Biomedical subjects

E L Wilding

Publications and source records attributed to E L Wilding.

At least 19 recordsLinked to original sources

PubMed2006

Electrophysiological correlates of familiarity in recognition memory and exclusion tasks.

ERPs were acquired in the test phases of three memory experiments, where three classes of word were presented. These were: (i) words encountered in a prior study phase (studied words), (ii) words presented at test for the first time (new words), and (iii) new words repeated after a lag of 7-9 intervening words (repeated test words). In experiments 1 and 2, participants were asked to respond on one key to studied words and on another to new as well as to repeated test words. In experiment 3, a binary response was again required, but in this case repeated test and studied words were assigned to the same key. In each experiment, the principal focus for analysis was on the differences between the ERPs at mid-frontal electrode locations from 300 to 500 ms post-stimulus that were associated with incorrect responses to studied words (misses) and correct responses to new words. It has been proposed that relatively greater positivity for studied than for new words at this locus reflects the greater familiarity of studied than of unstudied words. ERPs elicited by misses were reliably more positive-going than those elicited by correct rejections in experiments 1 and 2 only. These findings support the link between this modulation of the electrical record and familiarity in so far as the designs of the experiments lead to the prediction that the average level of familiarity associated with misses should be higher in the first two experiments than in the third. In combination with findings in other studies, these data support dual-process accounts of recognition memory.

Adult↗

PubMed2006

Brain and behavioral indices of retrieval mode.

In recent event-related potential (ERP) studies of episodic retrieval, ERPs have been acquired in tasks where participants have been cued trial-by-trial to prepare either to make episodic or semantic retrieval judgments. ERPs elicited during this preparatory cue period and separated according to retrieval task have diverged at right frontal scalp electrodes, with a relatively greater positivity associated with preparation for episodic rather than for semantic retrieval. Importantly, this pattern of differences has been observed only on 'stay' trials: those trials where the participant was cued to prepare for the same retrieval task on the previous trial. These findings have provided the basis for the proposal that the ERP modulations index processes that support the adoption or configuration of retrieval mode - a tonic process that can be sustained while recovery of episodic information is required and which facilitates the retrieval process. In these studies, however, the preparatory period on each trial was no more than 2000 ms, raising the possibility that, with more time available, neural correlates of these preparatory processes would not be restricted to stay trials. In this experiment, participants were cued trial-by-trial to complete either an episodic or a semantic retrieval task, and the preparatory period was greater than 4000 ms on the majority of trials. In keeping with previous findings, the ERPs elicited by these two cue types diverged principally on stay trials at right frontal electrode locations, suggesting that time to prepare is not the primary determinant of the onset of task-specific preparatory retrieval processing. In an important addition to previous findings, moreover, the accuracy of episodic memory judgments increased with the number of successive trials of the same task that participants completed, a finding consistent with the view that adopting a retrieval mode successfully can influence the accuracy of episodic memory judgments.

Adolescent↗

PubMed2006

The influence of criterion shifts on electrophysiological correlates of recognition memory.

The claim that event-related potentials (ERPs) index familiarity was assessed by acquiring ERPs during a recognition memory task in which participants were instructed to adopt different decision criteria in separate retrieval phases. In one, the instructions were to respond "old" only when confident that this was the correct response, and to respond "new" otherwise (the conservative condition). In the other, the instructions were to respond new only when confident that this was the correct response (the liberal condition). The rationale for this approach was that the level of familiarity licensing an old response would be higher in the conservative than in the liberal condition, and if ERPs index familiarity, this would be reflected in changes to the putative ERP index. This index comprises relatively more positive-going neural activity for correct judgments to old than to new items, which is evident from 300 to 500 msec poststimulus at mid-frontal scalp locations. In keeping with task instructions, participants made more old responses in the liberal than in the conservative condition. There were reliable mid-frontal ERP old/new effects in both conditions, and the ERPs evoked by correct judgments to words in the conservative condition were relatively more positive-going than those in the liberal condition. This finding is consistent with the view that the mid-frontal ERP old/new effect indexes familiarity, and in combination with other ERP findings, provides strong support for dual-process accounts of recognition memory.

