Publications by authors named "Robin Hellerstedt"

8 Publications

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Cognitive interference processing in adult survivors of childhood acute lymphoblastic leukemia using functional magnetic resonance imaging.

Acta Oncol 2021 Oct 12:1-8. Epub 2021 Oct 12.

Department of Oncology, Skåne University Hospital, Lund, Sweden.

Background: Childhood acute lymphoblastic leukemia (ALL) is associated with cognitive impairment in adulthood. Cognitive interference processing and its correlated functional magnetic resonance imaging (fMRI) activity in the brain have not yet been studied in this patient group.

Material: Twenty-six adult childhood ALL survivors (median [interquartile range {IQR}] age, 40.0 [37.0-42.3] years) were investigated at median age (IQR), 35.0 (32.0-37.0) years after treatment with intrathecal and intravenous chemotherapy as well as cranial radiotherapy (24 Gy) and compared with 26 matched controls (median [IQR] age, 37.5 [33.0-41.5] years).

Methods: Cognitive interference processing was investigated in terms of behavioral performance (response times [ms] and accuracy performance [%]) and fMRI activity in the cingulo-fronto-parietal (CFP) attention network as well as other parts of the brain using the multisource interference task (MSIT).

Results: ALL survivors had longer response times and reduced accuracy performance during cognitive interference processing (median [IQR] interference effect, 371.9 [314.7-453.3] ms and 6.7 [4.2-14.7]%, respectively) comparedwith controls (303.7 [275.0-376.7] ms and 2.3 [1.6-4.3]%, respectively), but did not exhibit altered fMRI activity in the CFP attention network or elsewhere in the brain.

Conclusion: Adult childhood ALL survivors demonstrated impaired behavioral performance but no altered fMRI activity when performing cognitive interference processing when compared with controls. The results can be used to better characterize this patient group and to optimize follow-up care and support for these individuals.
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http://dx.doi.org/10.1080/0284186X.2021.1987514DOI Listing
October 2021

Cognitive interference processing in adults with childhood craniopharyngioma using functional magnetic resonance imaging.

Endocrine 2021 Jul 22. Epub 2021 Jul 22.

Department of Endocrinology, Skåne University Hospital, Lund, Sweden.

Purpose: To assess cognitive interference processing in adults with childhood craniopharyngioma (CP), with and without hypothalamic injury, respectively, in terms of behavioral performance and functional magnetic resonance imaging (fMRI) activity, using the multi-source interference task (MSIT).

Methods: Twenty-eight CP patients (median age 34.5 [29.0-39.5] years) were investigated at median 20.5 (16.3-28.8) years after treatment with surgical resection and in some cases additional radiotherapy (n = 10) and compared to 29 matched controls (median age 37.0 [32.5-42.0] years). The subjects performed the MSIT during fMRI acquisition and behavioral performance in terms of response times (ms) and accuracy performance (%) were recorded.

Results: The MSIT activated the cingulo-fronto-parietal (CFP) attention network in both CP patients and controls. No differences were found in behavioral performance nor fMRI activity between CP patients (interference effect 333.9 [287.3-367.1] ms and 3.1 [1.6-5.6]%, respectively) and controls (309.1 [276.4-361.0] ms and 2.6 [1.6-4.9]%). No differences were found in behavioral performance nor fMRI activity between the two subgroups with (332.0 [283.6-353.4] ms and 4.2 [2.3-5.7]%, respectively) and without hypothalamic injury (355.7 [293.7-388.7] ms and 2.1 [1.0-5.2]%, respectively), respectively, and controls.

Conclusion: Adults with childhood CP performed cognitive interference processing equally well as controls and demonstrated no compensatory fMRI activity in the CFP attention network compared to controls. This was also true for the two subgroups with and without hypothalamic injury. The results can be useful to better characterize this condition, and to optimize treatment and support for these individuals.
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http://dx.doi.org/10.1007/s12020-021-02824-9DOI Listing
July 2021

Aging reduces EEG markers of recognition despite intact performance: Implications for forensic memory detection.

Cortex 2021 07 24;140:80-97. Epub 2021 Apr 24.

