Mind and Brain Learning and Memory Chapter 13

Mind and Brain Learning and Memory Chapter 13
Show Brenda Milner video (7:45) Learning and Memory Chapter 13

You are responsible for Chapter 13 (text and notes) for you final as well as all other chapters (and notes) covered in class.

http://www.youtube.com/watch?v=JliczINA__Y&feature=relat ed

Chapter Overview The Nature of Learning
Synaptic Plasticity: Long-Term Potentiation and Long-Term Depression Perceptual Learning Classical Conditioning Instrumental Conditioning Relational Learning

The Nature of Learning Introduction
Learning refers to the process by which experiences change our nervous system and hence our behavior; we refer to these changes as memories Experiences are not stored – they change the way we perceive, perform, think, and plan They do so by physically changing the structure of the nervous system, altering neural circuits that participate in perceiving, performing, thinking and planning.

The Nature of Learning Learning can take at least 4 basic forms
Perceptual Learning Stimulus-Response Learning Classical Conditioning Instrumental Conditioning Motor Learning Relational Learning

The Nature of Learning Perceptual Learning
Learning to recognize a particular stimulus Primary function: ability to identify and categorize objects and situations Each sensory system is capable of perceptual learning Accomplished by changes in the sensory association cortex

The Nature of Learning Stimulus-Response Learning
Learning to automatically make a particular response in the presence of a particular stimulus Involves the establishment of connections between circuits involved in perception and those involved in movement Classical conditioning Instrumental conditioning

The Nature of Learning Classical Conditioning
Unconditional Stimulus (US) – stimulus that produces a defensive or appetitive response. Unconditional Response (UR) – response to the US. Conditional Stimulus (CS) – stimulus, which when paired with the US during training, comes to elicit a learned response. Conditional Response (CR) – response to the presentation of the CS. Classical conditioning is a learning procedure that involves pairing a neutral stimulus with a biologically potent stimulus

Figure 13.1 A Simple Neural Model of Classical Conditioning
When CC takes place, what kinds of changes occur in the brain? present tone, nothing happens since the synapse connecting the tone-sensitive neuron and the motor neuron is weak….that is, when the AP reaches the terminal the EPSP that is produced in the motor neuron is too weak to make the neuron fire. However, if we present puff of air to the eye, the eye blinks…nature has provided the animal with a strong synapse between these 2 neurons. To produce CC we first present tone followed by puff of air…after several pairings, the tone elicits eyeblink by itself.

The Nature of Learning Hebb Rule
hypothesis proposed by Donald Hebb that the cellular basis of learning involves strengthening of a synapse that is repeatedly active when the postsynaptic neuron fires. About 60 years ago Hebb proposed a rule that might explain how neurons are changed by experience in a way that would cause changes in behavior…how would the Hebb rule apply to the circuit we just looked at?

Figure 13.1 A Simple Neural Model of Classical Conditioning
If Tone is presented first then weak synapse is active. If puff is presented immediately after then strong synapse P becomes active and makes the neuron fire. The act of firing then strengthens any synapse with the motor neuron that has just been active…in our case synapse T. After several pairings of the 2 stimuli, synapse T becomes strong enough to cause the motor neuron to fire….then we can say that learning has occurred.

The Nature of Learning Instrumental Conditioning (Operant conditioning) learning procedure whereby the effects of a particular behavior in a particular situation increase (reinforce) or decrease (punish) the probability of the behavior. Reinforcing Stimulus – appetitive stimulus that follows a particular behavior and thus makes the behavior become more frequent. Punishing Stimulus – aversive stimulus that follows a particular behavior and thus makes the behavior become less frequent. CC involves automatic or species-typical responses, but OC involves behaviors that have to be learned CC involves an association between 2 stimuli, OC involves an association between a response and a stimulus. OC is considered more flexible because it permits an organism to adjust its behavior according to the consequences of that behavior. CC involves automatic or species-typical responses, but OC involves behaviors that have to be learned CC involves an association between 2 stimuli, OC involves an association between a response and a stimulus. OC is considered more flexible because it permits an organism to adjust its beh according to the consequences of that beh.

