notes Psych 5600
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This 5 page Class Notes was uploaded by alvey.15 Notetaker on Saturday February 13, 2016. The Class Notes belongs to Psych 5600 at Ohio State University taught by Derek Lindquist in Spring 2016. Since its upload, it has received 37 views. For similar materials see Psychobiology of Learning and Memory in Psychlogy at Ohio State University.
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Date Created: 02/13/16
2/9/16-2/11/16 Psychobiology Notes. Dr. Linquist. Notes by Alexandra Alvey. The Rescorla-Wagner (RW) Model is driven by whether the US is present or not. This is shown in the equation by the prediction error (actual US- predicted US). So according to the RW model the mice that are presented with only the CS in phase 1 of learning will learn at the same rate as the mice that were presented with no stimuli in phase 1. This is where the RW model fails to predict the behavioral responses of the organism. The mice that were presented with the CS in phase 1 have a slower associative learning response in phase 2, when the CS is paired with the US, than the control mice. This phenomenon is called latent inhibition which states that if a CS (light, tone, etc.) is not paired with the US (food, shock, air puff, etc.) for many trials then when the pairing does occur it takes longer for the association learning to occur because of inhibition. This lead to production of models that explained the diminishing effect of the CS when presented alone. These models were called CS modulation models. You do not have to know the specifics of the Macintosh model or Pearce and Hall model, just know the general idea of CS modulation models. When the CS is presented without the US for many trials the salience of the CS diminishes and does not require the organism’s attention. When phase 2 of CS and US of pairing occurs it is more difficult for the organism to re-attend to the CS which decreases associative learning. The CS modulation models also explain to the blocking phenomenon that occurs with compound conditioning. The only thing that is different is that the organism does not have any attentional resources for the second CS. Sensitization is a transient increase of the gill withdrawal in the Aplysia and can be generalized to other stimuli. For example, the Aplysia is touched on the siphon and eventually habituates to the siphon touch. Then the Aplysia receives a shock to the siphon and after is sensitive to the touch on the siphon observed by a strong gill withdrawal. This response does not last as long as the response with Classical Conditioning. Classical conditioning is homosynaptic or only applies to the specific sensory neurons of the CS and motor neurons of the gill withdrawal. In the Aplysia the touch of the siphon is immediately followed by a tail shock so the conditioning is only associated with the sensory and motor neurons on the siphon and tail. The sensory neurons receiving the US (shock) have serotonin released on them by interneurons. The release of serotonin increases glutamate release by the sensory neurons that were active in the last half second which were the siphon sensory neurons receiving the touch information (CS). This produces a gill reflex and when conditioning is repeated over and over again the gill reflex becomes stronger due to more glutamate release. Eventually functional changes between the neurons become structural changes in the presynaptic terminal of the siphon by phosphorylating and decreasing potassium channels and addition of more calcium channels. These changes increase the depolarization of the neuron and eventually the presynaptic neuron creates new neurons by Creb1. Creb 2 decreases the amount of synapses on the neuron and this happens in LTD. Since the 1970’s eye blink conditioning has been used to study classical conditioning mainly in rabbits since they can hold still for long amounts of time and have very little spontaneous eye blink response. We know all the neural, physiological and behavioral components of eye blink conditioning. The CS (tone) is being relayed through the pontine nuclei in the brainstem. The afferents (ascending sensory axons) are called the mossy fibers ascend to the interpositus nucleus deep in the cerebellum. The mossy fibers also extend farther to innervate granule cells, parallel fibers and eventually the purkinje cells. All neurons in the CS tract are excitatory and they use glutamate as a neurotransmitter. The US pathway carries excitatory afferent information to and through the inferior olive of the brainstem. The excitatory afferents called the climbing fibers synapse on the interpositus nucleus deep in the cerebellum and the purkinje cells in the cerebellar cortex. The purkinje cells are synapsed by an excitatory afferent from the US and an excitatory afferent from the CS which indicates the purkinje cells perform complex computations. The purkinje cells send the CS and US information to the interpositus nucleus via inhibitory efferents. The GABA release on the interpositus nucleus helps develop the CR (blink) at the correct time. The interpositus sends inhibitory signals to the inferior olive and excitatory signals to the eye muscles to produce the CR (blink). There is evidence for the interpositus nucleus being the engram of classical conditioning. When lesioned the animal can not learn conditioned responses or perform previously learned conditioned responses. The inferior olive in the brainstem helps develop the CS-US relationship but will fire a evoked potential once the CR is developed due to the inhibitory effects of the interpositus nucleus. That is why the expected US is IO firing – inhibition of IO firing from the interpositus nucleus. In blocking of EBC the US (air puff) is the strong stimulus and the CS (tone) is the weak stimulus. Once the CR (eye blink) is presented at the correct time a compound stimulus of light and tone is presented. The new CS (light/tone) can not be associated with the US because the inferior olive has been inhibited by the interpositus nucleus. When the inferior olive is inhibited the purkinje cells are inhibited from responding to the US with complex