School of Psychology, University of Kent, UK. Electronic address:

ERP-based forensic memory detection is based on the logic that guilty suspects will hold incriminating knowledge about crimes they have committed, and therefore should show parietal ERP positivities related to recognition when presented with reminders of their crimes. We predicted that such forensic memory detection might however be inaccurate in older adults, because of changes to recognition-related brain activity that occurs with aging. We measured both ERPs and EEG oscillations associated with episodic old/new recognition and forensic memory detection in 30 younger (age < 30) and 30 older (age > 65) adults. EEG oscillations were included as a complementary measure which is less sensitive to temporal variability and component overlap than ERPs. In line with predictions, recognition-related parietal ERP positivities were significantly reduced in the older compared to younger group in both tasks, despite highly similar behavioural performance. We also observed aging-related reductions in oscillatory markers of recognition in the forensic memory detection test, while the oscillatory effects associated with episodic recognition were similar across age groups. This pattern of results suggests that while both forensic memory detection and episodic recognition are accompanied by aging-induced reductions in parietal ERP positivities, these reductions may be caused by non-overlapping mechanisms across the two tasks. Our findings suggest that EEG-based forensic memory detection tests are less valid in older than younger populations, limiting their practical applications.
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http://dx.doi.org/10.1016/j.cortex.2021.03.015DOI Listing
July 2021

Strategic retrieval prevents memory interference: The temporal dynamics of retrieval orientation.

Neuropsychologia 2021 04 5;154:107776. Epub 2021 Feb 5.

Department of Psychology, Lund University, Sweden.

Resolving interference between overlapping memories is crucial to remember the past. This study tests the novel prediction that orienting search focus benefits goal-relevant retrieval by reducing competition from unwanted memories. In a modified retrieval-practice paradigm, participants encoded word-pairs in one of two encoding tasks. Critically, to evaluate whether this retrieval orientation (RO) reduces memory interference, target and competitor memories were always related to different encoding tasks. At retrieval, instructions were provided for half of the blocks with the intention to bias remembering towards items encoded with one of the ROs. Behavioural data show that adopting an RO improved target accessibility, strengthened the testing effect, and reduced retrieval-induced forgetting (RIF) of competitors. Specifically, RIF - typically attributed to inhibitory control of memory interference - was prominent when no retrieval orientation (NRO) instruction was provided. Furthermore, a neural correlate of RO was calculated by training a linear discriminant analysis (LDA) to discriminate the electroencephalographic (EEG) spatial brain patterns correspondent to the two ROs over the time course of selective retrieval. RO was characterised by increases in the theta and decreases in the beta frequency band, evident both before and after category-cue onset. While the pre-cue RO reinstatement effect predicted both immediate retrieval-practice success and later target accessibility, the post-cue effect predicted disengagement of inhibitory control, such that participants showing a stronger RO reinstatement effect showed lower levels of RIF. These data suggest that strategically orienting search focus during retrieval both increases target memory accessibility and reduces memory interference, which consequently protects related memories from inhibition and later forgetting. Furthermore, they also highlight the roles of theta and beta oscillations in establishing and maintaining a task-relevant bias towards target memory representations during competitive memory retrieval.
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http://dx.doi.org/10.1016/j.neuropsychologia.2021.107776DOI Listing
April 2021

Distraction by unintentional recognition: Neurocognitive mechanisms and effects of aging.

Psychol Aging 2020 Aug;35(5):639-653

School of Psychology.

Sometimes, we intentionally evaluate stimuli to assess whether we recognize them, whereas, at other times, stimuli automatically elicit recognition despite our efforts to ignore them. If multiple stimuli are encountered in the same environment, intentional recognition judgments 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, event-related potentials (ERPs), and electroencephalography oscillations in old (age range = 60-74) and young (age range = 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 with 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. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
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http://dx.doi.org/10.1037/pag0000398DOI Listing
August 2020

Tracking the intrusion of unwanted memories into awareness with event-related potentials.

Neuropsychologia 2016 08 7;89:510-523. Epub 2016 Jul 7.

MRC Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge CB2 7EF, UK.

