Theneural basis of true memory and false memory for visual features:

Thesis advisor: Scott D. SlotnickEpisodic memory is a constructive process in which a system of sensory and control processes works to transport one’s conscious mind through time–in essence, recreating a previous perceptual experience. For instance, sensory-specific activity that was associated with an original encoding experience is reinstated during retrieval–almost as if the sensory regions are processing the stimulus again, albeit this activation is smaller in spatial extent. This process of sensory-specific reinstatement occurs across all sensory modalities (e.g., Gottfried et al., 2004; Nyberg et al., 2001; Vaidya et al., 2002; Wheeler et al., 2000). That is, retrieval of a visually encoded stimulus (e.g., a picture of a dog) reinstates activity in the visual cortex, while retrieval of an aurally encoded stimulus (e.g., a barking dog) reinstates activity in the auditory cortex. In Chapter 1 and Chapter 2, I demonstrate the specificity of such sensory reinstatement during true memory for visual features and investigate the role of such sensory regions during the construction of false memory for visual features. In addition to sensory processes, our conscious experience of memory also relies on control regions. At the center of this memory control network sits a key memory structure, the hippocampus, as well as other important control regions such as the dorsolateral prefrontal cortex and the parietal cortex. Furthermore, the parahippocampal cortex appears to play a critical role in memory; however, the exact role of this region has been debated (Aminoff, Kverga, & Bar, 2013). In Chapter 3, I investigate the functional role of the parahippocampal cortex during true memory and false memory, and provide evidence that the parahippocampal cortex mediates general contextual processing

Inference and False Memory Within Multielement Events

Recollection of multi-element events reflects a process of pattern completion in which one element retrieves the others. However, recollection is reconstructive and unseen associations can be inferred. To study this, I used multi-element events composed of overlapping pairs of items (locations, people, objects/animals) presented sequentially, interleaved with pairs from other events. For events with all associations presented (AB, BC, AC), retrievals of seen (‘direct’) pairs from the same event were statistically interdependent, indicating pattern completion. However, for events with only some associations presented (AB, BC, CD; AC, BD, AD not seen), direct pairs were retrieved independently but inferred ‘indirect’ pairs (AC, BD, AD) were interdependent, demonstrating their common reliance on direct pair BC. These results were unaffected by the order of testing direct and indirect pairs or by repeated presentation, are consistent with an auto-associative network model, and establish a role for pattern completion in inference. Although inferred associations can aid reconstructive retrieval, they might also cause false memories. To investigate further, I presented events comprising images of a person and an object superimposed onto a location, some events sharing an element with one other (e.g. Madonna-laptop-gym, Ronaldo-vase-gym). Inference-related false memories did arise (e.g. of seeing Madonna with the vase) but only showed weak (non-significant) dependency on direct associations (e.g. Madonna-laptop) unlike explicitly-tested indirect associations (e.g. Madonna-Ronaldo). Instead, false memories (e.g. Madonna-vase) were afforded by specific combinations of direct associations: those strongly linking the cue with the lure (e.g. Madonna-gym, gym-vase) but not those with their correct associates (i.e. Madonna-laptop). These experiments indicate that pattern completion supports reconstructive episodic memory and explicit inference for missing associations, while false memories can be created by false inference but have a more complex relationship with pattern completion. I discuss the implications for veridical memories, illusory memories, metacognitive awareness and explicit inference

Placing faces: recollection and familiarity in the own-race bias for face recognition

The research presented in this thesis examined the roles of recollection and familiarity in the own-race bias (ORB) in recognition memory for faces. In Paper 1, Jacoby’s (1991) process-dissociation procedure was used to estimate the relative contributions of recollection and familiarity in recognizing own- and other-race faces. Recollection estimates were higher for own-race faces than for other-race faces, although this effect disappeared when deep or shallow encoding strategies were encouraged. In Paper 2, participants were shown to be less accurate at ignoring previously seen other-race distractors than own-race distractors. Papers 3 and 4 examined how accurately participants were able to remember contextual information about correctly recognized faces. In the encoding phase of an old/new recognition test, each target face was paired with one of several different backgrounds. At testing, old judgments were followed by context judgments, in which the participant attempted to identify with which background the face had been paired. The context judgments were consistently more accurate for correctly recognized own-race faces than for correctly recognized other-race faces. This effect was robust to experimental manipulations such as context reinstatement and divided attention. The overall conclusion from this thesis is that recollection is inferior for other-race faces compared to own-race faces. This recollection deficit means that it is more difficult to retrieve specific information about the circumstances in which other-race faces were encountered. The implications of this recollection deficit for real world behaviour are discussed, with particular reference to eyewitness memory

