N-methyl-D-aspartate and dopamine receptor involvement in the modulation of locomotor activity and memory processes

In this study we report on the effects of N-methyl-D-aspartate (NMDA)- and dopamine (DA)-receptor manipulation on the modulation of one-trial inhibitory avoidance response and the encoding of spatial information, as assessed with a non-associative task. Further, a comparison with the well-known effects of the manipulation of these two receptor systems on locomotor activity is outlined. It is well assessed that NMDA-receptor blockage induces a stimulatory action on locomotor activity similar to that exerted by DA agonists. There is evidence showing that the nucleus accumbens is involved in the response induced by both NMDA antagonists and DA agonists. We show results indicating a functional interaction between these two neural systems in modulating locomotor activity, with D2 DA-receptor antagonists (sulpiride and haloperidol) being more effective than the D1 antagonist (SCH 23390) in blocking MK-801-induced locomotion. A different profile is shown in the effects of NMDA antagonists and DA agonists in the modulation of memory processes. In one-trial inhibitory avoidance response, NMDA antagonists (MK-801 and CPP) impair the response on test day, while DA agonists exert a facilitatory effect; furthermore, sub-effective doses of both D1 (SKF 23390) and D2 (quinpirole) are able to attenuate the impairing effect in a way similar to that induced by NMDA antagonists. The effects of NMDA- and DA-acting drugs on the response to spatial novelty, as assessed with a task designed to study the ability of animals to react to discrete spatial changes, are in good accord with the effects observed on passive avoidance. The results show that NMDA as well as DA antagonists, at low doses, selectively impair the reactivity of mice to spatial changes. In a last series of experiments, the possible role of NMDA receptors located in the nucleus accumbens was investigated regarding reactivity to spatial novelty. The experiments gave apparently contrasting results: while showing an impairing effect of focal administrations of NMDA antagonists in the nucleus accumbens on reactivity to spatial novelty, no effect of ibotenic acid lesions of the same structure was observed.     

TAP, implicit and explicit memory, and adult memory development.

This paper proposes a view of memory based on the notion of transfer appropriate processing (TAP) of Morris, Bransford, and Franks (1977). The author makes three specific assumptions to explain the disassociation between implicit and explicit memory. First, the author distinguishes between two memory organizing processes--integration and elaboration. Second, the author assumes that every kind of study task engages a combination of integrative and elaborative processing, but that some tasks focus primarily on integrative processing, and others focus more heavily on elaborative processing. Third, the author also assumes that every kind of test engages a combination of integrative and elaborative processing, but that implicit memory tests depend primarily on integrative processing, whereas explicit tests focus more heavily on elaborative processing. The long term goal of several on-going experiments is to learn more about the specific stimulus attributes that serve as cues for initialing/guiding integrative versus elaborative processing, and how these cues change across the life-span. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autobiographical memory processes and the course of depression.

The authors report a 6-month follow-up study of clinically depressed patients. At baseline, 2 indexes of autobiographical memory functioning were assessed: the presence of spontaneous intrusive memories of stressful life events and performance on the Autobiographical Memory Test (J. M. G. Williams & K. Broadbent, 1986), which measures overgeneral memory. The index of overgeneral memory was associated with greater levels of spontaneous intrusion of stressful memories. Overgeneral memory did not predict outcome, but depression at follow-up was predicted by the amount of intrusion and avoidance of stressful memories, even after controlling for initial severity of psychiatric symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploration, anxiety, and spatial memory in trasgenic anophthalmic mice.

Contradictory results are found in the literature concerning the role of vision in the perception of space or in spatial navigation, in part because of the lack of murine models of total blindness used so far. The authors evaluated the spatial abilities of anophthalmic transgenic mice. These mice did not differ qualitatively from their wild-type littermates in general locomotor activity, spontaneous altenation, object exploration, or anxiety, but their level of exploratory activity was generallty lower. In the spatial version of the water maze, they displayed persistent thigmotaxic behavior and showed severe spatial learning impairments. However, their performances improved with training, suggesting that they may have acquired a rough representation of the platform position. These results suggest that modalities other than vision enable some degree of spatial processing in proximal and structured spaces but that vision is critical for accurate spatial navigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Think before you speak: Pauses, memory search, and trace redintegration processes in verbal memory span.

