Familiar Stimuli Research Articles

Fixation durations on familiar items are longer due to attenuation of exploration.

Previous studies have shown that fixations on familiar stimuli tend to be longer than on unfamiliar stimuli, theorized to be a result of retrieval of information from memory. We hypothesize that extended fixations are due to a lesser need to explore an already familiar stimulus. Participant's gaze was tracked as they tried to encode or retrieve a familiar face displayed either alone or alongside other unfamiliar faces. Regardless of the memory task (encoding\retrieval), longer fixation durations were observed when a single familiar face was presented alone, and not when presented among unfamiliar ones. Thus, fixations were not prolonged when it was possible to explore other, unfamiliar stimuli. We conclude that prolonged fixations on familiar stimuli reflect a lesser need to explore an already familiar percept. The results underscore how memory representations influence active sensing, yielding fresh insights into efficient deployment of attention resources. We conclude that fixation durations could be used in applied memory detection tests, preferably together with other measures and when the familiar stimulus is presented alone.

Chronic high-dose testosterone disrupts social cognition and enhances social dominance in male long-Evans rats

While increased aggression is the most consistent behavioral effect of anabolic androgenic steroid (AAS) abuse, its cause remains unclear. AAS may promote aggression by disrupting social behaviors which maintain dominance hierarchies. To model AAS abuse, we treated male rats with chronic high-dose testosterone and tested social recognition, social learning, and competitive and aggressive dominance. Rats received daily injections s.c. of testosterone (7.5 mg/kg) or vehicle (n = 8/group). We tested social recognition by measuring investigation of a novel or familiar stimulus animal, social learning with the social transmission of food preference (STFP) test, aggressive dominance with the tube test, and competitive dominance with a food competition task. For social recognition, testosterone-treated rats did not prefer the novel stimulus rat (72.8 ± 9.3 s) over the familiar rat (68.8 ± 8.0 s, N.S.) rat. In the STFP test, testosterone-treated rats did not show a significant preference for the demonstrated flavor (59.9 ± 9.4 %, N.S.) compared with controls (70.1 ± 5.4 %, p < 0.05). In the tube test, testosterone did not increase the number of rounds won. However, when the testosterone-treated rat won, they were more likely to be lighter than their vehicle-treated opponent, χ2(1,N = 63) = 6.56, p < 0.05, Φ2 = 0.32. In the food competition task, testosterone-treated subjects won more often (48 rounds) than their vehicle-treated partners (15 rounds; p < 0.05). These results suggest that AAS disrupt recognizing and learning from the social hierarchy and increase the likelihood of challenging it. Collectively, these behavioral changes may contribute to AAS-induced aggression.

Evaluating the effects of continuous pitch and speech tempo modifications on perceptual speaker verification performance by familiar and unfamiliar listeners

A study was conducted to evaluate the effects of continuous pitch and speech tempo modifications on perceptual speaker verification performance by familiar and unfamiliar naive listeners. Speech recordings made by twelve male, native-French speakers were organised into three groups of four (two in-set, one out-of-set). Two groups of listeners participated, where one group was familiar with one in-set speaker group, while both groups were unfamiliar with the remaining in- and out-of-set speaker groups. Pitch and speech tempo were continuously modified, such that the first 75% of words spoken were modified with percentages of modification beginning at 100% and decaying linearly to 0%. Pitch modifications began at ± 600 cents, while speech tempo modifications started with word durations scaled 1:2 or 3:2. Participants evaluated a series of “go/no-go” task trials, where they were presented a modified speech recording with a face and tasked to respond as quickly as possible if they judged the stimuli to be continuous. The major findings revealed listeners overcame higher percentages of modification when presented familiar speaker stimuli. Familiar listeners outperformed unfamiliar listeners when evaluating continuously modified speech tempo stimuli, however, this effect was speaker-specific for pitch modified stimuli. Contrasting effects of modification direction were also observed. The findings suggest pitch is more useful to listeners when verifying familiar and unfamiliar voices.

Pop-out effects revisited: Within-array category pop-out and novel pop-out effects with picture stimuli.

