Announcements Experiment 2 due today Focus Questions for Weldon and Roediger (1987) Due Monday March 26th Exam 2 a week from Wednesday (March 28)
Neuropsychology of Memory Where is memory? Methods of study Neurons and Brains Role of the hippocampus Memory Disorders Amnesia Alzheimers Disease Mapping memory in 3DMemory The Brain
Neurons and Memory Connections between neurons change based on experiences Brain is less hard-wired than we used to believe Lashley provided evidence of plasticity in monkeys in the 1920s but not widely accepted until 1960s Neuroplasticity is fundamental property of brain (nervous system) Capacity of nervous system to modify its organization Changes in structure and function as a result of experience Changes largely within the synapses
Neurons and Memory Current dominant theory: Long-term potentiation (LTP)LTP Persistent increase in synaptic strength following high-frequency stimulation the molecular and cellular changes mediating the induction of LTP in the hippocampus are widely considered to provide a basis for memory (McGaugh, 2000) Not all learning-related changes involve changes in synaptic strength (Martin & Morris, 2002) Neurogenesis new evidence suggest that new neurons are formed in some regions of the brain Changes in neuronal excitability changes in the firing threshold Synaptic changes that could store memories
There are many steps between synaptic change and behavioral memory. Squire (pg 8, 1987) The Brain: networks of neurons Lots of interesting questions Does memory reside in single neurons, or in networks of neurons? Are all of the networks the same, or are there differences (i.e., do different regions of the brain deal with different kinds of things)?
The Brain Number of neurons: 100,000,000,000 (100 billion) Number of synapses (the gap between neurons): 100,000,000,000,000 (100 trillion) Vital Statistics Adult weight: about 3 pounds Adult size: a medium cauliflower These neurons are connected, organized into networks of neurons
Structure of the brain Cortex - four lobes Occipital - vision Parietal - sensation Temporal memory, hearing Frontal - reasoning, memory Frontal Lobe Temporal Lobe Occipital Lobe Parietal Lobe
Limbic system: controls emotions and instinctive behavior (includes the hippocampus and parts of the cortex) Thalamus : receives sensory and limbic information and sends to cerebral cortex Hypothalamus : monitors certain activities and controls bodys internal clock Hippocampus: where short-term memories are converted to long-term memories Other Crucial Parts Brain and Memory
McGaugh, 2000 memory consolidation involves interactions among neural systems as well as cellular changes within specific systems, and that the amygdala is critical for modulating consolidation in other brain regions Neurobiological systems regulating the consolidation of memory Networks of neurons hold memories The Brain: networks of neurons
So where is memory? It is complicated Multiple brain regions are involved in encoding (as shown by fMRI) -term memory.
Brain and Memory So where is memory? It is complicated Multiple brain regions are involved in encoding (as shown by fMRI) For recalling pictures, the right prefrontal cortex and parahippocampal cortex in both hemispheres are activated. For recalling words, the left prefrontal cortex and the left parahippocampal cortex are activated. Consolidation of memory involves the hippocampus but the hippocampal system does not store long-term memory. LTM storage occurs in the cortex, near where the memory was first processed and held in short-term memory.