Adult↗

PubMed2006

Electrophysiological measures of episodic memory control and memory retrieval.

Event-related potentials (ERPs) index processes that occur before, during and after retrieval of information from episodic memory. In this selective review we provide a loose theoretical framework within which retrieval processes operating at these different stages can be considered. We go on to describe how ERPs have been employed in order to index processes operating at each of these stages. These data have contributed to current understanding of the processes that are engaged around the time of episodic memory retrieval, and also illustrate the potential that ERPs have for understanding in detail how memory retrieval processes changes in populations with memory impairments.

Electroencephalography↗

PubMed2005

Memory retrieval processing: neural indices of processes supporting episodic retrieval.

Event-related potentials (ERPs) were acquired during separate test phases of a verbal recognition memory exclusion task in order to contribute to current understanding of the functional significance of differences between ERPs elicited by new (unstudied) test words, which are assumed to index processes engaged in pursuit of task-relevant information. Participants were asked to endorse old words from one study task (targets), and to reject new test words as well as those from a second study task (non-targets). The study task designated as the target category varied across test phases. The left-parietal ERP old/new effect - the electrophysiological signature of recollection - was reliable for targets and for non-targets in all test phases, consistent with the view that participants recollected information about both of these classes of test word. The contrast between the ERPs evoked by new test words separated according to target designation revealed no reliable differences. These findings contrast with those in a recent study in which the same tasks were used, but in which the accuracy of task judgments was markedly higher (Dzulkifli, M.A., & Wilding, E. L. (2005). Electrophysiological indices of strategic episodic retrieval processing. Neuropsychologia, 43, 1152-1162). In that study, there were reliable differences between the ERPs evoked by the two classes of new words, but reliable left-parietal ERP old/new effects for targets only. In combination, the findings suggest that differences between ERPs evoked by new test words can reflect processes that are important for controlling what kinds of information will and will not be recollected.

Adult↗

PubMed2005

Neural correlates of control processes engaged before and during recovery of information from episodic memory.

Preparing to retrieve episodic information engages content-specific pre-retrieval processes--retrieval orientations--that vary according to the episodic information that is to be retrieved [Rugg, M.D., Wilding, E.L., 2000. Retrieval processing and episodic memory. Trends Cogn. Sci. 4, 108-115]. Retrieval orientations are retrieval sets which can be maintained tonically and which influence the ways in which subsequent stimuli are processed, presumably in order to facilitate recovery of the required episodic information. Indices of processes related to the adoption of a retrieval orientation can therefore be obtained by acquiring measures of neural activity during preparation to retrieve, while processes contingent upon the successful adoption of an orientation can be obtained by measuring the neural activity that is elicited by stimuli to which memory judgments are required. Across three experiments, electrophysiological indices of the former class of process were obtained only when frequent switches between different retrieval tasks were required, confirming that this measure of brain activity reflects processes important for the adoption of a relevant retrieval orientation. Stimulus-specific indices of retrieval orientations were obtained primarily when few switches between retrieval tasks were required, consistent with the view that the engagement of stimulus-specific retrieval processing operations is achieved only when an appropriate retrieval orientation has been adopted fully.

Adolescent↗

PubMed2005

Electrophysiological indices of strategic episodic retrieval processing.

Event-related potentials (ERPs) were acquired during test phases of a recognition memory exclusion task, in order to contribute to current understanding of the processes responsible for the ways in which memory retrieval can be controlled strategically. Participants were asked to endorse old words from one study task (targets) and to reject new test words as well as those from a second study task (non-targets). The study task designated as the target category varied across test phases. The left-parietal ERP old/new effect--the electrophysiological signature of recollection--was reliable for targets only in all test phases, consistent with the view that participants control recollection strategically in service of task demands. The contrast between the ERPs evoked by new test words separated according to target designation revealed reliable differences at midline, anterior and right-hemisphere locations. These differences likely reflect processes that form part of a retrieval attempt and are interpreted here as indices of processes that are important for the strategic regulation of episodic retrieval.

