Post on 18-Dec-2015
transcript
Experience-Dependent Eye Movements, Awareness, and
Hippocampus-Dependent Memory
Christine N. Smith, Ramona O. Hopkins, and Larry R. Squire
The Journal of NeuroscienceVolume 26, Issue 44, November 1, Pages 11304 -11312
Purpose:Purpose:
What kind of memory is operating when What kind of memory is operating when eye movements change as a result of eye movements change as a result of experience?experience?
Background:Background:
Memory is composed of distinct abilities Memory is composed of distinct abilities that depend on different brain systemsthat depend on different brain systems
Eye movements are signs of behavior that Eye movements are signs of behavior that are measured and correlate with different are measured and correlate with different types of memorytypes of memory
Declarative vs. Implicit memoryDeclarative vs. Implicit memory
3 Experiments To Test:3 Experiments To Test:
1. If eye movements are influenced (changed) 1. If eye movements are influenced (changed) by experience memoryby experience memory
2. If eye movements reflect either conscious 2. If eye movements reflect either conscious or unconscious awarenessor unconscious awareness
3. If this type of identified memory and 3. If this type of identified memory and awareness is hippocampus dependent (relies awareness is hippocampus dependent (relies on this brain system)on this brain system)
Design:Design:
Participants viewed scenes that were either: Participants viewed scenes that were either: novel, repeated, or manipulatednovel, repeated, or manipulated 3 blocks (each with 24 images, 5s/image)3 blocks (each with 24 images, 5s/image) memory test for awarenessmemory test for awareness
E1 & E2: measured eye movements E1 & E2: measured eye movements fixations & scanning of critical regionsfixations & scanning of critical regions
E3: tested amnesic patients ability to correctly E3: tested amnesic patients ability to correctly identify novel, repeated or manipulated imagesidentify novel, repeated or manipulated images measured confidence ratingmeasured confidence rating
SubjectsSubjects
E1: 20 undergraduates; 16F, 4ME1: 20 undergraduates; 16F, 4M
E2: 20 undergraduates; 8F, 12ME2: 20 undergraduates; 8F, 12M
E3: 5 memory impaired patients; 4M, 1F E3: 5 memory impaired patients; 4M, 1F (bilateral lesions to the hippocampus) & 10 (bilateral lesions to the hippocampus) & 10 volunteers (controls); 7M, 4Fvolunteers (controls); 7M, 4F
Materials:Materials: Binocular Apparatus: Head-rest viewpoint eye Binocular Apparatus: Head-rest viewpoint eye
tracker (30hz) & PC-60 software (that detects tracker (30hz) & PC-60 software (that detects pupillary position, measured fixations)pupillary position, measured fixations) Fixations: scored as >100ms elapsed without a Fixations: scored as >100ms elapsed without a
saccade (eye movement of 0.7saccade (eye movement of 0.700 within 33ms) within 33ms)
Position was measured by a 4X4 grid that was Position was measured by a 4X4 grid that was superimposed on image following the experimentsuperimposed on image following the experiment
Results:Results:
Eye movements did differ depending on past Eye movements did differ depending on past viewing of scenes in E1 & E2, specifically simple viewing of scenes in E1 & E2, specifically simple repetitions of an image are sufficient to change repetitions of an image are sufficient to change behavior behavior
Findings were similar in E1 and E2, despite the Findings were similar in E1 and E2, despite the differences in when awareness was assesseddifferences in when awareness was assessed
Impaired performance on memory task & a Impaired performance on memory task & a decrease in confidence in responses of memory decrease in confidence in responses of memory impaired patients in E3impaired patients in E3
Conclusions:Conclusions:
Eye movements change as a function of experienceEye movements change as a function of experience
Eye movements could not reveal unconscious forms Eye movements could not reveal unconscious forms of memory, thus eye movements reflected conscious of memory, thus eye movements reflected conscious declarative memory for what scenes were novel & declarative memory for what scenes were novel & repeated, and manipulatedrepeated, and manipulated
Ability to classify images correctly & confidently relies Ability to classify images correctly & confidently relies on hippocampus-dependent, declarative memoryon hippocampus-dependent, declarative memory
Bottom Line:Bottom Line:
Experience-dependent eye movements in Experience-dependent eye movements in response to altered scenes reflect response to altered scenes reflect conscious, declarative memory that conscious, declarative memory that supports the link between:supports the link between: Aware (conscious) MemoryAware (conscious) Memory Declarative Memory &Declarative Memory & Hippocampus-dependent MemoryHippocampus-dependent Memory