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Chapter 12

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Janelle Leboutillier

Chapter 12 PSYB64 Chapter 12 Learning and Memory Learning  Three categories of behaviors o Reflexes o Instincts o Learning  Reflexes: involuntary responses to stimuli  Produced by prewired neural connections or reflex arcs  Advantage of producing rapid, reliable responses, but their inflexibility can be a disadvantage when the environment changes  Instincts: A stereotyped pattern of behavior elicited by particular environmental stimuli  Are automatic but resulting behaviors are more complex  Involve mating or parenting behavior o Male trying to attract a female  Instinctive behaviors are consistent enough throughout life but can be modified by experience  Learning: A relatively permanent change in behavior or the capacity for behavior due to experience  Human adaptability to live in different environments comes from our human capacity for learned behavior  Behavior that changes as a result of experience is only considered learned o Behavior that changes due to maturation or growth does not count  Fatigue, boredom, illness and mood influence behavior but in temporary manners Types of Learning  Associative learning: occurs when an organism forms a connection between two features of its environment o Classical conditioning: allows organism to learn about signal that predict important events  Nonassociatve learning: A type of learning that involves a change in the magnitude of responses to stimuli rather than the formation of connections between elements or events o Includes habituation and sensitization Habituation and Sensitization  Habituation: occurs when an organism reduces its response to unchanging, harmless stimuli (getting used to an environment; sounds, scents etc.)  Sensitization: occurs when repeated exposure to a strong stimulus increases responses to other environmental stimuli o People who have been in major disasters (earthquakes), those people experience exaggerated responses to movement, light and noise o Their overall level of responsiveness as a result of detecting one type of harmful stimulus makes them able to react more quickly to other sources of potential harm Classic Conditioning  Organism learn that stimuli act as signal that predict the occurrence of other important events o Ivan Pavlov discovered this  Conditioned Stimulus (CS): refers to an environment event whose significance is learned  Unconditioned stimulus (UCS): has innate/unlearned meaning to the organism  Conditioned Response (CR): behaviors that must be learned Chapter 12 PSYB64  Unconditioned Response (UCR): appear without prior experience with a stimulus Using Invertebrates to Study Learning  Researchers have relied on the sea slug Aplysia californica since its nervous system is easily observed and they are capable of learning  Dorsal surface of animal has gills which animal uses to breathe  Gill can be covered by a structure called a mantle shelf  One end of the mantle shelf is the siphon (tube through which animal releases waste and seawater)  Gill-withdrawal reflex: touching the animal’s siphon reliably produces a protective response in which gill is retracted o This reflex will eventually habituate to save energy Habituation in Aplysia  Aplysia have neural nets as opposed to brains  Within these neural nets, ganglia, or collections of cell bodies serve as major processing centers  Siphon is served by 24 touch receptors whose cell bodies are located in the animal’s abdominal ganglion  In the Aplysia abdominal ganglion, touch receptors from synapses with a number of excitatory and inhibitory interneurons as well as with six motor neurons serving the gill  Kendel demonstrated that repeated touching of the siphon reduced the size of excitatory postsynaptic potentials in both the interneurons and motor neurons  A smaller amount of input to the motor neurons resulted in diminished activity between the motor neurons and gill muscles which produced a weak withdrawal reflex  Also demonstrated that reduced activity at the synapse between the sensory and motor neurons in habituation was a direct result of the release of less neurotransmitter o Repeated stimulation depletes amount of available neurotransmitter in presynaptic sensory neuron producing short term habituation  PAGE 344 FOR DIAGRAM  Habituation can last up to three weeks  Long – term habituation probably depends on postsynaptic processes involving the NMDA glutamate receptor which participate in the structural changes that accompany learning o If blocked, it can prevent development of long-term habituation Sensitization in Aplysia  Habituation in Aplysia occurs in single pathway connecting sensory input from the siphon to neurons controlling movement of the gill  After Aplysia is sensitized by an electric shock to the head or tail, touching the siphon results in an enhanced gill-withdrawal response  Shocking the animal’s tail stimulates sensory neurons which form excitatory synapses with a group of interneurons o Interneurons in turn form synapses with the sensory neurons that serve siphon o The synapses between the interneurons and sensory neurons are axo-axonic in form (axon from interneuron forms a facilitating synapse at the axon terminal of the sensory neuron)  Interneurons release serotonin at these axo-axonic synapses  When receptors on the sensory axon terminal bind molecules of serotonin, a metabotropic process closes potassium channels o ^With that, action potentials reaching the sensory axon terminal last longer than they would in a typical response to a siphon touch  Longer action potentials produce