Figure 13.2 A Simple Neural Model of Instrumental Conditioning
Let’s look at case of reinforcement…rat in Skinner box bar-pressing for food. At first, doesn’t press lever but when it eventually does it receives food, this food increases the likelihood that he will bar press again…reinforcement causes the sight of the lever to serve as the stimulus that elicits the barpressing response.

The Nature of Learning Motor Learning Learning to make a new response
Component of stimulus-response learning Perceptual learning = making changes in the sensory systems of the brain S-R learning – making connections between sensory and motor systems in the brain Motor learning = making changes in the motor systems But motor learning can’t occur without sensory input from the environment…most skilled movement involves an interaction with objects

Figure 13.3 An Overview of Perceptual, Stimulus-Response (S-R), and Motor Learning.
Most learning situations involve all three types of learning described so far…e.g., teach an animal to make a response in the presence of a stimulus it has never seen before It must learn to recognize the stimulus, make the response and then a connection must be made between these 2 new memories. If you teach an animal to make an already learned response in the presence of a new stimulus, then only perceptual and S-R learning will occur.

The Nature of Learning Relational Learning
More complex form of learning Involves learning the relationships among individual stimuli Includes the ability to recognize objects through more than one sensory modality Involves learning the relative location of objects in the environment – spatial learning Remembering the sequence in which events occurred during particular episodes – episodic learning Hippocampus The 3 types of learning described so far consist of changes in one sensory system, between one sensory and one motor system, or in the motor system. But learning can be much more complex than that. Relational learning relies heavily on hippocampus

Synaptic Plasticity: Long-Term Potentiation and Long-Term Depression Electrical stimulation of circuits within the hippocampus can lead to long-term synaptic changes that seem to be responsible for learning Perceptual Learning Classical Conditioning Instrumental Conditioning Relational Learning

See Figure 13.4 Primary input to the HF comes from the EC
Axons of EC neurons pass through the perforant path and synapse with granule cells in the DG From these cells, the mossy fibers project to the pyramidal cells in CA3 From CA3, Schaffer collaterals project to CA1 cells The 3 synapses know as the trisynaptic loop Location of hippocampus in rats (HF – hippocampal formation; DG – dentate gyrus; EC – entorhinal cortex) Schaffer axons branch …the collateral fibers go the CA1 and the commissural fibers go the contralateral HIP via the CC

Induction of LTP A stimulating electrode is placed in the PP and a recording electrode is placed in the DG A single pulse of electrical stimulation is delivered to the PP and the resulting population EPSP is recorded in the DG Population EPSP is the evoked potential that represents EPSPs of a population of neurons. LTP can be induced by stimulating the PP axons with a burst of electrical pulses (i.e., 100) within a few seconds To induce LTP…PP – perforant path The size of the first population EPSP tells us the strength of the synaptic connections before LTP is induced Evidence that LTP has occurred is obtained by periodically delivering a single pulse and then measuring the response in the DG to see if it is bigger than the original response

The size of the first population EPSP tells us the strength of the synaptic connections before LTP is induced Evidence that LTP has occurred is obtained by periodically delivering a single pulse and then measuring the response in the DG to see if it is bigger than the original response LTP Picture from the original article by Berger (1984)

Synaptic Plasticity: LTP and LTD
Can be induced in other parts of the HF and in other brain regions Can last for several months Can be induced in slices and in living animals Can follow the Hebb Rule (in slices) Associative Long-Term Potentiation – long-term potentiation in which concurrent stimulation of weak and strong synapses to a given neuron strengthens the weak ones. Hebb rule in slices…when weak and strong synapses to a single neuron are stimulated at the same time, the weak synapse becomes strengthened …it is produced by the associationa (in time) between the activity of the two sets of synapses.

Figure 13.6 Associative Long-Term Potentiation

Figure 13.7 The Role of Summation in Long-Term Potentiation
Nonassociative LTP requires an additive effect Series of pulses delivered at high rate will produce LTP Same # of pulses given at slow rate will not (LTD) Rapid rate of stimulation causes EPSPs to summate Rapid stimulation depolarizes the postsynaptic membrane more than slow stimulation

Figure 13.8 Long-Term Potentiation
Experiments have shown that synaptic strengthening occurs when NTS binds with postsynaptic receptors located in a dendrite that is already depolarized LTP requires 2 events Activation of synapses Depolarization of the postsynaptic membrane The explanation for this phenomenon lies in the properties of the NMDA receptor….

