Zhong-Xu Liu

High-fat, high-sugar (HFS) diets have been linked to impairments in hippocampus-dependent memory and executive function in young adults. The present study investigated whether similar associations are observed in older adults and whether these effects vary with age. In an online sample of 470 participants aged 50~85 years, participants reported their HFS consumption and subjective memory complaints and completed tasks assessing hippocampus-dependent memory (Pattern-Separation Recognition and Face–name Associative Memory tasks) and executive functioning tasks (Trail Making and Stroop tasks). Results showed that higher HFS consumption was associated with increased subjective memory complaints in older adults. Critically, age moderated the relationship between HFS consumption and Pattern-Separation recognition memory, with higher HFS consumption associated with worse hippocampus-dependent recognition memory in participants < 65, but not ≥65 years old. When combined with a previously analyzed young-adult sample, results indicated that the negative association between HFS diet and both recognition memory and executive functioning was weaker with increased age and non-significant in older adults. These findings suggest that the cognitive effects of HFS diets are age-dependent and weaker in later life, highlighting the need for further research on aging and health-related factors that influence diet and cognition relationships across the lifespan.

As we interact with our environment, information from hippocampal representations guides further cognition and action on a moment-to-moment basis. We propose that eye movements modulate the organization of neural dynamics in humans and other primates with advanced visual systems, allowing reciprocal encoding and retrieval of information in service of predictive action. Gaze fixations and saccades allow the hippocampus to generate, test and update predictions about the external world in real time. Integrating evidence from computational modelling, neurophysiology and neuroimaging, we highlight viable anatomical and functional connections between the hippocampus and oculomotor control systems that support this bidirectional flow of information. We synthesize findings across spatial and temporal scales—from intracranial recordings showing saccade-related modulation in hippocampal and visuo-oculomotor neurons, to electrophysiological studies linking oscillatory dynamics to predictive processing, to functional magnetic resonance imaging work revealing network-level coupling shaped by viewing behaviour. Together, these converging results suggest that eye movements not only guide ongoing perceptual processing but also structure the neural dynamics underlying memory and prediction. We conclude by identifying open questions about how gaze modulates different types of hippocampally mediated predictions and under what conditions eye movements both reflect and update internal models of the world. This article is part of the theme issue ‘The role of hippocampal predictions in cognition: bridging perception and memory’.

As we interact with our environment, information from hippocampal representations guides further cognition and action on a moment-to-moment basis. We propose that eye movements modulate the organization of neural dynamics in humans and other primates with advanced visual systems, allowing for reciprocal encoding and retrieval of information in service of predictive action. Gaze fixations and saccades allow the hippocampus to generate, test, and update predictions about the external world in real time. Integrating evidence from computational modeling, neurophysiology, and neuroimaging, we highlight viable anatomical and functional connections between the hippocampus and oculomotor control systems that support this bidirectional flow of information. We synthesize findings across spatial and temporal scales—from intracranial recordings showing saccade-related modulation in hippocampal and visuo-oculomotor neurons, to electrophysiological studies linking oscillatory dynamics to predictive processing, to fMRI work revealing network-level coupling shaped by viewing behaviour. Together, these converging results suggest that eye movements not only guide ongoing perceptual processing but also structure the neural dynamics underlying memory and prediction. We conclude by identifying open questions about how gaze modulates different types of hippocampally mediated predictions and under what conditions eye movements both reflect and update internal models of the world.

How does sensory experience shape the development of the visual brain? To answer this eluding question, we examine brain responses to visual categories in a rare group of cataract-reversal individuals who experienced a short transient period of early blindness. Encoding of low-level visual properties is impaired in the early visual cortex (EVC) of cataract-reversal participants, whereas categorical responses in downstream ventral occipito-temporal cortex (VOTC) are preserved. In controls, degrading visual input to mimic the visual deficits of cataracts produces cascading disruptions extending from EVC to VOTC, unlike in the cataract group. A deep neural network trained on altered visual input reproduces this dissociation, supporting the brain findings. These results demonstrate that while EVC is permanently affected by early deprivation, categorical coding in VOTC shows resilience, highlighting different sensitive periods for specific brain regions and computations.

A large number of EEG studies have identified a distinct event related potential (ERP) component during error processing known as the Error-Related Negativity (ERN). In an influential study, Hajcak and Foti (2008) explored the idea that errors could trigger defensive motivational reactions and that the ERN might forecast the intensity of defensive reactions following errors. Using a flanker task, thirty-one college-aged participants responded to the direction of a central arrow with acoustic startle probes administered pseudo-randomly throughout. Hajcak and Foti’s (2008) findings indicated the ERN is indicative of individual variations in aversive reactions to errors. This has influenced understanding of the ERN being more than a simple error detection mechanism and sheds light on how people differ in their emotional responses to mistakes. As part of the #EEGManyLabs project, an international network of laboratories, we will test the replicability of the results from this influential study. The data will later be combined to compute global effect sizes of the ERN, startle potentiation, and their interaction. Collectively, these replications will help solidify the results from this highly-cited study. Given that the ERN is an integral part of a broader neural system responding to potentially threatening stimuli, this replication will provide a more solid foundation for our understanding of error processing and its relationship to defensive reactivity.

