Effects of Age on the Generalization and Incubation of Memory in the F344 Rat

Freezing (immobility) in the presence of aversive stimuli is a species-specific behavior that is used as an operational measure of fear. Conditioning of this response to discrete sensory stimuli and environmental context cues has been used as a tool to study the neuropsychology of memory dynamics and their development over the lifespan. Three age groups of F344 rats (3, 9, and 27 month) received tone–foot shock pairing (or tone only) in a distinctive chamber on two consecutive days. Separate subgroups of rats from each age group were then tested, at retention intervals of 1, 20, 40, or 60 days, for context-mediated fear in the environment in which they were trained, for generalization of the fear response to a novel chamber, and for fear of the tone. Beginning at day 20, the 27-month-old rats exhibited less freezing behavior than did younger rats when tested in the conditioning context. This age difference was a result of freezing behavior becoming progressively stronger with time in the two younger age groups, a phenomenon that has been referred to as memory incubation. Incubation of the contextual fear response was not detected in the old rats. In a novel context, all age groups exhibited significantly more freezing than did control animals. There was also pronounced incubation of this generalized freezing response, and the extent of incubation declined significantly with age. In the novel context, the freezing response to the tone was robust in all age groups and increased over time, in constant proportion to the degree of freezing elicited by the novel context itself, prior to tone onset. The fact that old animals are known to be relatively selectively impaired in forms of memory that depend on a functional hippocampus suggests a possible explanation for the reduced incubation effects seen in old rats; however, whether the increased expression of fear over time is mediated by a hippocampal-dependent memory consolidation process or whether it reflects a generalized increase in the gain of the circuitry mediating the fear response itself, remains to be determined.     

In defense of the advance specification hypothesis for motor control

Summary Choice reaction times often depend on the relations between the responses that are possible. Rosenbaum, Inhoff, and Gordon (1984) accounted for these effects with an advance specification (AS) hypothesis, according to which subjects prepare for a choice by creating a single motor program with the features shared by the response alternatives; after the choice signal is presented, subjects are assumed to fill in the features that were missing. In a recent article, Heuer (1987) argued that the AS hypothesis cannot account for a number of results that he has obtained. He suggested hat a better hypothesis relies on the idea of programming interactions (PI), according to which programs for alternative responses have mutual facilitative or inhibitory influences, depending on their similarity. Heuer (1987) reported an experiment that was partly consistent with the PI hypothesis and, as implied by him, inconsistent with the AS hypothesis. We show that the results of this experiment, as well as the results of Heuer's earlier experiments, are in fact consistent with the AS hypothesis and inconsistent with the PI hypothesis. We show in addition that there are a number of logical problems with the PI hypothesis which make it a less attractive model of choice than the AS hypothesis.Supported in part by National Science Foundation grant BNS-8710933 and a Research Career Development Award from the National Institutes of Health to the first author.     

Gender differences in response to spatial frequency and stimulus orientation

Male and female subjects with normal or corrected-to-normal visual acuity and less than .25 diopter of corrected astigmatism were asked to make contrast threshold judgments in response to both stationary and drifting grating displays. Results indicate a sex difference in contrast sensitivity as a function of spatial frequency for vertical and oblique orientations.     

Discourse after Early-Onset Hydrocephalus: Core Deficits in Children of Average Intelligence

A review of our studies of oral and written language in children with early-onset hydrocephalus suggests that hydrocephalus is associated with specific deficits in discourse as opposed to generalized linguistic deficit. It is proposed that the language skills that are impaired in hydrocephalus are those that require context to derive meaning, while those that are intact may function relatively independent of particular discourse contexts. This hypothesis was tested in two discourse studies comparing children with hydrocephalus of average verbal IQ to age-matched controls. Study 1 investigated narrative economy, syntactic complexity, and semantic content in the retellings of familiar and less familiar fairy tales. Despite producing quantities of story content similar to controls and using syntactic economy similar to controls, the hydrocephalus group produced less of the core semantic content of both familiar and less familiar tales. Study 2 investigated inferencing and figurative language understanding in a narrative comprehension task. Even when prior knowledge was controlled, the hydrocephalus group had difficulty making inferences and recalling factual information from the story. In contrast to their ability to understand idiomatic figurative expressions, the hydrocephalus group had difficulty interpreting novel figurative expressions. The results are compatible with the hypothesis that the core discourse deficits characteristic of children with hydrocephalus are concerned with computing meaning from context. Putative processing features underlying the proposed core discourse deficit are discussed.     

How Children with Head Injury Represent Real and Deceptive Emotion in Short Narratives

Narratives are not only about events, but also about the emotions those events elicit. Understanding a narrative involves not just the affective valence of implied emotional states, but the formation of an explicit mental representation of those states. In turn, this representation provides a mechanism that particularizes emotion and modulates its display, which then allows emotional expression to be modified according to particular contexts. This includes understanding that a character may feel an emotion but inhibit its display or even express a deceptive emotion. We studied how 59 school-aged children with head injury and 87 normally-developing age-matched controls understand real and deceptive emotions in brief narratives. Children with head injury showed less sensitivity than controls to how emotions are expressed in narratives. While they understood the real emotions in the text, and could recall what provoked the emotion and the reason for concealing it, they were less able than controls to identify deceptive emotions. Within the head injury group, factors such as an earlier age at head injury and frontal lobe contusions were associated with poor understanding of deceptive emotions. The results are discussed in terms of the distinction between emotions as felt and emotions as a cognitive framework for understanding other people's actions and mental states. We conclude that children with head injury understand emotional communication, the spontaneous externalization of real affect, but not emotive communication, the conscious, strategic modification of affective signals to influence others through deceptive facial expressions.     

The language dependence of accuracy

David Miller has demonstrated to the satisfaction of a variety of philosophers that the accuracy of false quantitative theories is language dependent (cf. Miller 1975). This demonstration renders the accuracy-based mode of comparison for such theories obsolete. The purpose of this essay is to supply an alternate basis for theory comparison which in this paper is deemed the knowledge-based mode of quantitative theory comparison. It is argued that the status of a quantitative theory as knowledge depends primarily on the soundness of the measurement procedure which produced the theory; such soundness is invariant, on my view, under Milleresque translations. This point is the basis for the linguistic invariance of knowledgelikeness. When the aim of science is not construed simply in terms of the truthlikeness or accuracy of theories, but in terms of the knowledge such theories embody, Miller's language dependence problem is overcome. One result of this analysis is that the possibility of objective scientific progress is restored, a possibility that Miller's analysis has prima facie defeated.I am grateful to Noretta Koertge for numerous comments and criticisms. Thanks are also due to David Miller for clarification of several points in his (1975). Veronica Barnes also made a number of pertinent observations.     

Procedural justice and preferential treatment: A brief review and comment

To put Singer’s (1992) work on relative deprivation and responses to preferential treatment in context, studies from a procedural justice perspective are reviewed. That review suggests that the psychological dynamics of preferential treatment are well accounted for by concepts derived from theories of procedural justice. It is thus argued that, to be parsimonious, Singer’s work is best conceptualized in procedural justice rather than relative deprivation terms.     

A longitudinal study of the self-concept of low-income youth

Children in grades five and six were interviewed in 1969 and a follow-up phase was conducted in 1978 using those children who had answered the 1969 phase and who were now out of high school. The purpose was to determine the stability of self-concept over a decade, and to investigate changes or differences that occurred within and between the groups over time. Data were analyzed using self-concept as the dependent variable. The independent variables measured in relation to self-concept were sex, race, and place of residence. Pearson product-moment correlations and paired t-tests indicated that the majority of youth undergo minimal changes during this age span.