Pop-out effects occur when a novel or different stimulus is presented in the context of an array of otherwise familiar or similar stimuli. The effect has been studied using words extensively, but little evidence exists for humans relating to nonverbal stimuli. Although the finding has implications for understanding features of stimuli that capture attention, contradictory findings exist, and previous paradigms have limited applicability to real world situations. Given this, an experiment employed a novel procedure to investigate whether category pop-out effects, where one item is drawn from a different category to the others, could be obtained with pictorial stimulus array. It also investigated whether pop-out effects could be generated with a single continuous pre-exposure procedure, as would be experienced in a naturalistic setting, or whether they were the results of biases introduced by the repetitive pre-exposure procedures, typically used in such studies. The latter finding would undermine the use of such findings to support ecologically-valid models of attention. Both of these questions were answered in the affirmative: category pop-out effects were obtained using picture stimuli; and such effects were obtained with a single continuous pre-exposure. Further development this novel procedure may allow exploration of evolutionary and neurological aspects of selective attention effects.

EEG-based responses of patients with disorders of consciousness and healthy controls to familiar and non-familiar emotional videos

ObjectiveTo investigate the differences in the brain responses of healthy controls (HC) and patients with disorders of consciousness (DOC) to familiar and non-familiar audiovisual stimuli and their consistency with the clinical progress. MethodsEEG responses of 19 HC and 19 patients with DOC were recorded while watching emotionally-valenced familiar and non-familiar videos. Differential entropy of the EEG recordings was used to train machine learning models aimed to distinguish brain responses to stimuli type. The consistency of brain responses with the clinical progress of the patients was also evaluated. ResultsModels trained using data from HC outperformed those for patients. However, the performance of the models for patients was not influenced by their clinical condition. The models were successfully trained for over 75% of participants, regardless of their clinical condition. More than 75% of patients whose CRS-R scores increased post-study displayed distinguishable brain responses to both stimuli. ConclusionsResponses to emotionally-valenced stimuli enabled modelling classifiers that were sensitive to the familiarity of the stimuli, regardless of the clinical condition of the participants and were consistent with their clinical progress in most cases. SignificanceEEG responses are sensitive to familiarity of emotionally-valenced stimuli in HC and patients with DOC.

Trustworthiness evaluation of workers in critical facilities using electroencephalography-based acquaintance test

This study emphasized the critical importance of prioritizing workers' trustworthiness in safeguarding critical facilities from the potential harm caused by insiders' betrayal. By noting the limitations of existing physical protection systems in critical facilities, this study showed that effectively characterizing and detecting malicious insider activity can be possible by observing immediate brain physiological reactions to specific stimuli. Based on the finding, a novel approach using electroencephalography (EEG)-based acquaintance tests was introduced to objectively assess ’a level of suspicion between colleagues by measuring their brain responses when he/she is exposed to familiar and unfamiliar stimuli. If a person claims falsely about one's acquaintance, the model assumes he/she has malicious or suspicious intent by violating the reporting obligation. The experiment was designed with a relatively short time of monitoring of less than 2 min and with a simple EEG headband device called MUSE. The experiment is to analyze whether the model could provide reliable prediction of disguised acquaintance avoiding complex preparation process. Averaged N170 peak analysis indicated that MUSE provided adequate signal characteristics to classify acquaintance. Also, a machine learning-based subject-wise classification model showed adequate capability to differentiate the EEG signals of acquaintances from unknowns. The final prediction combined multiple single-trial classification results, correctly detected the participant's acquaintance about 94.1 % of the cases, with similar performance when strangers were presented. The results indicated the possibility of using biosignal to enhance security culture and mitigate insider threats in critical facilities, by providing an indication of behavior that disregards security policies and procedures.

Oxidative stress as a potential mechanism linking gestational phthalates exposure to cognitive development in infancy

