Portrait of Dr Zara Bergström

Dr Zara Bergström

Senior Lecturer in Cognitive Psychology
Deputy REF coordinator

About

Dr Zara Bergström is a Senior Lecturer in Cognitive Psychology and Deputy REF coordinator in the School of Psychology. 

Key recent publications

  • Dhammapeera, P., Hu, X., & Bergström, Z. (in press). Imagining a false alibi impairs concealed memory detection with the autobiographical Implicit Association Test. Journal of Experimental Psychology: Applied. doi:10.1037/xap0000250
  • Allen, J., Hellerstedt, R., Sharma, D., & Bergström, Z. (in press). Distraction by unintentional recognition: Neurocognitive mechanisms and effects of aging. Psychology and Aging. doi:10.1037/pag0000398
  • Hu, X., Bergström, Z., Gagnepain, P., & Anderson, M. (2017). Suppressing Unwanted Memories Reduces Their Unintended Influences. Current Directions In Psychological Science, 26, 197-206.
  • Bergström, Z., Williams, D., Bhula, M., & Sharma, D. (2016). Unintentional and intentional recognition rely on dissociable neurocognitive mechanisms. Journal Of Cognitive Neuroscience, 28, 1838-1848.

Research interests

Zara's research investigates the neurocognitive mechanisms underlying episodic memory, with particular focus on memory retrieval control, forgetting, and memory distortions. 

She uses a combination of behavioural and cognitive neuroscience techniques (primarily EEG and fMRI) to address questions such as:

  • Is memory retrieval under voluntary control, and if so, what are the implications for tests that use markers of memory as evidence of criminal guilt?
  • What are the neurocognitive mechanisms that enable people to stop unwanted retrieval?
  • Can retrieval attempts enhance learning of new information and updating of existing memories?
  • What are the effects of healthy ageing on retrieval processes, retrieval-induced learning and memory updating?

Teaching

Zara teaches on a number of cognitive psychology/neuroscience modules at undergraduate and postgraduate levels. 

Supervision

Please contact Zara directly to discuss potential supervision of MSc, PhD or postdoctoral projects.  

Current PhD/MSc-R Students

  • Matthew Plummer: Retrieval-induced updating of face memories
  • Louisa Salhi: Factors that affect learning during retrieval across age
  • Akul Satish: Modification of episodic memories related to morality

Completed PhD/MSc-R supervision

  • John Allen (Kent MRes, 2019, 1st supervisor): Distraction by unintentional recognition: Neurocognitive mechanisms and effects of aging
  • Phot Dhammapeera (Kent PhD, 2019, 1st supervisor): Memory distortion via imagination: neural correlates and forensic applications
  • Fatma Ateş (Kent PhD, 2018, 2nd supervisor): Understanding spontaneous recognition: The role of working memory, emotions and mood
  • Yasemin Yazar (Cambridge PhD, 2014, advisor): The role of the lateral parietal lobe in episodic memory 

Professional

Grants and Awards

2018Leverhulme Trust Research Project Grant (Co-I)£192,118
2018Experimental Psychology Society Workshop Grant (PI)£4030
2017Faculty of Social Sciences Research Grant (PI)£4870
2016Public Engagement with Research Grant (PI)£900
2016Leverhulme Trust Research Project Grant (PI)£191,067
2013Experimental Psychology Society Workshop Grant (Co-I)£3500
2013Experimental Psychology Society Small Grant (PI)£2500
2013Faculty of Social Sciences Research Grant (PI)£2490

Ad hoc Reviewer

Journals: Brain and Cognition, Brain Research, British Journal of Psychology, Cerebral Cortex, Cognitive, Affective and Behavioural Neuroscience, European Journal of Neuroscience, Journal of Affective Disorders, Journal of Cognitive Neuroscience, Journal of Experimental Psychology: Learning, Memory and Cognition, Journal of Psychophysiology, Journal of Neuroscience, Learning & Memory, Memory, Nature Scientific Reports, Neurobiology of Learning and Memory, Neurobiology of Aging, NeuroImage, Neuropsychologia, Neuroscience & Biobehavioral Reviews, Psychonomic Bulletin and Review, Psychophysiology, Quarterly Journal of Experimental Psychology, Science Advances. Scientific Reports.
Funding Bodies: MRC, BBSRC, ESRC, and more. 

Professional Memberships

British Association for Cognitive Neuroscience. Full Member.
Experimental Psychology Society. Full Member. 

