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 1Cold 1D only when confident that this was the correct response, and to respond 1Cnew 1D 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

Retrieval processes supporting judgments of recency.

Abstract & The circumstances under which different retrieval processes can support judgments about how long ago events occurred remain a matter of debate, as do the ways in which retrieved information can be employed in support of such judgments. In order to contribute to an understanding of the nature and number of distinct retrieval processes that support time judgments, event-related potentials (ERPs) were acquired during a continuous verbal memory task, where the lag between presentation and re-presentation of words was varied. Participants made judgments of recency ( JORs), indicating the number of words that had intervened between presentation and re-presentation. Two spatially and temporally separable ERP effects predicted JORs, and the two effects bore correspondences with ERP modulations that have been linked to the processes of recollection and familiarity, suggesting that both of these processes contributed to JORs. The two effects predicting recency judgments also did so in the same way, with larger effects uniformly predicting shorter lag judgments. In so far as the sizes of the effects index memory strength, these findings are consistent with theoretical accounts of JORs where strength is employed heuristically: The more information recovered, the more recently the event occurred. &amp

Electrophysiological correlates of processes supporting memory for faces

The retrieval processes supporting recognition memory for faces were investigated using event-related potentials (ERPs). The focus for analyses was ERP old/new effects, which are the differences between neural activities associated with correct judgments to old (studied) and new (unstudied) test stimuli. In two experiments it was possible to identify three old/new effects that behaved as neural indices of the process of recollection. In both experiments there was one old/new effect that behaved as an index of the process of familiarity. These outcomes are relevant to the ongoing debate about the functional significance of ERP old/new effects and the implications that scalp-recorded electrophysiological data have for theories of the processes supporting long-term memory judgments

Neural Correlates of Subjective Familiarity and Choice Bias during Episodic Memory Judgments

Successful recognition memory decisions depend on mnemonic and decision making processes that are computed by multiple, distributed brain areas. However, little is known about what computations these areas perform or how these areas are connected. Here, I collected behavioral and functional magnetic resonance imaging data from humans during the performance of an old-new recognition memory task with retrospective confidence judgments. Across runs, choice bias was successfully manipulated by providing rewards for correct responses that were either symmetric (equal reward for hits and correct rejections) or asymmetric (one response worth more than the other). Successful recognition memory was associated with activation in anterior prefrontal, parahippocampal, posterior cingulate, and parietal cortex. Resting state functional connectivity demonstrated that these brain areas are organized into two distinct networks. The first network includes parahippocampal cortex and angular gyrus. The second network includes lateral prefrontal cortex and intraparietal sulcus. The hippocampal-cortical network was most active during old vs. new decisions, did not differentiate hits from false alarms, and was differentially active during low confidence old and new judgments. In contrast, while the frontoparietal network was robustly activated by hits, it was not activated during either false alarms or low confidence old judgments. Thus, these two distinct networks can be distinguished by their relative connectivity to the medial temporal lobe vs. lateral prefrontal cortex and their responses during uncertain old judgments and errors. The choice bias manipulation had opposing effects on the parietal components of these networks, which further suggests these networks make distinct contributions to mnemonic decision making.Psycholog

Electrophysiological investigations of recognition memory: The role of pre-existing representations in recollection

Dual-process models of recognition memory propose that recognition memory can be supported by either a general sense of familiarity or the recollection of the encoding context. One source of evidence supporting dual-process models comes from event-related potential (ERP) studies of recognition memory, which have identified distinct patterns of neural activity associated with familiarity and recollection (the mid frontal and left parietal old/new effects, respectively). In this thesis, dual-process accounts of recognition memory were investigated in a series of ERP studies using three categories of stimulus: previously unknown faces, famous faces, and names. For previously unknown faces, familiarity was associated with activity over posterior scalp electrodes while recollection was associated with topographically dissociable activity over anterior electrodes. These dissociable patterns of activity support dual-process models. However, the typical pattern of old/new effects was only observed for stimuli associated with pre-existing representations (i.e., names and famous faces), suggesting that the presence/absence of pre-existing representations may determine the particular retrieval processes that support recognition memory. Furthermore, recollection was associated with two different patterns of activity (anterior and left parietal effects), suggesting that recollection is not a homogenous process. Dual-process theories may represent an important starting point for investigating recognition memory, but neither familiarity nor recollection appear to be functionally homogenous processes when theorizing is constrained by the analysis of scalp recorded electrophysiological activity

