Publications
Publications
Broitman, A.W., & Kahana, M.J. (Under Invited Resubmission). Neural Context Reinstatement of Recurring Events. bioR𝝌iv.
Episodic recollection involves retrieving context information bound to specific events. However, autobiographical memory largely comprises recurrent, similar experiences that become integrated into joint representations. In the current study, we extracted a neural signature of temporal context from scalp electroencephalography (EEG) to investigate whether recalling a recurring event accompanies the reinstatement of one or multiple instances of its occurrence. We asked 52 young adults to study and recall lists of words that included both once-presented and repeated items. Participants recalled repeated items in association with neighboring list items from each occurrence, but with stronger clustering around the repetition’s initial occurrence. Furthermore, multivariate spectral EEG analyses revealed that neural activity from just prior to the recall of these words resembled patterns of activity observed near the item’s first occurrence, but not its second. Together, these results suggest that the initial occurrence of an event carries stronger temporal context associations than later repetitions.
Broitman, A.W., & Swallow, K.M. (2025). Target Detection Modulates Electroencephalographic Spectral Correlates of Successful Encoding. Journal of Cognitive Neuroscience. Advance online publication.
The current study investigates whether changes in scalp electroencephalographic activity over time reflect the effects of target detection and divided attention on memory encoding. We recorded electroencephalographic activity in 61 young adults as they memorized lists of words either under full attention (single-task) or while performing a secondary task (dual task). In both cases, colored squares appeared with each word. However, in the dual-task condition, participants also pressed a button when the colored squares were in a predefined color (target) but made no response when the squares were in a different color (distractor). Subsequent memory effects in the alpha (8–12 Hz) and high gamma (50–100 Hz) frequency bands changed throughout the trial, and these effects differed across conditions. Before word presentation, high gamma activity was associated with encoding success in the target and single-task conditions, but not in the distractor conditions. In contrast, alpha band activity decreased following word presentation, and these decreases were greater for successfully encoded words in the target condition than in the distractor or single-task conditions. The results are consistent with the view that alpha and gamma activity reflect distinct neural processes, which both contribute to memory formation, but are differentially sensitive to task demands and momentary shifts in attention.
Broitman, A. W., Healey, M.K., & Kahana, M.J. (2025). Psychology & Aging, 40(3), 265–277.
The present study investigates whether electroencephalogram activity reflects age-related memory changes during encoding. We recorded scalp electroencephalogram in 151 young adults (aged 18–30) and 37 older adults (aged 60–85) as they memorized lists of words. Participants studied the word lists either under full attention or while performing a secondary task that required them to make semantic judgments about each word. Although the secondary task reduced recall among all participants, differences in recall performance between the age groups were smaller when participants performed a secondary task at encoding. Older adults also exhibited distinct neural subsequent memory effects, characterized by less negativity in the alpha frequencies compared to young adults. Multivariate classifiers trained on neural features successfully predicted subsequent memory at the trial level in both young and older adults, and captured the differential effects of task demands on memory performance between young and older adults. The findings indicate that neural biomarkers of successful memory vary with both cognitive aging and task demands.
Broitman, A. W., & Swallow, K. M. (2024). Memory & Cognition, 52(5), 752-770.
With the attentional boost effect (ABE), responding to a briefly presented target in a detection task enhances the encoding of other items presented at the same time. However, the effects of target detection on context memory for the event in which the stimulus appeared remain unclear. Here, we present findings from verbal free recall and recognition experiments that test the effects of target detection during encoding on temporal and relational aspects of context memory. Consistent with prior demonstrations of limited effects of target detection on context memory, in Experiment 1 there was no evidence that target detection influenced the likelihood of transitioning to items that were presented at similar times during encoding, or that were in the same encoding condition. These null effects were replicated in a second experiment, which added an old/new recognition and relational memory test. These results indicate that target detection during encoding has minimal effects on the formation of temporal associations between words in memory.
Broitman, A. W., & Swallow, K. M. (2020). Quarterly Journal of Experimental Psychology, 73(5), 711-725.
