Chapter 2 :Chapter 2 The Neuroscience of Learning and Memory Slides prepared by Mary Waterstreet, St. Ambrose University


2.1 A Quick Tour of the Brain :2.1 A Quick Tour of the Brain


2.1 A Quick Tour of the Brain :3 2.1 A Quick Tour of the Brain The Brain and the Nervous System Observing Brain Structures and Function


Neuroscience and the Brain :4 Neuroscience and the Brain Neuroscience—study of the nervous system, especially the brain Neuroscientists believe the brain is the seat of learning and memory.


The Nervous System (Link) :5 The Nervous System (Link) Nervous system—distributes and processes information. Central nervous system (CNS)—brain and spinal cord Peripheral nervous system (PNS)—nerve fibers that connect CNS to rest of body Neurons—nerve fibers, collect and process incoming information.


Nervous Systems :6 Nervous Systems


Slide 7:7


The Human Brain :8 The Human Brain Cerebral cortex—tissue covering top and sides of brain. (Click Link) Divided into four lobes: Frontal (plan and perform actions) Parietal (sensory) Temporal (hearing) Occipital (vision) Subcortical structures—under cerebral cortex Thalamus, basal ganglia, hippocampus, amygdala involved in learning and memory.


The Human Brain :9 The Human Brain Cerebellum—behind cortex Important for coordinated movement Involved in learning that requires physical action. Brainstem—connects brain to spinal cord. Key in regulating automatic functions (e.g. breathing, body temperature)


The Visible Surface of the Human Brain :10 The Visible Surface of the Human Brain © Visuals Unlimited, Ltd.


The Human Brain :11 The Human Brain


Human Subcortical Structures :12 Human Subcortical Structures Thalamus—receives sensory information; relays it to brain. Basal ganglia—involved in learning skilled movements. Hippocampus—linked to learning new facts, memory. Amygdala—linked to emotion.


Comparative Brain Anatomy :13 Comparative Brain Anatomy Study of similarities and differences among organisms’ brains Vertebrates Have both CNS and PNS. Differ in overall brain size and brain structure size. The complex relationship between brain size and learning capacity needs further research.


Comparative Brain Anatomy in Several Vertebrate Species :14 Comparative Brain Anatomy in Several Vertebrate Species


Learning without a Brain :15 Learning without a Brain Invertebrates: With recognizable, decentralized, brains (e.g. octopus, bee). Capable of maze learning, learning by observation With no recognizable brain (e.g. jellyfish, worm) Can learn to avoid negative stimuli. Simple invertebrate nervous systems are useful in research. Mauro Fermariello/Photo Researchers


Observing Brain Structure and Function: The Dark Ages of Brain Science :16 Observing Brain Structure and Function: The Dark Ages of Brain Science To detect brain damage: Look through hole in skull. Remove brain. Franz Joseph Gall (1758–1828) Pseudoscience of phrenology © Charles Walker/Topfoto/The Image Works


Structural Neuroimaging: Looking inside the Living Brain :17 Structural Neuroimaging: Looking inside the Living Brain Structural Neuroimaging—modern methods to see brain size/shape, structures, lesions Computed tomography (CT)—takes many X-rays from different angles. Forms a three-dimensional representation of body structures, such as the brain. Magnetic resonance imaging (MRI)—uses changes in magnetic field to generate image; magnet aligns atoms in brain or body. More popular than CT


MRI Images :18 MRI Images Custom Medical Stock Photography Scott Camazine/Photo Researchers, Inc.


2.1 Interim Summary :19 2.1 Interim Summary Central nervous system (CNS) = brain and spinal cord Peripheral nervous system (PNS) = sensory and motor neurons Brain connects to PNS to control behavior. Most connections pass through spinal cord.


2.1 Interim Summary :20 2.1 Interim Summary Vertebrate brain organized into: Cerebral cortex Frontal, temporal, parietal, and occipital lobes Cerebellum Brainstem Cerebral cortex structures are specialized: Process sensory information. Generate motor outputs.


2.1 Interim Summary :21 2.1 Interim Summary Animals with simple nervous systems can learn. Study “simpler” nervous systems to learn how vertebrate (even human) brains work. Early study of the brain: Phrenology: relate personality/mental abilities to size and shape of skull. Study brain anatomy by examining post-mortem healthy or abnormal brains after death.


2.1 Interim Summary :22 2.1 Interim Summary Modern structural brain imaging techniques (e.g., MRI and CT): Provide ways to look at the physical structure of living brains Cause no harm. Lesions/abnormalities may be visible on images.


2.2 From Brain to Behavior :2.2 From Brain to Behavior


2.2 From Brain to Behavior :24 2.2 From Brain to Behavior Information Pathways in the Central Nervous System Observing Brain Systems in Action Unsolved Mysteries—What Do Functional Imaging Methods Really Measure?


Brain Function :25 Brain Function Brain systems are specialized for specific functions. Some localization of brain function: Many functions may depend on a single brain area. One function may rely on many brain areas.