The role of the self in episodic memory: the effect of closeness to others

It has been shown that processing information in relation to oneself as opposed to others benefits episodic memory. The cognitive and neural mechanisms underlying this self-reference effect (SRE) are mostly unknown. This thesis addressed these mechanisms by investigating (1) the effect of closeness to others on the SRE and (2) the electrophysiological activities associated with encoding and retrieving information about oneself. Three behavioural and two electrophysiological experiments are reported. In Experiment 1, healthy adults judged the degree to which trait adjectives described themselves, a close other or a distant other. Recognition memory for the adjectives showed a significant SRE for the self over both close and distant others. In Experiment 2, a source memory paradigm to elucidate the type of memory involved in the SRE again showed a significant SRE for the self relative to a close and distant other. In Experiment 3, subjective ratings of self-esteem and Big-Five personality traits were acquired to assess individual differences in the SRE. No significant correlations were found. In Experiments 4 and 5, memory-related brain activity was analysed via event-related potentials (ERPs) and oscillations. Retrieving information about oneself was associated with the mid-frontal and left-parietal ERP old/new effects, whereas retrieving information regarding a close other was associated with a late negative-going effect. Additionally, encoding information about oneself did not affect oscillatory power, but encoding information about a close or distant other was respectively associated with decreases in beta and theta power. In combination, the thesis suggests that (1) closeness to others does not explain the SRE and (2) there are distinct brain activities associated with the encoding and retrieval of information about oneself and others. The self thus seems a psychologically and anatomically specialised affiliation that affects information processing over time

A Type-2 signal detection analysis of gambling behaviour: cognitions, metacognitions, expertise and optimality

Cognitive gambling research has focused mainly on the irrational beliefs and cognitive biases that differentiate problem (PGs) and non-problem (RGs) gamblers. Whilst this research has been informative by highlighting that greater irrational beliefs are associated with gambling severity, the research has failed to determine cause and effect. This thesis proposes that metacognition is an area that may play a central role in the development and/or maintenance of problem gambling. Type-2 Signal Detection Theory (SDT) was used to analyse the data to measure three cognitive and metacognitive components of gambling performance: accuracy, resolution (metacognitive monitoring) and gambling criterion (metacognitive control). Optimality of gambling decisions was also explored. Experiment 1 used a simplified blackjack task, which demonstrated resolution differences between non-gamblers(NGs) and RGs. Experiments 2 to 5 examined the transference of gambling expertise of RGs and NGs in a novel dice gambling task. Experiment 6 demonstrated that the type of task can account for some cognitive and metacognitive variation observed between PGs and RGs, but impaired gambling criterion setting is a pertinent component of PGs’ gambling performance that is not dependent on gambling task. Finally, Experiment 7 showed that feedback enables participants to effectively shift gambling criteria to a more optimal position - and may have considerable implications for the treatment of problem gambling. The results are discussed in relation to four specific research questions and underscore the relative contribution of using a SDT approach in the study of gambling behaviour

Associative Recognition: Exploring the Contributions of Recollection and Familiarity