There is more to memory than recollection and familiarity.

Theoretical models of memory retrieval have focused on processes of recollection and familiarity. Research suggests that there are still other processes involved in memory reconstruction, leading to experiences of knowing and inferring the past. Understanding these experiences, and the cognitive processes that give rise to them, seems likely to further expand our understanding of the neural substrates of memory

The role of phonology in visual word recognition: evidence from Chinese

Posters - Letter/Word Processing V: abstract no. 5024The hypothesis of bidirectional coupling of orthography and phonology predicts that phonology plays a role in visual word recognition, as observed in the effects of feedforward and feedback spelling to sound consistency on lexical decision. However, because orthography and phonology are closely related in alphabetic languages (homophones in alphabetic languages are usually orthographically similar), it is difficult to exclude an influence of orthography on phonological effects in visual word recognition. Chinese languages contain many written homophones that are orthographically dissimilar, allowing a test of the claim that phonological effects can be independent of orthographic similarity. We report a study of visual word recognition in Chinese based on a mega-analysis of lexical decision performance with 500 characters. The results from multiple regression analyses, after controlling for orthographic frequency, stroke number, and radical frequency, showed main effects of feedforward and feedback consistency, as well as interactions between these variables and phonological frequency and number of homophones. Implications of these results for resonance models of visual word recognition are discussed.postprin

Interactive effects of orthography and semantics in Chinese picture naming

Posters - Language Production/Writing: abstract no. 4035Picture-naming performance in English and Dutch is enhanced by presentation of a word that is similar in form to the picture name. However, it is unclear whether facilitation has an orthographic or a phonological locus. We investigated the loci of the facilitation effect in Cantonese Chinese speakers by manipulating—at three SOAs (2100, 0, and 1100 msec)—semantic, orthographic, and phonological similarity. We identified an effect of orthographic facilitation that was independent of and larger than phonological facilitation across all SOAs. Semantic interference was also found at SOAs of 2100 and 0 msec. Critically, an interaction of semantics and orthography was observed at an SOA of 1100 msec. This interaction suggests that independent effects of orthographic facilitation on picture naming are located either at the level of semantic processing or at the lemma level and are not due to the activation of picture name segments at the level of phonological retrieval.postprin

From Cue to Recall : The Temporal Dynamics of Long-Term Memory Retrieval

A fundamental function of long-term memory is the ability to retrieve a specific memory when encountering a retrieval cue. The purpose of this dissertation was to further our understanding of such cued recall by investigating the temporal dynamics from the presentation of the retrieval cue until the target memory is recalled. Retrieval cues are often related with several memories. When such a retrieval cue is presented, the associated memories will compete for retrieval and this retrieval competition needs to be handled in order to retrieve the sought after target memory. Study 1 and Study 2 investigated the temporal dynamics of such competitive semantic cued recall. Interestingly, previous research has shown that the ability to retrieve the currently relevant target memory comes with a cost, namely retrieval-induced forgetting of the competing memories. These studies also investigated the role of competitor activation and target retrieval in this forgetting phenomenon. Study 1 investigated the electrophysiological correlates of reactivation of competing currently irrelevant memories and the role of such competitor activation in retrieval-induced forgetting. Competitor activation was related to an FN400 event-related potential (ERP) effect and this effect predicted increased levels of retrieval-induced forgetting, indicating that this forgetting effect is dependent on competitor activation. Study 2 examined processes involved in target retrieval in a similar competitive semantic cued recall task. The main finding in this study was that attempts to retrieve the target memory were related to a late posterior negativity ERP effect. Another important finding was that behavioural and ERP measures of target retrieval were unrelated to retrieval-induced forgetting. Retrieval cues can sometimes elicit involuntary retrieval of unwanted memories. Such memory intrusions are a core symptom of post-traumatic stress disorder. Study 3 investigated the temporal dynamics of such memory intrusions. One of the key findings was that memory intrusions were related to a negative slow wave ERP effect possibly reflecting the activation of the intruding memory in working memory. Taken together the findings in the dissertation indicate that cued recall involves several cognitive processes ranging from early automatic memory reactivation to conscious processes such as working memory activation and recollection. The findings have implications for cognitive theories of memory and have relevance for several clinical conditions including depression and post-traumatic stress disorder

