ERP correlates of retrieval orientation: cue-related and item-related measures
Jane E. Herron and Edward L. Wilding,
School of Psychology, Cardiff University
Introduction
• Episodic retrieval can be fractionated into pre-retrieval processes, retrieval
itself, and post-retrieval monitoring and evaluation processes.
• Tulving (1983) introduced the notion of ‘retrieval mode’, a generic mnemonic
set that allows stimuli to be processed primarily as cues for episodic retrieval.
Mode was thought to remain invariant across different episodic tasks.
• Different episodic memory tasks have been hypothesised to additionally invoke
task-specific pre-retrieval processes - retrieval ‘orientations’ – that vary
according to the type of episodic information that is to be retrieved (Rugg &
Wilding, 2000).
• Retrieval orientations are thought to operate as tonically maintained ‘sets’ that
influence the way in which stimuli are processed, in order to facilitate retrieval
of the required episodic information.
• Recent studies have provided neural evidence for the existence of retrieval
orientations (e.g. Dobbins et al., 2003; Werkle-Bergner et al., in press; Simons
et al. 2005; Robb & Rugg, 2002; Herron & Wilding, 2004), some using cue-
related designs and others item-related designs;
1. Cue-related: Cue subjects item-by-item as to what type of episodic
information they should retrieve and examine correlates of the cue.
2. Item-related: Examine item-related activity for differences due to
the type of retrieval task, either by examining correlates of correct rejections or
by looking for main effects of retrieval task that do not interact with old/new
item type.
• Despite the variation in experimental design, a common finding is that
correlates of orientation appear at left fronto-temporal scalp and brain regions.
• The following four experiments from our lab employ a combination of cue-
related and item-related analyses to examine retrieval orientation.
• Designed to dissociate correlates of retrieval mode from correlates of retrieval
orientation using a cue-related method (10 study-test blocks):
Experiment 1
• Correlates of retrieval mode and retrieval orientation should be evident as
commonalities (mode) and differences (orientation) between ERPs elicited by
the episodic cues relative to the semantic cue.
• ‘Task?’ = Operations; ‘Location?’ = Location; ‘Movement?’ = Semantic
STUDY
• 12 items per block.
• 6 items rated for animacy (3 shown on the left of the screen, 3 on the right).
• 6 items rated for pleasantness (3 on the left, 3 on the right).
• Binary response (i.e. X = animate, Z = inanimate).
TEST
• 24 items (12 old, 12 new).
• Episodic (‘Task?’ or ‘Location?’) and semantic (‘Movement?’) cues each appear before 8 items.
• Cue-types presented in pairs
• Self-paced, 3-way response for each cue-type (e.g. old left, old right, new)
Cue Test item2 second interval
Recording Parameters
• Sampling rate = 8 ms (epoch length = 2048 ms, pre-stimulus baseline = 104
ms, cue-target interval = 2 seconds).
• EOG correction employed for all participants. Linked-mastoid reference.
• 25 channel recordings (based on 10/20 system):
Results: Behaviour
• Accuracy was not affected
by task or switch/stay status
(although greater for new
than for old items).
Accuracy
RT Hits
CRs
Ops (switch)
Ops (stay)
Location (switch)
Location (stay)
Semantic (switch)
Semantic (stay)
Ops (switch)
Ops (stay)
Location (switch)
Location (stay)
Semantic (switch)
Semantic (stay)
• RTs were faster for ‘stay’
than for ‘switch’ trials, and
slower for the Operations
task than for the other two
tasks.
• Correlates of mode and orientation were evident on stay trials only:
Results: ERPs
F5 F6
0 800ms 0 800ms
+
10µV
Operations Location Semantic
C5 C6
Operations - Semantic
1.4
0.8
-0.2
0.4
-0.6
Location - Semantic
0.0
-1.0
-0.5
1.5
1.0
Operations - Location
1.6
1.2
0.2
-0.2
0.8
• As in previous studies, correlates of retrieval mode were observed over right
frontal scalp regions and had a delayed onset. The data also provided neural
evidence to support the concept of retrieval orientation, indicating that orientation
also had a delayed onset.
• However, switch trials had a mixed cue history (i.e. which task participants were
switching from) and correlates of retrieval orientation may have been influenced by
the task that participants were switching from, as well as the task into which they
were switching.
