Infant Memory Research Articles

Individual differences in generalization and imitation: what is the role of brain development?

Jones and Herbert describe research on deferred imitation and how this research reflects on the development of explicit memory in infancy. The article raises several interesting questions about how the medial temporal lobe memory system develops. In this commentary, I discuss some of the additional theoretical and empirical questions that are raised by the target article, and propose ways that these questions could be addressed in future research. Copyright © 2006 John Wiley & Sons, Ltd.

In war and famine: missionaries in China's Honan Province in the 1940's

In War and Famine uses a small key - the author's family letters and infant memories - to unlock a whole world. Erleen Christensen was a mish kid, the daughter of one of about two hundred missionaries who remained in China's Honan province during World War II and the civil war that followed. She provides an eye-witness account using letters, diaries, and personal accounts, many still in private hands, of one of the worst famines in China's history and the great devastation caused by advancing Japanese troops. Christensen chronicles how a religiously diverse group of Westerners tried to distribute famine relief and conduct humanitarian and educational missions in the face of rising nationalism, autonomy, and resistance to foreign intervention. While the principle narrator is Christensen's father, a young missionary doctor who, in a hair-raising journey, smuggled his family behind Japanese battlelines the year before Pearl Harbor, Christensen also tells the story of the many other missionaries who also sought to relieve the suffering of innocents caught in the crossfire of war and revolution - brave women who marched orphans through enemy lines, missionaries turned OSS intelligence officers, a Canadian Anglican cleric, a Swiss trainer of seeing-eye dogs, and a diplomat who travelled the province by bicycle.

Immunogenicity and Immunologic Memory of Meningococcal C Conjugate Vaccine in Premature Infants

Protein-polysaccharide conjugate vaccines against Neisseria meningitidis serogroup C were introduced into the U.K. routine immunization schedule in 1999. This study is the first to describe both persistence of antibody and evidence for induction of immune memory using meningococcal C conjugate (MCC) vaccine in preterm infants. Immunogenicity and induction of immunologic memory by as MCC vaccine was assessed in premature infants; 62 preterm and 60 term controls received MCC at the accelerated schedule (2, 3 and 4 months of age). A meningococcal C polysaccharide challenge was administered at 12 months of age. Both groups achieved similar protective titers after primary immunization that then waned significantly by 1 year of age. Postchallenge serum bactericidal activity was significantly lower in preterm infants (P = 0.03); 73% of preterm versus 88% of term controls achieved a 4-fold rise in serum bactericidal activity (P = 0.07). MCC vaccine is immunogenic and primes for immunologic memory in preterm infants. The decreased memory responses in these preterm infants in conjunction with waning clinical efficacy data for all U.K. infants suggest a role for a routine booster dose of vaccine in all infants receiving MCC, especially those born preterm.

Relational information processing of novel unrelated actions by infants

Declarative memory in infants is often assessed via deferred imitation. Not much is known about the information processing basis of the memory effect found in these experiments. While in the typical deferred imitation study the order of actions remains the same during demonstration and retrieval, in two experiments with n = 30 respective n = 25, 10- and 11-month-old infants, the order of novel unrelated actions in demonstration and retrieval was varied ( same, reversed, mixed). This allowed a separation of item-specific from item-relational information processing. In both experiments best memory performance was found when the order of target actions remained the same during encoding and recall, demonstrating that infants seem to rely on item-specific as well as item-relational information which has to be ad hoc constructed while encoding.

Cortisol, contingency learning, and memory in preterm and full-term infants

Cortisol plays an important role in learning and memory. An inverted-U shaped function has been proposed to account for the positive and negative effects of cortisol on cognitive performance and memory in adults, such that too little or too much impair but moderate amounts facilitate performance. Whether such relationships between cortisol and mental function apply to early infancy, when cortisol secretion, learning, and memory undergo rapid developmental changes, is unknown. We compared relationships between learning/memory and cortisol in preterm and full-term infants and examined whether a greater risk for adrenal insufficiency associated with prematurity produces differential cortisol-memory relationships. Learning in three-month old (corrected for gestational age) preterm and full-term infants was evaluated using a conjugate reinforcement mobile task. Memory was tested by repeating the same task 24h later. Salivary cortisol samples were collected before and 20 min after the presentation of the mobile. We found that preterm infants had lower cortisol levels and smaller cortisol responses than full-term infants. This is consistent with relative adrenal insufficiency reported in the neonatal period. Infants who showed increased cortisol levels from 0 to 20 min on Day 1 had significantly better memory, regardless of prematurity, than infants who showed decreased cortisol levels.