Adolescent↗

PubMed2005

Indexing strategic retrieval of colour information with event-related potentials.

Event-related potentials (ERPs) were acquired during two experiments in order to determine boundary conditions for when recollection of colour information can be controlled strategically. In initial encoding phases, participants saw an equal number of words presented in red or green. In subsequent retrieval phases, all words were shown in white. Participants were asked to endorse old words that had been shown at encoding in one colour (targets), and to reject new test words as well as old words shown in the alternate colour (non-targets). Study and test lists were longer in Experiment 1, and as a result, the accuracy of memory judgments was superior in Experiment 2. The left-parietal ERP old/new effect--the electrophysiological signature of recollection--was reliable for targets in both experiments, and reliable for non-targets in Experiment 1 only. These findings are consistent with the view that participants were able to restrict recollection to targets in Experiment 2, while recollecting information about targets as well as non-targets in Experiment 1. The fact that this selective strategy was implemented in Experiment 2 despite the close correspondence between the kinds of information associated with targets and non-targets indicates that participants were able to exert considerable control over the conditions under which recollection of task-relevant information occurred.

Adult↗

PubMed2005

An electrophysiological investigation of factors facilitating strategic recollection.

Episodic memory is thought to be mediated by executive processes that facilitate the retrieval of task-relevant information at the expense of irrelevant information. The exclusion task [A process dissociation framework: Separating automatic from intentional uses of memory. Journal of Memory and Language, 30, 513-541, 1991] can be used to explore these processes. In this task, studied items from one source ("targets") are endorsed on one response key, whereas new and studied items from another source ("nontargets") are rejected on another key. Herron and Rugg [Strategic influences on recollection in the exclusion task: Electrophysiological evidence. Psychonomic Bulletin and Review, 10, 703-710, 2003] reported that nontargets elicited the ERP correlate of recollection (the "left parietal old/new effect") when target accuracy was low, but not when it was high. Their explanation for this was that participants only focused exclusively on the recollection of target information when the likelihood of target recollection was high, as under these conditions this strategy is one that that will give rise to accurate task performance. The fact, however, that targets were encoded in different tasks in the high- and low-accuracy groups means that the results can also be explained in terms of the encoding operations performed at study rather than in terms of target accuracy. This study was designed to distinguish between these competing accounts. All targets were encoded elaboratively. Target accuracy was reduced in one condition with a 40-min study-test interval. Nontargets elicited no left parietal effect in either condition, suggesting that target-specific strategic retrieval is facilitated by certain classes of encoding operations rather than simply high target accuracy per se.

Adolescent↗

PubMed2004

Separating item-related electrophysiological indices of retrieval effort and retrieval orientation.

The relationship between two classes of retrieval process-retrieval orientation and retrieval effort-was investigated using electrophysiological (ERP) and behavioural measures. ERPs were recorded during retrieval phases of exclusion tasks in which participants focused on retrieval of either phonological or semantic associates that were generated in a prior study phase. Participants were separated into two groups on the basis of the relative accuracy of their memory judgments in the retrieval tasks (high vs. low relative difficulty) as a means of assessing retrieval effort. The critical contrasts were between the ERPs evoked by unstudied test items separated according to group and emphasis of the retrieval task (semantic vs. phonological). Reliable differences according to task were evident in the high relative difficulty group only. This finding is consistent with the view that, for this task pair at least, ERPs are sensitive to the processes set in train in pursuit of task relevant information (retrieval orientations) only when relative difficulty is high.