Publications

Forthcoming

  • Allen, J., Hellerstedt, R., Sharma, D., & Bergström, Z. (2019). Distraction by unintentional recognition: Neurocognitive mechanisms and effects of aging. Psychology and Aging. doi:10.1037/pag0000398
    Sometimes, we intentionally evaluate stimuli to assess if we recognise them, whereas other times, stimuli automatically elicit recognition despite our efforts to ignore them. If multiple stimuli are encountered in the same environment, intentional recognition judgements can be biased by unintentional recognition of to-be-ignored stimuli. Aging is associated with increased distractibility and impaired intentional retrieval processes, which can make older adults more susceptible to distraction-induced recognition biases. We measured recognition memory performance, ERPs and EEG oscillations in old (60-74) and young (18-24) adults to investigate how aging affects unintentional and intentional memory processes, and how these processes interact over time to produce distraction-induced recognition biases. Older participants had poorer intentional recognition memory, but the biasing effect of unintentional distractor recognition was similar across age groups. ERP effects related to intentional and unintentional recognition that were strongly expressed in the younger group were reduced or absent in the older group. Furthermore, the older group showed qualitatively different ERP activity during intentional recognition compared to the younger group. However, similar patterns of theta and alpha oscillations were found in both age groups, who showed theta power increases for both intentional and unintentional recognition, whereas alpha power was enhanced for intentional recognition but reduced for unintentional recognition. Overall, the findings show that unintentional and intentional recognition involve multiple dissociable memory processes that have different time-courses and functional characteristics, and are differentially affected by aging. Whereas aging has strong effects on the neurocognitive mechanisms underlying intentional recognition memory, unintentional recognition mechanisms are less affected.
  • Dhammapeera, P., Hu, X., & Bergström, Z. (2019). Imagining a false alibi impairs concealed memory detection with the autobiographical Implicit Association Test. Journal of Experimental Psychology: Applied. doi:10.1037/xap0000250
    Imagining counterfactual versions of past events can distort memory. In three experiments, we examined whether imagining a false alibi for a mock crime would make suspects appear less guilty in a concealed memory detection test, the autobiographical Implicit Association Test (aIAT), which aims to determine which of two autobiographical events are true. First, “guilty” participants completed a mock crime, whereas “innocent” participants completed an innocent act. Next, some of the guilty participants were asked to imagine a false alibi that corresponded to the innocent act. Finally, all groups completed the aIAT. Across experiments, we varied the type of aIAT used and also compared the effectiveness of the false alibi countermeasure when only imagined once, versus when it was repeatedly imagined over a week long period. The aIAT accurately detected the mock crime as true for guilty participants without a false alibi, but was consistently less able to detect the mock crime as true for guilty participants who had imagined a false alibi. The findings suggest that if guilty suspects fabricate an alibi, this may create a memory for the alibi that appears to be true based on the aIAT, which is problematic for its real-life applications in concealed memory detection.

Article

  • Salhi, L., & Bergström, Z. (2020). Intact strategic retrieval processes in older adults: No evidence for age-related deficits in source-constrained retrieval. Memory. doi:10.1080/09658211.2020.1719161
    Aging is thought to involve impairments to cognitive control functions that support episodic memory, for example by enabling people to strategically constrain their retrieval search towards a specific context (“source”) in order to facilitate retrieval of goal-relevant memories. The “memory-for-foils” paradigm investigates source-constrained retrieval by assessing whether incidental encoding of new foils during an old/new recognition test differs depending on the type of processing that was previously used during study of the old items in the test. If it does, it suggests that people process foils differently as a result of engaging in source-constrained retrieval attempts. Young adults typically show differences in incidental encoding foils, but such differences have not been found in older adults. Here, we compared source-constrained retrieval and reward effects on incidental foil encoding between younger and older adults, to assess if age-related reductions in strategic retrieval processing are accompanied by differences in responsiveness to external rewards. The results showed only minor effects of rewards on memory processing, in younger adults only. Contrary to prior findings, older adults had equivalent overall memory performance and spontaneously constrained retrieval to the same extent as the young group, showing that aging-related impairments to strategic retrieval processes are not inevitable.
  • Vogelsang, D., Gruber, M., Bergström, Z., Ranganath, C., & Simons, J. (2018). Alpha oscillations during incidental encoding predict subsequent memory for new "foil" information. Journal of Cognitive Neuroscience, 30, 667-679. doi:10.1162/jocn_a_01234
    People can employ adaptive strategies to increase the likelihood that previously encoded information will be successfully retrieved. One such strategy is to constrain retrieval towards relevant information by re-implementing the neurocognitive processes that were engaged during encoding. Using electroencephalography (EEG), we examined the temporal dynamics with which constraining retrieval towards semantic versus non-semantic information affects the processing of new “foil” information encountered during a memory test. Time-frequency analysis of EEG data acquired during an initial study phase revealed that semantic compared to non-semantic processing was associated with alpha decreases in a left frontal electrode cluster from around 600ms after stimulus onset. Successful encoding of semantic versus non-semantic foils during a subsequent memory test was related to decreases in alpha oscillatory activity in the same left frontal electrode cluster, which emerged relatively late in the trial at around 1000-1600ms after stimulus onset. Across subjects, left frontal alpha power elicited by semantic processing during the study phase correlated significantly with left frontal alpha power associated with semantic foil encoding during the memory test. Furthermore, larger left frontal alpha power decreases elicited by semantic foil encoding during the memory test predicted better subsequent semantic foil recognition in an additional surprise foil memory test, although this effect did not reach significance. These findings indicate that constraining retrieval towards semantic information involves re-implementing semantic encoding operations that are mediated by alpha oscillations, and that such re-implementation occurs at a late stage of memory retrieval perhaps reflecting additional monitoring processes.
  • Hu, X., Bergström, Z., Gagnepain, P., & Anderson, M. (2017). Suppressing Unwanted Memories Reduces Their Unintended Influences. Current Directions in Psychological Science, 26, 197-206. doi:10.1177/0963721417689881
    The ability to control unwanted memories is critical for maintaining cognitive function and mental health. Prior research has shown that suppressing the retrieval of unwanted memories impairs their retention, as measured on intentional (direct) memory tests. Here we review emerging evidence revealing that retrieval suppression can also reduce the unintended influence of suppressed traces. In particular, retrieval suppression (1) gradually diminishes the tendency for memories to intrude into awareness, and (2) reduces memories’ unintended expressions on indirect memory tests. We present a neural account in which, during suppression, retrieval cues elicit hippocampally-triggered neocortical activity that briefly reinstates features of the original event, which, in turn, are suppressed by targeted neocortical and hippocampal inhibition. This reactivation-dependent reinstatement principle could provide a broad mechanism by which suppressing retrieval of intrusive memories limits their indirect influences.
  • Yazar, Y., Bergström, Z., & Simons, J. (2017). Reduced multimodal integration of memory features following continuous theta burst stimulation of angular gyrus. Brain Stimulation, 10, 624-629. doi:10.1016/j.brs.2017.02.011
    Background: Lesions of the angular gyrus (AnG) region of human parietal cortex do not cause amnesia, but appear to be associated with reduction in the ability to consciously experience the reliving of previous events.