BackgroundGestational exposure to phthalates, endocrine disrupting chemicals widely used in consumer products, has been associated with poor recognition memory in infancy. Oxidative stress may represent one pathway linking this association. Hence, we examined whether exposure to phthalates was associated with elevated oxidative stress during pregnancy, and whether oxidative stress mediates the relationship between phthalate exposure and recognition memory. MethodsOur analysis included a subset of mother-child pairs enrolled in the Illinois Kids Development Study (IKIDS, N = 225, recruitment years 2013–2018). Concentrations of 12 phthalate metabolites were quantified in 2nd trimester urine samples. Four oxidative stress biomarkers (8-isoprostane-PGF2α, 2,3-dinor-5,6-dihydro-8-isoPGF2α, 2,3-dinor-8-isoPGF2α, and prostaglandin-F2α) were measured in 2nd and 3rd trimester urine. Recognition memory was evaluated at 7.5 months, with looking times to familiar and novel stimuli recorded via infrared eye-tracking. Novelty preference (proportion of time looking at a novel stimulus when paired with a familiar one) was considered a measure of recognition memory. Linear mixed effect models were used to estimate associations between monoethyl phthalate (MEP), sum of di(2-ethylhexyl) phthalate metabolites (ΣDEHP), sum of di(isononyl) phthalate metabolites (ΣDINP), and sum of anti-androgenic phthalate metabolites (ΣAA) and oxidative stress biomarkers. Mediation analysis was performed to assess whether oxidative stress biomarkers mediated the effect of gestational phthalate exposure on novelty preference. ResultsThe average maternal age at delivery was 31 years and approximately 50 % of participants had a graduate degree. A natural log unit increase in ΣAA, ΣDINP, and ΣDEHP was associated with a statistically significant increase in 8-isoPGF2α, 2,3-dinor-5,6-dihydro-8-isoPGF2α, and 2,3-dinor-8-isoPGF2α. The association was greatest in magnitude for ΣAA and 2,3-dinor-5,6-dihydro-8-isoPGF2α (β = 0.45, 95 % confidence interval = 0.14, 0.76). The relationship between ΣAA, ΣDINP, ΣDEHP, and novelty preference was partially mediated by 2,3-dinor-8-isoPGF2α. ConclusionsGestational exposure to some phthalates is positively associated with oxidative stress biomarkers, highlighting one mechanistic pathway through which these chemicals may impair early cognitive development.

Persistent activity during working memory maintenance predicts long-term memory formation in the human hippocampus.

Working memory (WM) and long-term memory (LTM) are often viewed as separate cognitive systems. Little is known about how these systems interact when forming memories. We recorded single neurons in the human medial temporal lobe while patients maintained novel items in WM and completed a subsequent recognition memory test for the same items. In the hippocampus, but not in the amygdala, the level of WM content-selective persistent activity during WM maintenance was predictive of whether the item was later recognized with high confidence or forgotten. By contrast, visually evoked activity in the same cells was not predictive of LTM formation. During LTM retrieval, memory-selective neurons responded more strongly to familiar stimuli for which persistent activity was high while they were maintained in WM. Our study suggests that hippocampal persistent activity of the same cells supports both WM maintenance and LTM encoding, thereby revealing a common single-neuron component of these two memory systems.

Maternal oral probiotic use is associated with decreased breastmilk inflammatory markers, infant fecal microbiome variation, and altered recognition memory responses in infants-a pilot observational study.

Early life gut microbiomes are important for brain and immune system development in animal models. Probiotic use has been proposed as a strategy to promote health via modulation of microbiomes. In this observational study, we explore if early life exposure to probiotics via the mother during pregnancy and lactation, is associated with decreased inflammation in breastmilk, maternal and infant microbiome variation, and altered infant neurodevelopmental features. Exclusively breastfeeding mother-infant dyads were recruited as part of the "Mothers and Infants Linked for Healthy Growth (MILk) Study." Probiotic comparison groups were defined by exposure to maternal probiotics (NO/YES) and by timing of probiotic exposure (prenatal, postnatal, total). C-reactive protein (CRP) and IL-6 levels were determined in breastmilk by immunoassays, and microbiomes were characterized from 1-month milk and from 1- and 6-month infant feces by 16S rDNA sequencing. Infant brain function was profiled via electroencephalogram (EEG); we assessed recognition memory using event-related potential (ERP) responses to familiar and novel auditory (1 month) and visual (6 months) stimuli. Statistical comparisons of study outcomes between probiotic groups were performed using permutational analysis of variance (PERMANOVA) (microbiome) and linear models (all other study outcomes), including relevant covariables as indicated. We observed associations between probiotic exposure and lower breastmilk CRP and IL-6 levels, and infant gut microbiome variation at 1- and 6-months of age (including higher abundances of Bifidobacteria and Lactobacillus). In addition, maternal probiotic exposure was associated with differences in infant ERP features at 6-months of age. Specifically, infants who were exposed to postnatal maternal probiotics (between the 1- and 6-month study visits) via breastfeeding/breastmilk, had larger differential responses between familiar and novel visual stimuli with respect to the late slow wave component of the EEG, which may indicate greater memory updating potential. The milk of mothers of this subgroup of infants had lower IL-6 levels and infants had different 6-month fecal microbiomes as compared to those in the "NO" maternal probiotics group. These results support continued research into "Microbiota-Gut-Brain" connections during early life and the role of pre- and postnatal probiotics in mothers to promote healthy microbiome-associated outcomes in infants.