Information Pathways in the CNS :26 Information Pathways in the CNS Reflex—an involuntary, automatic response to a stimulus (“hardwired”). Newborn sucking reflex Newborn palmar grasp reflex Human knee-jerk reflex Eye blink reflex


Reflexes Present at Birth :27 Reflexes Present at Birth


Behavior Without the Brain: Spinal Reflexes :28 Behavior Without the Brain: Spinal Reflexes Bell-Magendie law of neural specialization Spinal cord has two parallel nerve systems. Sensory nerves—sensory information from PNS to spinal cord Motor nerves—motor signals from spinal cord to muscles Charles Sherrington (1857–1952) Simple “spinal reflexes” combine into complex movements.


Behavior Without the Brain: Spinal Reflexes :29 Behavior Without the Brain: Spinal Reflexes


Incoming Stimuli: Sensory Pathways into the Brain :30 Incoming Stimuli: Sensory Pathways into the Brain Primary sensory cortices are the first stage of sensory processing. More advanced processing occurs in adjacent cortical regions.


Outgoing Responses: Motor Control :31 Outgoing Responses: Motor Control Primary motor cortex gets input from frontal lobes, cerebellum, basal ganglia, brainstem: Sends output to the spinal cord via the brain stem. Spinal cord activates motor fibers that control muscles.


Motor Control: How to Pick Up a Coffee Cup :32 Motor Control: How to Pick Up a Coffee Cup


Observing Brain Systems in Action :33 Observing Brain Systems in Action Human neuropsychology—studies relationship of brain function to behavior. Generally, studies case studies of patients with brain damage. Cognitive testing may guide patient rehabilitation and provide further knowledge of normal brain function.


Experimental Brain Lesions :34 Experimental Brain Lesions Research on animal brains: Follow strict ethical guidelines. Carefully lesion or deactivate animal brain regions. Create animal “models” of human patients. Animal lesions more precise. Coordination of human and animal studies provide better view of brain and behavior.


Memory and the Brain :35 Memory and the Brain Karl Lashley (1890–1958) Conducted brain lesion studies to find location of engram (physical change in brain, basis for memory). Theory of equipotentiality—brain acts a a whole to store memories (no single area).


Functional Neuroimaging: Watching the Brain in Action :36 Functional Neuroimaging: Watching the Brain in Action Functional Neuroimaging—shows activity or function of the living brain. Positron emission tomography (PET)— measures brain activity by detecting positrons. M.E. Raichle, Mallinckrodt of Radiology, Washington University School of Medicine


Functional Neuroimaging: Watching the Brain in Action :37 Difference image—subtract image of a relaxed, baseline brain from the image of a brain engaged in specific activity. Images show which brain regions change or remain constant. Also made using functional MRI (fMRI). PET and fMRI produce similar, but not exact, imaging of brain’s localized use of oxygen. Functional Neuroimaging: Watching the Brain in Action


Comparing PET and fMRI :38 Comparing PET and fMRI Custom Medical Stock Photography Adapted from Devlin et al., 2002.


Unsolved Mysteries: What Do Functional Neuroimaging Techniques Really Measure? :39 Unsolved Mysteries: What Do Functional Neuroimaging Techniques Really Measure? fMRI reflects local blood oxygenation. PET reflects blood flow or glucose utilization. Assumption is that neurons in highly active brain areas use more oxygen (seen on fMRI), which required more blood flow to supply this oxygen (seen on PET).


Electroencephalography: Charting Brain Waves :40 Electroencephalography: Charting Brain Waves Electroencephalography (EEG)— electrodes on scalp measure roar of axons firing in brain areas. Form two-dimensional “brain wave.” Event-related potentials (ERPs)— averaged EEGs from a repeated event Can measure changes in brain activity during learning and memory tasks.


2.2 Interim Summary :41 2.2 Interim Summary Reflexes = hardwired (unlearned) responses. Sherrington and other early neuroscientists believed complex learning was built up from combinations of simple spinal reflexes. Bell and Magendie = propose/demonstrate parallel fiber systems. Carry sensory information into spinal cord. Commands go from the spinal cord out to muscles and organs.


2.2 Interim Summary :42 2.2 Interim Summary Sensory information is (initially) processed in brain’s cortical regions. Regions are specialized: Primary auditory cortex (A1) for sounds Primary visual cortex (V1) for sights Primary somatosensory cortex (S1) for touch Regions transmit signals to other brain areas for further processing.


2.2 Interim Summary :43 2.2 Interim Summary Primary motor cortex (M1): outputs guide coordinated movements. Portion of motor cortex devoted to a given body part reflects (innate or learned) degree of motor control for that part. Human and animal brain lesions reveal: Brain function. Neurobiology of learning and memory.


2.2 Interim Summary :44 2.2 Interim Summary Lashley conducts early brain lesion studies. Brain’s engram = physical trace of a memory Not stored in a single place; rather, a function of the whole brain. Modern brain studies show localized evidence of engrams. Particularly in subcortical structures (e.g., cerebellum)


2.2 Interim Summary :45 2.2 Interim Summary Functional neuroimaging methods (e.g., fMRI and PET): Track brain activity indirectly. Measure increases or decreases in brain’s blood flow during task performance. Create difference image to identify more (or less) active brain areas.


