14. Memory & EEG

14. Memory & EEG

1. Memory

   • Need to make a decision whether we have encountered something before or not (Old/New) and sometimes context (Remember/Know)
   • Dual Process Theory
     • 2 processes underlie recognition memory
     • Familiarity = how familiar a stimulus seems. Awareness of an encounter, but no recovery of contextual details
     • Recollection = Particulars of an experience. Contextual and qualitative details recovered
   • Signal Detection Model
     • Old/New judgements of stimuli
     • recognition based on general assessment of memory strength
     • Memory strength for older items is better
     • old/new items normally distributed and overlap slightly
     • response criterion = above criterion = old and below = new
     • conservative criterion = criteria for response is higher, have to be more confident
     • Hit, Miss, Correct rejection and false alarm

2. Memory Control

   • Post-retrieval processing operations: ERP after interactions between retrieval cues and memory traces, should be no earlier than the onset of left-parietal and mid-frontal effects
   • Retrieval Orientations: more than 1 operations are engaged when recovering information, based on the specific demands of tasks.
   • Pre-Retrieval processing operations: ERP before interactions of cue and trace

3. EEG

   • Electroencephalography (EEG)
     • Non invasive technique
     • Records electrical activity of the brain
     • electrodes attached to scalp
     • good temporal resolution
   • Event related potentials (ERP)
     • recorded while participants study series of items or while they are tested on items
     • Stages: Show p's old/new items mixed > record response and the EEG associated > cut the EEG on the onset of the item > filter the data > average the trials of same data together
     • high temporal resolution
     • differences in neural activity by old (hit) and new (correct rejection) responses
     • Issues: participants move their eyes to look at stimulus (need to have a fixation point or small stimulus) and experiment must yield large number of trials for each condition of interest

4. Dissociations

   • MAIN POINTS
     • Temporally distinct: Mid-frontal occurs 300-500ms and Left-parietal occurs 500-800 after stimulus
     • Topographically distinct: Mid-frontal activates mid frontal scalp locations. Left-parietal activated left parietal locations
     • Functionally distinct: Midfrontal involved in familiarity and left-parietal involved in recollection.
     • Supports dual-process model
   • Left-Parietal Effect
     • Onset 400-500ms after target
     • largest activation at left-parietal scalp locations
     • duration of 500-800ms post-stimulus
     • correlate of recollection (Remember)
     • Wilding et al (1995) presented words auditorily or verbally to participants. Test of old/new and if old verbal or visual. ERP was larger when correct source judgements (modality) compared to incorrect after hit. Suggests source correct signifiicantly different = recollection
   • Mid-Frontal Effect
     • onset around 300-500ms after target
     • Activation largest at the midline, frontal sites
     • greater positivity for hits, not correct rejections = familiarity judgements
     • Azimian, Faridani & Wilding (2006) gave particpants a conservative or liberal decision criteria. Conservative = old responses when confident (familiarity) and liberal = new responses when confident (recollection). Hits in conservative condition significantly larger
   • Woodruff et al (2006) participants studied words, then asked if they remembered or knew the items on 4 point scale. Left-parietal activated when remember responses. Mid-frontal activated for confidence ratings
   • Yu & Rugg (2010) considered dissociate correlated of recollection (remember) and familiarity (know) responses. Remember, confident old, unconfident old, unconfident new, confident new. Mid-frontal activated largest for confident old, then confident new then unconfident old. Left-parietal activated for remember and confident old