Adolescent↗

PubMed2004

The influence of response-time demands on electrophysiological correlates of successful episodic retrieval.

Event-related potentials (ERPs) were acquired in two memory retrieval tasks. In Experiment 1 a 2.5 s response-time limit was imposed at test, while in Experiment 2 there was no explicit upper limit. There were no other structural differences between the two experiments. The response-time manipulation did not influence the accuracy of memory judgements, but resulted in qualitative changes in the ERP old/new effects that were elicited in the two tasks. In Experiment 2, the ERP old/new effects from 700 ms post-stimulus onwards comprised a relatively greater positivity for correct judgements to old items in comparison to correct judgements to new items. In keeping with findings in previous studies, this relative positivity was largest at anterior sites over the right hemisphere. In Experiment 1, by contrast, the ERP old/new effects during the same time window were most prominent at right hemisphere central electrode locations, and comprised a relatively greater positivity for correct judgements to new rather than to old test items. In combination, the findings in the two experiments are consistent with the view that the imposition of different response-time demands results in the engagement of neurally and functionally distinct processes during episodic retrieval. The time course of these distinct ERP old/new effects suggests that different post-retrieval monitoring operations were engaged according to the time available to make memory judgements.

Adult↗

PubMed2004

An electrophysiological dissociation of retrieval mode and retrieval orientation.

The relationship between two classes of retrieval process-retrieval orientation and retrieval mode-was investigated by recording event-related potentials (ERPs) during the period in which participants were preparing to retrieve information from memory. Participants were cued on a trial-by-trial basis to complete either a semantic retrieval task or one of two episodic retrieval tasks (remember spatial location or remember encoding task). ERPs were recorded time-locked to the cues indicating which task to complete. There were commonalities between the ways in which ERPs evoked by the two episodic retrieval cues diverged from those evoked by the semantic cue. These shared differences are a likely correlate of processes related to retrieval mode. Critically, there were also reliable differences between the ERPs evoked by the two episodic cues. This novel finding is consistent with the view that participants adopted task-specific retrieval sets-retrieval orientations-which varied according to the kinds of episodic information that were to be retrieved.

Adolescent↗

PubMed2001

Task-switching and memory retrieval processing: electrophysiological evidence.

Participants attempted to retrieve phonological or imagery-based information under conditions where either the two kinds of retrieval were required in separate blocks, or where frequent switches between retrieval tasks were required within blocks. Electrophysiological indices of processes engaged in pursuit of accurate memory judgments, elicited by contrasting ERPs evoked by correctly identified new test items, differed according to retrieval task only when the tasks were completed in separate blocks. The principal conclusion suggested by these findings is that the requirement to alternate frequently between the two retrieval tasks attenuated the engagement of task-specific processes that form part of a retrieval attempt.

Analysis of Variance↗

PubMed2001

Event-related functional imaging and episodic memory.

Electrical and haemodynamic measures of neural activity can be time-locked to an event-of-interest, such as the presentation of a stimulus or a behavioural response. Both of these measures can be employed in studies where the aim is to elucidate the relationship between neural activity and cognitive processes. This review highlights a number of considerations that arise when these techniques are employed in pursuit of this goal, with a particular emphasis on functional imaging studies of retrieval from episodic memory. The review includes: a discussion of some limitations that each technique imposes at the stage of experimental design, consideration of the relative strengths and weaknesses of each technique, a commentary on assumptions that are common to both, and a brief review of the ways in which these techniques can be extended in order to index two distinct classes of cognitive operations that have correspondingly distinct neural signatures.

Brain↗

PubMed2000

In what way does the parietal ERP old/new effect index recollection?