    Objectives/Hypothesis: We used continuous theta burst stimulation to test the hypothesis that the cognitive mechanism implicated in this memory deficit might be the integration of retrieved sensory event features into a coherent multimodal memory representation.

    Methods: Healthy volunteers received stimulation to AnG or a vertex control site after studying stimuli that each comprised a visual object embedded in a scene, with the name of the object presented auditorily. Participants were then asked to make memory judgments about the studied stimuli that involved recollection of single event features (visual or auditory), or required integration of event features within the same modality, or across modalities.

    Results: Participants’ ability to retrieve context features from across multiple modalities was significantly reduced after AnG stimulation compared to stimulation of the vertex. This effect was observed only for the integration of cross-modal context features but not for integration of features within the same modality, and could not be accounted for by task difficulty as performance was matched across integration conditions following vertex stimulation.

    Conclusion: These results support the hypothesis that AnG is necessary for the multimodal integration of distributed cortical episodic features into a unified conscious representation that enables the experience of remembering.
  • Williams, D., Bergström, Z., & Grainger, C. (2016). Metacognitive monitoring and the hypercorrection effect in autism and the general population: Relation to autism(-like) traits and mindreading. Autism: International Journal of Research and Practice, in Press. doi:10.1177/1362361316680178
    Among neurotypical adults, errors made with high confidence (i.e., errors a person strongly believed they would not make) are corrected more reliably than errors made with low confidence. This “hypercorrection effect” is thought to result from enhanced attention to information that reflects a “metacognitive mismatch” between one’s beliefs and reality. In Experiment 1, we employed a standard measure of this effect. Participants answered general knowledge questions and provided confidence judgements about how likely each answer was to be correct, after which feedback was given. Finally, participants were retested on all questions answered incorrectly during the initial phase. Mindreading ability and ASD-like traits were measured. We found that a representative sample of (n = 83) neurotypical participants made accurate confidence judgements (reflecting good metacognition) and showed the hypercorrection effect. Mindreading ability was associated with ASD-like traits and metacognition. However, the hypercorrection effect was non-significantly associated with mindreading or ASD-like traits. In Experiment 2, 11 children with ASD and 11 matched comparison participants completed the hypercorrection task. Although ASD children showed significantly diminished metacognitive ability, they showed an undiminished hypercorrection effect. The evidence in favour of an undiminished hypercorrection effect (null result) was moderate, according to Bayesian analysis (Bayes factor = 0.21).
  • Bergström, Z., Williams, D., Bhula, M., & Sharma, D. (2016). Unintentional and intentional recognition rely on dissociable neurocognitive mechanisms. Journal of Cognitive Neuroscience, 28, 1838-1848. doi:10.1162/jocn_a_01010
    Distractibility can lead to accidents and academic failures, as well as memory problems. Recent evidence suggests that intentional recognition memory can be biased by unintentional recognition of distracting stimuli in the same environment. It is unknown whether unintentional and intentional recognition depend on the same underlying neurocognitive mechanisms. We assessed whether human participants’ recognition of previously seen (old) or not seen (new) target stimuli was affected by whether a to-be-ignored distractor was old or new. ERPs were recorded to investigate the neural correlates of this bias. The results showed that the old/new status of salient distractors had a biasing effect on target recognition accuracy. Both intentional and unintentional recognition elicited early ERP effects that are thought to reflect relatively automatic memory processes. However, only intentional recognition elicited the later ERP marker of conscious recollection, consistent with previous suggestions that recollection is under voluntary control. In contrast, unintentional recognition was associated with an enhanced late posterior negativity, which may reflect monitoring or evaluation of memory signals. The findings suggest that unintentional and intentional recognition involve dissociable memory processes.
  • Vogelsang, D., Bonnici, H., Bergström, Z., Ranganath, C., & Simons, J. (2016). Goal-directed mechanisms that constrain retrieval predict subsequent memory for new "foil" information. Neuropsychologia, 89, 356-363. doi:10.1016/j.neuropsychologia.2016.07.016
    To remember a previous event, it is often helpful to use goal-directed control processes to constrain what comes to mind during retrieval. Behavioral studies have demonstrated that incidental learning of new “foil” words in a recognition test is superior if the participant is trying to remember studied items that were semantically encoded compared to items that were non-semantically encoded. Here, we applied subsequent memory analysis to fMRI data to understand the neural mechanisms underlying the “foil effect”. Participants encoded information during deep semantic and shallow non-semantic tasks and were tested in a subsequent blocked memory task to examine how orienting retrieval towards different types of information influences the incidental encoding of new words presented as foils during the memory test phase. To assess memory for foils, participants performed a further surprise old/new recognition test involving foil words that were encountered during the previous memory test blocks as well as completely new words. Subsequent memory effects, distinguishing successful versus unsuccessful incidental encoding of foils, were observed in regions that included the left inferior frontal gyrus and posterior parietal cortex. The left inferior frontal gyrus exhibited disproportionately larger subsequent memory effects for semantic than non-semantic foils, and significant overlap in activity during semantic, but not non-semantic, initial encoding and foil encoding. The results suggest that orienting retrieval towards different types of foils involves re-implementing the neurocognitive processes that were involved during initial encoding.
  • Hu, X., Bergström, Z., Bodenhausen, G., & Rosenfeld, J. (2015). Suppressing Unwanted Autobiographical Memories Reduces Their Automatic Influences: Evidence from Electrophysiology and an Implicit Autobiographical Memory Test. Psychological Science. doi:10.1177/0956797615575734
