Preschoolers' aggression, affiliation, and social dominance relationships: An observational, longitudinal study

This study of 61 preschool children used an observational, longitudinal design to examine the degree to which social dominance relationships account for time-related change in rates of aggression and affiliation across a school year. Specific hypotheses reflected the view that, over time, behavioral function should change in accord with the stability of social dominance relationships, social norms, and on-going developmental processes. Results showed that change in rates of aggression was non-linear (i.e., increasing then decreasing over the year), that physical and verbal forms of aggression were associated with distinct longitudinal trajectories, and that these trajectories were related to rates of affiliation and visual regard. As predicted, social dominance accounted for significant variation in these patterns. Implications for theory, future research, and school practitioners are discussed.     

Using TD learning to simulate working memory performance in a model of the prefrontal cortex and basal ganglia

Delayed-response tasks (DRTs) have been used to assess working memory (WM) processes in human and nonhuman animals. Experiments have shown that the basal ganglia (BG) and dorsolateral prefrontal cortex (DLPFC) subserve DRT performance. Here, we report the results of simulation studies of a systems-level model of DRT performance. The model was trained using the temporal difference (TD) algorithm and uses an actor-critic architecture. The matrisomes of the BG represent the actor and the striosomes represent the critic. Unlike existing models, we hypothesize that the BG subserve the selection of both motor- and cognitive-related information in these tasks. We also assume that the learning of both processes is based on reward presentation. A novel feature of the model is the incorporation of delay-active neurons in the matrisomes, in addition to DLPFC. Another novel feature of the model is the subdivision of the matrisomal neurons into segregated winner-take-all (WTA) networks consisting of delay- versus transiently-active units.Our simulation model proposes a new neural mechanism to account for the occurrence of perseverative responses in WM tasks in striatal-, as well as in prefrontal damaged subjects. Simulation results also show that the model both accounts for the phenomenon of time shifting of dopamine phasic signals and the effects of partial reinforcement and reward magnitude on WM performance at both behavioral and neural levels. Our simulation results also found that the TD algorithm can subserve learning in delayed-reversal tasks.     

Hippocampal differentiation without recognition: an fMRI analysis of the contextual cueing task

A central role of the hippocampus is to consolidate conscious forms of learning and memory, while performance on implicit tasks appears to depend upon other structures. Recently, considerable debate has emerged about whether hippocampal-dependent tasks necessarily entail task awareness. In the contextual cueing task, repetition facilitation is implicit, but impaired in patients with amnesia. Whether the hippocampus alone or other MTL structures are required is unclear. Event-related functional magnetic resonance imaging revealed hippocampal activity that differentiates novel from repeated arrays. This pattern of results was observed without recognition of the repeating arrays. This finding provides support for the claim that the hippocampus is involved in processes outside the domain of conscious learning and memory.     

Some characteristics of inmates transferred from prison to a state mental hospital

Forty-four inmates transferred to a state mental hospital from a maximum-security prison and its adjacent trusty unit were compared with a randomly selected group of thirty-seven inmates from the same prison. Transferred inmates were found over-represented in terms of assignment to restrictive housing units, sentences of life or some form of life imprisonment, prior hospitalization in a state mental hospital, and conviction for murder. The two groups were not statistically different in terms of age, race, conduct, or prior incarcerations. Implications for planning psychological services in prisons are discussed.