Immediate memory span and speed of memory search were assessed for words and nonwords of short and long spoken duration. Memory span was substantially greater for words than for nonwords and for short than for long items, though speed of memory search was unaffected by either length or lexicality. An analysis of the temporal pattern of responses in the memory span task indicated that inter-item pauses were longer between nonwords than words but that these pause durations were unaffected by item length. A model of verbal short-term memory span is described in which trace selection from a short-term store and the redintegration (restoration) of degraded phonological traces both occur in the pauses between saying successive items. Both trace selection and trace redintegration appear to play important roles in accounting for individual differences in memory span. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perseverative neural processes and consolidation of the memory trace.

Perseveration theory as a behavioral theory of retroactive inhibition has generally lost favor and has been replaced with the concepts of associative interference. Various experimental approaches to inducing retrograde amnesia and recent evidence to support the existence of a system within the brain responsible for the permanent fixation of memory traces indicates that the application of available physiological procedures offers a promising approach to defining the structures involved in the fixation of memory traces. From Psyc Abstracts 36:02:2CL18G. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Echoic memory processes in good and poor readers.

Conducted 4 experiments to determine whether echoic memory plays a role in differences between good and poor readers. In Exp I, with 9 poor (mean age 11.05 yrs) and 9 good (mean age 10.9 yrs) readers, and Exp II, with 12 poor (mean age 10.85 yrs) and 12 good (mean age 10.7 yrs) readers, a suffix procedure was used in which the S was read a list of digits with either a tone control or the word go appended to the list. For lists that exceeded the length of the Ss' memory span by 1 digit (i.e., that avoided ceiling effects), poor readers showed a larger decrement in the suffix condition than did good readers. In Exp III, with 14 poor (mean age 10.64 yrs) and 14 good (mean age 10.83 yrs) readers, Ss shadowed words presented to 1 ear at a rate determined to give 75–85% shadowing accuracy. The item presented to the nonattended ear were words and an occasional digit. At various intervals after the presentation of the digit, a light signaled that the S was to cease shadowing and attempt to recall any digit that had occurred in the nonattended ear recently. Whereas good and poor readers recalled the digit equally if tested immediately after presentation, poor readers showed a faster decline in recall of the digit as retention interval increased. In Exp IV, using Ss from Exp II, bursts of white noise were separated by 9–400 msec of silence, and the S was to say whether there were 1 or 2 sounds presented. There were no differences in detectability functions for good and poor readers. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Internal clock and memory processes in animal timing.

Two experiments, involving a total of 6 male pigeons, investigated temporal control of behavior within the framework of an internal clock model. Ss were exposed to signaled fixed interval (FI) 30-sec trials mixed with extended unreinforced (baseline) trials. On unreinforced break trials, the signal was interrupted for a period of time after trial onset. In Exp 1, comparisons between the peak time obtained on baseline and on break trials produced peak time shifts that were longer than those expected if the clock had stopped during the break but shorter than if the clock had reset. In Exp 2, systematic manipulations of duration and location of breaks produced peak time shifts that were nonlinear functions of break duration and that varied linearly with break location. The obtained peak times were more consistent with a continuous memory decay model than with the stop-retain or the reset hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual and conceptual memory processes in global amnesia.

To determine whether global amnesia reflects a selective deficit in conceptual processing, amnesic and control Ss performed 4 memory tasks that varied processing and retrieval requirements. A study-phase modality (auditory/visual) manipulation validated the nature of processing (perceptual and conceptual) engaged by each task. Amnesic patients were impaired on perceptual and conceptual explicit memory tasks (word-fragment and word-associate cued recall) and were intact on perceptual and conceptual implicit memory tasks (word-fragment completion and word association). These results are consistent with the view that limbic-diencephalic structures damaged in amnesia mediate, in part, processes typically engaged during explicit retrieval. The results are inconsistent, however, with the characterization of that deficit as being one of conceptual processing per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory list memory and interference processes in monkeys.

Memory of 2 rhesus monkeys (Macaca mulatta) was tested in a serial probe recognition task with lists of 4 natural or environmental sounds, different retention intervals, and different manipulations of interference. At short retention intervals, increasing the separation of list items reduced the primacy effect and produced a recency effect. Similar results were shown by increasing interference across lists through item repetitions or making the first 2 list items high-interference items. These results indicated that decreasing first-item performance reduced proactive interference on memory of the last list items. At long (20 sec) retention intervals, making the last list items of high interference reduced the recency effect, reduced retroactive interference, and produced a primacy effect. Taken together, interference plays a role in determining the primacy and recency effects of the serial-position function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monitoring and control processes in the strategic regulation of memory accuracy.

