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									 Recall to reject and contextual discrimination:
 The influence of contextual distinctiveness on
  the control of recollection in exclusion tasks

                        Marianne de Chastelaine
            PhD Supervisors: Mick Rugg & Chris Brewin
                   Institute of Cognitive Neuroscience
                        University College London

Acknowledgements
Wellcome Trust
                  The exclusion task
Study List 1 – deep encoding           Test phase
    LAMP
                  ‘non-targets’   KITE - target: ‘old’
       HOSE

           DOLL
                                  LAMP - non-target: ‘new’
Study List 2 – shallow encoding

    TENT
                   ‘targets’      TREE - unstudied: ‘new’
        BEAR

           KITE
      Process dissociation procedure
Study List 1 – deep-encoding       Test phase - exclusion
   LAMP
                  ‘non-targets’ (1991)
                         Jacoby     KITE - target: ‘old’
       HOSE
              • Correctly classified ‘targets’ –
            DOLL
                 based on familiarity OR
                 recollection.     LAMP - non-target: ‘old’
Study List 2 – shallow-encoding
             •    Correctly rejected ‘non-targets’
    TENT         – based on recollection.
                    ‘targets’        TREE - unstudied: ‘new’
       BEAR

           KITE
                Alternative proposal
Study List 1 – deep-encoding        Test phase - exclusion
   LAMP
                  ‘non-targets’ Rugg (2003a)
                    Herron &         KITE - target: ‘old’
       HOSE
              • Correctly classified ‘targets’ –
            DOLL
                  based on recollection.
                                      LAMP - non-target: ‘old’
Study List 2 –• deep-encoding
                   Correctly rejected ‘non-targets’
                  – based on the absence of
    TENT          ‘target’ source information.
                     ‘targets’        TREE - unstudied: ‘new’
       BEAR

           KITE
         ERP correlate of recollection

Recollection: a left-lateralised
parietal positivity




                                               +
                                                            NEW
                                               5µV          DEEP HIT

  0            600ms



            Data from Rugg et al., Nature, 1998, 392, 595-598
    Herron & Rugg (2003a) – design
Study List 1 – Exps 1 & 2: deep        Test phase
    LAMP
                  ‘non-targets’   KITE - target: ‘old’
       HOSE

           DOLL
                                  LAMP - non-target: ‘new’
Study List 2 – Exp 1: deep
              Exp 2: shallow
    TENT
                                  TREE - unstudied: ‘new’
        BEAR       ‘targets’
           KITE
          Herron & Rugg (2003a) – ERP data
                                        Good target                Poor target
                                         memory                     memory



          +        NTARG
                   TARG
          5µV      NEW
                                   0     600 msec              0     600 msec



§ Good target memory: target recognition based on information diagnostic of study source
– non-target rejection based on absence of this information.
§ Poor target memory: relatively little source information available for targets –
recollection of non-target source necessary for their rejection.
§ Findings suggest the adoption of a retrieval strategy.
Ø‘retrieval orientation’: enables test cues to be processed in a way that selectively probes
for target recollection.
            Effect of study task similarity (1)
q In contrast to these findings, left parietal old/new effects for correctly rejected non-
   targets have been reported, despite good target accuracy (e.g., Cycowicz, Friedman &
   Snodgrass, 2001; Cycowicz, Friedman & Duff, 2003; Wilding & Rugg, 1997; Wilding
   & Sharpe, 2004).

                             Why do these findings differ?

q One difference between these ERP studies concerns the degree of similarity between
   target and non-target study contexts.

Ø Presumably, the adoption of a retrieval orientation, allowing exclusive recollection of
   targets, will be more successful when there are fewer overlapping contextual features
   associated with targets and non-targets engendered during the study phase.

Ø One factor that should modulate non-target recollection is the degree of similarity
   between target and non-target study contexts (cf. Wilding & Sharpe, 2004).
                        Aims of current study
q To investigate whether the ERP correlates of recollection would differ according to the
degree of similarity between target and non-target study contexts:

Ø For the ‘similar group’, target and non-target study tasks were identical and, for the
‘different group’, target and non-target study tasks were more distinct.

                                       Predictions:
q Similar group: Given greater similarity between target and non-target study contexts,
attempts to retrieve target source will, to some extent, give rise to the recollection of non-
target source – correctly rejected non-targets will elicit a left parietal old/new ERP effect.

q Different group: With greater differences between target and non-target study contexts,
a retrieval orientation allowing exclusive recollection of target source will be more
successfully adopted – non-targets will be rejected on the basis of the absence of this
information and, thus, will fail to elicit a left parietal old/new ERP effect.
                                                Design
   Study list 1 – non-targets                Study list 2 - targets                Test phase
                                                                          Both groups:

   KITE                                   BABY
                                                                           LAMP          60 targets: ‘old’
                      - 60 items                             - 60 items
      BOAT                                  LAMP

         DOLL                                   COIN
                                                                            KITE
                                                                                         60 non-targets: ‘new’
Task 1:                                Task 1:
Both groups: colour association        Both groups: colour association
Task 2:                                Task 2:
Similar group: pleasantness rating     Both groups: pleasantness rating     TREE
                                                                                         60 unstudied: ‘new’
Different group: indoor/outdoor task


 q Retaining the above correspondence of group and item type to study task, word colour
 and tasks were fully counterbalanced across study list and group.