    The present study investigated the extent to which people can suppress unwanted autobiographical memories in a mock crime memory detection context. Participants encoded sensorimotor-rich memories by enacting a lab crime (stealing a ring) and received direct suppression instructions so as to evade guilt detection in a brainwave-based concealed information test. Aftereffects of suppression on automatic memory processes were measured in an autobiographical implicit association test (aIAT). Results showed that suppression attenuated brainwave activity (P300) that is associated with crime-relevant memory retrieval, rendering innocent and guilty/suppression participants indistinguishable. However, guilty/suppression and innocent participants could nevertheless be discriminated via the late posterior negative slow wave, which may reflect the need to monitor response conflict arising between voluntary suppression and automatic recognition processes. Lastly, extending recent findings that suppression can impair implicit memory processes; we provide novel evidence that suppression reduces automatic cognitive biases that are otherwise associated with actual autobiographical memories.
  • Yazar, Y., Bergström, Z., & Simons, J. (2014). Continuous Theta Burst Stimulation of Angular Gyrus Reduces Subjective Recollection. PLoS ONE, 9, e110414. doi:10.1371/journal.pone.0110414
    The contribution of lateral parietal regions such as the angular gyrus to human episodic memory has been the subject of
    much debate following widespread observations of left parietal activity in healthy volunteers during functional
    neuroimaging studies of memory retrieval. Patients with lateral parietal lesions are not amnesic, but recent evidence
    indicates that their memory abilities may not be entirely preserved. Whereas recollection appears intact when objective
    measures such as source accuracy are used, patients often exhibit reduced subjective confidence in their accurate
    recollections. When asked to recall autobiographical memories, they may produce spontaneous narratives that lack richness
    and specificity, but can remember specific details when prompted. Two distinct theoretical accounts have been proposed to
    explain these results: that the patients have a deficit in the bottom-up capturing of attention by retrieval output, or that
    they have an impairment in the subjective experience of recollection. The present study aimed to differentiate between
    these accounts using continuous theta burst stimulation (cTBS) in healthy participants to disrupt function of specific left
    parietal subregions, including angular gyrus. Inconsistent with predictions of the attentional theory, angular gyrus cTBS did
    not result in greater impairment of free recall than cued recall. Supporting predictions of the subjective recollection
    account, temporary disruption of angular gyrus was associated with highly accurate source recollection accuracy but a
    selective reduction in participants’ rated source confidence. The findings are consistent with a role for angular gyrus in the
    integration of memory features into a conscious representation that enables the subjective experience of remembering.
  • Brandt, V., Bergström, Z., Buda, M., Henson, R., & Simons, J. (2014). Did I turn off the gas? Reality monitoring of everyday actions. Cognitive, Affective, & Behavioral Neuroscience, 14, 209-219. doi:10.3758/s13415-013-0189-z
    Failing to remember whether we performed, or merely imagined performing, an everyday action can occasionally be inconvenient but, in some circumstances, can have potentially dangerous consequences. In this fMRI study, we investigated brain activity patterns, and objective and subjective behavioral measures, associated with recollecting such everyday actions. We used an ecologically-valid 'reality monitoring' paradigm in which participants performed, or imagined performing, specified actions with real objects drawn from one of two boxes. Lateral brain areas, including prefrontal cortex, were active when participants recollected both the actions that had been associated with objects and the locations from which they had been drawn, consistent with a general role in source recollection. By contrast, medial prefrontal and motor regions made more specific contributions, with supplementary motor cortex activity associated with recollection decisions about actions but not locations, and medial prefrontal cortex exhibiting greater activity when remembering performed rather than imagined actions. The results support a theoretical interpretation of reality monitoring that entails the fine-grained discrimination between multiple forms of internally- and externally-generated information.
  • Bergström, Z., Vogelsang, D., Benoit, R., & Simons, J. (2014). Reflections of Oneself: Neurocognitive Evidence for Dissociable Forms of Self-Referential Recollection. Cerebral Cortex, 25, 2648-2657. doi:10.1093/cercor/bhu063
    Research links the medial prefrontal cortex (mPFC) with a number of social cognitive processes that involve reflecting on oneself and other people. Here, we investigated how mPFC might support the ability to recollect information about oneself and others relating to previous experiences. Participants judged whether they had previously related stimuli conceptually to themselves or someone else, or whether they or another agent had performed actions. We uncovered a functional distinction between dorsal and ventral mPFC subregions based on information retrieved from episodic long-term memory. The dorsal mPFC was generally activated when participants attempted to retrieve social information about themselves and others, regardless of whether this information concerned the conceptual or agentic self or other. In contrast, a role was discerned for ventral mPFC during conceptual but not agentic self-referential recollection, indicating specific involvement in retrieving memories related to self-concept rather than bodily self. A subsequent recognition test for new items that had been presented during the recollection task found that conceptual and agentic recollection attempts resulted in differential incidental encoding of new information. Thus, we reveal converging fMRI and behavioural evidence for distinct neurocognitive forms of self-referential recollection, highlighting that conceptual and bodily aspects of self reflection can be dissociated.
  • Bergström, Z., Henson, R., Taylor, J., & Simons, J. (2013). Multimodal imaging reveals the spatiotemporal dynamics of recollection. NeuroImage, 68, 141-153. doi:10.1016/j.neuroimage.2012.11.030
    Functional MRI research suggests that different frontal and parietal cortical regions support strategic processes that are engaged at different stages of recollection, from pre-retrieval processing of a cue to post-retrieval maintenance and evaluation of recollected information. Whereas some of these regions respond in a domain-general way, other regions are sensitive to the type of information being recollected. However, the low temporal resolution of fMRI cannot distinguish component processes at the time-scale at which recollection occurs. We therefore combined fMRI with the excellent temporal resolution of source localised EEG/MEG to investigate the spatiotemporal neural dynamics of recollection. fMRI and EEG/MEG data were collected from the same participants in two sessions while they retrieved different types of episodic information. This multimodal imaging approach revealed striking consistency between the regions identified with fMRI and EEG/MEG, providing novel evidence of how these brain areas interact over time to support source recollection. For domain-general recollection, results from both modalities converged in showing the strongest activations in medial parietal cortex, which according to EEG/MEG was reliable at a late retrieval stage. Domain-specific source recollection increased fMRI and EEG/MEG activation in the left lateral prefrontal cortex, which EEG/MEG indicated also to be recruited during a post-recollection stage. The findings suggest that although medial parietal and left lateral prefrontal regions mediate functionally different retrieval processes, they are both engaged at a late stage of episodic retrieval.