Sex-Specific Effects of Early Life Unpredictability on Hippocampal and Amygdala Responses to Novelty in Adolescents.

Unpredictable childhood experiences are an understudied form of early life adversity that impacts neurodevelopment in a sex-specific manner. The neurobiological processes by which exposure to early-life unpredictability impacts development and vulnerability to psychopathology remain poorly understood. The present study investigates the sex-specific consequences of early-life unpredictability on the limbic network, focusing on the hippocampus and the amygdala. Participants included 150 youth (54% female). Early life unpredictability was assessed using the Questionnaire of Unpredictability in Childhood (QUIC). Participants engaged in a task-fMRI scan between the ages of 8 and 17 (223 total observations) measuring BOLD responses to novel and familiar scenes. Exposure to early-life unpredictability associated with BOLD contrast (novel vs. familiar) in a sex-specific manner. For males, but not females, higher QUIC scores were associated with lower BOLD activation in response to novel vs. familiar stimuli in the hippocampal head and amygdala. Secondary psychophysiological interaction (PPI) analyses revealed complementary sex-specific associations between QUIC and condition-specific functional connectivity between the right and left amygdala, as well as between the right amygdala and hippocampus bilaterally. Exposure to unpredictability in early life has persistent implications for the functional operations of limbic circuits. Importantly, consistent with emerging experimental animal and human studies, the consequences of early life unpredictability differ for males and females. Further, impacts of early-life unpredictability were independent of other risk factors including lower household income and negative life events, indicating distinct consequences of early-life unpredictability over and above more commonly studied types of early life adversity.

Ventrolateral prefrontal cortex in macaques guides decisions in different learning contexts.

Flexibly adjusting our behavioral strategies based on the environmental context is critical to maximize rewards. Ventrolateral prefrontal cortex (vlPFC) has been implicated in both learning and decision-making for probabilistic rewards, although how context influences these processes remains unclear. We collected functional neuroimaging data while rhesus macaques performed a probabilistic learning task in two contexts: one with novel and another with familiar visual stimuli. We found that activity in vlPFC encoded rewards irrespective of the context but encoded behavioral strategies that depend on reward outcome (win-stay/lose-shift) preferentially in novel contexts. Functional connectivity between vlPFC and anterior cingulate cortex varied with behavioral strategy in novel learning blocks. By contrast, connectivity between vlPFC and mediodorsal thalamus was highest when subjects repeated a prior choice. Furthermore, pharmacological D2-receptor blockade altered behavioral strategies during learning and resting-state vlPFC activity. Taken together, our results suggest that multiple vlPFC-linked circuits contribute to adaptive decision-making in different contexts.

Meaningfulness and Familiarity Expand Visual Working Memory Capacity

Visual working memory is traditionally studied using abstract, meaningless stimuli. Although studies using such simplified stimuli have been insightful in understanding the mechanisms of visual working memory, they also potentially limit our ability to understand how people encode and store conceptually rich and meaningful stimuli in the real world. Recent studies have demonstrated that meaningful and familiar visual stimuli that connect to existing knowledge are better remembered than abstract colors or shapes, indicating that meaning can unlock additional working memory capacity. These findings challenge current models of visual working memory and suggest that its capacity is not fixed but depends on the type of information that is being remembered and, in particular, how that information connects to preexisting knowledge.

Reduced expression of fMRI subsequent memory effects with increasing severity across the Alzheimer’s disease risk spectrum

