Learning to remember: The early ontogeny of episodic memory

AbstractOver the past 60 years the neural correlates of human episodic memory have been the focus of intense neuroscientific scrutiny. By contrast, neuroscience has paid substantially less attention to understanding the emergence of this neurocognitive system. In this review we consider how the study of memory development has evolved. In doing so, we concentrate primarily on the first postnatal year because it is within this time window that the most dramatic shifts in scientific opinion have occurred. Moreover, this time frame includes the critical age (∼9 months) at which human infants purportedly first begin to demonstrate rudimentary hippocampal-dependent memory. We review the evidence for and against this assertion, note the lack of direct neurocognitive data speaking to this issue, and question how demonstrations of exuberant relational learning and memory in infants as young as 3-months old can be accommodated within extant models. Finally, we discuss whether current impasses in the infant memory literature could be leveraged by making greater use of neuroimaging techniques, such as magnetic resonance imaging (MRI), which have been deployed so successfully in adults

School distress and the school attendance crisis: a story dominated by neurodivergence and unmet need

BackgroundThe Covid-19 pandemic has brought into sharp focus a school attendance crisis in many countries, although this likely pre-dates the pandemic. Children and young people (CYP) struggling to attend school often display extreme emotional distress before/during/after school. We term this School Distress. Here we sought to elucidate the characteristics of the CYP struggling to attend school in the United Kingdom.MethodsUsing a case–control, concurrent embedded mixed-method research design, 947 parents of CYP with experience of School Distress completed a bespoke online questionnaire (February/March 2022), alongside an age-matched control group (n = 149) and a smaller group of parents who electively home-educate (n = 25).ResultsIn 94.3% of cases, school attendance problems were underpinned by significant emotional distress, with often harrowing accounts of this distress provided by parents. While the mean age of the CYP in this sample was 11.6 years (StDev 3.1 years), their School Distress was evident to parents from a much younger age (7.9 years). Notably, 92.1% of CYP currently experiencing School Distress were described as neurodivergent (ND) and 83.4% as autistic. The Odds Ratio of autistic CYP experiencing School Distress was 46.61 [95% CI (24.67, 88.07)]. Autistic CYP displayed School Distress at a significantly earlier age, and it was significantly more enduring. Multi-modal sensory processing difficulties and ADHD (among other neurodivergent conditions) were also commonly associated with School Distress; with School Distress CYP having an average of 3.62 NDs (StDev 2.68). In addition, clinically significant anxiety symptomology (92.5%) and elevated demand avoidance were also pervasive. Mental health difficulties in the absence of a neurodivergent profile were, however, relatively rare (6.17%). Concerningly, despite the striking levels of emotional distress and disability reported by parents, parents also reported a dearth of meaningful support for their CYP at school.ConclusionWhile not a story of exclusivity relating solely to autism, School Distress is a story dominated by complex neurodivergence and a seemingly systemic failure to meet the needs of these CYP. Given the disproportionate number of disabled CYP impacted, we ask whether the United Kingdom is upholding its responsibility to ensure the “right to an education” for all CYP (Human Rights Act 1998)

Prolonged rote learning produces delayed memory facilitation and metabolic changes in the hippocampus of the ageing human brain

Background: Repeated rehearsal is one method by which verbal material may be transferred from short- to long-term memory. We hypothesised that extended engagement of memory structures through prolonged rehearsal would result in enhanced efficacy of recall and also of brain structures implicated in new learning. Twenty-four normal participants aged 55-70 (mean = 60.1) engaged in six weeks of rote learning, during which they learned 500 words per week every week (prose, poetry etc.). An extensive battery of memory tests was administered on three occasions, each six weeks apart. In addition, proton magnetic resonance spectroscopy (H-1-MRS) was used to measure metabolite levels in seven voxels of interest (VOIs) (including hippocampus) before and after learning.Results: Results indicate a facilitation of new learning that was evident six weeks after rote learning ceased. This facilitation occurred for verbal/episodic material only, and was mirrored by a metabolic change in left posterior hippocampus, specifically an increase in NAA/(Cr+Cho) ratio.Conclusion: Results suggest that repeated activation of memory structures facilitates anamnesis and may promote neuronal plasticity in the ageing brain, and that compliance is a key factor in such facilitation as the effect was confined to those who engaged fully with the training

Suppressing the Encoding of New Information in Memory: A Behavioral Study Derived from Principles of Hippocampal Function