Brain and Memory So where is memory? It is complicated Seven Sins of Memory Hippocampus and nearby structures related to sin of transience Parts of the frontal lobe related to transience, but even more central to absent-mindedness and misattribution (and maybe suggestibility ) Area near front of temporal lobe related to blocking Amygdala closely related to persistence Not much is known about bias
Hippocampus Important for formation of new episodic memories Important for encoding perceptual aspects of memories Novel events, places, and stimuli Important for declarative memory Especially as part of medial temporal lobe Supported by case of HM Video (location, 1 min ) Video Brain and Memory
Recollection vs. Knowing (familiarity) Eldridge et al have shown the hippocampus is selectively involved in R, not with K. Verfaelle & Treadwell (1993), using process dissociation procedure showed similar pattern (discussed in detail in your textbook) (Eldridge et al., Nature Neuroscience 2000) Brain and Memory Hippocampus
Brain and Memory: Amnesia Diencephalic amnesia - damage to the medial thalamus and mammillary nuclei Medial temporal lobe amnesia - damage to the hippocampal formation, uncus, amygdala, and surrounding cortical areas Other implicated regions include Anterior Lateral Temporal Lobe and Frontal Lobes
Amnesia Loss of memory ability - usually due to lesion or surgical removal of various parts of the brain Relatively spared performance in other domains A pure amnesia is relatively rare video ( #18, 10 mins ) video Video ( ~ 7 mins ) Video Video 3 ( Clive Wearing, 7 mins ) Video 3
Amnesia Loss of memory ability - usually due to lesion or surgical removal of various parts of the brain Three different kinds of classifications Source of the disease (e.g., illness, injury) Location of the area of damage Functional deficit (i.e., what kind of memory is impaired) This mixed way of categorizing amnesia causes some difficulties
Amnesia Loss of memory ability - usually due to lesion or surgical removal of various parts of the brain Two broad categories: Retrograde : loss of memories for events prior to damage Anterograde : loss of ability to store new memories of events after damage Injury Time
Causes of Amnesia Korsakoffs syndrome Traumatic Brain Injury (TBI) (Concussion) Alzheimers disease Other causes include Specific brain lesions (i.e. surgical removal) Psychological Dissociative Fugue Psychogenic Migraines Hypoglycemia Epilepsy Electroconvulsive shock therapy Drugs (esp. anesthetics) Infection Nutritional deficiency
Amnesia Results from chronic alcoholism and consequent thiamine deficiency Lesions to Medial Thalamus Neuropathology: most sources attribute the amnesia to combined lesions in two diencephalic structures: the dorsomedial nucleus of the thalamus and the mammillary bodies of the hypothalamus Korsakoffs syndrome: Korsakoffs syndrome
Amnesia Generally preserved IQ, including a normal digit span. Personality changes, the most common of which is apathy, passivity and indifference inability to formulate and follow through a series of plans Lack of insight into their condition. How can someone with a shattered memory remember that he has become unable to remember? Korsakoffs syndrome
Amnesia Korsakoffs syndrome Retrograde amnesia with a temporal gradient Anterograde amnesia Confabulation, which is a tendency to "fill in the gaps" of one's memories with plausible made-up stories. confabulations are rare among chronic Korsakoff patients who've had the disease for more than 5 years. Patients in the chronic stage are more likely to say "I don't know" or remain silent when faced with memory failures rather than to invent stories.
Amnesia Korsakoffs syndrome Worst impairments are on episodic memory tests, including list learning of words, figures, or faces, paragraph recall. Relatively preserved semantic memory, including normal verbal fluency, vocabulary, rules of syntax, and basic arithmetic operations Intact sensori-motor memory (mirror tracing, mirror reading, pursuit rotor) Intact performance on perceptual tasks (e.g., perceptual identification, generating category exemplars)
Post-traumatic amnesia Damage due to lesions as well as twisting and tearing of microstructure of brain Symptomology After severe TBI, individuals typically lose consciousness After they begin to regain consciousness, there is often a gradual recovery during which patients have difficulty keeping tracking of and remembering on-going events, though there may be islands of lucidity and memory In the news Football (ESPN video)ESPN video Soldiers (6 part video series)6 part video series Amnesia
Retrograde amnesia Refers to difficulty remembering events that occurred prior to injury The duration of amnesia varies but can extend back for several years Rare, short-lived Typically due to brain trauma Case Study: Doug Bruce ( Unknown White Male )Doug Bruce His case is exceptional (the extent and persistence of the memory loss) Amnesia Injury Time
Retrograde amnesia Duration of retrograde amnesia typically shrinks as time passes e.g., Russell (1959) described case of TBI as a result of a motorcycle accident 1 week post accident patient had lost 11 years of memory extending back from injury 2 weeks post accident patient had last 2 years of memory about 10 weeks post injury memories of the last two years gradually returned This pattern of results suggests that retrograde amnesia is a retrieval problem The pattern of damage/recovery -- from most distant to most recent -- has been argued by some to reflect a failure of consolidation (Ribots Law) Amnesia Injury Time
Retrograde amnesia Butters & Cermak (1986) reported a case study of an eminent scientist (born 1914) who had written his autobiography only two years prior to becoming amnesic Tested him by asking him questions all drawn from his autobiography Amnesia Injury Time
Anterograde amnesia Refers to problems of learning new facts Specific to episodic memories Procedural memories intact Implicit memory performance normal Famous Cases: H.M. N.A. Clive Wearing Video 3a, b, c, d (each ~10 mins)3abcd Amnesia Injury Time
Amnesia Case Study: HM Henry Molaison (Patient H. M.) (brief news video following his death) Henry Molaison (Patient H. M.video Bilateral mesial temporal lobe resection extending 8 cm. back from the temporal tips, including the uncus and amygdala, and destroying the anterior two-thirds of the hippocampus and hippocampal gyrus Scoville & Milner (1957)Milner Suffered from extreme epilepsy
Amnesia Case Study: HM prototype of amnesia attributable to hippocampal damage Surgery led to a permanent, severe anterograde amnesia, limited retrograde amnesia, and normal intelligence. Henry Molaison (Patient H. M.)