Role of NMDA Receptors NMDA Receptor – specialized ionotropic glutamate receptor that controls a calcium channel that is normally blocked by Mg2+ ions. Calcium ions enter the cells through channels controlled by NMDA receptors only when glutamate is present and the postsynaptic membrane is depolarized NTS- and voltage dependent ion channel Found in HIP, esp CA1

Figure 13.9 The NMDA Receptor

Role of NMDA Receptors AP5 – 2-amino-5-phosphonopentanoate, a drug that blocks NMDA receptors. Blocks the establishment of LTP Ca entry is essential step in LTP…AP5 blocks LTP

Need glutamate & depolarization….but how do dendrites become depolarized if only axons can produce action potential? Dendritic Spike – action potential that occurs in the dendrite of some types of pyramidal cells. Threshold for activation is very high Only occurs when action potential is triggered in the axon Backwash of depolarization across cell body triggers dendritic spike Whenever the axon of a pyramidal cell fires, all of its dendritic spines become depolarized for a brief time.

Simultaneous occurrence of synaptic activation and a dendritic spike strengthens the active synapse. Magee and Johnston (1997) injected individual CA1 pyramidal cells in hippocampal slices with a fluorescent dye that permitted them to see the influx of calcium When individual synapses became active at the same time that a dendritic spike had been triggered, Ca “hot spots” occurred near the activated synapses Size of EPSPs produced by these activated synapses became larger – synapse became strengthened TTX (blocks Na current) injected near dendrite – prevented dendritic spikes, no LTP!

Role of NMDA receptors in Associative LTP If weak synapses are active by themselves, nothing happens (NMDA receptors don’t open) However, if the activity of strong synapses located elsewhere on the postsynaptic cell has caused the cell to fire, then a dendritic spike will depolarize the postsynaptic membrane enough to eject Mg ions from the Ca channels (of NMDA receptor) If some synapses then become active, Ca will enter the dendritic spines and cause the synapses to become strengthened

What is responsible for the increase in synaptic strength that occurs during LTP? Dendrites on CA1 neurons contain 2 types of glutamate receptors: NMDA and AMPA

Mechanisms of Synaptic Plasticity AMPA Receptors – ionotropic glutamate receptor that controls a sodium channel; when open it produces EPSPs. Strengthening of individual synapses is accomplished by the insertion of more AMPA receptors into the postsynaptic membrane of the dendritic spine CaM-KII – type of calcium-calmodulin kinase, an enzyme that must be activated by calcium; may play a role in the establishment of LTP. Nitric Oxide Synthase – enzyme responsible for the production of nitric oxide. Drugs that block this enzyme prevent the establishment of LTP in CA1 More AMPA receptors means bigger EPSP when stimulated by glutamate; CaM-KII involved in moving AMPA receptors..CaM-KII located in postsynaptic density after LTP induced LTP might also involve presynaptic changes…NO is a soluble gas that could diffuse back to terminal button from the dendritic spine (retrograde messenger)

Figure 13.16 Chemistry of LTP
Activation of terminal button releases glutamate, which binds with NMDA receptors in the postsynaptic membrane of the dendritic spine If the membrane was depolarized by a dendritic spike, then calcium ions enter and activate CAM-KII CAM-KII travels to the postsynaptic density and causes the insertion of AMPA receptors LTP also initiates changes in synaptic structure and production of new synapses

Figure 13.16 Chemistry of LTP
The entry of calcium also activates NO synthase This produces NO which diffuses out of the dendritic spine and back to the terminal button The NO may then trigger chemical reactions that increase the release of glutamate Long-lasting LTP also requires the synthesis of new proteins and the presence of dopamine