 q At test, the requirement was to respond with one key press to targets and with another
 key press to non-targets and unstudied items.
                               ERP recording
Test phase only:

q     EEG recorded from 29
                                                         50                 36
    silver/silver chloride electrodes
                                              49                                       37
    and   referenced    to   linked
                                         48        33              8              22
    mastoids                                                  19        9                   38


q Blink corrected using linear          47              17         1         11                  39
                                              31                                       24
    regression
                                         46        30                             25        40
                                                                   14
q Sampling rate = 125 Hz for
                                                         29                 26
    2048 ms (pre-stimulus baseline            45                                       41

    = 104 ms)                                            44                 42


q N=16 (each group)
                             Behavioural data
                  Accuracy                   targets                RT
                                             non-targets
                                             new




q There were no differences in accuracy or RTs as a function of group.

q Accuracy for new items was higher than for targets and non-targets. Accuracy for
   targets and non-targets did not differ.

q RTs for new items were faster than for targets and non-targets. RTs for targets and
   non-targets did not differ.
               Non-target left parietal ERP effects
                Similar group                                                  Different group

+

5µV

                                                           Non-target
                                                           New
           0               800 ms                                          0         800 ms




    NT – New: 300-500 ms            NT – New: 500-800 ms
                                                                q For the similar group only, correctly
                                                                rejected non-targets elicited a left-parietal
                                                                old/new effect (red bar) which onset
                                                                around 200-300 msec (blue bar).
                     Target left parietal ERP effects
                    Similar group                                              Different group



+

5µV                                                      Target
                                                         New
             0            800 ms                                         0           800 ms


    T – New: 300-500 ms            T – New: 500-800 ms         T – New: 300-500 ms        T – New: 500-800 ms




q For both groups, left parietal (500-800 msec) old/new effects were elicited by targets.
The same items also elicited early-onsetting (300-500 msec) left parietal effects.
                             Interim discussion
q As predicted, for the similar group only, correctly rejected non-targets elicited a left
parietal old/new effect. In this case, as there was greater overlapping contextual
information between targets and non-targets engendered during the study phase, attempts
to retrieve target source gave rise to the recollection of non-target source.

q For the different group, non-targets failed to elicit a left parietal old/new effect. As
target and non-target study contexts were partially distinct, here a retrieval orientation,
allowing exclusive recollection of target source, was more successfully adopted.

q However, in contrast to the above oberservations, there is some reason to believe that,
for the different group, non-targets may well have been recollected even though there was
no reliable left parietal effect elicited by these items.
               Non-target left parietal ERP effects
                Similar group                                                  Different group

+

5µV

                                                           Non-target
                                                           New
           0               800 ms                                          0         800 ms




    NT – New: 300-500 ms            NT – New: 500-800 ms
                                                                q For the similar group only, correctly
                                                                rejected non-targets elicited a left-parietal
                                                                old/new effect (red bar) which onset
                                                                around 200-300 msec (blue bar).
                 Late posterior negativity
    Similar group                              Different group




                        +     Target
                              Non-target
0       800 ms                             0         800 ms
                              New
                        5µV
    Late negativity - functional significance?

qA   combination of processes that are both response-locked and stimulus-
locked.

q Often reported in ERP studies in which source judgements have been
required.

q Stimulus-locked component suggested to reflect processes related to the
search for and/or maintenance of the conjunction of item and associated
contextual information (Johansson & Mecklinger, 2003).
                 Late posterior negativity
    Similar group                              Different group




                        +     Target
                              Non-target
0       800 ms                             0         800 ms
                              New
                        5µV
                Specified retrieval search
          Study list 1 – non-targets              Study list 2 - targets



     KITE                                   BABY


          BOAT                                   LAMP


              DOLL                                 COIN


Task 1:                                Task 1:
Both groups: colour association        Both groups: colour association

Task 2:                                Task 2:
Similar group: pleasantness rating     Similar group: pleasantness rating
Different group: indoor/outdoor task   Different group: pleasantness rating
            Mis-matched contextual details
Similar group:

q Targets = contextual details of 2nd study task

q Non-targets = contextual details of 2nd study task
                Specified retrieval search
          Study list 1 – non-targets              Study list 2 - targets



     KITE                                   BABY


          BOAT                                   LAMP


              DOLL                                 COIN


Task 1:                                Task 1:
Both groups: colour association        Both groups: colour association

Task 2:                                Task 2:
Similar group: pleasantness rating     Similar group: pleasantness rating
Different group: indoor/outdoor task   Different group: pleasantness rating
            Mis-matched contextual details
Similar group:
q Targets = contextual details associated with the 2nd study task
q Non-targets = contextual details associated with the 2nd study task
Different group:
q Targets = contextual details associated with the visualisation task
q Non-targets = details of cognitive operations associated with the
visualisation task AND the 2nd study task allocated to non-targets
Ø Processes acting upon a mis-match between the target memory
representation and retrieved irrelevant memories – likely to have been
engaged to the greatest extent for non-targets from the different group.
Ø Is this reflected in the greater negativity elicited by these items?
                            Final conclusions
q There is some evidence that the adoption of a specific retrieval orientation can account
for the finding that test words can be used to selectively retrieve episodic information
involving target words as opposed to non-target pictures (Herron & Rugg, 2003b).
q However, data from the present experiment suggest that even a partial overlap between
target and non-target study contexts will lead to the failure of the adopted retrieval
orientation to focus retrieval operations exclusively on target context.
q It seems that additional mechanisms would be required to assess and possibly act upon
mismatches between the targeted memory representation and the contextual details that
were actually retrieved – it is proposed that the late posterior negativity reflects such
processes.
q Whether such processes tentatively proposed to be reflected by the late negativity act to
suppress irrelevant information or to simply register a mismatch, it would seem that these
may act in concert with the adoption of a specific retrieval orientation to bias initial
retrieval, and subsequent attention, towards relevant memories amongst competing
alternatives.

								
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