Involuntary retrieval of unwanted memories is a common symptom in several clinical disorders, including post-traumatic stress disorder. With an aim to track the temporal dynamics of such memory intrusions, we recorded electrophysiological measures of brain activity while participants engaged in a Think/No-Think task. We presented the left hand word (the cue) of previously encoded word pairs in green or red font. We asked participants to think of the associated right hand word (the associate) when the cue appeared in green (Think condition) and to avoid thinking of the associate when the cue appeared in red (No-Think condition). To isolate cases when participants experienced an intrusive memory, at the end of each trial, participants judged whether the response had come to mind; we classified memories that came to mind during No-Think trials, despite efforts to stop retrieval, as intrusions. In an event-related potential (ERP) analysis, we observed a negative going slow wave (NSW) effect that indexed the duration of a trace in mnemonic awareness; whereas voluntary retrieval and maintenance of the associate was related to a sustained NSW that lasted throughout the 3-s recording epoch, memory intrusions generated short-lived NSWs that were rapidly truncated. Based on these findings, we hypothesize that the intrusion-NSW reflects the associate briefly penetrating working memory. More broadly, these findings exploit the high temporal resolution of ERPs to track the online dynamics of memory intrusions.
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http://dx.doi.org/10.1016/j.neuropsychologia.2016.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5010041PMC
August 2016

Competitive Semantic Memory Retrieval: Temporal Dynamics Revealed by Event-Related Potentials.

PLoS One 2016 22;11(2):e0150091. Epub 2016 Feb 22.

Department of Psychology, Lund University, Lund, Sweden.

Memories compete for retrieval when they are related to a common retrieval cue. Previous research has shown that retrieval of a target memory may lead to subsequent retrieval-induced forgetting (RIF) of currently irrelevant competing memories. In the present study, we investigated the time course of competitive semantic retrieval and examined the neurocognitive mechanisms underlying RIF. We contrasted two theoretical accounts of RIF by examining a critical aspect of this memory phenomenon, namely the extent to which it depends on successful retrieval of the target memory. Participants first studied category-exemplar word-pairs (e.g. Fruit-Apple). Next, we recorded electrophysiological measures of brain activity while the participants performed a competitive semantic cued-recall task. In this task, the participants were provided with the studied categories but they were instructed to retrieve other unstudied exemplars (e.g. Fruit-Ma__?). We investigated the event-related potential (ERP) correlates of retrieval success by comparing ERPs from successful and failed retrieval trials. To isolate the ERP correlates of continuous retrieval attempts from the ERP correlates of retrieval success, we included an impossible retrieval condition, with incompletable word-stem cues (Drinks-Wy__) and compared it with a non-retrieval presentation baseline condition (Occupation-Dentist). The participants' memory for all the studied exemplars was tested in the final phase of the experiment. Taken together, the behavioural results suggest that RIF is independent of target retrieval. Beyond investigating the mechanisms underlying RIF, the present study also elucidates the temporal dynamics of semantic cued-recall by isolating the ERP correlates of retrieval attempt and retrieval success. The ERP results revealed that retrieval attempt is reflected in a late posterior negativity, possibly indicating construction of candidates for completing the word-stem cue and retrieval monitoring whereas retrieval success was reflected in an anterior positive slow wave.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150091PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4762689PMC
July 2016

Electrophysiological correlates of competitor activation predict retrieval-induced forgetting.

Cereb Cortex 2014 Jun 30;24(6):1619-29. Epub 2013 Jan 30.

Department of Psychology, Lund University, Lund, Sweden.

The very act of retrieval modifies the accessibility of memory for knowledge and past events and can also cause forgetting. A prominent theory of such retrieval-induced forgetting (RIF) holds that retrieval recruits inhibition to overcome interference from competing memories, rendering these memories inaccessible. The present study tested a fundamental tenet of the inhibitory-control account: The competition-dependence assumption. Event-related potentials (ERPs) were recorded while participants engaged in a competitive retrieval task. Competition levels were manipulated within the retrieval task by varying the cue-item associative strength of competing items. In order to temporally separate ERP correlates of competitor activation and target retrieval, memory was probed with the sequential presentation of 2 cues: A category cue, to reactivate competitors, and a target cue. As predicted by the inhibitory-control account, competitors with strong compared with weak cue-competitor association were more susceptible to forgetting. Furthermore, competition-sensitive ERP modulations, elicited by the category cue, were observed over anterior regions and reflected individual differences in ensuing forgetting. The present study demonstrates ERP correlates of the reactivation of tightly bound associated memories (the competitors) and provides support for the inhibitory-control account of RIF.
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http://dx.doi.org/10.1093/cercor/bht019DOI Listing
June 2014
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