D-Lactate inhibition of memory in a single trial discrimination avoidance task in the young chick

L-Lactate is a metabolite possibly able to meet some neuronal energy demands. However, a clear role for L-lactate in behaviour remains elusive. Administration of the inactive isomer D-lactate (1.75 mM; ic), immediately post-training, resulted in a persistent retention loss from 40 min post-training when used in conjuction with a single trial discrimination avoidance task designed for the young chick. Furthermore, 1mM noradrenaline (ic) administered 20 min post-training overcame the retention loss induced by D-lactate. Although not directly demonstrated in the current study, it is plausible that D-lactate inhibited memory processing by competing with L-lactate for uptake into neurons. The time of onset of the retention loss induced by D-lactate is in accord with findings where the action of noradrenaline is inhibited. The successful challenge of D-lactate inhibition by a high concentration of noradrenaline may suggest a relationship by some unidentified mechanism.     

A scavenger of peroxynitrite prevents long-term memory formation using a single trial passive avoidance task for the day-old chick

The important role of nitric oxide (NO) in memory processing has been recognised for some time. However, the mechanisms through which NO may act are only partially understood. One highly reactive radical brought about by the reaction of NO and superoxide ions is peroxynitrite. The current study investigated the effect of peroxynitrite scavenging on retention for a single trial passive avoidance task developed for the day-old chick. Administration of a range of concentrations of the peroxynitrite scavenger Trolox (0.1 microM-1.2 mM) yielded a bimodal retention curve. This dose-response curve had nadirs at 300 and 800 microM. A time of administration study was conducted for each optimal concentration of Trolox and in both studies, the effective range of administration times extended from at least 10 min before training to 20 min post-training. Finally, a retention function was conducted for each optimum concentration of Trolox and in both studies a persistent retention loss was observed from 40 min post-training until the conclusion of the experiment 24 h post-training. The findings suggest that physiological levels of peroxynitrite may be required for the consolidation of long-term memory in this model of memory formation. Interestingly, the effective times of administration and time of retention loss onset are consistent with previous studies which blocked NO synthesis. Therefore it may be suggested that NO acts to facilitate long-term memory formation through the production of peroxynitrite.     

Inhibition of endogenous carbon monoxide production induces transient retention losses in the day-old chick when trained using a single trial passive avoidance learning task

Carbon monoxide (CO) is most often thought of as an exogenous toxin rather than as a possible endogenous nootrope. However, a limited number of studies have suggested that CO is necessary in memory processing for at least some tasks. While nitric oxide (NO) and CO are known activators of guanylyl cyclase (GC), only the effect of NO on GC has been extensively investigated as a mechanism underlying memory processing. The aim of the present study was to determine if inhibition of CO production would have an effect on memory processing. Using chicks trained on a single trial passive avoidance task, inhibition of CO production using zinc (II) deuteroporphyrin IX 2,4-bis ethylene glycol (ZnBG; 5 microM) resulted in two transient retention losses occurring at around 40 and 130 min post-training. The timing of these transient retention losses was similar to those observed following inhibition of GC, using the same species and task in a previous study. This supports the notion that CO is necessary in memory processing for this task and may act through a GC-dependent mechanism. As ZnBG also directly inhibits GC or nitric oxide synthase (NOS) at high concentrations, a second experiment was carried-out to confirm the specificity of ZnBG for heme oxygenase (HO) at the concentration used. The action of ZnBG was challenged with the HO agonist hemin (100 microM) and the transient deficits were abolished. This confirmed that the action of ZnBG on memory was through a CO-related mechanism rather than directly on GC or NOS. In this way the specificity of ZnBG (5 microM) for HO could be confirmed. The results support a role for endogenous CO in memory processing, possibly through activation of GC. In addition, the transient retention losses observed following administration of ZnBG suggest that CO may be necessary for memory retrieval and not formation as previously thought.     

Exposure to a rhythmic auditory stimulus facilitates memory formation for the passive avoidance task in the day-old chick.

Previous research regarding the beneficial effects of auditory stimuli on learning and memory in humans has been inconsistent. In the current study, day-old chicks were used to reduce the impact of individual differences on responses. Chicks were trained on a passive avoidance task and exposed to various auditory stimuli. Exposure to a complex rhythmic sequence for 1 min strongly facilitated chicks' long-term memory. The optimal time of presentation of the stimulus was between 10 min before and 20 min after training. Moreover, the enhancing effect was not generalized to the other auditory stimuli tested. It is suggested that this effect may be due to arousal because arousal hormones are critical to long-term memory formation. This study indicates that the temporal characteristics and type of stimulus may be important considerations when investigating the effects of auditory stimuli on cognitive functioning.     

Inhibition of monoADP-ribosylation prevents long-term memory consolidation of a single-trial passive avoidance task in the day-old chick

The cytosolic posttranslational protein-modifying mechanism of monoADP-ribosylation has been implicated in long-term potentiation, a synaptic model of memory formation. The current study investigated the effect of inhibiting mono(ADP-ribosyl) transferase on memory for the passive avoidance task in day-old chicks (white Leghorn-black Australorp). Various doses of novobiocin or menadione sodium bisulfite were administered intracranially at different times before or after training. Control chicks were administered saline at matched times. Novobiocin (650 microM) or menadione sodium bisulfite (250 microM) administered between 5.0 min pretraining and 2.5 min posttraining was found to cause a persistent loss of retention from 120 min posttraining. These data provide the first demonstration that monoADP-ribosylation is required for the maintenance of long-term memory. Furthermore, the temporal characteristics of the memory loss caused by monoADP-ribosylation inhibition appears to exclude this mechanism as a downstream effect of the well-established nitric oxide activity previously shown to occur within 40 min of passive avoidance training.     