Low-frequency stimulation of the synaptic inputs to a cell can decrease their strength Long-Term Depression (LTD) also plays a role in learning…some synapses are strengthened and others weakened long-term decrease in the excitability of a neuron to a particular synaptic input caused by stimulation of the terminal button while the postsynaptic membrane is hyperpolarized or only slightly depolarized. Like LTP, requires activation of NMDA receptors LTD involves a decrease in AMPA receptors

Other Forms of LTP Some forms of LTP do not involve NMDA receptors and are not blocked by AP5 (CA3). For example, mossy fiber input from dentate gyrus to CA3 Presynaptic changes only – no alterations in structure of dendritic spines

Figure 13.18 The Major Divisions of the Visual Cortex of the Rhesus Monkey
Primary visual cortex receives information from the lateral geniculate nucleus of the thalamus Ventral Stream – pathway of information from the primary visual cortex to the temporal lobe, which is involved in object recognition (‘what’ pathway). Dorsal Stream – pathway of information from the primary visual cortex to the parietal lobe, which is involved with perception of the location of objects (‘where’ pathway). Primary visual cortex = striate cortex; then sent to extrastriate cortex (analyze form, color and movement) Lesions to the inferior temporal cortex disrupt object discrimination Other areas important for perception of movement (MT/MST..part of extrastriate cortex)

Figure 13.21 Conditioned Emotional Responses
Information about the CS & US converge in the LA so synaptic changes responsible for learning could take place in this area Hebb rule - weak synapses (from tone) are strengthened when US activates neurons in the LA….LA neurons fire and activate CN …which evokes the response (Ch 11)

Classical Conditioning
Evidence for the involvement of lateral nucleus of the amygdala in CER Changes in the LA responsible for CER learning involve LTP…and is accomplished through activation of the NMDA receptor LTP Injection of drugs that block LTP into the amygdala prevents the establishment of conditioned emotional responses CER training (tone-shock pairings) causes AMPA receptors to be driven into dendritic spines of synapses between LA neurons and axons that provide auditory input CER training causes AMPA insertion

Rumpel et al., (2005) used a virus to insert a gene for a fluorescent dye coupled to a subunit of the AMPA receptor into the LA of rats…learning caused AMPA insertion They also inserted a gene for a dye coupled to a defective subunit of the AMPA receptor…the defective subunit prevented AMPA insertion and conditioning did not take place

Infusion of many drugs into the LA that prevent LTP disrupt acquisition of a CER Conclusion: LTP in the amygdala, mediated by NMDA receptors, plays a critical role in the establishment of CER

Instrumental Conditioning
Instrumental conditioning involves a connection between a particular stimulus and a particular response 2 major pathways between sensory association cortex and motor association cortex Direct transcortical connections Involved in episodic memory (along with HIP) Connections via the basal ganglia and thalamus 2 pathways play different roles Circuits must involve sensory association cortex and motor association cortex

Basal Ganglia Learned behaviors become automatic and routine, they are transferred to the basal ganglia Leaving the transcortical circuits free to learn new tasks

Figure 13.23 The Basal Ganglia and Their Connections
Neostriatum (caudate nucleus & putamen) receives sensory input from all regions of the cerebral cortex. Also receives information from frontal lobes about movement (planned or in progress). Outputs are sent to GP which sends information back to frontal cortex to premotor cortex (where plans for movement are made) and motor cortex (where movement is executed)

Basal Ganglia Studies of laboratory animals have indicated that: lesions of the basal ganglia disrupt instrumental conditioning without affecting other forms of learning. Fernadez-Ruiz et al., (2001) destroyed portions of the caudate and putamen that receive visual information from the ventral stream Lesions did not disrupt visual perceptual learning Impaired the monkeys’ ability to learn to make a visually guided operant response Williams and Eskandar (2006): as monkeys learned a operant response, the rate of firing of single neurons in the caudate nucleus increased The activity of caudate neurons is correlated with rate of learning Blocking NMDA receptors in the basal ganglia with an injection of AP5 disrupts learning guided by a simple visual cue Many of these studies involve learning to make a particular response in the presence of a particular visual cue