Babies' Baths, Babies' Remembrances: A Beng Theory of Development, History and Memory

AbstractMemory is often considered a monopoly of adults and older children: the younger the child, the less significant the capacity for recollecting. In Côte d'Ivoire, the Beng posit a radically different theory of cognitive development: adults say that the younger the child, the keener the memory. Moreover, such recall is of a specific sort – infants allegedly hold strong memories of a previous existence before birth (wrugbe), where people reportedly live harmoniously and there is never material want. Nevertheless, remembering this space of plenitude can prove agonizing for babies, making their hold on life precarious, and a distressing array of culturally shaped diseases threaten their survival. Protecting against illness requires an elaborate bathing, jewellery and make-up routine twice daily that begins at birth and continues for the first year. All this somatic activity is meant to lure the child fully and definitively into this world, and to counteract the strong call of the afterlife that adults say is created by the infant's own memories. Why iswrugbe, as purportedly remembered by infants, envisaged as a place of plenitude? And why is it located in an historically identified past? In this essay – which is necessarily to some extent speculative given its subject of infant memory – I explore the allegorical implications of the Beng afterlife, suggesting that the attribution of heightened infant memory of an idyllicwrugbeserves as an indirect critique of French colonialism and its aftermath. I conclude by discussing the ways in which memory and forgetting are mutually constructed, with the Beng model offering substantial support for the contention that reproduction in general – and babies in particular – are crucial to this intertwined process.

“Bloody Feet”

This article describes the brief analysis of an eight-year-old, born prematurely, who appeared to have body memories going back to the time he spent in an incubator in a neonatal intensive care unit. These memories were responsible later in his life for behavior that first appeared psychotic, but that eventually were understood to be a result of posttraumatic stress dating back to painful medical treatments and tests that he had to undergo as an infant. In a nine-session analysis conducted according to the tripartite therapy model, his past experiences were reconstructed and worked through. His bizarre behaviors stopped, and his development resumed along more normal lines. The author discusses the implications of this case for neonatal care, for child psychiatric diagnosis and intervention, and for the understanding of psychiatric symptoms that develop later in life. With the support of recent research, she also challenges some ideas of Freud and Mahler about the limits of memory in infants.

Detecting continuity violations in infancy: a new account and new evidence from covering and tube events

Recent research on infants' responses to occlusion and containment events indicates that, although some violations of the continuity principle are detected at an early age e.g. Aguiar, A., & Baillargeon, R. (1999). 2.5-month-old infants' reasoning about when objects should and should not be occluded. Cognitive Psychology 39, 116–157; Hespos, S. J., & Baillargeon, R. (2001). Knowledge about containment events in very young infants. Cognition 78, 207–245; Luo, Y., & Baillargeon, R. (in press). When the ordinary seems unexpected: Evidence for rule-based reasoning in young infants. Cognition; Wilcox, T., Nadel, L., & Rosser, R. (1996). Location memory in healthy preterm and full-term infants. Infant Behavior & Development 19, 309–323, others are not detected until much later e.g. Baillargeon, R., & DeVos, J. (1991). Object permanence in young infants: Further evidence. Child Development 62, 1227–1246; Hespos, S. J., & Baillargeon, R. (2001). Infants' knowledge about occlusion and containment events: A surprising discrepancy. Psychological Science 12, 140–147; Luo, Y., & Baillargeon, R. (2004). Infants' reasoning about events involving transparent occluders and containers. Manuscript in preparation; Wilcox, T. (1999). Object individuation: Infants' use of shape, size, pattern, and color. Cognition 72, 125–166. The present research focused on events involving covers or tubes, and brought to light additional examples of early and late successes in infants' ability to detect continuity violations. In Experiment 1, 2.5- to 3-month-old infants were surprised (1) when a cover was lowered over an object, slid to the right, and lifted to reveal no object; and (2) when a cover was lowered over an object, slid behind the left half of a screen, lifted above the screen, moved to the right, lowered behind the right half of the screen, slid past the screen, and finally lifted to reveal the object. In Experiments 2 and 3, 9- and 11-month-old infants were not surprised when a short cover was lowered over a tall object until it became fully hidden; only 12-month-old infants detected this violation. Finally, in Experiment 4, 9-, 12-, and 13-month-old infants were not surprised when a tall object was lowered inside a short tube until it became fully hidden; only 14-month-old infants detected this violation. A new account of infants' physical reasoning attempts to make sense of all of these results. New research directions suggested by the account are also discussed.

