Age-related differences in recognition memory for items and associations: Contribution of individual differences in working memory and metamemory

Ability to form new associations between unrelated items is particularly sensitive to aging, but the reasons for such differential vulnerability are unclear. In this study, we examined the role of objective and subjective factors (working memory and beliefs about memory strategies) on differential relations of age with recognition of items and associations. Healthy adults (N = 100, age 21 to 79) studied word pairs, completed item and association recognition tests, and rated the effectiveness of shallow (e.g., repetition) and deep (e.g., imagery or sentence generation) encoding strategies. Advanced age was associated with reduced working memory (WM) capacity and poorer associative recognition. In addition, reduced WM capacity, beliefs in the utility of ineffective encoding strategies, and lack of endorsement of effective ones were independently associated with impaired associative memory. Thus, maladaptive beliefs about memory in conjunction with reduced cognitive resources account in part for differences in associative memory commonly attributed to aging. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Less is more: the effects of very brief versus clearly visible exposure

This study compared the effects of exposure to masked and unmasked phobic stimuli on phobic behavior. Participants were identified as spider-phobic with a questionnaire and a Behavioral Avoidance Test (BAT) with a live tarantula (N = 101). One week later, they were administered one of three types of exposure: very brief (25 ms) or clearly visible (120 ms) images of spiders, or very brief images of flowers. They reported ratings of subjective distress just before and after these exposures, and engaged in the BAT again thereafter. Two weeks later, 57 participants returned for a follow-up BAT. The results indicated a double dissociation between the effects of very brief and clearly visible exposure: the former reduced avoidance of the tarantula and did not affect distress, whereas the latter increased distress but did not affect avoidance. The behavioral effect lasted for two weeks. These findings suggest that avoidance of a feared object can be reduced without full conscious awareness. The theoretical implications are discussed.     

Genes and the parsing of cognitive processes

Now that the human genome has been sequenced there exists the possibility of identifying specific genes that affect human cognition. In this article, recent studies that have found associations between common gene variants and specific cognitive processes are reviewed. Several principles for evaluating this new field are also discussed. The interpretation of results is far from simple because a single gene can affect multiple processes, multiple genes can impact on a single process, and multiple cognitive processes are intercorrelated. In general, functional neuroimaging has been a more sensitive assay of cognitive processing than behavioral measures used alone, although there are important caveats regarding its use. Replicated findings so far involve associations between a COMT polymorphism and prefrontally-based executive functions and neurophysiology, and a BDNF polymorphism and medial-temporal-cortex based declarative memory processes. Implicit in this review is a concern that many of the cognitive paradigms used evolved for purposes well outside those described here. As such it may be necessary to view cognition in novel ways, based on constraints imposed by genomics and neurobiology, in order to increase the effect size of genotypic influences on cognition.     

Age differences in the organization of emotion knowledge: effects involving valence and time frame

Older and younger adults attend to and remember emotion information differently. The present study builds on this work by investigating age-related differences in the schematic organization of emotion knowledge. Younger and older adults reported on their experiences of positive and negative affect, both today and in general. Of primary interest was judgment speed as a function of matches (e.g., positive-positive) or mismatches (e.g., negative-positive) in valence and time frame across consecutive trials. Older adults exhibited stronger valence-related priming effects and weaker time-frame-related priming effects, relative to younger adults. Results remained significant when controlling for individual differences in speed, speed variability, motor priming, temperament, and life satisfaction. The discussion focuses on the manner in which age differences in the schematic organization of emotion knowledge might contribute to age differences in the self-concept, affective processing, and emotional experience.     

Rapid induction of specific associative behavioral memory by stimulation of the nucleus basalis in the rat