Amnesia Case Study: HM Functional characteristics Declarative and nondeclarative memories Although patients can learn other tasks, they cannot recall ever learning them Learning and memory involve different processes 2 major categories of memories Declarative memories memory that can be verbally expressed, such as memory for events, facts, or specific stimuli; this is impaired with anterograde amnesia Nondeclarative memories memory whose formation does not depend on the hippocampal formation; a collective term for perceptual, stimulus- response, and motor memory; not affected by anterograde amnesia; these control behavior; cannot always be described in words Henry Molaison (Patient H. M.)
Amnesia Case Study: HM Functional characteristics Episodic memory is impaired Both autobiographical and nonautobiographical episodic memory even for emotionally charged information such as the death of his favorite uncle Verbal learning is disrupted in anterograde amnesia e.g. H.M. did not learn any new words after his surgery (biodegradable = two grades ) Henry Molaison (Patient H. M.)
Amnesia Case Study: HM Functional characteristics Perceptual learning e.g. recognize broken drawings; also faces and melodies Stimulus-response learning Can acquire a classical conditioned eyeblink response Working memory is intact Essentially normal STM, seen on the Brown-Peterson task, digit span, and conversation Semantic memory is spared Procedural memory is intact Henry Molaison (Patient H. M.)
Amnesia Case Study: HM HM shows normal procedural and implicit memory despite extensive declarative and explicit memory deficits. In particular, he shows normal motor priming on pursuit- rotor and mirror tracing tasks (Milner video start 5:45)Milner video start 5:45
Amnesia Anatomy of anterograde amnesia Damage to the hippocampus or to regions that supply its inputs and receive its outputs causes anterograde amnesia How does the hippocampus form new declarative memories? Hippocampus receives info about what is going on from sensory and motor assc. cortex and from some subcortical regions It processes this info and then modifies the memories being consolidated by efferent connections back to these regions Experiences that lead to declarative memories activate the hippocampal formation The hippocampal formation enables us to learn the relationship between the stimuli that were present at the time of an event (i.e. context) and then events themselves
Amnesia Anatomy of anterograde amnesia Damage to other subcortical regions that connect with the hippocampus can cause memory impairments Limbic cortex of the medial temporal lobe Semantic memories a memory of facts and general info; different from episodic memory Destruction of hippocampus alone disrupts episodic memory only; must have damage to limbic cortex of medial temporal lobe to also impair semantic memory (and thus all declarative memory) Fornix and mammillary bodies Patients with Korsakoff s syndrome suffer degeneration of the mammillary bodies where the efferent axons of the fornix terminate in the mammillary bodies Damage to any part of the neural circuit that includes the hippocampus, fornix, mammillary bodies and anterior thalamus cause memory impairments
Amnesia Theoretical implications of amnesia Provides evidence for STM versus LTM distinction Supports the notion that there are different systems mediating explicit (episodic) and implicit (procedural memory) May indicate that semantic and episo...