The development of landmarks in spatial memory: the role of differential experience

To assess how differential experience with objects in a spatial array might serve to establish relative landmarks within the array, first and fifth graders learned models of a town and farm under two conditions. In a homogeneous condition, all elements in the array were visited an equal number of times. In a landmark condition, the relative landmark status of an element was established by distributing the same total number of visits unequally across the elements. The effects of such landmarks on spatial memory were assessed both in reconstructions of the entire array and by pairwise distance estimations. The landmark condition led to a general improvement in spatial recall accuracy as well as providing a relative landmark within the array to help organize the space. The results suggest that different levels of experience (controlling for overall experience and object salience) can establish elements as relative landmarks in spatial memory. Although there was clear developmental improvement in spatial memory, the specific landmark effects were similar for both first and fifth graders.     

Neural functions of calcineurin in synaptic plasticity and memory

Major brain functions depend on neuronal processes that favor the plasticity of neuronal circuits while at the same time maintaining their stability. The mechanisms that regulate brain plasticity are complex and engage multiple cascades of molecular components that modulate synaptic efficacy. Protein kinases (PKs) and phosphatases (PPs) are among the most important of these components that act as positive and negative regulators of neuronal signaling and plasticity, respectively. In these cascades, the PP protein phosphatase 2B or calcineurin (CaN) is of particular interest because it is the only Ca(2+)-activated PP in the brain and a major regulator of key proteins essential for synaptic transmission and neuronal excitability. This review describes the primary properties of CaN and illustrates its functions and modes of action by focusing on several representative targets, in particular glutamate receptors, striatal enriched protein phosphatase (STEP), and neuromodulin (GAP43), and their functional significance for synaptic plasticity and memory.     

Path dependent preferences: The role of early experience and biased search in preference development

What is the role of early experiences in shaping preferences? What are the mechanisms by which such early encounters influence the way preferences are formed? In this research, we examine the impact of the entry position and favorability of initial (and ongoing) experiences on preference development. We predict that the starting point will heavily influence which particular region people select from initially, and favorableness of early experiences and myopic search will both limit their search to that particular region. Across four studies, we find that when the initial experiences are favorable, subjects engage in lower levels of search, experience only a narrow breadth of possible alternatives, demonstrate less ongoing experimentation, and have a reduction in the amount of preference development.     

Socio-cultural selection and the sculpting of the human genome: Cultures’ directional forces on evolution and development

This paper argues for culture as a significant determinant of the modern human genome. As progress in the fields of genetics and evolutionary biology have gained greater insights into evolutionary process, aspects of classical proposals explaining how phenotypic responses to environmental experience could make their way into the genotype have returned in new guises. Recent proposals recognize environmental context as a key source of genetic variation by directly altering selection pressures to mask and unmask adaptive value of expressed traits, by reorganizing the combination and expression of genes during ontogeny to provide novel variants for selection, and by influencing developmental trajectories through epigenetic systems acutely sensitive to ontogenetic contexts. The emergence of a robust human socio-cultural niche, shielding humans from more proximate evolutionary pressures that marked our ancestral evolution, has arguably provided the strongest directive force on modern human evolution. Language is discussed as an exemplar of a cultural niche with a powerful self-organizing dynamic and the potential to dramatically alter the human genome.     

Neural representations in human spatial memory

Ekstrom et al. report the responses of single neurons recorded from the brains of human subjects performing a spatial navigation task in virtual reality. They found cells encoding the subject's current location, view and destination. These data, and related findings in animals, directly reveal some of the representations underlying spatial cognition. They highlight the potential for cognitive psychology and systems neuroscience to combine to provide a neuronal-level understanding of human behaviour.     

Dissociable spatial memory systems revealed by typical and atypical human development

Rodent lesion studies have revealed the existence of two causally dissociable spatial memory systems, localized to the hippocampus and striatum that are preferentially sensitive to environmental boundaries and landmark objects, respectively. Here we test whether these two memory systems are causally dissociable in humans by examining boundary‐ and landmark‐based memory in typical and atypical development. Adults with Williams syndrome (WS)—a developmental disorder with known hippocampal abnormalities—and typical children and adults, performed a navigation task that involved learning locations relative to a boundary or a landmark object. We found that boundary‐based memory was severely impaired in WS compared to typically‐developing mental‐age matched (MA) children and chronological‐age matched (CA) adults, whereas landmark‐based memory was similar in all groups. Furthermore, landmark‐based memory matured earlier in typical development than boundary‐based memory, consistent with the idea that the WS cognitive phenotype arises from developmental arrest of late maturing cognitive systems. Together, these findings provide causal and developmental evidence for dissociable spatial memory systems in humans.     