Instrumental Conditioning - Reinforcement
Neural circuits involved in reinforcement discovered by Olds & Milner, 1954. Reinforcement Neural Circuits Involved in Reinforcement Ventral Tegmental Area (VTA) – group of dopaminergic neurons in the ventral midbrain whose axons form the mesolimbic and mesocortical systems and are important in reinforcement. Nucleus Accumbens – nucleus of the basal forebrain near the septum; receives dopamine from neurons of the VTA and is thought to be involved in reinforcement and attention. See Figure 13.24 Neural circuits involved in reinforcement discovered by Olds & Milner, 1954. The activity of the dopaminergic pathway (see chapter 4) very important in reinforcement. Mesolimbic DA pathway begins in the VTA and projects to forebrain regions including AMG, HIP and NA…NA project to BG

Figure 4.13 Dopaminergic Pathways in a Rat Brain
Mesolimbic = VTA to limbic system including NA, AMYG, & HIP (NA impt for rewarding effects of stimuli including drugs of abuse) Mesocortical = VTA to prefrontal cortex also plays a role in reinforcement)

Reinforcement Microdialysis studies have revealed that release of DA in the NA is caused by: reinforcing electrical stimulation of the medial forebrain bundle (connects VTA to NA) or the VTA administration of cocaine or amphetamine presence of natural reinforcers such as water, food, sex partner fMRI indicates activity in NA during reinforcing events

Functions of the Reinforcement System: To detect reinforcing stimuli. To strengthen the connections between the neurons that detect the discriminative stimulus (i.e., sight of lever) and the neurons that produce the instrumental response (i.e., lever press).

Reinforcement occurs when neural circuits detect a reinforcing stimulus and cause the activation of dopaminergic neurons in the VTA A stimulus that serves as a reinforcer on one occasion may fail to do so on another Reinforcement system is not automatically activated when particular stimuli are present; activation also depends on the state of the animal

Detecting reinforcing stimuli Reinforcement system appears to be activated by unexpected reinforcing stimuli First – DA in VTA responded rapidly when the reinforcing stimuli was present Once the animals learn the task, VTA neurons are activated to the “learned” stimuli If a reinforcing stimulus does not occur when expected, the activity of dopaminergic neurons decreases Berns et al., (2001): increased activity in NA (fMRI) when tasty drink was given unpredictably, no increase if predictable Activity of these neurons sends a signal that there is something to be learned Reinforcement occurs when neural circuits detect a reinforcing stimulus and cause activation of DAergic neurons in the VTA PFC axons secrete glut which causes VTA neurons to fire in a bursting pattern which increases DA to NA

Prefrontal cortex provides input to VTA PFC involved in devising strategies, making plans, evaluating progress toward a goal. May turn on reinforcement mechanism when it determines that ongoing behavior is close to goal

Strengthening neural connections DA induces synaptic plasticity by facilitating associative LTP NA, amygdala, prefrontal cortex

Relational Learning Includes the establishment and retrieval of memories of events, episodes and places More complex type of learning

Relational Learning Human Anterograde Amnesia
Anterograde Amnesia – amnesia for events that occur after some disturbance to the brain. Retrograde Amnesia – amnesia for events that happened before some disturbance to the brain. Anterograde amnesia is basically an inability to learn new information…BUT some learning is usually spared (perceptual learning, S-R, motor learning) Pure anterograde amnesia is rare; brain damage usually involves some retrograde amnesia as well

Figure 13.27 A Schematic Definition of Retrograde Amnesia and Anterograde Amnesia

Relational Learning Human Anterograde Amnesia
Korsakoff’s Syndrome – permanent anterograde amnesia caused by brain damage from chronic alcoholism or malnutrition. Medial temporal lobe damage – also produces anterograde amnesia (i.e., H.M.) Based on extensive work with H.M., Milner & colleagues concluded: The hippocampus is not the location of LT memories; nor is it necessary for the retrieval of LT memories The hippocampus is not the site of immediate (ST) memories The hippocampus is important for converting ST memories into LT memories Sergei Korsakoff 1889—first described a severe memory impairment Scoville & Milner 1957 – reported that bilateral removal of the MTL produced a memory impairment similar to that seen in Korsakoff’s syndrome