  • Bergström, Z., Anderson, M., Buda, M., Simons, J., & Richardson-Klavehn, A. (2013). Intentional retrieval suppression can conceal guilty knowledge in ERP memory detection tests. Biological Psychology, 94, 1-11. Retrieved from http://www.sciencedirect.com/science/article/pii/S0301051113001154
    Brain-activity markers of guilty knowledge have been promoted as accurate and reliable measures for
    establishing criminal culpability. Tests based on these markers interpret the presence or absence of
    memory-related neural activity as diagnostic of whether or not incriminating information is stored in
    a suspect’s brain. This conclusion critically relies on the untested assumption that reminders of a crime
    uncontrollably elicit memory-related brain activity. However, recent research indicates that, in some
    circumstances, humans can control whether they remember a previous experience by intentionally
    suppressing retrieval. We examined whether people could use retrieval suppression to conceal neural
    evidence of incriminating memories as indexed by Event-Related Potentials (ERPs). When people were
    motivated to suppress crime retrieval, their memory-related ERP effects were significantly decreased,
    allowing guilty individuals to evade detection. Our findings indicate that brain measures of guilty knowledge
    may be under criminals’ intentional control and place limits on their use in legal settings.
  • Yazar, Y., Bergström, Z., & Simons, J. (2012). What is the parietal lobe contribution to long-term memory?. Cortex, 48, 1381-1382. doi:10.1016/j.cortex.2012.05.011
    Until relatively recently, the lateral parietal lobe (PL) was not considered an important region for long-term memory, typically associated instead with functions such as visuospatial attention and visually-guided reaching. Scientific interest in a possible link with episodic memory was fuelled by the realisation of an intriguing discrepancy between functional imaging studies of episodic memory retrieval, which showed consistent PL activation, and the seemingly unaffected memory performance in patients with PL lesions. Shallice and Cooper dedicated a section in their book The Organisation of Mind to this newly emerged topic, reflecting how it has rapidly become an established research focus in the cognitive neurosciences.
  • Bergström, Z., O’Connor, R., Li, M., & Simons, J. (2012). Event-related potential evidence for separable automatic and controlled retrieval processes in proactive interference. Brain Research, 1455, 90-102. doi:10.1016/j.brainres.2012.03.043
    Interference between competing memories is a major source of retrieval failure, yet, surprisingly little is known about how competitive memory activation arises in the brain. One possibility is that interference during episodic retrieval might be produced by relatively automatic conceptual priming mechanisms that are independent of strategic retrieval processes. Such priming-driven interference might occur when the competing memories have strong pre-existing associations to the retrieval cue. We used ERPs to measure the neural dynamics of retrieval competition, and investigated whether the ERP correlates of interference were affected by varying task demands for selective retrieval. Participants encoded cue words that were presented either two or four times, paired either with the same or different strongly associated words across repetitions. In a subsequent test, participants either selectively recalled each cue's most recent associate, or simply judged how many times a cue had been presented, without requiring selective recall. Interference effects on test performance were only seen in the recall task. In contrast, ERPs during test revealed an early posterior positivity for high interference items that was present in both retrieval tasks. This early ERP effect likely reflects a conceptual priming-related N400 reduction when many associations to a cue were pre-activated. A later parietal positivity resembling the ERP correlate of conscious recollection was found only in the recall task. The results suggest that early effects of proactive interference are relatively automatic and independent of intentional retrieval processes, consistent with suggestions that interference can arise through conceptual priming.
  • Buda, M., Fornito, A., Bergström, Z., & Simons, J. (2011). A specific brain structural basis for individual differences in reality monitoring. Journal of Neuroscience, 31, 14308-13. doi:10.1523/?JNEUROSCI.3595-11.2011
    Much recent interest has centered on understanding the relationship between brain structure variability and individual differences in cognition, but there has been little progress in identifying specific neuroanatomical bases of such individual differences. One cognitive ability that exhibits considerable variability in the healthy population is reality monitoring; the cognitive processes used to introspectively judge whether a memory came from an internal or external source (e.g., whether an event was imagined or actually occurred). Neuroimaging research has implicated the medial anterior prefrontal cortex (PFC) in reality monitoring, and here we sought to determine whether morphological variability in a specific anteromedial PFC brain structure, the paracingulate sulcus (PCS), might underlie performance. Fifty-three healthy volunteers were selected on the basis of MRI scans and classified into four groups according to presence or absence of the PCS in their left or right hemisphere. The group with absence of the PCS in both hemispheres showed significantly reduced reality monitoring performance and ability to introspect metacognitively about their performance when compared with other participants. Consistent with the prediction that sulcal absence might mean greater volume in the surrounding frontal gyri, voxel-based morphometry revealed a significant negative correlation between anterior PFC gray matter and reality monitoring performance. The findings provide evidence that individual differences in introspective abilities like reality monitoring may be associated with specific structural variability in the PFC.
  • Bergström, Z., de Fockert, J., & Richardson-Klavehn, A. (2009). ERP and behavioural evidence for direct suppression of unwanted memories. NeuroImage, 48, 726-737. doi:10.1016/j.neuroimage.2009.06.051