Autobiographical memory entails reconstructing the visual features of past events. Eye movements are associated with vivid autobiographical recollection, but this research has yet to capitalize on the high temporal resolution of eye-tracking data. We aligned eye movement data with participants’ simultaneous free recall of a verified real-life event, allowing us to assess the temporal correspondence of saccades to production of episodic and non-episodic narrative content at the millisecond level. Eye movements reliably predicted subsequent episodic – but not non-episodic – details by 250-1100 ms, suggesting that they facilitate episodic recollection by reinstating spatiotemporal context during vivid recollection. Assessing the relationship of oculomotor responses to naturalistic memory informs theory as well as diagnosis and treatment of conditions involving pathological recollection, such as Alzheimer’s disease and post-traumatic stress disorder (PTSD).

The Behavioral Inhibition System (BIS) and the Behavioral Activation System (BAS) are cornerstones of neurobehavioral research. Personality scales have been developed to capture the behavioral and motivational tendencies associated with these systems, and many studies have attempted to link these scales with basic neurocognitive processes. The results, however, have been inconclusive. Here, we aim to replicate a seminal study on this topic by Amodio et al. (2008), in which the authors used a Go/No-Go task to test the association of the trait BIS with cognitive control and the BAS trait with approach tendency. The authors found significant correlations that were mutually exclusive from each other; BAS did not correlate with measures of cognitive control, and BIS did not correlated with measures of approach tendency. Despite the paper’s high citation frequency and influence on the field, there has been no direct replication to date. These factors motivated the inclusion of this study in the #EEGManyLabs project, an international community-driven effort to replicate influential EEG results and this registered report forms a part of this initiative. Following the original study, a Go/No-Go experiment will be performed with a total of 320 participants across eight replicating labs. EEG will be recorded both during the experiment and in an eight-minute resting period. Target variables are the amplitude of the N2 during a successfully inhibited response, the amplitude of the error-related negativity (ERN) after an erroneous response, left frontal asymmetry (LFA) during rest, and trait BIS/BAS measured by the Carver and White questionnaire. Both Pearson’s and Spearman rank sum correlations, as well as regression analyses will be used to test the hypotheses that trait BIS is associated with ERN and N2 amplitudes, and that trait BAS is associated with LFA during rest.

The hippocampus is known to support processing of precise spatial information in recently learned environments. It is less clear, but crucial for theories of systems consolidation, to know whether it also supports processing of precise spatial information in familiar environments learned long ago and whether such precision extends to objects and numbers. In this fMRI study, we asked participants to make progressively more refined spatial distance judgments among well-known Toronto landmarks (whether landmark A is closer to landmark B or C) to examine hippocampal involvement. We also tested whether the hippocampus was similarly engaged in estimating magnitude regarding sizes of familiar animals and numbers. We found that the hippocampus was only engaged in spatial judgment. Activation was greater and lasted longer in the posterior than anterior hippocampus, which instead showed greater modulation as discrimination between spatial distances became more fine grained. These findings suggest that the anterior and posterior hippocampus have different functions which are influenced differently by estimation of differential distance. Similarly, parahippocampal-place-area and retrosplenial cortex were involved only in the spatial condition. By contrast, activation of the intraparietal sulcus was modulated by precision in all conditions. Therefore, our study supports the idea that the hippocampus and related structures are implicated in retrieving and operating even on remote spatial memories whenever precision is required, as posted by some theories of systems consolidation.

To better understand working memory (WM) deficits in Mild Cognitive Impairment (MCI), we examined information precision and associative binding in WM in 21 participants with MCI, compared to 16 healthy controls, using an item-location delayed reproduction task. WM, along with other executive functions (i.e. Trail Making Task (TMT) and Stroop task), were measured before and after a 2-h nap. The napping manipulation was intended as an exploratory element to this study exploring potential impacts of napping on executive functions. Compared to healthy participants, participants with MCI exhibited inferior performance not only in identifying encoded WM items but also on item-location associative binding and location precision even when only one item was involved. We also found changes on TMT and Stroop tasks in MCI, reflecting inferior attention and inhibitory control. Post-napping performance improved in most of these WM and other executive measures, both in MCI and their healthy peers. Our study shows that associative binding and WM precision can reliably differentiate MCIs from their healthy peers. Additionally, most measures showed no differential effect of group pre- and post-napping. These findings may contribute to better understanding cognitive deficits in MCI therefore improving the diagnosis of MCI.