When people are allowed freedom to volunteer or withhold information, they can enhance the accuracy of their memory reports substantially relative to forced-report performance. A theoretical framework addressing the strategic regulation of memory reporting is put forward that delineates the mediating role of metamemorial monitoring and control processes. Although the enhancement of memory accuracy is generally accompanied by a reduction in memory quantity, experimental and simulation results indicate that both of these effects depend critically on (a) accuracy incentive and ( b ) monitoring effectiveness. The results are discussed with regard to the contribution of metamemory processes to memory performance, and a general methodology is proposed that incorporates these processes into the assessment of memory-accuracy and memory-quantity performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encoding processes and memory for categorically related words by schizophrenic patients.

Hypothesized that schizophrenics display a deficit in recall relative to recognition (as well as other memory deficits) because they encode the conceptual attributes of to-be-remembered items less frequently than normals. An experimental procedure consisting of 2 phases, incidental learning and long-term retention, was used to test 30 schizophrenics and 26 normal adults. During incidental learning, Ss were presented with 36 short word lists. After each, they recalled a single word that was detectable (i.e., encoded) on the basis of its conceptual category. Two variables were manipulated orthogonally: the probability that items were encoded conceptually and the number of times items were presented. Long-term retention of all items presented during incidental learning was tested in free-recall, category cued recall, and recognition tests, administered in that order. Results show an overriding similarity of schizophrenics to normals in patterns of response to the major variables, providing no support for the hypothesis. Data are consistent, however, with the hypothesis that schizophrenics encode items less elaborately than normals do. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The use of null mutant mice to study complex learning and memory processes

Fractionation of the rat lung yielded a 54,000 g supernate, and DOC-solubilized 775 g, 3100 g and 54,000 g sediments, each of these preparations displaying an increasing angiotensin-converting enzyme activity with increasing dilution, suggesting the presence of freely reversible angiotensin-converting enzyme inhibitors. The solubilized 775 g sediment was applied to an immobilized captopril column, eluted successively with 20 mM Pi(K+), pH 7.8 buffer, buffer/0.5 M NaCl, and buffer/0.01M cysteine to obtain four major protein bands, two of which appeared with the cysteine eluant. The first two protein peaks were each pooled and subjected to ultrafiltration with 10,000 molecular weight cutoff filters. The pooled peaks, retentates and ultrafiltrates each inhibited the angiotensin-converting enzyme activity, suggesting the presence of large and small molecular weight reversible angiotensin-converting enzyme inhibitors in association with the solubilized (membranous) particulate angiotensin-converting enzyme fraction. These results expand upon earlier observations on the existence of angiotensin-converting enzyme inhibitors in mammalian serum by observing an increasing angiotensin-converting enzyme activity with increasing dilution. This activity was eluted in multiple peaks, including elution with the cysteine eluate, suggesting that the angiotensin-converting enzyme, as well as other proteins, may react covalently with the sulfhydryl functional group of the immobilized captopril in a transsulfhydration reaction cleaving the disulfide bonds in proteins. Subsequent elution with cysteine affects an additional transsulfhydration reaction, releasing the proteins from the column. It is further postulated that air oxidation of the proteins permits reformation of disulfide bonds, yielding some active angiotensin-converting enzyme. Having in mind the possibility of lipophilic angiotensin-converting enzyme inhibitors crossing the blood-brain barrier as a means of treatment of alcohol abuse, the intriguing presence of a naturally occurring angiotensin-converting enzyme inhibitors in the particulate, lipid-rich fraction of the lung cell raises the theory that inhibitors such as these might cross the blood-brain barrier to serve as downregulators of alcohol consumption.     

Automatic and effortful processes in auditory memory reflected by event-related potentials. Age-related findings

The structures of the N-linked sugar chains in the PAS-6 glycoprotein (PAS-6) from the bovine milk fat globule membrane were determined. The sugar chains were liberated from PAS-6 by hydrazinolysis, and the pyridylaminated sugar chains were separated into a neutral (6N) and two acidic chains (6M and 6D), the acidic sugar chains then being converted to neutral sugar chains (6MN and 6DN). 6N was separated into two neutral fractions (6N13 and 6N5.5), while 6MN and 6DN each gave a single fraction (6MN13 and 6DN13). The structure of 6N5.5, which was the major sugar chain in PAS-6, is proposed to be Man alpha1 --> 6 (Man alpha1 --> 3) Man beta1 --> 4GlcNAc beta1 --> 4GlcNAc-PA; 6N13, 6MN13 and 6DN13 are proposed to be Gal beta1 --> 3Gal beta1 --> 4GlcNAc beta1 --> 2Man alpha1 --> 6 (Gal beta1 --> 3Gal beta1 --> 4GlcNAc beta1 --> 2Man alpha1 --> 3) Man beta1 --> 4GlcNAc beta1 --> 4 (Fuc alpha1 --> 6)GlcNAc-PA; 6M and 6D had 1 or 2 additional NeuAc residues at the non-reducing ends of 6MN13 and 6DN13, respectively.     