Relational Learning Human Anterograde Amnesia Consolidation – process by which short-term memories are converted to long-term memories. Figure A Simple Model of the Learning Process Many psychologists believe that learning consists of 2 stages; STM and LTM STM – stores a limited amount of info temporarily LTM – stores unlimited info permanently Simplest model of memory says sensory info enters STM and rehearsal keeps it there and eventually it is stored in LTM

Relational Learning Spared Learning Abilities
Not a total failure in learning ability Perceptual Learning Visual recognition of incomplete objects (Figure 13.29) Face Recognition Stimulus-Response Learning HM could learn a classically conditioned eyeblink response Instrumental conditioning task – visual discrimination task in which pennies were given for correct responses Motor Learning Serial reaction time task While HM’s memory deficit is profound, can perform well on many tasks

Figure 13.30 The Serial Reaction Time Task
Press button below asterisk…if same 10 item sequence is repeated, reaction time decreases…suggests they learn the pattern…change pattern and reaction time increases.

Relational Learning So, even though amnesics can perform some tasks they have no memory of having ever learned them…led to the notion that the brain has multiple memory systems Declarative and Nondeclarative Memories Declarative (explicit) Memory – memory that can be verbally expressed. Nondeclarative (implicit) Memory – memory whose formation does not depend on the hippocampal formation; a collective term for perceptual, stimulus-response, and motor memory. Appear to be automatic, do not require deliberate attempts to memorize Acquisition of specific behaviors and skills Do not need to be able to describe these activities in order to do them

Table 13.1 Declarative Memory Tasks Nondeclarative Memory Tasks
Remembering past experiences Finding one’s way in new environment Nondeclarative Memory Tasks Learning to recognize broken drawings Learning to recognize pictures and objects Learning to recognize faces Learning to recognize melodies Classical conditioning Instrumental conditioning Learning sequence of button presses

Relational Learning Anatomy of Anterograde Amnesia
Damage to the hippocampus or to regions of the brain that supply its inputs and receive its outputs causes anterograde amnesia HIP formation = CA fields, DG and SUB; major input is from EC Outputs of Hip (from CA1 and SUB) also go back to EC, and PC and parahip cortex Perirhinal Cortex – region of limbic cortex adjacent to the hippocampal formation that relays information between entorhinal cortex and other regions of the brain. Parahippocampal cortex – region of the limbic cortex adjacent to the hippocampal formation that shares the same general role as the perirhinal cortex. Damage to hippocampus and surrounding cortical tissue seems to cause anterograde amnesia

Cortical Connections of the Hippocampal Formation
Figure 13.31 Monkey brain

Figure 13.32 The Major Subcortical Connections of the Hippocampal Formation
Hip also receives subcortical input via the fornix Fornix carries dopaminergic input from VTA Fornix also connects the HIP with the mammillary bodies (located in post. Hypo.) MMB degenerate in Korsakoff’s syndrome

Relational Learning Role of the Hippocampal Formation in Consolidation of Declarative Memories HIP not really important for STM or LTM but seems to be important for declarative memory formation HIP receives input from sensory and motor cortex and from subcortical regions (BG and AMG), it then processes this information and sends projections back to these same regions and somehow modifies the memories being stored there Hippocampus is involved in modifying memories as they are being formed. The order in which events occurred Contextual information Relationships among elements

Rational Learning Hippocampus Time-limited role
Anterograde amnesia is usually accompanied by retrograde amnesia The duration of the retrograde amnesia related to the amount of damage to the MTL Damage limited to hipp – retrograde amnesia lasting ~ few years Damage to hipp + entrorhinal cortex – retrograde amnesia ~ 1-2 decades Damage to MTL – spared memories from early life Gradual process controlled by hipp transforms memories located elsewhere Before transformation is complete, hipp is required for retrieval of memories Later, retrieval of memories can occur if hipp has been damaged

Relational Learning Declarative Memory Episodic and Semantic Memories
Episodic Memory – memory of a collection of perceptions of events organized in time and identified by a particular context. Specific to a particular time and place Semantic Memory – memory of facts and general information. Do not include information about the context in which the facts were learned Episodic memory – must be learned all at once Semantic Memory - can be acquired gradually Requires the hippocampus Remember earlier breakdown of memory systems….declarative memory actually 2 different kinds of memories