Episodic memory refers to the storage and retrieval of information about events in our past. According to dual process models, episodic memory is supported by familiarity which refers to the rapid and automatic sense of oldness about a previously encoded stimulus, and recollection which refers to the retrieval of contextual information, such as spatial, temporal or other contextual details that bring a specific item to mind. To be clear, familiarity is traditionally assumed to support recognition of item information, whereas recollection supports the recognition of associative information. Event Related Potential (ERP) studies provide support for dual process models, by demonstrating qualitatively distinct patterns of neural activity associated with familiarity (Mid-Frontal old/new effect) and recollection (Left-Parietal old/new effect). In the current thesis, ERPs were used to address two important questions regarding associative recognition – namely, the function of the neural signal supporting recollection and whether familiarity can contribute to the retrieval of novel associative information. The first series of experiments was aimed at addressing how recollection operates by employing a recently developed continuous source task designed to directly measure the accuracy of retrieval success. To date, the function of recollection has been fiercely debated, with some arguing that recollection reflects the operation of a continuous retrieval process, whereby test cues always elicit some information from memory. Alternatively, recollection may reflect the operation of a thresholded process that allows for retrieval failure, whereby test cues sometimes elicit no information from memory at all. In the current thesis, the Left Parietal effect was found to be sensitive to the precision of memory responses when recollection succeeded, but was entirely absent when recollection failed. The result clarifies the nature of the neural mechanism underlying successful retrieval whilst also providing novel evidence in support of threshold models of recollection. The second series of experiments addressed whether familiarity could contribute to the retrieval of novel associative information. Recent associative recognition studies have suggested that unitization (whereby multi-component stimuli are encoded as a single item rather than as a set of associated parts) can improve episodic memory by increasing the availability of familiarity during retrieval. To date, however, ERP studies have failed to provide any evidence of unitization for novel associations, whereas behavioural support for unitization is heavily reliant on model specific measures such as ROC analysis. Over three separate associative recognition studies employing unrelated word pairs, the magnitude of the Mid-Frontal old/new effect was found to be modulated by encoding instructions designed to manipulate the level of unitization. Importantly, the results also suggest that different encoding strategies designed to manipulate the level of unitization may be more successful than others. Finally, the results also revealed that differences in behavioural performance and modulation of the Mid-Frontal old/new effect between unitized and non-unitized instructions is greater for unrelated compared to related word pairs. In essence, the results suggest that unitization is better suited to learning completely novel associations as opposed to word pairs sharing a pre-existing conceptual relationship. Overall, the data presented in this thesis supports dual process accounts of episodic memory, suggesting that at a neural level of analysis, recollection is both thresholded and variable, whilst also supporting the assumption that familiarity can contribute to successful retrieval of novel associative information. The results have important implications for our current understanding of cognitive decline and the development of behavioural interventions aimed at alleviating associative deficits

Development of declarative memory in preterm and full-term born children : evidence from neuropsychological tests, structural brain imaging, and event-related potentials