Abstract In functional magnetic resonance imaging (fMRI) studies, episodic memory is commonly investigated with the subsequent memory paradigm in which brain activity is recorded during encoding and analyzed as a function of subsequent remembering and forgetting. Impaired episodic memory is common in individuals with or at risk for Alzheimer’s disease (AD), but only few studies have reported subsequent memory effects in AD or its risk states like mild cognitive impairment (MCI). One reason for this might be that subsequent memory responses may be blunted in AD or MCI and thus less likely to manifest in fMRI signal differences. Here, we used Bayesian model selection of single-subject fMRI general linear models (GLMs) for a visual novelty and memory encoding experiment to compare the model performance of categorical and parametric subsequent memory models as well as memory-invariant models in a clinical cohort (N = 468) comprising healthy controls (HC) as well as individuals with subjective cognitive decline (SCD), MCI, and AD, plus healthy relatives of AD patients (AD-rel). We could replicate the previously reported superiority of parametric subsequent memory models over categorical models (Soch, Richter, Schütze, Kizilirmak, Assmann, Knopf, et al., 2021) in the HC and also in the SCD and AD-rel groups. However, memory-invariant models outperformed any model assuming subsequent memory effects in the MCI and AD groups. In the AD group, we additionally found substantially lower model preference for models assuming novelty compared to models not differentiating between novel and familiar stimuli. Our results suggest that voxel-wise memory-related fMRI activity patterns in AD and also MCI should be interpreted with caution and point to the need for additional or alternative approaches to investigate memory function.

Prefrontal neuronal dynamics in the absence of task execution

Prefrontal cortical activity represents stimuli in working memory tasks in a low-dimensional manifold that transforms over the course of a trial. Such transformations reflect specific cognitive operations, so that, for example, the rotation of stimulus representations is thought to reduce interference by distractor stimuli. Here we show that rotations occur in the low-dimensional activity space of prefrontal neurons in naïve male monkeys (Macaca mulatta), while passively viewing familiar stimuli. Moreover, some aspects of these rotations remain remarkably unchanged after training to perform working memory tasks. Significant training effects are still present in population dynamics, which further distinguish correct and error trials during task execution. Our results reveal automatic functions of prefrontal neural circuits allow transformations that may aid cognitive flexibility.

Adapting and facilitating responses in mouse somatosensory cortex are dynamic and shaped by experience

Sensory adaptation is the process whereby brain circuits adjust neuronal activity in response to redundant sensory stimuli. Although sensory adaptation has been extensively studied for individual neurons on timescales of tens of milliseconds to a few seconds, little is known about it over longer timescales or at the population level. We investigated population-level adaptation in the barrel field of the mouse somatosensory cortex (S1BF) using invivo two-photon calcium imaging and Neuropixels recordings in awake mice. Among stimulus-responsive neurons, we found both adapting and facilitating neurons, which decreased or increased their firing, respectively, with repetitive whisker stimulation. The former outnumbered the latter by 2:1 in layers 2/3 and 4; hence, the overall population response of mouse S1BF was slightly adapting. We also discovered that population adaptation to one stimulus frequency (5Hz) does not necessarily generalize to a different frequency (12.5Hz). Moreover, responses of individual neurons to repeated rounds of stimulation over tens of minutes were strikingly heterogeneous and stochastic, such that their adapting or facilitating response profiles were not stable across time. Such representational drift was particularly striking when recording longitudinally across 8-9days, as adaptation profiles of most whisker-responsive neurons changed drastically from one day to the next. Remarkably, repeated exposure to a familiar stimulus paradoxically shifted the population away from strong adaptation and toward facilitation. Thus, the adapting vs. facilitating response profile of S1BF neurons is not a fixed property of neurons but rather a highly dynamic feature that is shaped by sensory experience across days.

Persistent activity during working memory maintenance predicts long-term memory formation in the human hippocampus.

Working Memory (WM) and Long-Term Memory (LTM) are often viewed as separate cognitive systems. Little is known about how these systems interact when forming memories. We recorded single neurons in the human medial temporal lobe while patients maintained novel items in WM and a subsequent recognition memory test for the same items. In the hippocampus but not the amygdala, the level of WM content-selective persist activity during WM maintenance was predictive of whether the item was later recognized with high confidence or forgotten. In contrast, visually evoked activity in the same cells was not predictive of LTM formation. During LTM retrieval, memory-selective neurons responded more strongly to familiar stimuli for which persistent activity was high while they were maintained in WM. Our study suggests that hippocampal persistent activity of the same cell supports both WM maintenance and LTM encoding, thereby revealing a common single-neuron component of these two memory systems.

Familiarity Alters the Bandwidth of Perceptual Awareness.