Semantic Dementia – loss of semantic memories caused by progressive degeneration of the neocortex of the lateral temporal lobes. Difficulty naming objects Difficulty understanding the meaning of words

Relational Learning Spatial Memory
Memory for spatial information used to move around one’s environment and get from one place to another. Role of Hippocampus in Spatial Memory Damage to (right) HIP causes spatial memory impairments London taxi drivers have bigger HIP than control subjects longer an taxi driver had spent in this occupation, the larger the volume of rt hipp Place Cells – special neurons in the hippocampus that are directly involved in navigation in space (rats). Virtual-reality towns Spatial Strategy – maze learning strategy based on spatial cues; activation of HIP (fMRI). Response Strategy – maze learning strategy based on a series of responses (turns); activation of caudate nucleus. People who tend to use spatial strategies – larger hipp People who tend to follow response strategies – larger caudate Patients like HM have difficulty finding their way around Damage to HIP causes spatial impairment in people; London taxi drivers have bigger HIP than control subjects

Relational Learning Relational Learning in Laboratory Animals
Spatial Perception and Learning Morris Water Maze Starting with HM, people became interested in idea of MMS and developing animal models of memory…what role does the hip play in animals, can we develop animal models of declarative and episodic memory, what is a relational task in animals??? Deficit in spatial learning is the most consistent effect of HIP damage in rodents (fixed start vs variable start)

Morris Water Maze

Spatial Learning Damage to the hippocampus – animals swim in what appears to be an aimless fashion until they finally encounter the platform Hippocampal lesions disrupt navigation in homing pigeons Hippocampus of birds and rodents that store seeds in hidden caches and later retrieve them is larger than that of animals that don’t

Hippocampal Place Cells Found in dorsal hippocampus in rats (corresponds to the posterior hippocampus in humans) “fire” at a high rate when the animal is in a particular location, called the cell’s place field “fire” at a low rate when the animal is in a different location First discovered by O’Keefe & Dostrovsky

O’Keefe & Dostrovsky (1971)

Role of Hippocampal Formation in Memory Consolidation Time limited role in memory Mice trained in water maze; inactivate HIP with lidocaine 1 day later or 30 days later (Figure 13.40) Memory Reconsolidation A process of consolidation of a memory that occurs subsequent to the original consolidation that can be triggered by a reminder of the original stimulus. Mice expt…inactivate hippocampus with lidocaine or inactivate areas of cortex…see opposite pattern Reconsolidation involves a modification of LT memories

Phases of Memory Reconsolidation
Acquisition - the pairing of the context/cue to the aversive stimuli 24 hours Consolidation—blocked by protein synthesis inhibitors (anisomycin) 3-4 hours Reconsolidation—blocked by protein synthesis inhibitors (anisomycin) Train Reactivate Test Evidence suggests that reactivation of a memory can return it to a labile state requiring reconsolidation via protein synthesis

Figure 13.41 A Schematic Description of the Experiment by Misanin, Miller, and Lewis (1968)
Eyewitness testimony PTSD

Reconsolidation of Memories
Reconsolidation requires LTP Injection of anisomycin (blocks protein synthesis and prevents memory consolidation), blocks reconsolidation

Role of LTP in memory When rats learn mazes, strength of population EPSP in CA3 increases Mutations targeted at NMDA receptors in CA1 Prevented establishment of LTP Poor spatial learning on Morris water maze Hippocampal Neurogenesis New neurons can be produced in the hippocampus of the adult brain (DG) Training on relational tasks increases neurogenesis Easier to establish LTP with these ‘new’ neurons When animals learn tasks that require HIP, the learning induces the same type of changes produced by LTP

Mind and Brain Learning and Memory Chapter 13

Similar presentations

Presentation on theme: "Mind and Brain Learning and Memory Chapter 13"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Mind and Brain Learning and Memory Chapter 13

Similar presentations

Presentation on theme: "Mind and Brain Learning and Memory Chapter 13"— Presentation transcript:

Similar presentations

About project

Feedback