Event-related potentials (ERPs) were recorded while subjects performed a memory retrieval task requiring old/new judgements to visually presented old (previously studied) and new words. For words judged old, subjects made two binary forced-choice context (hereafter source) judgements, denoting the voice (male/female) and task (action/liking) with which the test word had been associated at study. By separating the ERPs according to the accuracy of the voice and task judgements, it was possible to test the prediction that the differences between ERPs to correctly identified old and new words at parietal scalp sites (parietal old/new effects) are sensitive to the amount or quality of information that is retrieved from episodic memory (Rugg, M.D., Cox, C.J.C., Doyle, M.C., Wells, T., 1995. Event-related potentials and the recollection of low and high frequency words. Neuropsychologia 33, 471-484). In keeping with this proposal, the magnitude of the parietal old/new effects co-varied with the number of accurate source judgements. This finding is consistent with proposals that the parietal old/new effect indexes recollection in a graded fashion.

Adult↗

PubMed1999

Separating retrieval strategies from retrieval success: an event-related potential study of source memory.

Event-related potentials (ERPs) were recorded while subjects performed two different source memory retrieval tasks. Each task was preceded by a study phase in which subjects heard an equal number of words spoken in a male or a female voice. A cue preceding each word indicated whether the subjects should make an active/passive (action) or a pleasant/unpleasant (liking) judgment to the word. In one retrieval task (the voice condition), subjects made a three-way distinction between new (unstudied) words, and words that had been spoken by the male or the female voice at study. In the second retrieval task (the task condition), subjects distinguished between new words, and words to which they had made an action or a liking judgment. All test words were presented visually. In keeping with previous findings, the differences between the ERPs to correct memory judgments for old and new items were characterised by two temporally and topographically dissociable modulations, with right-frontal and left-parietal maxima respectively. These 'old/new effects' displayed different sensitivities to successful retrieval of either voice or task information, providing further evidence that they index functionally dissociable processes. The direct comparison of the ERPs to correct rejections in the voice and task retrieval conditions revealed reliable differences over frontal scalp, suggesting that, irrespective of whether retrieval is successful, neural processing differs according to the source retrieval demands of the task.

Adolescent↗

PubMed1999

Orienting attention in time. Modulation of brain potentials.

With the aim of casting light on the neural mechanisms that support our ability to modulate visual attention over time, we recorded event-related potentials (ERPs) while normal human subjects performed a target detection task with temporal contingencies between cue and target stimuli. The task used two central cues, which predicted (80% validity) when a subsequent target would occur (either 600 or 1400 ms after cue onset). Unlike previous tasks of attentional orienting, there was no spatial information provided and all stimuli were presented foveally. Reaction times and ERPs linked to targets presented at the shorter interval showed significant effects linked to attentional orienting. Reaction times were faster when the cues correctly predicted the cue-target interval, suggesting the ability of the brain to use information about time to deploy attentional resources. ERPs differed according to the predicted time interval. In particular, the P300 amplitude and latency were enhanced when the cue predicted the cue-target interval accurately. The ERPs elicited by the cues also differed according to the time interval that they predicted. Differences were observed in potentials linked to motor preparation and expectancies. The results reveal dynamic neural activity involved in orienting attention to time intervals, as well as the consequent modulation of target-related neural activity resulting from differing temporal expectations.

Adult↗

PubMed1998

Electrophysiological evidence for dissociable processes contributing to recollection.

This paper reviews a number of studies in which we have employed event-related potentials (ERPs) to investigate the cognitive processes which contribute to conscious recollection. Across a range of tasks (including recognition memory, source memory, associative recall and word-stem cued recall) there is evidence for the proposal that recollection involves processes which are both functionally and neurologically dissociable. This evidence takes the form of temporally and topographically dissociable ERP effects, which attain their maximum amplitude when elicited by items that satisfy operational definitions for having been recollected. The ERP effects are interpreted as reflecting retrieval and post-retrieval processes which, we argue, constitute two separate components of recollection as defined within the process dissociation framework of Jacoby and colleagues. The ERP findings suggest that post-retrieval processing is particularly sensitive to task variables, implying that recollection may be neither functionally nor neurologically homogeneous.

Association Learning↗