A model of episodic memory: Mental time travel along encoded trajectories using grid cells

The definition of episodic memory includes the concept of mental time travel: the ability to re-experience a previously experienced trajectory through continuous dimensions of space and time, and to recall specific events or stimuli along this trajectory. Lesions of the hippocampus and entorhinal cortex impair human episodic memory function and impair rat performance in tasks that could be solved by retrieval of trajectories. Recent physiological data suggests a novel model for encoding and retrieval of trajectories, and for associating specific stimuli with specific positions along the trajectory. During encoding in the model, external input drives the activity of head direction cells. Entorhinal grid cells integrate the head direction input to update an internal representation of location, and drive hippocampal place cells. Trajectories are encoded by Hebbian modification of excitatory synaptic connections between hippocampal place cells and head direction cells driven by external action. Associations are also formed between hippocampal cells and sensory stimuli. During retrieval, a sensory input cue activates hippocampal cells that drive head direction activity via previously modified synapses. Persistent spiking of head direction cells maintains the direction and speed of the action, updating the activity of entorhinal grid cells that thereby further update place cell activity. Additional cells, termed arc length cells, provide coding of trajectory segments based on the one-dimensional arc length from the context of prior actions or states, overcoming ambiguity where the overlap of trajectory segments causes multiple head directions to be associated with one place. These mechanisms allow retrieval of complex, self-crossing trajectories as continuous curves through space and time.     

Curriculum bias in standardized tests of reading decoding

This study examined overlap between four basal reading programs and the phonetic analysis subtest of three standardized achievement measures. Raw scores, percentages of items correct, grade equivalents, and percentile scores were computed for a hypothetical student who had mastered all grapheme-phoneme correspondences taught at each grade level. The results indicated that (a) programs differed in the number and sequence of phonics skills taught; (b) percentile and grade-equivalent scores differed across programs at each grade level for a given test; and (c) the proportion of grade-equivalent scores falling at or above expected grade levels differed across tests for a given program (range of 29%–71%). The implications for selecting and interpreting standardized measures of reading decoding are discussed.     

The effects of word class on children's reading and spelling

Children's oral language functioning has been shown to be affected by word class (i.e., content vs. noncontent words). The present study reveals comparable effects on children's written language performance. In spelling and reading, third and fifth graders show faster and more accurate responses to nouns and verbs than to noncontent words of matched length and frequency. Further, when the children's performance is examined in relation to level of reading skill, it is found that the less-skilled readers exhibit a greater content/noncontent differential than do the more skilled readers. The results are discussed with reference to differential access for the two word classes and its implication for both oral and written language functioning.     

Effects of felt adequacy and opportunity to reciprocate on help seeking

This experiment was prompted by the belief that felt inadequacy and lack of opportunity to reciprocate act as deterrents to help seeking when help is needed. The experiment was conducted on 56 freshmen by modifying Greenberg and Shapiro's physical disability paradigm. Subjects were told that they could not meet the quota on a manual task but had done well (poorly) for persons similarly handicapped (by arm in sling). Later they learned that the electricity would be shut off in 2 hr (15 min), making it possible (impossible) to help the visually handicapped fellow worker later on a visual task. The hypothesis that felt inadequacy inhibits help seeking was fully supported, while the corresponding hypothesis regarding lack of opportunity to reciprocate received only partial support. There were no sex differences. The relevance of these data for embarrassment theory is discussed.     

Social isolation as a punishment procedure: a controlled study

Contingent social isolation was investigated as a punishment procedure for the disruptive behavior of emotionally disturbed children in a classroom setting. The methodological limitations of previous studies were outlined, and alternatives adopted. Within a reversal and multiple baseline design, contingent social isolation was found to be an effective and relatively specific punisher. By introducing a new observation procedure, “pseudo-timeout”, it was determined that the punishing effect of social isolation was not attributable to observation artifact. A means for resolving the terminological confusion in the present use of timeout and social isolation was recommended.     

Effect of achievement motivation on cognitive control adaptations

Previous research addressing motivational effects on cognitive control adaptations primarily manipulated external rewards. In the present study, we examined whether achievement motivation, reflecting intrinsic motivation, modulates cognitive control adaptations. In each of two experiments, students were divided into a high achievement motivation group (HAM; Experiment 1: N?=?36; Experiment 2: N?=?39) and a low achievement motivation group (LAM; Experiment 1: N?=?30; Experiment 2: N?=?39) on the basis of the Achievement Motivation Scale. Cognitive control adaptations were assessed by sequential congruency effects (SCEs) in Flanker tasks. Using a standard Flanker task in Experiment 1 and examining response times, the HAM but not LAM participants showed evidence of cognitive control adaptations. Because SCEs in a standard Flanker task may reflect lower-level, bottom-up processes rather than cognitive control adaptations, we used an adapted version of the Flanker task in Experiment 2 that controlled for the potential influence of such processes. Experiment 2 again revealed evidence of SCEs in the HAM but not LAM participants. These results suggest that cognitive control adaptions may be modulated by achievement motivation. Such potential modulation could be taken into account when evaluating results of previous and future fundamental and applied studies on cognitive control adaptations.     

The emotional geographies of education: Beginning a conversation

While emotional geography is a burgeoning field of inquiry, to our knowledge no emotional geographies of education exist. Educational research on space and place largely ignores emotionality. In this special issue we begin to rectify this situation through the development of what we call socio-cultural-spatial analyses of education and emotion.     

Theoretical accounts of spatial learning: A neurobiological view (commentary on Pearce, 2009)

Theories of learning have historically taken, as their starting point, the assumption that learning processes have universal applicability. This position has been argued on grounds of parsimony, but has received two significant challenges: first, from the observation that some kinds of learning, such as spatial learning, seem to obey different rules from others, and second, that some kinds of learning take place in processing modules that are separate from each other. These challenges arose in the behavioural literature but have since received considerable support from neurobiological studies, particularly single neuron studies of spatial learning, confirming that there are indeed separable (albeit highly intercommunicating) processing modules in the brain, which may not always interact (within or between themselves) according to classic associative principles. On the basis of these neurobiological data, reviewed here, it is argued that rather than assuming universality of associative rules, it is more parsimonious to assume sets of locally operating rules, each specialized for a particular domain. By this view, although almost all learning is associative in one way or another, the behavioural-level characterization of the rules governing learning may vary depending on which neural modules are involved in a given behaviour. Neurobiological studies, in tandem with behavioural studies, can help reveal the nature of these modules and the local rules by which they interact.