Memory Impairments Amnesia

Memory Impairments: Amnesia ______________________________________ 1) Describe the different ways of categorizing amnesia. 2) Present two famous case studies and examine the extent to which each is 'typical'. 3) Evaluate the major theoretical explanations for the memory deficits associated with amnesia. 4) Differentiate semantic dementia from amnesia and examine research directed at understanding its causes. 5) Discuss some of the challenges faced by researchers interested in learning more about the amnesic syndrome. Distinguishing different kinds of amnesia ______________________________________ By cause • Head trauma • Blood loss • Neural infection • Toxic effects By location • Hippocampal damage • Temporal lobe damage • Frontal lobes By functional deficit • retrograde amnesia o Shrinking RA o Temporal gradient (Ribot’s law) • anterograde amnesia What is typically spared? • Procedural memory / Implicit Memory • Semantic memory • Immediate / Working Memory tasks • IQ test performance • New declarative knowledge?? EX: errorless learning Famous Case Studies ______________________________________ Schnider’s patient (SP) Cause: Stroke Location: Both medial temporal lobes; left hippocampus, neighboring regions (not amygdala) Deficits: Orientation to time and place Anterograde amnesia Semantic memory Autobiographical memory Procedural memory ______________________________________ Clive Wearing: Cause: Encephalitis Location: temporal lobes hippo were GONE diencephelon was damaged Deficits: Orientation Confabulation Semantic Memory Autobiographical memory Music skills ______________________________________ What about HM? Theoretical explanations ______________________________________ Encoding problems – This theory was quickly dismissed. Why? Faster forgetting – If we control for initial levels of learning (by slowing the presentation rate), Korsakoff’s patients Interference theory – Errorless learning Amnesiacs benefit Binding / Context / Consolidation – Amnesiacs are particularly bad at connecting disparate elements of an experience Evidence: • Huppert & Piercy (1978) ______________________________________ Which of these theories does the best job of explaining why amnesiacs typically perform normally on implicit memory tests? ___________________________________________ Do eye movements reveal implicit knowledge? • Fewer fixations • Fewer transitions Big theoretical question: What is the nature of the memory deficit in amnesia? • Relational binding • Declarative memory Big empirical question: Will amnesiacs demonstrate a relational binding deficit on an implicit memory task? Smaller empirical questions: • How will changing a scene influence eye movements? • Will this behavior be influenced by awareness of the change? • Will amnesiacs show normal eye movement patterns on a change detection paradigm? ___________________________________________ Experiment 1: Methods Results 3 picture types; Eye movement DM Novel viewed More viewing of Experiment 2: Methods Results Same as E1, Same as E1 Experiment 3: Methods Results Effect of explicit awareness DMs only differed Experiment 4: Methods Results Amnesiacs Amnesiacs did ___________________________________________ Do eye movements reveal implicit knowledge? Smaller empirical questions: • Did changing a scene influence eye movements? • Was this behavior be influenced by awareness of the change? • Did amnesiacs show normal eye movement patterns on a change detection paradigm? Big empirical question: Will amnesiacs demonstrate a relational binding deficit on an implicit memory task? Big theoretical question: What is the nature of the memory deficit in amnesia? • Relational binding • Declarative memory Semantic dementia ______________________________________ Symptoms: • Loss of semantic memory • Preservation of phonology and syntax • Non-verbal problem solving • Visuo-spatial skills • Episodic memory EX: Verbal Non-Verbal (complex figures) Relationship to aphasia: • Fluent aphasia (Semantic Dementia) • Non-fluent aphasia Relation to typical amnesia: • Semantic memory • Episodic memory Dissociations within semantic dementia • Living vs. man-made Explanation: Perceptual features Functional features Note of caution: Generalizability ______________________________________ Theoretical Question: What role do the neocortex and hippocampus play in long term memory? Empirical question: How are semantic and autobiographical memory distributed across the lifespan in AD and SD patients? Ribot’s Law (temporal gradient): All things being equal, memory for remote events will be spared relative to recent events. Explanation: consolidation. Supporting evidence: • Hippocampus damage: Dense RA • Fornix damage: smaller RA • ECT: time-limited RA Temporal neocortex damage: • Non-fluent aphasia • Fluent aphasia / semantic dementia o Semantic memory loss (vocab) o Preservation of syntax, phonology and nonverbal problem solving/episodic memory o Normal orientation ______________________________________ Prediction: Hippocampus damage will interfere with newly learned information Resulting pattern: Neocortex damage will interfere with LTM Resulting pattern: Experiment 1 Semantic memory and AM in both AD and SD Results NC: at ceiling AD: no gradient temporal gradient SD: Reverse gradient for ______________________________________ Experiment 2: Detailed study of AM in one SD patient Results: Interpretation: Data are consistent with the consolidation view. ______________________________________ Points to ponder: 1. Why is there not a version of Figure 6 for the control subjects? 2. How come we don't need the hippocampus to mediate LTM? What neural changes occur to eliminate its necessity? 3. Don’t ever write 'clearly obvious' (pg. 83). 4. Why do we care so much about contrasting semantic dementia with AD/amnesia? 5. Does the fact that there was no temporal gradient for the AD patients mean that there IS no temporal gradient in semantic memory for AD? Research challenges in studying amnesia ______________________________________ Subject variability – Individual amnesiacs are behaviorally and anatomically Consequence – drawing firm conclusions is not always easy/warranted. EX: Implicit memory in AD Basketball toss Choosing appropriate tasks – Avoiding the Problem: Does IV have an effect? EX: Distribution of AM in AD Dissociations are insufficient EX: Maze learning Drug trials Knowing where vs. knowing how – • Neuropsych should be used to evaluate theories • Of course, knowing where Applications – Can any of these findings be used to help people? EX: Errorless learning Other mnemonic strategies