The present thesis examines developmental differences in declarative long-term memory between preterm born children with uncomplicated neonatal courses and full-term born children at early school-age by applying different scientific methods (i.e., neuropsychological tests, structural brain imaging, and event-related potentials (ERPs)). Besides investigating the development of declarative memory in general (Study 1), a particular focus is laid on episodic memory and its specific retrieval processes (familiarity and recollection; Study 1, 2, 3, and 4). Recent studies detected reduced memory performance and marked volume reductions in the hippocampus (which is an important brain structure for episodic memory) that may account for the memory deficits in preterm children. By applying neuropsychological tests, the results showed no group differences in episodic memory performance, whereas preterm children showed impairments in semantic memory tasks relative to full-term children (Study 1). Furthermore, preterm children showed reduced hippocampal volumes relative to full-term children. Since hippocampal volume seems to mediate episodic memory performance in full-term children but not in preterm children, the findings of the thesis suggest the conclusion that preterm children at that age recruit a neural network for episodic memory that differs from the one used by full-term children. The results in the ERP studies (Study 2 & 3) showed that the ERP correlate of recollection but not the ERP correlate of familiarity is reduced in preterm children relative to full-term born controls. In addition, Study 3 revealed that within the preterm children group the gestational age at birth is positively correlated with the magnitude of the ERP correlate of recollection and is negatively correlated with the magnitude of the ERP correlate of familiarity. Together with the finding that the magnitude of the ERP correlate of recollection was negatively correlated with the magnitude of the ERP correlate of familiarity, tentative support is provided for compensational mechanisms within the brains of preterm children. This means that within the brains of preterm children reduced recollective processing may be compensated by enhanced familiarity-based remembering. Finally, Study 4 extended the knowledge on the proposed relationship between prematurity and recollective processing, because evidence was provided that the findings of Study 3 were not confounded or influenced by the level of task difficulty. Taken together, these findings provide evidence for the presence of alterations in declarative long-term memory processing in preterm children at early school-age.Die vorliegende Dissertation untersucht Entwicklungsunterschiede im deklarativen Langzeitgedächtnis zwischen frühgeborenen Kindern ohne zusätzliche neonatale Komplikationen und reifgeborenen Kindern im Grundschulalter mittels verschiedener wissenschaftlicher Methoden (neuropsychologischer Tests, struktureller Magnetresonanztomografie und ereigniskorrelierten Potentialen (EKPs)). Neben der Untersuchung der Entwicklung des deklarativen Gedächtnisses im Allgemeinen (Studie 1), wurde ein besonderer Fokus auf das episodische Gedächtnis und seine spezifischen Abrufprozesse (Vertrautheit und Rekollektion, Studie 1, 2, 3 und 4) gelegt. Jüngste Studien konnten bei Frühgeborenen Gedächtnisdefizite und ausgeprägte Volumenreduktionen im Hippocampus (welches eine wichtige Gehirnstruktur für das episodische Gedächtnis ist) nachweisen. Diese Volumenreduktion könnte möglicherweise die Gedächtnisdefizite verursacht haben. Mittels der Anwendung von neuropsychologischen Tests konnte gezeigt werden, dass sich die beiden Gruppen nicht in ihrer episodischen Gedächtnisleistung unterscheiden, jedoch die frühgeborenen im Vergleich zu den reifgeborenen Kindern in semantischen Gedächtnisaufgaben beeinträchtigt sind (Studie 1). Außerdem zeigten die frühgeborenen Kinder ein reduziertes hippocampales Volumen im Vergleich zu den reifgeborenen Kindern. Da das hippocampale Volumen nur bei den reifgeborenen Kindern nicht aber bei den frühgeborenen Kindern die episodische Gedächtnisleistung mediierte, liegt die Vermutung nahe, dass frühgeborene im Vergleich zu reifgeborenen Kindern in diesem Alter andere neuronale Netzwerke für das episodische Gedächtnis rekrutieren. Die Ergebnisse aus den EKP Studien (Studie 2 & 3) zeigten, dass das EKP Korrelat der Rekollektion, aber nicht das EKP Korrelat der Vertrautheit, bei den frühgeborenen im Vergleich zu den reifgeborenen Kindern reduziert ist. Zudem zeigte Studie 3, dass innerhalb der frühgeborenen Kindergruppe die Schwangerschaftsdauer positiv mit dem Ausmaß des EKP Korrelats der Rekollektion und negativ mit dem Ausmaß des EKP Korrelats der Vertrautheit korreliert war. Zusammen mit dem Befund, dass das Ausmaß des EKP Korrelats der Rekollektion negativ mit dem Ausmaß des EKP Korrelats der Vertrautheit korreliert war, liegt die Vermutung nahe, dass es einen Kompensationsmechanismus im Gehirn der frühgeborenen Kinder gibt. Das heißt, dass im Gehirn der frühgeborenen Kinder reduzierte rekollektions-basierte Verarbeitung durch erhöhtes vertrautheits-basiertes Erinnern kompensiert wird. Studie 4 erweiterte schließlich das Wissen über die vorgeschlagene Beziehung zwischen Frühgeburt und rekollektions-basierter Verarbeitung. Diese Studie gab weitere Hinweise darauf, dass die Ergebnisse von Studie 3 nicht durch das Ausmaß der Aufgabenschwierigkeit konfundiert sind. Insgesamt deuten die Ergebnisse auf Veränderungen in der Verarbeitung im deklarativen Langzeitgedächtnis bei frühgeborenen Grundschulkindern hin