Familiarization, attention, and recognition memory in infancy: an event-related potential and cortical source localization study.

This study investigated the effects of familiarization and attention on event-related potential (ERP) correlates of recognition memory in infants. Infants 4.5, 6, or 7.5 months of age were either familiarized with 2 stimuli that were used during later testing or presented 2 stimuli that were not used later. Then, infants were presented with a recording of Sesame Street to elicit attention or inattention and presented with familiar and novel stimuli. A negative ERP component over the frontal and central electrodes (Nc) was larger in the preexposure familiarization group for novel- than for familiar-stimulus presentations, whereas the Nc did not differ for the group not receiving a familiarization exposure. Spatial independent components analysis of the electroencephelogram and "equivalent current dipole" analysis were used to examine putative cortical sources of the ERP components. The cortical source of Nc was located in areas of prefrontal cortex and anterior cingulate cortex.

Altered pathways for auditory discrimination and recognition memory in preterm infants

Preterm infants are at increased risk for cognitive disorders, including impairments in recognition memory. This study evaluated the effects of extreme prematurity on the neural pathway for auditory recognition memory using event‐related potentials (ERPs), a neurophysiological technique widely used in cognitive neuroscience. ERPs were recorded at term postmenstrual age in 35 preterm infants born at less than 32 weeks’gestation (22 males, 13 females; mean birthweight ([BW] 1154g, SD 374g) with normal brain ultrasounds, compared with 40 healthy, term newborns (1 to 3 days of age; 20 males, 20 females; BW 3672g, SD 420g). Because infants must be able to detect and discriminate sounds before recognizing them, two paradigms were used to assess these functions. The first evaluated the detection and discrimination of speech sounds. The second tested recognition of the mother's voice compared with a stranger's. Results showed significantly different patterns of speech sound discrimination in preterm infants compared with term infants. No evidence of maternal voice recognition was elicited from the preterm infants. No specific patterns of auditory detection or discrimination were associated with patterns of recognition memory, suggesting that the function of multiple neural pathways may have been altered in this group of preterm infants. These results provide a functional corroboration of magnetic resonance imaging studies showing effects of prematurity on early brain development, even among preterm infants with normal cranial ultrasonography.