Episodic memory across the lifespan: The contributions of associative and strategic components

The structural and functional brain circuitries supporting episodic memory undergo profound reorganization in childhood and old age. We propose a two-component framework that combines and integrates evidence from child development and aging. It posits that episodic memory builds on two interacting components: (a) the strategic component, which refers to memory control operations, and (b) the associative component, which refers to mechanisms that bind different features of a memory episode into a compound representation. We hypothesize that: (a) children's difficulties in episodic memory primarily originate from low levels of strategic operations, and reflect the protracted development of the prefrontal cortex (PFC); (b) deficits in episodic memory performance among older adults originate from impairments in both strategic and associative components, reflecting senescent changes in the PFC and the medio-temporal lobes (MTL). Initial behavioral and neural evidence is consistent with both hypotheses. The two-component framework highlights the specificities of episodic memory in different age periods, helps to identify and dissociate its components, and contributes to understanding the interplay among maturation, learning, and senescence

Emotion’s Influence on the Evaluation of Familiarity

Emotion enhances the encoding and consolidation of memory traces, leading to the salient reliving of emotional experiences. In the recognition memory literature, the induction of somatic arousal and feelings of perceptual fluency during retrieval have been associated with illusory familiarity. Understudied in this literature is an investigation into how one’s emotional state, independent of stimulus content, influences recollective and familiarity-based recognition memory retrieval. Two priming paradigms were employed in the current thesis research to contrast the effects of affective priming and identity priming on familiarity and recollection using the Remember/Know procedure. Enhanced familiarity-based discrimination was revealed using affective priming, selective to participants with low overall recognition performance. Identity-priming resulted in a response bias, indicative of an induction of erroneous feelings of familiarity. Both manipulations failed to influence recollection. These results illustrate that a heightened affective state can provide selective benefits to familiarity, dissociating from a confused sense of familiarity induced through increased perceptual fluency

Electrophysiological and Behavioural Markers of Associative Source Memory Decline in Normal Ageing