• Experiment 2 replicated Experiment 1, but only employed the two episodic cues in
alternating pairs so that all switch trial ERPs had identical trial histories within each
retrieval task, and subjects were no longer switching in and out of retrieval mode.
There were also now sufficient trials to examine item-related ERPs for orientation
effects.
Experiment 1: Summary
Experiment 2: Behaviour
• Accuracy did not differ either by cue-type or by switch/stay status.
• Hit RTs were significantly slower for the Operations than for the Location
task, and for switch than for stay trials.
• CR RTs were significantly faster than Hit RTs, but were not affected either
by cue-type or by switch/stay status.
ACCURACY (%) RT (ms)
0102030405060708090
100
Ops(switch)
Location(switch)
Ops(stay)
Location(stay)
Hits
CRs
0
500
1000
1500
2000
2500
Ops(switch)
Location(switch)
Ops (stay)
Location(stay)
Switch Cues:
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS CUE (SWITCH)
LOCATION CUE (SWITCH)
Experiment 2: ERPs
Stay Cues:
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS CUE (STAY)
LOCATION CUE (STAY)
• No independent retrieval task effects were detected for item-related ERPs.
• A significant effect of cue type was found for switch trials but not for stay trials.
Although this effect had similar spatio-temporal characteristics as that seen in
Experiment 1, the polarity of the effect was reversed. It is possible that this
polarity reversal was due to differences in cue history.
• The finding that this effect was significant on switch trials suggests two
possibilities:
1. A retrieval orientation is not adopted until retrieval mode is engaged.
2. As switch trials were predictable in this experiment (due to alternating
pairs), subjects had sufficient time to adopt a retrieval orientation by
predicting the switch cues.
Experiment 2: Summary
• Experiment 3 tested the second hypothesis by replicating experiment 2, but
inserting randomised ‘catch’ trials into the memory test sequence:
• Accuracy did not differ either by cue-type or by switch/stay status.
• Hit RTs slower for the Operations than the Location task, and for switch than for
stay trials.
Experiment 3: Rationale and Behaviour
ACCURACY (%)
0102030405060708090
100
Ops(switch)
Location(switch)
Ops(stay)
Location(stay)
Hits
CRs
RT (ms)
0
500
1000
1500
2000
2500
Ops(switch)
Location(switch)
Ops (stay)
Location(stay)
Switch trials:
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS CUE (SWITCH)
LOCATION CUE (SWITCH)
Experiment 3: ERPs
Stay trials:
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS CUE (STAY)
LOCATION CUE (STAY)
• No independent retrieval task effects were detected for item-related ERPs.
• As in Experiment 2, a significant effect of cue type was found for switch trials but
not for stay trials. This effect was again maximal over left fronto-temporal sites
between 700-1900 ms, and was of the same polarity as that observed in
Experiment 2.
• The finding that correlates of retrieval orientation were significant on switch trials
in Experiments 2 & 3 suggests that one is able to switch retrieval orientation
immediately, as long as one is already in retrieval mode (and that engagement
in retrieval mode must be achieved before orientation can be adopted).
• The findings of Experiments 2 & 3 indicate that this correlate of retrieval
orientation reflects the initial adoption of an orientation.
Experiment 3: Summary
• Other studies employing blocked designs have reported item-related correlates
of retrieval orientation, arguably reflecting processes related to orientation
maintenance. These effects were not evident in our experiments, probably
because they required rapid switching between different orientations (Wilding &
Nobre, 2001).
• We attempted to induce significant item-related orientation effects in Experiment
4 by blocking the two retrieval tasks used in the previous experiments (all other
aspects of the design remained identical). Occasional ‘catch’ trials ensured that
subjects still attended to the cues.
• Item-related orientation effects should be evident in a blocked design if these
are related to the maintenance of an orientation. Conversely, if our cue-related
orientation effects reflect the initial adoption of a retrieval orientation, then these
effects should not be observed in a blocked design.
Experiment 4
Results: Behaviour
ACCURACY (%) RT (ms)
• Accuracy did not differ by cue-type.
• Hit RTs slower for the Operations than for the Location task.