Vaccination against encapsulated bacteria in humans: paradoxes

Infection with encapsulated bacteria can be prevented by vaccination with capsular polysaccharides, either plain or conjugated to a protein carrier. However, results concerning these vaccinations raise several paradoxes. Polysaccharides from encapsulated bacteria are generally considered to be T cell-independent antigens which are unable to trigger a T cell-dependent germinal center reaction, but, strikingly, anti-polysaccharide antibodies are often mutated in humans. Polysaccharide–protein conjugate vaccines are able to induce a true T cell-dependent memory response with a rise in antibody titers and a switch to high-affinity IgG antibodies in children below two years of age, but neither the plain nor the conjugated vaccine can induce memory in older infants and adults. We propose some explanations for these paradoxes based on our recent observation that humans display a circulating splenic marginal zone B-cell population with a pre-diversified immunoglobulin repertoire in charge of the immune response to T cell-independent antigens. Infection with encapsulated bacteria can be prevented by vaccination with capsular polysaccharides, either plain or conjugated to a protein carrier. However, results concerning these vaccinations raise several paradoxes. Polysaccharides from encapsulated bacteria are generally considered to be T cell-independent antigens which are unable to trigger a T cell-dependent germinal center reaction, but, strikingly, anti-polysaccharide antibodies are often mutated in humans. Polysaccharide–protein conjugate vaccines are able to induce a true T cell-dependent memory response with a rise in antibody titers and a switch to high-affinity IgG antibodies in children below two years of age, but neither the plain nor the conjugated vaccine can induce memory in older infants and adults. We propose some explanations for these paradoxes based on our recent observation that humans display a circulating splenic marginal zone B-cell population with a pre-diversified immunoglobulin repertoire in charge of the immune response to T cell-independent antigens. An antigen that can induce an antibody response without the help of Th cells. Bacterial capsular polysaccharides are TI antigens. An antigen that requires interaction between Th cells and B cells to induce an antibody response. Most protein antigens are T-dependent. T-dependent responses take place in germinal centers. Mutations occurring with high frequency in the variable (V) regions of rearranged immunoglobulin (Ig) genes. In most mammalian species, hypermutation is used for the generation of high-affinity antibodies in response to td antigens. It can also be used as a diversification process (e.g. in sheep) to generate the pre-immune antibody repertoire. The process whereby IgM+ B cells switch, after antigen encounter, to the expression of a different isotype (or class, e.g. IgG, IgA or IgE) by replacing its Ig heavy chain constant region gene. Specialized structures that form transiently in secondary lymphoid organs (e.g. spleen, lymph nodes) during immune responses to TD antigens. Hypermutation, isotype switch, affinity maturation and memory B cell formation take place within these structures. Refers to the increase in the affinity of antibodies produced during the course of T cell-dependent responses. This process results from the selection within germinal centers of B cells harboring mutated receptors with higher affinity for the antigen. A B lymphocyte that has been stimulated by a TD antigen, and has differentiated into a class-switched, long-lived, non-secreting B cell-carrying mutated Ig. Memory B cells, when re-exposed to the immunizing antigen, are responsible for generating faster responses with higher affinity. A primary immunodeficiency characterized by normal or increased serum IgM levels and low or absent IgG, IgA and IgE serum levels, owing to a defect in isotype switch.

Altered pathways for auditory discrimination and recognition memory in preterm infants

Preterm infants are at increased risk for cognitive disorders, including impairments in recognition memory. This study evaluated the effects of extreme prematurity on the neural pathway for auditory recognition memory using event-related potentials (ERPs), a neurophysiological technique widely used in cognitive neuroscience. ERPs were recorded at term postmenstrual age in 35 preterm infants born at less than 32 weeks' gestation (22 males, 13 females; mean birthweight ([BW] 1154g, SD 374g) with normal brain ultrasounds, compared with 40 healthy, term newborns (1 to 3 days of age; 20 males, 20 females; BW 3672g, SD 420g). Because infants must be able to detect and discriminate sounds before recognizing them, two paradigms were used to assess these functions. The first evaluated the detection and discrimination of speech sounds. The second tested recognition of the mother's voice compared with a stranger's. Results showed significantly different patterns of speech sound discrimination in preterm infants compared with term infants. No evidence of maternal voice recognition was elicited from the preterm infants. No specific patterns of auditory detection or discrimination were associated with patterns of recognition memory, suggesting that the function of multiple neural pathways may have been altered in this group of preterm infants. These results provide a functional corroboration of magnetic resonance imaging studies showing effects of prematurity on early brain development, even among preterm infants with normal cranial ultrasonography.

Development of flexible visual recognition memory in human infants

Research using the visual paired comparison task has shown that visual recognition memory across changing contexts is dependent on the integrity of the hippocampal formation in human adults and in monkeys. The acquisition of contextual flexibility may contribute to the change in memory performance that occurs late in the first year of life. To assess this skill, the images are presented on a background of one colour during familiarization and on a different coloured background during the recognition test. Our research showed that recognition memory is impaired by a change in context at 6 and 12 months of age but is unaffected at 18 and 24 months of age. The findings are discussed in relation to hippocampal development and the proposed developmental step in memory at 9-10 months of age.