Dissociations in infant memory: Rethinking the development of implicit and explicit memory.

Extending the Jacksonian principle of the hierarchical development and dissolution of function to the development and dissolution of memory, researchers have concluded that implicit (procedural) memory is a primitive system, functional shortly after birth, that processes information automatically, whereas explicit (declarative) memory matures late in the 1st year and mediates the conscious recollection of a prior event. Support for a developmental hierarchy has only been inferred from the memory performance of adults with amnesia on priming and recognition-recall tests in response to manipulations of different independent variables. This article reviews evidence that very young infants exhibit memory dissociations like those exhibited by adults with normal memory on analogous memory tests in response to manipulations of the same independent variables. These data demonstrate that implicit and explicit memory follow the same developmental timetable and challenge the utility of conscious recollection as the defining characteristic of explicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in component processes of working memory.

Working memory deficits in normal aging have been well documented, and studies suggest that high memory load plus the presence of distraction negatively impacts successful memory performance to a greater degree in older individuals. However, characterization of the component processes that are impaired by these task manipulations is not clear. In this behavioral study, younger and older subjects were tested with a delayed-recognition and recall task in which the encoding and delay period were both manipulated. During the encoding period, the subjects were presented with either a single letter or multiple letters at their predetermined forward letter span, and the delay period was either uninterrupted or interrupted with a visual distraction. There was an age-related impairment of working memory recognition accuracy only in the combination of high memory load and distraction. These results suggest that when working memory maintenance systems are taxed, faulty recognition processes may underlie cognitive aging deficits in healthy older individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive short-term and long-term memory processes in spatial habituation.

Exposure to a spatial location leads to habituation of exploration such that, in a novelty preference test, rodents subsequently prefer exploring a novel location to the familiar location. According to Wagner's (1981) theory of memory, short-term and long-term habituation are caused by separate and sometimes opponent processes. In the present study, this dual-process account of memory was tested. Mice received a series of exposure training trials to a location before receiving a novelty preference test. The novelty preference was greater when tested after a short, rather than a long, interval. In contrast, the novelty preference was weaker when exposure training trials were separated by a short, rather than a long interval. Furthermore, it was found that long-term habituation was determined by the independent effects of the amount of exposure training and the number of exposure training trials when factors such as the intertrial interval and the cumulative intertrial interval were controlled. A final experiment demonstrated that a long-term reduction of exploration could be caused by a negative priming effect due to associations formed during exploration. These results provide evidence against a single-process account of habituation and suggest that spatial habituation is determined by both short-term, recency-based memory and long-term, incrementally strengthened memory. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Serial and parallel processes in working memory after practice.

Six young adults practiced for 36 sessions on a working-memory updating task in which 2 digits and 2 spatial positions were continuously updated. Participants either did 1 updating operation at a time, or attempted 1 numerical and 1 spatial operation at the same time. In contrast to previous research using the same paradigm with a single digit and a single dot, dual-task costs were not eliminated with practice. Costs of switching between digits and between spatial positions were found throughout practice, supporting the existence of a focus of attention in working memory that can hold 1 digit and 1 spatial position simultaneously, but is not expanded to hold 2 elements of the same kind. The results can be understood by assuming that observed limits on parallel processing, as well as on the capacity of the focus of attention, arise not from structural constraints but rather reflect the optimal configuration of the cognitive system for avoiding information cross-talk in a given task. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cognitive and consensus processes in group recognition memory performance.

This experiment applies signal detection theory and social decision schemes to investigate the potential impact of information pooling, error correction, and effective decision-making processes in the general finding that groups perform better than individuals on memory tasks. Groups and individuals completed a true/false recognition test regarding material presented in a videotaped simulated job interview. Various indexes of memory performance indicated that each of the processes contributed to the superiority of group recognition memory performance. Social decision scheme analyses indicated that the plurality-correct-wins decision scheme was the best summary of the decision process. Subsequent analyses suggested that the confidence that group members held in their initial preferences influenced the group decision process. Discussion emphasized the impact of consensus, correctness, and confidence on group memory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)