2.2 Interim Summary :46 2.2 Interim Summary Electroencephalography (EEG): Detect electrical activity (“brain waves”). Electrodes placed on scalp. Brain waves = summed electrical charges of many neurons. Event-related potentials = EEG recordings averaged across many repeated stimulations. Allow enhanced detection of electrical signals.


2.3 Learning and Synaptic Plasticity :2.3 Learning and Synaptic Plasticity


2.3 Learning and Synaptic Plasticity :48 2.3 Learning and Synaptic Plasticity The Neuron Measuring and Manipulating Neural Activity Synaptic Plasticity


The Neuron (Link) :49 The Neuron (Link) Dendrites—inputs; receive signals. Cell body (soma)—integrates dendrite signals. Axons—transmit information. Glia cells—give functional and structural support to neurons.


The Neuron :50 The Neuron Biophoto Associates/Photo Researchers


The Synapse: Where Neurons Connect :51 The Synapse: Where Neurons Connect Synapse—gap between neurons; pass chemical signals across (neurotransmitters) Presynaptic neuron—sending neuron Postsynaptic neuron—receiving neuron Receptors—molecules specialized to received specific neurotransmitters Action Potentials; Neurotransmission


The Synapse :52 Dennis Kunkel/Phototake The Synapse


Information Flow across a Synapse :53 Information Flow across a Synapse


Neuromodulators: Adjusting the Message :54 Neuromodulators: Adjusting the Message Neuromodulators—alter how neurons exchange messages. Some neurons (especially in the brain stem) release chemicals into broad areas to affect many neurons simultaneously. e.g., acetylcholine Change the conditions for neural firing.


Measuring and Manipulating Neural Activity :55 Measuring and Manipulating Neural Activity Neurophysiology—study of neural activation. Single-cell recording—researchers implant electrodes into an animal’s brain, which are held in place by a hat-like “head stage.”


Stimulating Neurons into Activity :56 Stimulating Neurons into Activity Researchers can deliberately stimulate neurons to observe corresponding behavior. A way to map cortical areas (homunculus) Transcranial magnetic stimulation (TMS) involves placing a magnet on the skull.


Homunculus and Motor Cortex :57 Homunculus and Motor Cortex The British Museum, Natural History


Manipulating Neuronal Function with Drugs :58 Manipulating Neuronal Function with Drugs Drugs—chemicals that change the body’s biochemical functioning Can affect: Neurotransmitter release. Neural firing. e.g., morphine can fit into opioid receptors. Neurotransmitter reuptake.


Synaptic Plasticity :59 Synaptic Plasticity Synaptic plasticity—ability of synapses to change with experience According to Donald Hebb, the connection between two contiguously firing neurons will strengthen.


Long-Term Potentiation :60 Long-Term Potentiation Long-Term Potentiation (LTP click link) synaptic transmission is sensitized by recent experience. Occurs in many brain regions of many organisms. What is the relationship of LTP to learning? Drugs that block LTP can impair learning. Rats bred to produce more LTP are better learners.


Long-Term Potentiation :61 Long-Term Potentiation


Associative Long-Term Potentiation :62 Associative Long-Term Potentiation


How is LTP Implemented in a Neuron? :63 How is LTP Implemented in a Neuron? Postsynaptic receptors may become more responsive and fire more easily for hours. Presynaptic neurons may release more neurotransmitter for hours. Postsynaptic neurons may permanently change.


Long-Term Depression :64 Long-Term Depression Long-Term Depression (LTD)—Neurons that do not fire together become disengaged. Possible reasons: Decrease in postsynaptic receptor responsiveness Decrease in presynaptic neurotransmitter release Long-term structural changes in neurons and synapses


2.3 Interim Summary :65 2.3 Interim Summary Neurons: Dendrites collect signals (input). Axon transmits messages (output). Neuronal communication occurs across synapses (tiny gaps). Presynaptic (sending) neuron releases neurotransmitter (chemical message) into synapse. Message activates receptors on postsynaptic (receiving) neuron.


2.3 Interim Summary :66 2.3 Interim Summary Single-cell recordings monitor and record single neurons as they become active (“fire”). Implanted electrodes deliver electrical charges that stimulate a neuron into activity. Observe evoked behavior. Drugs alter body’s biochemical functioning. Brain-affecting drugs increase or decrease transfer of information between subsets of neurons.


2.3 Interim Summary :67 2.3 Interim Summary Learning requires physical changes in neural circuits. Physical changes affect firing behavior. Changes involve neuron’s shape/size and/or number of neuronal connections. Synaptic plasticity = ability of synapses to change with experience. Strengthening or weakening connections influences firing.


2.3 Interim Summary :68 2.3 Interim Summary Long-term potentiation (LTP): transmission becomes more effective with experience. Hebb’s rule: Synapses strengthened by conjoint presynaptic and postsynaptic neuronal activity. “neurons that fire together, wire together” Long-term depression (LTD): transmission becomes less effective with experience. Weakens neuronal connections.