Meningococcal conjugate vaccine in the UK: an update

In November, 1999, the UK became the first country to incorporate a meningococcal serogroup C conjugate (MCC) vaccine into a routine paediatric immunisation schedule. 1 Anon Vaccination programme for group C meningococcal infection is launched. CDR Weekly. 1999; 9: 261-264 PubMed Google Scholar Within a year, about 90% of infants and 85% of adolescents were immunised—a remarkable achievement. The Department of Health was compelled to give the MCC vaccine for several reasons. First, meningococcus serogroup C infected 1500 children and adolescents and killed 150 of them every year in the UK. 1 Anon Vaccination programme for group C meningococcal infection is launched. CDR Weekly. 1999; 9: 261-264 PubMed Google Scholar Second, on the basis of technology that had successfully linked proteins to Haemophilus influenza type b (Hib) and pneumococcal polysaccharides, the capsular polysaccharide of meningococcus was linked to tetanus toxoid and an avirulent diphtheria toxin. 2 Jennings HJ Lugowski C Immunochemistry of groups A, B, and C meningococcal polysaccharide-tetanus toxoid conjugates. J Immunol. 1981; 127: 1011-1018 PubMed Google Scholar Protein conjugation of bacterial polysaccharides converted a T-cell-independent immune response to a T-cell-dependent response, resulting in increased antibody titres and polysaccharide-specific immunological memory in infants and young children. 3 MacDonald NE Halperin SA Law BJ Forrest B Danzig LE Granoff DM Induction of immunologic memory by conjugated vs plain meningococcal C polysaccharide vaccine in toddlers. JAMA. 1998; 280: 1685-1689 Crossref PubMed Scopus (200) Google Scholar Third, the MCC vaccine was safe and immunogenic in infants and children. 4 MacLennan JM Shackley F Heath PT et al. Safety, immunogenicity, and induction of immunologic memory by a serogroup C meningococcal conjugate vaccine in infants. JAMA. 2000; 283: 2795-2801 Crossref PubMed Scopus (171) Google Scholar , 5 Lieberman JM Chiu SS Wong VK et al. Safety and immunogenicity of a serogroups A/C Neisseria meningitides oligosaccharide-protein conjugate vaccine in young children. JAMA. 1996; 275: 1499-1503 Crossref PubMed Google Scholar Fourth, the vaccine reduced bacterial carriage in the upper respiratory tract, which suggested that the vaccine could provide herd immunity. 6 Zhang Q Lakshman R Burkinshaw R et al. Primary and booster mucosal immune responses to meningococcal group A and C conjugate and polysaccharide vaccines administered to university students in the United Kingdom. Infect Immun. 2001; 69: 4337-4341 Crossref PubMed Scopus (36) Google Scholar Effectiveness of meningococcal serogroup C conjugate vaccine 4 years after introductionThe meningococcal serogroup C conjugate (MCC) vaccine programme in England has successfully controlled the incidence of serogroup C disease, as a result of high short-term vaccine effectiveness and substantial herd immunity. However, the long-term effectiveness of the vaccine remains unknown. We assessed surveillance data from the 4 years since introduction of the programme. Vaccine effectiveness remained high in children vaccinated in the catch-up campaign (aged 5 months to 18 years). However, for children vaccinated in the routine infant immunisation programme, the effectiveness of the MCC vaccine fell to low levels after only 1 year. Full-Text PDF

The Onset of Working Memory in Infants

AbstractWe used an optimized configuration of the delayed‐response task to explore the ability of young infants to remember which of 2 locations was correct across 12 trials after a 1‐ to 2‐sec delay. Performance improved with age, particularly after 5.5 months. These findings suggest an onset of appreciable working memory for many infants in the middle of their 6th month.

Effect of sighs on breathing memory and dynamics in healthy infants.

