Dreaming and bereavement

Bereavement dreams provide an important, though seldom mentioned or recognized, component of the grief process. As the unconscious presses for recognition of the pain and extent of the loss, dream material is presented to help the bereft move to a new and integrative life position. Religious symbols present themselves to give the grieving a new sense of themselves as individuals and an expanding view of the world. Grief therapists have generally ignored this important component of the grief process, and as a result, little significant clinical research has been done. A comprehensive picture of bereavement will not be developed until increased attention is given to this important area.     

More than mere mimicry? The influence of emotion on rapid facial reactions to faces

Within a second of seeing an emotional facial expression, people typically match that expression. These rapid facial reactions (RFRs), often termed mimicry, are implicated in emotional contagion, social perception, and embodied affect, yet ambiguity remains regarding the mechanism(s) involved. Two studies evaluated whether RFRs to faces are solely nonaffective motor responses or whether emotional processes are involved. Brow (corrugator, related to anger) and forehead (frontalis, related to fear) activity were recorded using facial electromyography (EMG) while undergraduates in two conditions (fear induction vs. neutral) viewed fear, anger, and neutral facial expressions. As predicted, fear induction increased fear expressions to angry faces within 1000 ms of exposure, demonstrating an emotional component of RFRs. This did not merely reflect increased fear from the induction, because responses to neutral faces were unaffected. Considering RFRs to be merely nonaffective automatic reactions is inaccurate. RFRs are not purely motor mimicry; emotion influences early facial responses to faces. The relevance of these data to emotional contagion, autism, and the mirror system-based perspectives on imitation is discussed.     

A nitric oxide-independent and beta-adrenergic receptor-sensitive form of metaplasticity limits theta-frequency stimulation-induced LTP in the hippocampal CA1 region

The induction of long-term potentiation (LTP) and long-term depression (LTD) at excitatory synapses in the hippocampus can be strongly modulated by patterns of synaptic stimulation that otherwise have no direct effect on synaptic strength. Likewise, patterns of synaptic stimulation that induce LTP or LTD not only modify synaptic strength but can also induce lasting changes that regulate how synapses will respond to subsequent trains of stimulation. Collectively known as metaplasticity, these activity-dependent processes that regulate LTP and LTD induction allow the recent history of synaptic activity to influence the induction of activity-dependent changes in synaptic strength and may thus have an important role in information storage during memory formation. To explore the cellular and molecular mechanisms underlying metaplasticity, we investigated the role of metaplasticity in the induction of LTP by υ-frequency (5-Hz) synaptic stimulation in the hippocampal CA1 region. Our results show that brief trains of υ-frequency stimulation not only induce LTP but also activate a process that inhibits the induction of additional LTP at potentiated synapses. Unlike other forms of metaplasticity, the inhibition of LTP induction at potentiated synapses does not appear to arise from activity-dependent changes in NMDA receptor function, does not require nitric oxide signaling, and is strongly modulated by β-adrenergic receptor activation. Together with previous findings, our results indicate that mechanistically distinct forms of metaplasticity regulate LTP induction and suggest that one way modulatory transmitters may act to regulate synaptic plasticity is by modulating metaplasticity.     

Priming and trial spacing in extinction: effects on extinction performance, spontaneous recovery, and reinstatement in appetitive conditioning

Previous research in this laboratory suggests that priming of the conditional stimulus (CS) in short-term memory may play a role in the trial-spacing effects in appetitive conditioning. For example, a nonreinforced presentation of a CS 60 s before a reinforced trial with the same CS produced slower acquisition than a CS presentation that occurred 240 s before the reinforced trial. The results were consistent with the self-generated priming mechanism proposed by Wagner (e.g., Wagner 1978, 1981). The present experiments extended the earlier work by examining the effects of trial spacing in extinction rather than acquisition. After conditioning with a mixture of intertrial intervals (ITIs), rats received extinction with ITIs of 60 or 240 s, longer or shorter values, or different ways of “chunking” extinction trials in time. Although trial spacing produced effects on extinction performance that were consistent with our previous research on acquisition, there were few long-term differences in spontaneous recovery or in reinstatement. Short ITIs in extinction appear to affect extinction performance more than they affect extinction learning. Mechanisms of trial spacing in conditioning and extinction are discussed.     

Reconsolidation reconsidered

Some of the considerations that led to a consolidation interpretation of retrograde amnesia (RA), which states that RA results from the disruption of memory processing and storage when neural activity is interrupted by a brain insult, are reviewed here. The time-dependent gradient of memory loss (i.e., new memories are more vulnerable to amnesia than old memories) that characterizes RA seemed to fit nicely with the notion of a cascade of cellular events occurring during the immediate post-acquisition period that would transform a labile representation into a more stable form (i.e., consolidate the memory). However, a variety of observations came to challenge the storage-disruption model, and among these was the finding of amnesia for old but reactivated memories. A recent study by Nader, Schafe, and LeDoux (2000) provides an important analytic extension of the work on “reconsolidation” by showing that inhibition of protein synthesis in the lateral and basal nuclei of the amygdala immediately following the reactivation of old memory will induce retrograde amnesia. We offer a retrieval-oriented conceptualization to account for the temporal gradient and the “reconsolidation” phenomena.     

Detection thresholds for intensity increments in a single harmonic of synthetic Japanese macaque (Macaca fuscata) monkey coo calls

There is evidence that Japanese macaques (Macaca fuscata) are extremely sensitive to dynamic changes in the relative amplitudes of coo call harmonics during discrimination tests. To verify this evidence using more controlled stimulus configurations, the authors examined threshold sensitivity of macaque monkeys to amplitude increments added to the standard level of coo call harmonics. Psychophysical threshold determination methods paralleled those used previously to determine macaque sensitivity to amplitude increments added to vowel-like stimuli. Variation was detectable although thresholds were elevated relative to those obtained with vowel-like stimuli in another investigation (C. G. Le Prell, A. J. Niemiec, & D. B. Moody, 2001). This elevation was probably a function of natural amplitude modulation in the standard stimuli.     

Validity of the Five Minute Speech Sample in families with infants from low-income backgrounds

Caregivers of 169 infants from low-income and multi-ethnic backgrounds completed the Five Minute Speech Sample (FMSS). Validity of the FMSS was supported by demonstrating significant associations among positive and negative affect dimensions of the FMSS and other indices of the caregiving environment.     

Diminished testing benefits in young adults with attention-deficit hyperactivity disorder

Memory retrieval has been shown to enhance the long-term retention of tested material; however, recent research suggests that limiting attention during retrieval can decrease the benefits of testing memory. The present study examined whether testing benefits are reduced in young adults with attention-deficit hyperactivity disorder (ADHD). College students with and without ADHD read three short prose passages, each followed by a free recall test, a restudy period or a distractor task. Two days later participants recalled the passages. Although participants without ADHD did not show a significant benefit of testing over restudying, testing did produce recall benefits relative to not taking a test. These testing benefits were diminished in participants with ADHD, who did not show any advantage of testing over either restudying or no test. The absence of testing benefits in the ADHD group is likely due in part to decreased recall on the initial test. These findings have implications for improving educational practices among individuals with ADHD and also speak to the need to examine individual differences in the effectiveness of testing as a learning strategy.