a greater influx of calcium into the sensory neurons which in turn results in release of larger amounts of neurotransmitter by the sensory axon terminal Chapter 12 PSYB64  Increased release of neurotransmitter produces a stronger response by the motor neurons and the gill muscles, leading to the stronger gill-withdrawal reflex  Sensitization also involves postsynaptic changes as well o Increase in the number of another type of glutamate receptor (AMPA receptor)  Coordination of pre- and postsynaptic changes occurs through retrograde signals from the postsynaptic motor cell back to the presynaptic sensory cell or interneuron Classical Conditioning in Aplysia  A slight touch of the mantle shelf serves as a CS and an electrical shock to the tail serves as a UCS  Prior to training, touching the mantle shelf produces little to no movement of gill  Mantle shelf touch (CS) was paired with electrical shock o the tail (UCS) o The mantle shelf by itself elicited a strong gill-withdrawal reflex (CR) o No changes to siphon touch response (CS)  Change in the gill-withdrawal reflex parallels change in amount of neurotransmitter released by sensory neurons onto the motor neurons serving the gill muscles  Mantle shelf touch produces action potential in the sensory neuron  When these action potential reach axon terminal, calcium enters the cell and determine the amount of neurotransmitter to be released on motor neuron controlling the gill-withdrawal reflex  Shock to the tail results in release of serotonin by an interneuron onto the sensory axon serving the mantle  Potassium channels close, increasing neurotransmitter amount that is released by sensory neurons onto the motor neuron  When large concentrations of calcium are present, the processes leading to potassium channel closing are enhanced Memory Types of Memory  Information processing models: assume that information flows through a series of stages on its way to permanent storage in memory  Atkinson-Shiffrin model: any information sensed by an organism initially enters the sensory memory  Sensory memory: An initial stage in memory formation in which large amounts of data can be held for very short periods of time  We then select information for further processing and move it to the next-stage of memory (short-term memory)  Short-term memory: AKA working memory; an intermediate memory store in which limited amounts of data can be held for a limited amount of time; without further processing, such information is permanently lost o Info is sorted into temporary storage areas for audio, visual or combine types of information which are managed by a ‘central executive’ process  Long-term memory: A memory store in which apparently unlimited amounts of data an be held for an unlimited amount of time o Few to no limitations on capacity or duration unlike short-term memory o Three categories: semantic, episodic and procedural  Semantic memory: contain basic knowledge of facts and language  Episodic memory: relates to your own personal experience  Procedural memory: stores information about motor skills and procedures such as riding a bicycle, using software program, or cooking a meal  Declarative memory/Explicit: A explicit memory for semantic and episodic information that can be easily verbalized or declared Chapter 12 PSYB64 o Are typically recalled consciously unlike procedural memories which are usually unconscious or implicit  Nondeclarative/Implicit memory also include classical conditioning, habituation, and sensitization  However, trace conditioning is actually similar to declarative memory  Anterograde amnesia: Memory loss for information processed following damage to the brain o Their inability to remember the present is due to having issues with explicitly remembering information o Their implicit memory to solve puzzles and such was not affected  Engram: a physical memory trace in the brain Brain Mechanisms in Memory Early Efforts to Locate Memory Functions  Karl Lashley was one of the first psychologists to try to find engram o Thought it might be located in the association cortex (areas of cortex that are not locked into a specific sensory or motor function)  Tested this on rats  Rats received cortical lesions before and after they were trained to run through mazes  Rats that received cortical lesions prior to any training were slow to learn their way through  Rats that received lesions after seemed to have forgotten many of their previously learned behavior  Lashley thought the engram was distributed evenly across the cortex and no one area is more responsible for learning and memory o He also thought that the more cortex you have the better memory you have o This is wrong  Memory is distributed across the cortex rather than stored in one specific location  Penfield contributed to theory of localization of memory in the brain  Single neurons are correlated to memory for different kinds of information The Temporal Lobe and Memory  Damage to medial temporal lobes affects explicit but not implicit memories o Does not affect long-term memory that has already been stored before anterograde amnesia but it does affect the transfer of new information from short-term to long-term memory  Delayed nonmatching to sample (DNMS) task: a standard test of memory in which the subject must identify the novel member of a stimulus pair following a delay o Monkeys with damage to medial temporal lobes (lesions) in both hemisphere performed poorly on the DNMS takes esp. as delay period increased o Therefore, lesions do no compromise short-term memory  Areas damaged in medial temporal lobe include amygdala, h
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