spikes. This inhibition of the purkinje cells produces the CS (tone) and CR (eye blink) but will not produce the same CR to the compound stimulus because the US can not be associated with the new stimulus due to the inhibition of the inferior olive. If the inferior olive was disinhibited, then the animal would be able to perform the conditioned response to the new and old CS. Latent inhibition and the salience of the CS is performed by the hippocampus. When the hippocampus is damaged in rodents and a CS is presented without the US the CR is the same as when the CS and US are presented together. Clinical Perspectives The underlying neurobiology of eye blink conditioning is conserved across species. Cerebellar damage in a human disrupts acquisition of EBC. Almost every neurodevelopmental disorder produces a delay in the CR (blink) except for Autism because these individuals are attuned to sensory stimuli. Conditioned Compensatory Response is best demonstrated in the example of dog’s given an adrenaline shot (US) in a specific environment say a vet’s office (CS). The dog receives the adrenaline shot many times in the same vet’s office and starts to show a decrease in heart rate (CCR) right before the adrenaline is administered. The dog’s body is compensating for the effects of the adrenaline (UR) due to the environmental cues of the vet’s office. If the dog was given the adrenaline shot in a different environment, like outside, then we would not see the initial drop in heart rate right before the shot. Conditioned Compensatory Response also applies to human’s and drugs. If you are a first time user of a drug, then your CCR will not be large enough to counteract the effects of the drugs and you will experience a greater high but could possibly die if the dose is large enough. If you are a consistent user of the drug, then your CCR will continue to grow with your use of drugs and you will have to keep on increasing the amount of drugs taken to get the same high. You are now tolerant to the drug but only in a specific context with certain cues. If you change where you are administering the drug, then the effects will be greater but there is a possibility of death. Pre exposure to drug cues will cause latent inhibition. If your friends do drugs and you are around the cues (CS) but don’t take the drugs (US) then when if you decide to take the drugs the CR will not be as strong for you in the presence of the CS. In other words, you will associate the drugs with the particular cues of the environment much slower than your friends who have been doing drugs in that environment for a while. So they might walk in to the room, see the cues and then start doing drugs while it will take you longer to walk in to the room and automatically start doing drugs. Withdrawal is a form of extinction learning. When the CS is presented alone multiple times then addictions can be broken. It is hard for drug addicts to do this because the CS stimulates the need for the US. There body will trigger the CCR and they will want to do drugs (US). Chapter 5 The curve of instrumental conditioning is in the opposite direction of classical conditioning because it is measuring the time it takes for an animal to produce a particular response. The time decreases with every trial. The Law of effect is based on the stimulus and response relationship that is either strengthened by a satisfying consequence or weakened by a annoying consequence. Remember Tolman observed that rats don’t just automatically respond to stimuli but learn in the absence of stimulus as well. The consequence of the response determines if the animal will continue to respond strongly to the stimulus or not. The difference between instrumental and classical conditioning is that instrumental conditioning is mandated by the stimulus. The consequence does not occur unless the animal responds correctly to the stimulus. This requires a lot of pre training before testing the animal. Classical conditioning does not require pre training and the US occurs even if the CR does not occur right away. Ask yourself if the stimulus is dependent on consequence? If not, then it is classical conditioning. If so then it is instrumental conditioning. Free-operant conditioning is a form of instrumental conditioning but it let’s the animal control when it responds to the stimulus instead of the experimenter like in discrete trial paradigm. The skinner box is used in operant conditioning. A discrete stimulus is usually used to let the animal know when to make the response. The discrete stimulus is usually a tone or a light. Conversely the absence of the tone or light will let the animal know when to not make the response. A response can be reinforced or punished. Reinforcing will increase the response and punishment will decrease the response. Reinforcing objects could be food, praise, exercise, etc. Primary reinforcers are food, water, sex and sleep. Secondary reinforcers have no intrinsic value on it’s own but a very effective in humans. Examples are money, fame, status, etc. The secondary reinforcers are more effective that primary reinforcers because it is not dependent on bodily state. Punishment is less effective than reinforcement. Take cops giving speeding tickets for example. The cop car is the discriminating stimulus that makes you slow down (CR) in order to avoid the punishment of a ticket. When the discriminating stimulus (cop car) is not present then we will continue to speed. Concurrent reinforcement can undermine punishment. If children in a classroom are laughing while the teacher is scolding a child, then the punishment will hold less weight than the children’s laughter and the behavior will continue. Also the initial intensity of the punishment matters because incremental increase in punishers can habituate the animal to the sensation. To work your way through these S-R-C association problems first ask yourself are we trying to increase or decrease the response? If increase, then you need reinforcement and if decrease then you need punishment. Then ask is the consequence being presented or removed? If presented, then it is positive and removed is negative.
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