Deep inspirations (sighs) play a significant role in altering lung mechanical and airway wall function; however, their role in respiratory control remains unclear. We examined whether sighs act via a resetting mechanism to improve control of the respiratory regulatory system. Effects of sighs on system variability, short- and long-range memory, and stability were assessed in 25 healthy full-term infants at 1 mo of age [mean 36 (range 28-57) days] during quiet sleep. Variability was examined using moving-window coefficient of variation, short-range memory using autocorrelation function, and long-range memory using detrended fluctuation analysis. Stability was examined by studying the behavior of the attractor with use of phase-space plots. Variability of tidal volume (VT) and minute ventilation (VE) increased during the initial 15 breaths after a sigh. Short-range memory of VT decreased during the 50 breaths preceding a sigh, becoming uncorrelated (random) during the 10-breath presigh window. Short-range memory increased after a sigh for the entire 50 breaths compared with the randomized data set and for 20 breaths compared with the presigh window. Similar, but shorter duration, changes were noted in VE. No change in long-range memory was seen after a sigh. Coefficient of variation and range of points located within a defined attractor segment increased after a sigh. Thus control of breathing in healthy infants shows long-range stability and improvement in short-range memory and variability after a sigh. These results add new evidence that the role of sighs is not purely mechanical.

Iron deficiency alters auditory recognition memory in newborn infants of diabetic mothers.

Infants of diabetic mothers (IDMs) are at risk for perinatal brain iron deficiency that may target the developing hippocampus. The objective of this study was to evaluate hippocampally based recognition memory and infant development in IDMs with suspected brain iron deficiency (BID; cord ferritin </=34 microg/L) compared with IDMs with sufficient brain iron stores (BIS; cord ferritin >34 microg/L) using event-related potentials (ERPs). ERPs assessed neonatal auditory cortical responses to sounds and auditory recognition memory in response to the mother's voice compared with a stranger's voice. Thirty-two newborn IDMs had cord serum ferritin concentrations and provided neonatal ERP data (n = 23) and/or blinded 1 y developmental assessments (n = 28). Auditory cortical responses to speech and nonspeech sounds were similar in the BID and BIS groups. In the maternal voice recognition paradigm, peak latencies were shorter in the BID group than in the BIS group. Infants in the BIS group displayed a significant negative slow wave for the strangers' voices compared with the mothers' voices, whereas the BID group did not. Higher cord ferritin concentrations were correlated with larger negative slow waves at the right temporal (T4) electrode site. At 1 y of age, motor development was slower in the BID group than in the BIS group. IDMs suspected to have BID demonstrated impaired neonatal auditory recognition memory and lower psychomotor developmental scores at 1 y of age than IDMs with BIS. These impairments map onto areas of the developing brain known to be vulnerable to iron deficiency.

Long‐term memory for music: infants remember tempo and timbre

We show that infants' long-term memory representations for melodies are not just reduced to the structural features of relative pitches and durations, but contain surface or performance tempo- and timbre-specific information. Using a head turn preference procedure, we found that after a one week exposure to an old English folk song, infants preferred to listen to a novel folk song, indicating that they remembered the familiarized melody. However, if the tempo (25% faster or slower) or instrument timbre (harp vs. piano) of the familiarized melody was changed at test, infants showed no preference, indicating that they remembered the specific tempo and timbre of the melodies. The results are consistent with an exemplar-based model of memory in infancy rather than one in which structural features are extracted and performance features forgotten.

Working Memory in Infancy

Working Memory in Infancy

Infant memory development: Implications for childhood amnesia

When asked to recall their earliest personal memories, most children and adults have virtually no recollection of their infancy or early childhood. This phenomenon is commonly referred to as childhood amnesia. The fate of our earliest memories has puzzled psychologists for over 50 years, particularly in light of the importance of early experience in human development. Empirical research has shown that infants can both learn and remember very early in development, making the ultimate fate of early memories even more mysterious. The theoretical explanation of childhood amnesia outlined here relies on age-related changes in encoding, retention, and retrieval that occur during infancy and early childhood. Data obtained using a host of different memory tasks support the conclusion that quantitative changes in these basic memory processes can account for the decline of childhood amnesia during the third or fourth year of life.