Memory is the ability to encode and subsequently recall information (Brickman & Stern, 2009) and source memory refers to the ability to recall the source of the information, including all contextual aspects related to an event (Glisky & Kong, 2008; M. Johnson, Hashtroudi, & Lindsay, 1993). The ageing process shows a progressive decline in memory (Cabeza, Anderson, Locantore, & Mcintosh, 2002) which is thought to be related to atrophy in regions of the brain which are essential for memory (Pasquier, 1999). Source memory is particularly sensitive to cognitive ageing and is one of the first types of memory to show impairment (Jennings & Jacoby, 1997; Siedlecki, Salthouse, & Berish, 2005). In the current thesis different aspects of memory were measured to determine the extent of memory decline in ageing using associative, episodic and particularly source memory tasks. Both behavioural and electrophysiological methods were used to investigate cognitive changes in performance due to the ageing process between young and older adults along with an intervention at the time of acquisition to determine if source memory recall can be enhanced in older adults. In Chapter 3 memory retrieval was examined between young (18-30 years, n=27) and older (55-70 years, n=25) adults at three computer-based tasks, indexing source memory (an Opposition task), associative memory (a Visual Paired-Associates task) and episodic memory (a False Memory paradigm). Young and older adults were matched on estimated scores of IQ, short-term memory and self-ratings of their own memory. The results indicated that older adults have poorer accuracy and slower response times on memory tasks of associative and source memory, with the latter showing particularly large decrements due to ageing. Source deficits were clear on the Opposition task but context had little effect on accuracy on the VPAc task, while few differences were evident on the False Memory paradigm; therefore appears that memory for temporal context (i.e. the timing of an event) suffers more impairment in ageing. These results suggest that aspects of memory binding may be among the first memory processes to suffer a decline in healthy ageing. Chapter 4 examined young (18-30 years, n = 14) and older (50-75 years, n = 14) adults’ differences in recorded EEG for three computer-based memory tasks which assess source, episodic/associative and false memory. Reduced scalp electrical activity was observed in older adults on the source memory task coupled with a poorer behavioural performance. Reduced activity in older adults was also evident for mistaken lures and the correct identification of lures in the false memory task, but no behavioural differences were evident. For successful trials in associative memory tasks, increased activity was present in older adults while behavioural performance was either equal to or poorer than that of young adults. These data are mostly consistent with the idea that young adults show larger mean ERP amplitudes than older adults, suggesting a reduction in cognitive functioning in older adults which may have resulted in reduced memory accuracy capacity. In Chapter 5 data is reported from young (18-30, n = 15) and older (55+, n = 15) adults during behavioural measures of source memory and the associated electrophysiology. Participants completed the Opposition task and a Where-Who-What task. Results generally indicated that older adults displayed poorer behavioural performance and reduced amplitude P1 and P3 components on both tasks in comparison to young adults, which may reflect enhanced perceptual ability (linked to the P1) and recognition of the source of information (linked to the P3) in young adults compared to older. However, the electrophysiology predominantly showed enlarged waveform components in older participants at approximately 200ms for source memory tasks, and revealed more anterior positive scalp activity in the older compared to posterior topographies in the young which may indicate an automatic compensatory function in older adults. These patterns may reflect the recruitment of additional cortical areas acting in a compensatory manner to alleviate the age-related impairment in source memory tasks. An intervention with two source memory tasks was employed in Chapter 6. Three groups of adults, young control (18-30 years, n = 20), older control (55+ years, n = 20) and older intervention (55+ years, n = 20), took part in the experiment. Both control groups completed two computer-based source memory tasks without the use of an intervention, while the older intervention group used a strategy at the time of acquisition for both source memory tasks under two methods: firstly, sentence generation to enhance semantic binding; and secondly, story generation to increase contextual binding. Results indicate that the use of an intervention allowed for enhanced source memory recall in older adults compared to both control groups. In addition, the interventions led to faster response times compared to the older control group but not the young control group. It is concluded that while an intervention can alleviate the age-related deterioration of source memory accuracy, it does not entirely counteract the impairment in speed of processing typically seen in older adults. The behavioural results of this series of experiments indicate that source memory is negatively affected by the ageing process and that accuracy on source memory tasks is more affected than tasks involving associative and episodic memory. This supports previous findings indicating that memory for source is one of the first to decline with ageing. However, despite this discrepancy in source memory, an intervention strategy at the time of acquisition can lead to enhanced source memory recall in older adults compared to older and younger control adults. The electrophysiology may suggest that older adults have a decline in the perceptual processing of the source of information compared to young adults which may be reflected by the poorer behavioural performance on memory tasks. Furthermore older adults may attempt to compensate for these reductions in perceptual processing, as reflected by enlarged components at approximately 200ms. However, this compensation does not appear to be fully effective as the older adults retain poorer accuracies on source memory tasks. Additionally, the electrophysiology indicates further compensation as positive-going activity appears to occur more anteriorly in older adults which may reflect compensation for dysfunction in regions of the brain responsible for perceptual processing. These results provide additional support for two models of cognitive ageing, the Compensatory Related Utilisation of Neural Circuits Hypothesis (CRUNCH; Reuter-Lorenz & Cappell, 2008) and Posterior Anterior Shift in Ageing (PASA) models (S. W. Davis, Dennis, Daselaar, Fleck, & Cabeza, 2008)