Early experience,relative plasticity,and social development

This paper examines the roles of early experience and relative plasticity in the development of social behavior in animals and humans. It is concluded that (1) long-term effects of early experience variables can be found in the animal and human literature; (2) there are age differences in the relative susceptibility to environmental influences during development; and (3) the power of environmental events and the buffering ability of the organism are crucial variables affecting the outcome of organism-environment interactions.     

Early experience,relative plasticity,and cognitive development

This paper examines the roles of early experience and relative plasticity in the cognitive development of animals and humans. It is concluded that: (a) long-term effects of early experience variables can be found in the animal and human literature; (b) there are age differences in the relative susceptibility to environmental influences during development; (c) despite qualitative differences in the mechanisms underlying the dependent variables studied in the early experience literature, there are generally applicable principles involving the intensity of environmental stimulation and the buffering ability of the organism which are crucial in affecting the outcome of organism-environment interactions; (d) a variety of models is required to adequately describe the mediation of environmental effects in the early experience literature.     

Measuring transactive memory systems in the field: scale development and validation

This study describes the development and validity testing of a field measure of transactive memory systems. Transactive memory systems are especially important for teams designed to leverage members' expertise, but field research has lagged because there are no adequate measures of the construct. The author developed and tested a 15-item scale in a laboratory sample of 124 teams, a field sample of 64 Master of Business Administration consulting teams, and a field sample of 27 teams from technology companies. Results from the present study demonstrate that the scale is internally consistent, related to alternative measures and hypothesized causes and effects, and unrelated to theoretically distinct constructs, providing evidence of convergent, criterion-related, and discriminant validity. Suggestions for improving the scale, future validity testing, and possible boundary conditions are discussed.     

Thinking about the future early in life: The role of relational memory

The constructive episodic simulation hypothesis suggests that we imagine possible future events by flexibly recombining details of past experiences to produce novel scenarios. Here we tested this hypothesis by determining whether episodic future thinking is related to relational memory ability during the preschool years. Children (3- to 5-year-olds) were asked to remember a past event and imagine a possible future event using an adapted version of the recombination paradigm. Relational learning and inference were assessed using a task adapted from the neuroimaging literature. The results show that preschoolers were able to describe both past and possible future events; however, they produced more specific episodic details in relation to past events relative to future events. Episodic future thinking performance was correlated with performance on the relational inference task, consistent with the idea that the ability to flexibly recombine relational knowledge is critical in episodic future thinking.     

Stress effects in the hippocampus: synaptic plasticity and memory

It is now well-documented that exposures to uncontrollable (inescapable and unpredictable) stress in adulthood can have profound effects on brain and behavior. Converging lines of evidence from human and animal studies indicate that stress interferes with subsequent performances on a variety of hippocampal-dependent memory tasks. Animal studies further revealed that stress impedes ensuing induction of long-term potentiation (LTP) in the hippocampus. Because the hippocampus is important for key aspects of memory formation and because LTP has qualities congruent to an information storage mechanism, it is hypothesized that stress-induced modifications in hippocampal plasticity contribute to memory impairments associated with stress. Recent studies provide evidence that the amygdala, a structure important in stress- and emotion-related behaviors, plays a necessary role in the emergence of stress-associated changes in hippocampal LTP and memory. Early life stress also alters hippocampal plasticity and memory in a manner largely consistent with effects of adult stress exposure. This review focuses on endocrine-system-level mechanisms of stress effects in the hippocampus, and how stress, by altering the property of hippocampal plasticity, can subsequently influence hippocampal memory.     