    There are some past experiences that we would prefer not to remember. Previous research has shown that repeatedly stopping retrieval of an unwanted memory increases the probability of later forgetting of that memory, and engages prefrontal control mechanisms to attenuate activity in the hippocampus. However, the mechanisms of preventing memory retrieval, and how these relate to the later forgetting, are yet to be fully understood. Here we present neural and behavioural evidence that two distinct strategies for retrieval stopping - direct memory suppression and self-distracting thought substitution - contribute to forgetting of unwanted memories in qualitatively different ways. Only direct memory suppression reduced centro-parietal positivity in the event-related potentials (ERP) between 300 and 600 ms post-stimulus, consistent with a reduction in the ERP correlate of recollection. Furthermore, only direct memory suppression produced later inhibitory forgetting that was predicted by an earlier negative ERP effect that may be associated with motor inhibition. In contrast, thought substitution produced later non-inhibitory forgetting and had no effect on the ERP correlate of recollection. Our findings demonstrate the first ERP and behavioural dissociation between inhibitory and non-inhibitory forgetting, and suggest that unwanted memories may be directly suppressed without selective retrieval of alternative memories.
  • de Fockert, J., Ramchurn, A., van Velzen, J., Bergström, Z., & Bunce, D. (2009). Behavioral and ERP evidence of greater distractor processing in old age. Brain Research, 1282, 67-73. doi:10.1016/j.brainres.2009.05.060
    The ability to minimize processing for irrelevant information is a central component of goal-directed behavior, which has been suggested to be compromised in old age. In this study, we investigate age differences in distractor rejection by presenting target names alongside to-be-ignored distractor faces. Older adults (mean age 70) showed greater behavioral slowing than young adults (mean age 24) when the distractor face was incompatible with the target name. That this increased interference in the older adults was indeed associated with more distractor processing, was shown by the face-related N170 component of the EEG, which had greater amplitude in older adults when faces were unattended, but not when they were attended. These findings suggest a reduced ability to prevent distractor processing in old age.
  • Bergström, Z., de Fockert, J., & Richardson-Klavehn, A. (2009). Event-related potential evidence that automatic recollection can be voluntarily avoided. Journal of Cognitive Neuroscience, 21, 1280-1301. doi:10.1162/jocn.2009.21075
    Voluntary control processes can be recruited to facilitate recollection in situations where a retrieval cue fails to automatically bring to mind a desired episodic memory. We investigated whether voluntary control processes can also stop recollection of unwanted memories that would otherwise have been automatically recollected. Participants were trained on cue-associate word-pairs, then repeatedly presented with the cue and asked to either recollect or avoid recollecting the associate, while having the event-related potential (ERP) correlate of conscious recollection measured. Halfway through the phase, some cues switched instructions so that participants had to start avoiding recall of associates they had previously repeatedly recalled, and vice versa. ERPs during recollection avoidance showed a significantly reduced positivity in the correlate of conscious recollection, and switching instructions reversed the ERP effect even for items that had been previously repeatedly recalled, suggesting that voluntary control processes can override highly practiced, automatic recollection. Avoiding recollection of particularly prepotent memories was associated with an additional, earlier ERP negativity that was separable from the later voluntary modulation of conscious recollection. The findings have implications for theories of memory retrieval by highlighting the involvement of voluntary attentional processes in controlling conscious recollection.
  • Wimber, M., Bäuml, K., Bergström, Z., Markopoulos, G., Heinze, H., & Richardson-Klavehn, A. (2008). Neural markers of inhibition in human memory retrieval. Journal of Neuroscience, 28, 13419-13427. doi:10.1523/JNEUROSCI.1916-08.2008
    Retrieving particular information from memory facilitates the later retrieval of that information, but also impairs the later retrieval of related, interfering information. It has been theorized that this retrieval-induced forgetting reflects inhibition of interfering memory representations. We used event-related fMRI to investigate the functional neuroanatomy of this impaired retrieval, at the time the impairment is observed. Neural activity differences between impaired and facilitated information occurred in left ventrolateral prefrontal cortex (VLPFC, BA 45 and 47), precuneus (BA 7), and right inferior parietal lobule (IPL, BA 40). Activity in left anterior VLPFC (BA 47) and left posterior temporal cortex (BA 22), regions implicated in the controlled retrieval of weak semantic memory representations, predicted the degree of retrieval-induced forgetting. In contrast, activity in precuneus and right IPL predicted the degree of retrieval-induced facilitation. Our findings demonstrate that impairment of interfering memories and facilitation of practiced memories involve distinct neural processes, and suggest that the impairment reflects inhibition that weakens interfering memory representations.
  • Bergström, Z., Velmans, M., de Fockert, J., & Richardson-Klavehn, A. (2007). ERP evidence for successful voluntary avoidance of conscious recollection. Brain Research, 1151, 119-133. doi:10.1016/j.brainres.2007.03.014
    We investigated neurocognitive processes of voluntarily avoiding conscious recollection by asking participants to either attempt to recollect (the Think condition) or to avoid recollecting (the No-Think condition) a previously exposed paired associate. Event-related potentials (ERPs) during Think and No-Think trials were separated on the basis of previous learning success versus failure. This separation yielded temporal and topographic dissociations between early ERP effects of a Think versus No-Think strategy, which were maximal between 200 and 300 ms after stimulus presentation and independent of learning status, and a later learning-specific ERP effect maximal between 500 and 800 ms after stimulus presentation. In this later time-window, Learned Think items elicited a larger late left parietal positivity than did Not Learned Think, Learned No-Think, and Not Learned No-Think items; moreover, Learned No-Think and Not Learned Think items did not differ in late left parietal positivity. Because the late left parietal positivity indexes conscious recollection, the results provide firm evidence that conscious recollection of recollectable information can be voluntarily avoided on an item-specific basis and help to clarify previous neural evidence from the Think/No-Think procedure, which could not separate item-specific from strategic processes.