Results from paradigms like change blindness and inattentional blindness indicate that observers are unaware of numerous aspects of the visual world. However, intuition suggests that perceptual experience is richer than these results indicate. Why does it feel like we see so much when the data suggests we see so little? One possibility stems from the fact that experimental studies always present observers with stimuli that they have never seen before. Meanwhile, when forming intuitions about perceptual experience, observers reflect on their experiences with scenes with which they are highly familiar (e.g., their office). Does prior experience with a scene change the bandwidth of perceptual awareness? Here, we asked if observers were better at noticing alterations to the periphery in familiar scenes compared with unfamiliar scenes. Here, we found that observers noticed changes to the periphery more frequently with familiar stimuli. Signal detection theoretic analyses revealed that when observers are unfamiliar with a stimulus, they are less sensitive at noticing (d') and are more conservative in their response criterion (c). Taken together, these results suggest that prior knowledge expands the bandwidth of perceptual awareness. It should be stressed that these results challenge the widely held idea that prior knowledge fills in perception. Overall, these findings highlight how prior knowledge plays an important role in determining the limits of perceptual experience and is an important factor to consider when attempting to reconcile the tension between empirical observation and personal introspection.

Glutamatergic signaling from melanin-concentrating hormone-producing neurons: A requirement for memory regulation, but not for metabolism control.

Melanin-concentrating hormone-producing neurons (MCH neurons), found mainly in the lateral hypothalamus and surrounding areas, play essential roles in various brain functions, including sleep and wakefulness, reward, metabolism, learning, and memory. These neurons coexpress several neurotransmitters and act as glutamatergic neurons. The contribution of glutamate from MCH neurons to memory- and metabolism-related functions has not been fully investigated. In a mouse model, we conditionally knocked out Slc17a6 gene, which encodes for vesicular glutamate transporter 2 (vGlut2), in the MCH neurons exclusively by using two different methods: the Cre recombinase/loxP system and in vivo genome editing using CRISPR/Cas9. Then, we evaluated several aspects of memory and measured metabolic rates using indirect calorimetry. We found that mice with MCH neuron-exclusive vGlut2 ablation had higher discrimination ratios between novel and familiar stimuli for novel object recognition, object location, and three-chamber tests. In contrast, there was no significant change in body weight, food intake, oxygen consumption, respiratory quotient, or locomotor activity. These findings suggest that glutamatergic signaling from MCH neurons is required to regulate memory, but its role in regulating metabolic rate is negligible.

How material sensory properties and individual differences influence the haptic aesthetic appeal of visually presented stimuli

Touch plays a crucial role for humans. Despite its centrality in sensory experiences, the field of haptic aesthetics is underexplored. So far, existing research has revealed that preferences in the haptic domain are related to stimulus properties and the Gestalt laws of grouping. Additionally, haptic aesthetics is influenced by top-down processes, e.g., stimulus familiarity, and is likely to be modulated by personality and expertise. To further our understanding of these influences on haptic aesthetic appraisal, the current study investigated the imagined haptic aesthetic appeal of visually presented material surfaces, considering the role of haptic expertise, Need for touch, personality traits. The results revealed a positive influence of familiarity, simplicity, smoothness, warmth, lightness, dryness, slipperiness and a negative influence of complexity on individuals' aesthetic responses. While the study failed to support the predicted influence of Need for touch and haptic expertise on aesthetic responses, results did reveal an influence of openness to experience, conscientiousness and neuroticism. Despite the limitations related to the indirect stimuli presentation (vision only), the findings contribute to the relatively unexplored role of bottom-up and top-down features in haptic aesthetics that might be incorporated into the design of consumers’ products to better meet their preferences.

Adult-born granule cells modulate CA2 network activity during retrieval of developmental memories of the mother.

Adult-born granule cells (abGCs) project to the CA2 region of the hippocampus, but it remains unknown how this circuit affects behavioral function. Here, we show that abGC input to the CA2 of adult mice is involved in the retrieval of remote developmental memories of the mother. Ablation of abGCs impaired the ability to discriminate between a caregiving mother and a novel mother, and this ability returned after abGCs were regenerated. Chemogenetic inhibition of projections from abGCs to the CA2 also temporarily prevented the retrieval of remote mother memories. These findings were observed when abGCs were inhibited at 4-6 weeks old, but not when they were inhibited at 10-12 weeks old. We also found that abGCs are necessary for differentiating features of CA2 network activity, including theta-gamma coupling and sharp wave ripples, in response to novel versus familiar social stimuli. Taken together, these findings suggest that abGCs are necessary for neuronal oscillations associated with discriminating between social stimuli, thus enabling retrieval of remote developmental memories of the mother by their adult offspring.