Hypothesized circuitry enabling behavioral memory formation can be tested by its direct activation in the absence of normal experience. Neuromodulation via the cortical release of acetylcholine by the nucleus basalis (NB) is hypothesized to be sufficient to induce specific, associative behavioral memory. Previously, we found that tone paired with stimulation of the nucleus basalis (NBs) for 3000 trials over 15 days induced such memory, supporting the hypothesis. However, as standard associative memory can be established much more rapidly, we asked whether NB-induced memory develops rapidly. Adult male Sprague-Dawley rats, trained and tested in the same calm, waking state, were divided into Paired (n=5) and control (n=4) groups, each of which received a single session of 200 trials of an 8.0 kHz conditioned stimulus (CS) either paired with NBs or with unpaired presentation of NBs. Respiration, cardiac activity, and evoked potentials in the primary auditory cortex (ACx) were recorded. Memory and its degree of specificity were assessed 24 h later by presenting tones of various frequencies (1-15 kHz) in the absence of NBs to yield behavioral frequency generalization gradients. Behavioral responses to test tones consisted of interruption of ongoing respiration and changes in heart rate. Post-training behavioral generalization gradients exhibited response peaks centered on the CS frequency for the Paired group alone. Tone evoked potentials from the ACx also developed CS-specific plasticity. The findings indicate that NB induction of specific behavioral associative memory, like normal memory, can develop rapidly and is accompanied by specific cortical plasticity, supporting the view that NB engagement during normal learning produces memory.     

The nucleus basalis and memory codes: auditory cortical plasticity and the induction of specific, associative behavioral memory

Receptive field (RF) plasticity develops in the primary auditory cortex (ACx) when a tone conditioned stimulus (CS) becomes associated with an appetitive or aversive unconditioned stimulus (US). This prototypical stimulus-stimulus (S-S) association is accompanied by shifts of frequency tuning of neurons toward or to the frequency of the CS such that the area of best tuning of the CS frequency is increased in the tonotopic representation of the ACx. RF plasticity has all of the major characteristics of behavioral associative memory: it is highly specific, discriminative, rapidly induced, consolidates (becomes stronger and more specific over hours to days) and can be retained indefinitely (tested to two months). Substitution of nucleus basalis (NB) stimulation for a US induces the same associative RF plasticity, and this requires the engagement of muscarinic receptors in the ACx. Pairing a tone with NB stimulation actually induces specific, associative behavioral memory, as indexed by post-training frequency generalization gradients. The degree of acquired behavioral significance of sounds appears to be encoded by the number of neurons that become retuned in the ACx to that acoustic stimulus, the greater the importance, the greater the number of re-tuned cells. This memory code has recently been supported by direct neurobehavioral tests. In toto, these findings support the view that specific, learned auditory memory content is stored in the ACx, and further that this storage of information during learning and the instantiation of the memory code involves the engagement of the nucleus basalis and its release of acetylcholine into target structures, particularly the cerebral cortex.     

Enkephalins and learning and memory: a review of evidence for a site of action outside the blood-brain barrier

A series of studies indicate that enkephalins exert dramatic influences on learning and memory in rats and mice, when studied with conditioning tasks that are both negatively and positively motivated. Pharmacological analysis of these enkephalin actions on conditioning suggests that the [leu]enkephalin acts through a delta opioid receptor which is located outside the blood-brain barrier. Control studies indicate that enkephalins do not simply affect the performance of a conditioned response through actions on shock sensitivity or locomotor activity. Characterization of the peripheral enkephalin mechanism that affects behavior suggests an action through an enzymatic system that controls the concentrations of enkephalin present at its receptors in the periphery. This enzymatic mechanism is sensitive to experience, since its activity changes following conditioning, which suggests that it may be a regulatory mechanism for behavior.     

Styles of Inhibiting Emotional Expression: Distinguishing Repressive Coping from Impression Management

ABSTRACT Although repressors' avoidant coping style seems genuinely defensive, an alternative hypothesis is that repressors are actually distress-prone impression managers who provide “socially desirable” verbal reports. To establish discriminant validity, 30 repressors and 30 self-identified impression managers participated in a timed phrase-completion task. Half of the subjects were encouraged to be emotionally expressive and half to be restrained. Repressors were highly defensive regardless of the social demand, and impression managers only managed to match the repressors' level of distancing during the first segment of the inhibitive condition. Repressors were as physiologically reactive when they made defensive claims as they were when they made more negative disclosures to others. Moreover, when confronted, only the repressors denied that their heart rate elevations might be related to their emotional responses. These findings suggest that repressors' limited emotional expression is more determined by defenses against awareness of affect than by self-presentational concerns.     

Binge eating and outcome of behavioral treatment of obesity: a preliminary report

A survey was carried out of binge-eating behavior in a group of 44 patients who had completed group behavioral treatment for obesity. Obese binge eaters, defined by DSM-III criteria for bulimia, lost significantly less weight immediatedly posttreatment and at 6-month follow-up than non-binge eaters.