Book section

  • Richardson-Klavehn, A., Bergström, Z., Magno, E., Markopoulos, G., Sweeney-Reed, C., & Wimber, M. (2009). On the intimate relationship between neurobiology and function in the theoretical analysis of human learning and memory. In F. Rösler, C. Ranganath, B. Röder, & R. H. Kluwe (Eds.), Neuroimaging of human memory: Linking cognitive process to neural systems.. Oxford, UK: Oxford University Press.

Conference or workshop item

  • Williams, D., Nicholson, T., Carruthers, P., & Bergström, Z. (2016). Metacognition, Mindreading, and the Hypercorrection Effect in ASD. In International Meeting for Autism Research. doi:10.1177/1362361316680178
    Among neurotypical adults, errors made with high confidence (i.e. errors a person strongly believed they would not make) are corrected more reliably than errors made with low confidence. This ‘hypercorrection effect’ is thought to result from enhanced attention to information that reflects a ‘metacognitive mismatch’ between one’s beliefs and reality. In Experiment 1, we employed a standard measure of this effect. Participants answered general knowledge questions and provided confidence judgements about how likely each answer was to be correct, after which feedback was given. Finally, participants were retested on all questions answered incorrectly during the initial phase. Mindreading ability and autism spectrum disorder–like traits were measured. We found that a representative sample of (n?=?83) neurotypical participants made accurate confidence judgements (reflecting good metacognition) and showed the hypercorrection effect. Mindreading ability was associated with autism spectrum disorder–like traits and metacognition. However, the hypercorrection effect was non-significantly associated with mindreading or autism spectrum disorder–like traits. In Experiment 2, 11 children with autism spectrum disorder and 11 matched comparison participants completed the hypercorrection task. Although autism spectrum disorder children showed significantly diminished metacognitive ability, they showed an undiminished hypercorrection effect. The evidence in favour of an undiminished hypercorrection effect (null result) was moderate, according to Bayesian analysis (Bayes factor?=?0.21).
  • Ates, F., Sharma, D., & Bergström, Z. (2016). Spontaneous recognition: Underlying neural mechanisms and the role of confidence. In International Conference on Memory. Budapest, Hungry. Retrieved from http://www.icom2016.com/
    Intentional recognition judgements to a target stimulus can be biased by spontaneous, unintentional recognition of familiar but task-irrelevant distractors. We investigated the underlying neural processes of such biases using EEG, focusing on how behavioural and EEG markers of bias correlate with participants’ confidence in their recognition judgements. Preliminary results suggest that spontaneous recognition of distractors elicited an early frontal-central positivity that has been linked with a relatively automatic familiarity process, whilst intentional target recognition also produced a later left-parietal positivity that reflects recollection. This latter ERP effect was particularly modulated by recognition confidence. The findings suggest dissociable neurocognitive processes contribute to unintentional and intentional recognition.