<div><p>Cognitive processes do not occur in isolation. Interactions between cognitive processes can be observed as a cost in performance following a switch between tasks, a cost that is greatest when the cognitive requirements of the sequential tasks compete. Interestingly, the long-term mnemonic goals associated with specific cognitive tasks can also directly compete. For example, encoding the sequential order in which stimuli are presented in the commonly-utilised 2-Back working memory (WM) tasks is counter-productive to task performance, as this task requires the continual updating of the contents of one's current mental set. Performance of this task consistently results in reduced activity within the medial temporal lobe (MTL), and this response is believed to reflect the inhibitory mnemonic component of the task. Conversely, there are numerous cognitive paradigms in which participants are explicitly instructed to encode incoming information and performance of these tasks reliably increases MTL activity. Here, we explore the behavioural cost of sequentially performing two tasks with conflicting long-term mnemonic goals and contrasting neural profiles within the MTL. We hypothesised that performing the 2-Back WM prior to a hippocampal-dependent memory task would impair performance on the latter task. We found that participants who performed the 2-Back WM task, prior to the encoding of novel verbal/face-name stimuli, recollected significantly fewer of these stimuli, compared to those who had performed a 0-Back control task. Memory processes believed to be independent of the MTL were unaffected. Our results suggest that the inhibition of MTL-dependent mnemonic function persists beyond the cessation of the 2-Back WM task and can alter performance on entirely separate and subsequently performed memory tasks. Furthermore, they indicate that performance of such tasks may induce a temporarily-sustained, virtual lesion of the hippocampus, which could be used as a probe to explore cognitive processes in the absence of hippocampal involvement.</p> </div

The <i>n</i>-Back task paradigm.

<p>In both conditions stimulus presentation was identical i.e. stimuli remained on-screen for 1800 ms, followed by a blank screen (ISI = 200 ms). Stimuli were presented in a pseudo-random sequence i.e. every nine randomly presented numerical stimuli were followed by two blank diamond arrays. This signaled a pause in the number sequence. Each <i>n</i>-Back (0-Back or 2-Back) block consisted of 77 visual stimuli presentations (11 visual stimuli x 7 number sequences) and total block duration was 154 seconds. <i>0-Back Control Task:</i> Participants were required to respond by pressing the number corresponding to the number in the diamond on screen. <i>2-Back WM Task</i>: Participants were required to respond by pressing the button corresponding to the number presented 2 diamonds previously. (Blank screen omitted between stimuli).</p

Results: Experiment 1.

<p><i>Panel A</i>: <i>Free Recall</i>. Participants who performed the 2-Back WM task recalled significantly fewer words from Lists B, C and D. <i>Panel B</i>: <i>Hippocampal-Dependent/Direct Recognition</i> (the proportion of previously studied words successfully recognized). Individuals in the 2-Back condition performed significantly less accurately than those in the 0-Back condition. <i>Panel C</i>: <i>Hippocampal-independent/Indirect Recognition</i>. The proportion of studied and unstudied words successfully read aloud by participants. All participants successfully read more of the studied than the unstudied words. However, no performance difference was observed between the two conditions. Error bars indicate SEM. * <i>P</i>≤0.05; ** <i>P</i><0.01.</p

Task Design: Experiment 3.

<p><i>Panel A: Phase 1</i>. The experimental group performed four blocks of the face-name task, which consisted of an encoding phase (10 face-name pairs; duration = 40 s) and a subsequent retrieval phase (duration = 40 s), separated in time with a ‘distractor’ task of visual attention (duration = 154 s). The control group performed the Sustained Attention to Response Task (SART), which was again divided into two blocks of 40 seconds (corresponding to the face-name encoding and face-name retrieval task blocks in the experimental condition), which were also separated with the ‘distractor’ task of visual attention (duration = 154 s). This sequence was repeated a total of four times. <i>Panel B: Phase 2</i>. This phase was identical to Phase 1, with two exceptions. Firstly, the experimental group was presented with novel face-name pairs to encode and retrieve. Secondly, prior to each of the four task blocks, all participants (in both the experimental and control groups) performance the 2-Back WM task (duration = 154 s/block). Performance on this task was the dependent variable of interest.</p

Results: Experiment 3.

<p>Overall, participants in the experimental group, who performed the Face-Name Learning and Recall task, performed significantly worse on the subsequent 2-Back Working Memory task than those in the control group, who performed the SART instead of the Face-Name task. This difference was significant at the first and second 2-Back Task blocks (but not at blocks 3 and 4). Error bars indicate SEM. * <i>P</i><0.05.</p