Abstract: How does attending to a brief, behaviourally relevant stimulus affect episodic memory encoding? In the attentional boost effect, increasing attention to a brief target in a detection task boosts memory for items that are presented at the same time (relative to distractor-paired items). Although the memory advantage for target-paired items is well established, the effects of attending to targets on other aspects of episodic memory encoding are unclear. This study examined the effects of target detection and goal-directed attention on memory for task-irrelevant information from a single event, focusing on the contributions of recollection and familiarity during recognition. In Experiment 1, participants viewed a series of briefly presented faces as they performed a detection task on unrelated squares, pressing the space bar only when the square was a target colour (e.g., blue) rather than a distractor colour (e.g., orange). Half of the participants were told to memorize the faces, and half were told to ignore them. Results indicated that both recollection and familiarity were greater for target-paired faces than for distractor-paired faces, regardless of whether the faces were intentionally encoded. Experiment 2 examined whether these effects are present for single events, replicating the recollection benefit when encoding time is sufficient. Attending to behaviourally relevant targets appears to facilitate both intentional and incidental memory for the background item and the context in which it occurred, boosting subsequent recollection as well as familiarity.
Broitman, A. W., Kahana, M. J. & Healey, M. K. (2019). Computational Brain & Behavior, 2(5), 1-8.
Abstract: Longitudinal designs must deal with the confound between increasing age and increasing task experience (i.e., retest effects). Most existing methods for disentangling these factors rely on large sample sizes and are impractical for smaller scale projects. Here, we show that a measurement burst design combined with a model of retest effects can be used to study age-related change with modest sample sizes. A combined model of age-related change and retest-related effects was developed. In a simulation experiment, we show that with sample sizes as small as n = 8, the model can reliably detect age effects of the size reported in the longitudinal literature while avoiding false positives when there is no age effect. We applied the model to data from a measurement burst study in which eight subjects completed a burst of seven sessions of free recall every year for five years. Six additional subjects completed a burst only in years 1 and 5. They should, therefore, have smaller retest effects but equal age effects. The raw data suggested slight improvement in memory over five years. However, applying the model to the yearly-testing group revealed that a substantial positive retest effect was obscuring stability in memory performance. Supporting this finding, the control group showed a smaller retest effect but an equal age effect. Measurement burst designs combined with models of retest effects allow researchers to employ longitudinal designs in areas where previously only cross-sectional designs were feasible.
Swallow, K.M., Broitman, A.W., Riley, E. & Turker, H.B. (2022). Frontiers in Psychology, 13, 892416.
Abstract: Attention and memory for everyday experiences vary over time, wherein some moments are better attended and subsequently better remembered than others. These effects have been demonstrated in naturalistic viewing tasks with complex and relatively uncontrolled stimuli, as well as in more controlled laboratory tasks with simpler stimuli. For example, in the attentional boost effect (ABE), participants perform two tasks at once: memorizing a series of briefly presented stimuli (e.g., pictures of outdoor scenes) for a later memory test, and responding to other concurrently presented cues that meet pre-defined criteria (e.g., participants press a button for a blue target square and do nothing for a red distractor square). However, rather than increasing dual-task interference, attending to a target cue boosts, rather than impairs, subsequent memory for concurrently presented information. In this review we describe current data on the extent and limitations of the attentional boost effect and whether it may be related to activity in the locus coeruleus neuromodulatory system. We suggest that insight into the mechanisms that produce the attentional boost effect may be found in recent advances in the locus coeruleus literature and from understanding of how the neurocognitive system handles stability and change in everyday events. We consequently propose updates to an early account of the attentional boost effect, the dual-task interaction model, to better ground it in what is currently known about event cognition and the role that the LC plays in regulating brain states.
Kahana, M.J., Lohnas, L.J., Healey, M.K., Aka, A., Broitman, A.W., et al. (2024) Journal of Experimental Psychology: Learning, Memory, & Cognition, 50(9), 1421–1443.
Abstract: The Penn Electrophysiology of Encoding and Retrieval Study (PEERS) aimed to characterize the behavioral and electrophysiological (EEG) correlates of memory encoding and retrieval in highly practiced individuals. Across five PEERS experiments, 300+ subjects contributed more than 7,000 90 minute memory testing sessions with recorded EEG data. Here we tell the story of PEERS: it’s genesis, evolution, major findings, and the lessons it taught us about taking a big science approach to the study of memory and the human brain.