The role of memory and integration in early time concepts

The nature of 5- to 8-year-old childrens ' time concepts was examined by analyzing two possible explanations for the greater difficulty children demonstrate in comparing durations that differ in beginning times as compared to those that differ in ending times. The explanations were (a) poor recall of beginnings as compared to endings due to their lower salience, (b) difficulty in integrating information from both points and reliance on endings only due to their greater salience. The subjects were 630 boys and girls from kindergarten to second grade. The children were presented with a series of two lights in different orders and combinations and were asked to compare order of beginnings and endings, and duration of the two lights. Results contradicted the memory explanation. In addition, repetitious questioning about order of one point (beginning or ending) appeared to have shifted children's attention from that point to the complementary point. Possible sources of children's failure to integrate beginning and end points when comparing durations were discussed.     

The role of crawling and walking experience in infant spatial memory

This research explored infants' use of place learning and cue learning in a locomotor task across the transition from crawling to walking. Novice and expert crawling and walking infants were observed in a novel locomotor task-finding a hidden goal location in a large space. In Experiment 1, infants were tested with distal landmarks. Infants with fewer than 6 weeks of experience, either crawling or walking, could not find the goal location. All infants with more locomotor experience were more successful. Learning did not transfer across the transition to walking. In Experiment 2, novice and expert crawlers and walkers were tested with a direct landmark. Again, novice crawlers and walkers with fewer than 6 weeks of experience could not find the goal, whereas those with more experience could. Taken together, these findings suggest that infants' spatial learning is inextricably linked to mode of locomotion.     

The role of source memory in older adults' recollective experience

Younger adults' "remember" judgments are accompanied by better memory for the source of an item than "know" judgments. Furthermore, remember judgments are not merely associated with better memory for individual source features but also with bound memory for multiple source features. However, older adults, independent of their subjective memory experience, are generally less likely to "bind" source features to an item and to each other in memory (i.e., the associative deficit). In two experiments, we tested whether memory for perceptual source features, independently or bound, is also the basis for older adults' remember responses or if their associative deficit leads them to base their responses on other types of information. The results suggest that retrieval of perceptual source features, individually or bound, forms the basis for younger but not for older adults' remember judgments even when the overall level of memory for perceptual sources is closely equated (Experiment 1) and when attention is explicitly directed to the source information at encoding (Experiment 2).     

Complex prospective memory: development across the lifespan and the role of task interruption

Prospective memory (PM) reflects the product of cognitive processes associated with the formation, retention, delayed initiation, and execution of intentions. It has been proposed that developmental changes in PM across the lifespan are heavily dependent upon the developmental trajectory of executive control functions. This study is the first to apply a complex PM task to children, young adults, and older adults. The procedure allows for the assessment of each of the 4 phases of PM. During intention execution, the authors additionally manipulated whether participants had to actively interrupt attention to the current 'ongoing' task in order to switch to the execution of the next intended task. Group differences mirroring inverted U-shaped functions were observed in those phases conceptualized as relying on executive control (intention formation, initiation, and execution). Age differences in intention execution were substantially greater when active task interruption was necessary. The current study provides the first evidence of growth and decline of complex PM across the lifespan and suggests that the degree of inhibitory control needed to succeed in the task may be one factor underlying this development.     

The role of landmarks and boundaries in the development of spatial memory

It has been suggested that learning an object's location relative to (1) intramaze landmarks and (2) local boundaries is supported by parallel striatal and hippocampal systems, both of which rely upon input from a third system for orientation. However, little is known about the developmental trajectories of these systems' contributions to spatial learning. The present study tested 5- and 7-year-old children and adults on a water maze-like task in which all three types of cue were available. Participants had to remember the location of an object hidden in a circular bounded environment containing a moveable intramaze landmark and surrounded by distal cues. Children performed less accurately than adults, and showed a different pattern of error. While adults relied most on the stable cue provided by the boundary, children relied on both landmark and boundary cues similarly, suggesting a developmental increase in the weighting given to boundary cues. Further, adults were most accurate in coding angular information (dependent on distal cues), whereas children were most accurate in coding distance, suggesting a developing ability to use distal cues to orient. These results indicate that children as young as 5 years use boundary, intramaze landmark, and distal visual cues in parallel, but that the basic accuracy and relative weighting of these cues changes during subsequent development.