Thesis

  • Plummer, M. (2020). Recognition-induced updating of face memories: behavioural and electrophysiological evidence.
    Episodic memories are prone to 'updating', that is, memories can be strengthened or distorted after their initial encoding. The majority of research has examined the cognitive and neurocognitive mechanisms for the updating of elaborate episodic memories, however the goal of this thesis was to examine mechanisms for the updating of simpler episodic memories, such as memories for faces. For all experiments, a novel repeated recognition paradigm required participants to complete two recognition tests, with target faces (shown during a previous learning phase) presented amongst four distractor faces (not seen prior to the first test). Critically, face stimuli were derived from artificial face space models to control perceptual differences between images, as well as to use the Euclidean distance between face images as a continuous metric of recognition (details in Chapter 2). Within Chapter 3, it was found that elevated confidence judgements during initial recognition attempts predicted whether participants would recognise the same face in a subsequent test, regardless of the accuracy of recognition judgements on the initial test. In Chapter 4, it was queried whether face memory updating would be increased after retrieving vs. re-studying face memories. Results showed that retrieval enhanced the updating of face memories compared to re-study tasks, despite these tasks encouraging participants to encode faces that were cued to participants (Experiment 4a & c) or were selected according to distinctiveness (Experiment 4c). Finally, the electrophysiological correlates of face memory retrieval and updating were examined with ERPs (Chapter 5) and oscillations (Chapter 6). ERPs largely corresponded to the retrieval and reactivation of target memories recognised with high confidence. However, oscillatory markers of objective, subjective and updating processes were found. Together, this thesis provides the first evidence of the cognitive and neurocognitive mechanisms underlying the retrieval- induced updating of face memories.
  • Ates, F. (2018). The Role of Working Memory in Spontaneous Recognition: Neural Correlates and Behavioural Influences in the Memory Stroop Paradigm.
    Research suggests that unintentional recognition of distracting non-target stimuli can bias goal-related, intentional recognition judgements to target stimuli encountered in the same environment. Spontaneous recognition (SR) effect can be defined as the unintentional recognition of stimuli and is measured by the effect of familiarity to distractors on a recognition task. This thesis investigated how previously seen or not-seen distractors affect recognition of targets when working memory (WM) resources are manipulated by a secondary WM load task (chapter 2), using both behavioural and ERP measures (Chapter 3). The findings suggest that when working memory resources are low, SR is then easier to observe. Additionally, neural and memory processes are dissociable for unintentional and intentional recognition and retrieval monitoring is found to be enhanced when the new targets were paired with old distractors. Furthermore, the findings on the early ERPs may suggest that the proactive control might be activated. Finally, a set of experiments revealed that, SR effect may not be related to conscious awareness since having a low or high confidence did not modulate the SR effect indicating a lack of conscious awareness of the SR effect (Chapter 4). Together these findings may help to understand the mechanisms underlying the SR effect.
  • Etchells, D. (2017). Understanding how unfamiliar faces become familiar.
    For most people, visual recognition of familiar faces is excellent and seems effortless, but recognition of unfamiliar faces is often poor. But how does an unfamiliar face become familiar? Seven behavioural and two event-related brain potential (ERP) experiments were carried-out to investigate the perceptual encoding process and subsequent recognition ability of same or other views when single-views or two-views had been learned. By systematically changing the types of views to be learned and tested, results from the behavioural experiments revealed that when two-views were accessed during recognition, integration and summation between these views and the information each view type afforded (i.e., its 'view type utility') directly influenced recognition performance of a novel view. ERP experimental findings further suggested that the FN400 'familiarity' ERP component found during learning represented access to an established representation in memory, and in the recognition phase represented an approaching significant marker of 'familiarity', but only when two-views had been learned. This suggested that the FN400 two-view recognition effect, which was not present for single-views, represented access to a memorial representation that was qualitatively different from that of single-views. Taken together, behavioural and ERP results indicated that face learning occurred through the encoding of all visual information available at the time, and that learning more than one view imparted an advantage when tested on a novel view that was based on 'view type utility'. Furthermore, the FN400 memorial representation for two-views may represent an association in memory that occurs due to within-identity variation between the two-views learned.
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