Biomedical subjects

E L Wilding

Publications and source records attributed to E L Wilding.

10 recordsLinked to original sources

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↗

PubMed1997

Event-related potentials and the recognition memory exclusion task.

Subjects heard words that were presented in either a male or a female voice, and were required to perform one of two encoding tasks according to the gender of the voice. At test studied words were presented visually, along with a set of words new to the experiment. Subjects were required to respond on one key to words belonging to one of the two classes of studied word (targets), and to respond on a different key both to words belonging to the other study class (non-targets), and to words new to the experiment. In comparison to the event-related potentials (ERPs) elicited by new words, the ERPs elicited by correctly detected targets exhibited two temporally and topographically distinct positive going effects: one of these was phasic, showed a parietal maximum, and was larger over the left than the right hemisphere. The second effect was more sustained in time, frontally distributed, and was larger over the right hemisphere. The ERPs elicited by correctly classified non-targets contained the parietal effect only. These findings confirm that retrieval of contextual information in tests of recognition memory (recollection) is associated with two distinct ERP modulations. While one of these may be closely tied to process necessary for recollection, the other may reflect less obligatory processes which operate on the products of successful retrieval.

Adolescent↗

PubMed1997

An event-related potential study of memory for words spoken aloud or heard.

Subjects made old/new recognition judgements to visually presented words, half of which had been encountered in a prior study phase. For each word judged old, subjects made a subsequent source judgement, indicating whether they had pronounced the word aloud at study (spoken words), or whether they had heard the word spoken to them (heard words). Event-related potentials (ERPs) were compared for three classes of test item; words correctly judged to be new (correct rejections), and spoken and heard words that were correctly assigned to source (spoken hit/hit and heard hit/hit response categories). Consistent with previous findings (Wilding, E. L. and Rugg, M. D., Brain, 1996, 119, 889-905), two temporally and topographically dissociable components, with parietal and frontal maxima respectively, differentiated the ERPs to the hit/hit and correct rejection response categories. In addition, there was some evidence that the frontally distributed component could be decomposed into two distinct components, only one of which differentiated the two classes of hit/hit ERPs. The findings suggest that at least three functionally and neurologically dissociable processes can contribute to successful recovery of source information.

Adolescent↗

PubMed1996

An event-related potential study of recognition memory with and without retrieval of source.

Event-related potentials (ERPs) were recorded during the test phase of a recognition memory task in two experiments. In both experiments subjects made initial old/new judgements to visually presented words, and for words judged old, indicated in which of two voices (male/female) the words had been heard at study. In the second experiment only subjects had the option to signal that they were uncertain about the status of a test word. Two positive-going ERP effects differentiated the ERPs evoked by correctly recognized old words from those evoked by words correctly judged new. The two effects differed in their scalp topography and time course, and were both of greater magnitude in the ERPs evoked by recognized words for which a correct voice judgement was made. The findings are consistent with the view that multiple neural systems underlie the ability to recognize an item and to recall its study context. However, the findings offer little support for the view, articulated in certain 'dual-process' models of recognition memory, that recognition judgements with and without retrieval of study context depend upon qualitatively different memory processes or systems.

Analysis of Variance↗

PubMed1995

Recognition memory with and without retrieval of context: an event-related potential study.

In two recognition memory tests subjects made initial old/new judgements and subsequently judged whether 'old' words had been presented auditorily or visually at study. Test words were presented visually in Experiment 1 and auditorily in Experiment 2. ERPs evoked at test by words correctly judged 'old' were separated according to whether they were correctly or incorrectly assigned to their study modality. In both experiments, ERPs to correctly assigned words were more positive than those evoked by words correctly judged to be new. This ERP old/new effect was absent for words incorrectly assigned to study modality in Experiment 1, and was observed over a restricted latency range in Experiment 2. The findings are consistent with the hypothesis that the old/new effect is associated with recognition memory based on recollection of the study episode, rather than familiarity.

Acoustic Stimulation↗