0
500
1000
1500
2000
Operations Location
0
20
40
60
80
100
Operations Location
Hits
CRs
Cues:
Fz
Cz
Pz
F5 F6
C5 C6
P5 P6
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS CUE
LOCATION CUE
Results: ERPs
Items:
Fz
Cz
Pz
F5 F6
C5 C6
P5 P6
0 800ms 0 800ms 0 800ms
+
10µV
OPERATIONS ITEMS
LOCATION ITEMS
• Unlike Experiments 1-3, no cue-related retrieval task effects were detected in
Experiment 4.
• A significant main effect of retrieval task was observed for item-related ERPs in
Experiment 4, maximal over left- and mid-temporal sites. As this effect did not
interact with item type, it fulfils the criteria for a correlate of retrieval orientation.
The distribution of this effect is similar to item-related orientation effects reported
in other studies, and arguably reflects processes contingent upon the
maintenance of orientation across items.
• The findings from Experiments 1-4 provide evidence for two dissociable
correlates of retrieval orientation. The cue-related orientation effects reported in
Experiments 1-3 appear to reflect the initial adoption of a retrieval orientation,
whereas the item-related effect reported in Experiment 4 appears to reflect
processes contingent upon the maintenance of an orientation across items.
General Summary
Cz
F5
C5
Fz
+
10µV OPERATIONS (SWITCH) LOCATION (SWITCH)
OPERATIONS (SWITCH) LOCATION (SWITCH)
+
10µV
Cz
F5
C5
Fz
CzC5
+
10µV OPERATIONS LOCATION
2.0
1.0
0.5
0.0
1.2
0.4
0.0
-0.2
2.0
.0
0.5
-1
800ms 800ms
800ms 800ms
800ms 800ms
EXPERIMENT 2: CUES
EXPERIMENT 3: CUES
EXPERIMENT 4: ITEMS
800 – 1900 ms
800 – 1900 ms
800 – 1900 ms
References
• Dobbins I.G., Rice H.J., Wagner A.D., Schacter D.L. (2003) ‘Memory orientation and success:
separable neurocognitive components underlying episodic recognition.’ Neuropsychologia, 41(3),
318-33.
• Herron J.E. & Wilding E.L. (2004) ‘An electrophysiological dissociation of retrieval mode and retrieval
orientation.’ Neuroimage, 22(4), 1554-62.
• Simons J.S., Gilbert S.J., Owen A.M., Fletcher P.C., Burgess P.W. (in press) ‘Distinct Roles for Lateral
and Medial Anterior Prefrontal Cortex in Contextual Recollection.’ Journal of Neurophysiology.
• Tulving, E., (1983) ‘Elements of Episodic Memory’. Oxford: Oxford University Press.
• Robb W.G. & Rugg, M.D. (2002) ‘Electrophysiological dissociation of retrieval orientation and retrieval
effort.’ Psychonomic Bulletin and Review, 9(3), 583-9.
• Rugg, M. D., Wilding, E. L., (2000) ‘Retrieval processing and episodic memory.’ Trends in Cognitive
Sciences, 4, 108-115.
• Werkle-Bergner, M., Mecklinger, A., Kray, J., Meyer, P. & Duzel, E. (in press) ‘The control of memory
retrieval: Insights from event-related potentials.’ Cognitive Brain Research.
• Wilding E.L. & Nobre A.C. (2001) ‘Task-switching and memory retrieval processing:
electrophysiological evidence.’ Neuroreport, 16;12(16), 3613-7.
Experiment 2 – ‘Operations’ Old/New: Switch Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 2 – ‘Operations’ Old/New: Stay Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 2 – ‘Location’ Old/New: Switch Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 2 – ‘Location’ Old/New: Stay Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 3 – ‘Operations’ Old/New: Switch Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 3 – ‘Operations’ Old/New: Stay Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 3 – ‘Location’ Old/New: Switch Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 3 – ‘Location’ Old/New: Stay Trials
Cz
Pz
F5 F6
C5 C6
P5 P6
Fz
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 4 – ‘Operations’ Old/New
Fz
Cz
Pz
F5 F6
C5 C6
P5 P6
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
Experiment 4 – ‘Location’ Old/New
Fz
Cz
Pz
F5 F6
C5 C6
P5 P6
0 800ms 0 800ms 0 800ms
+
10µV
HITS
CRS
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