Short-term visual memory for contour curvature in a delayed discrimination task

Abstract: A two-interval forced-choice of constant stimuli was used to measure the point of subjective equality (PSE) and discrimination threshold for standard contour curvature (1.91, 3.24 deg⁻¹) held in short-term visual memory (STVM). At both standard curvatures, the PSE for remembered curvature was nearly constant for standard curvature from 2 s to 16 s retention intervals, while the discrimination threshold increased as a linear function of retention interval. These results show that the decay in STVM for contour curvature is due to the noisy representation of curvature, neither to fading of the represented curvature nor to converging to the constant curvature. Furthermore, the Weber fraction was nearly constant for both standard curvatures at any delay from 2 to 16 s.     

An experimental investigation of the effect of worry on responses to a discrimination learning task

The current study examined the impact of both the tendency to worry (trait worry) and the process of worry (state worry) on subsequent behavioral responding in a schedule discrimination learning task. High and low trait worriers were randomly assigned to a state worry or relaxation incubation condition and completed a test of executive functioning and a dual contingency learning task that utilized neutral discriminative cues over the course of 2 contingency phases. Although state and trait worry did not impact executive functioning, the state worry condition was associated with diminished sensitivity to learning task contingencies over the course of the first contingency learning trials in comparison to the relaxation condition. This relationship was unique to the state worry condition above and beyond shared variance with subjective anxiety level. Results suggest that state worry may lead to a decrement in selective behavioral responding to neutral discriminative cues in the environment. The findings suggest that the process of worry may lead to less adaptive responding to neutral cues and interfere with adaptive behaviors, which may thereby contribute to and maintain anxiety.     

Environmental context-dependent recognition memory using a short-term memory task for input

Although many studies have demonstrated that recall is better when tested in the learning environmental context (EC) than in a new EC, almost all of the studies have failed to find EC-dependent memory when recognition was used to measure memory. Evidence of EC-dependent recognition, however, was found in the three experiments of the present study, in which an incidental short-term memory task was used for input of learned material. The results suggest that type of processing during input is a predictor of context-dependent recognition; material studied for a long-term memory test is not susceptible to background context effects, whereas material merely maintained for a short-term memory test is more apt to lead to EC-dependent recognition.     

Comparability of a single-trial passive avoidance learning task in the young chick across different laboratories

The discrepant results noted by the La Trobe/Monash, Sussex, Open, and Berkeley University memory research groups employing the passive avoidance task (PAT) with the chick indicate that some of these differences may be due to differences in training procedures between the various groups. The procedures employed by each group were replicated as closely as possible and compared using the same strain of chick. Higher levels of pecking and lower training latencies were observed in the La Trobe/Monash chicks. Improved training latency was observed following a change in the day of experimentation with Sussex chicks, and in white light in Open chicks. A powerful reinforcing effect was observed when pretraining was conducted with a wet lure across multiple pretraining trials, indicating the importance of this difference between groups. The observed impact on chick performance of these variables indicates that differences between PAT procedures may have important interactive effects with aversive learning. The results of data gathered using different procedures may only be superficially comparable, and further investigation of the effects of these variables is indicated.     

Anxiety and speaking in people who stutter: An investigation using the emotional Stroop task

People with anxiety disorders show an attentional bias towards threat or negative emotion words. This exploratory study examined whether people who stutter (PWS), who can be anxious when speaking, show similar bias and whether reactions to threat words also influence speech motor planning and execution. Comparisons were made between 31 PWS and 31 fluent controls in a modified emotional Stroop task where, depending on a visual cue, participants named the colour of threat and neutral words at either a normal or fast articulation rate. In a manual version of the same task participants pressed the corresponding colour button with either a long or short duration. PWS but not controls were slower to respond to threat words than neutral words, however, this emotionality effect was only evident for verbal responding. Emotionality did not interact with speech rate, but the size of the emotionality effect among PWS did correlate with frequency of stuttering. Results suggest PWS show an attentional bias to threat words similar to that found in people with anxiety disorder. In addition, this bias appears to be contingent on engaging the speech production system as a response modality. No evidence was found to indicate that emotional reactivity during the Stroop task constrains or destabilises, perhaps via arousal mechanisms, speech motor adjustment or execution for PWS.Educational objectives: The reader will be able to: (1) explain the importance of cognitive aspects of anxiety, such as attentional biases, in the possible cause and/or maintenance of anxiety in people who stutter, (2) explain how the emotional Stroop task can be used as a measure of attentional bias to threat information, and (3) evaluate the findings with respect to the relationship between attentional bias to threat information and speech production in people who stutter.     

Hemispheric dissociation of the involvement of NOS isoforms in memory for discriminated avoidance in the chick

Previous research has indicated a role for both the neuronal (nNOS) and endothelial (eNOS) nitric oxide isoforms in memory formation. In addition, two distinct periods of activity of nitric oxide activity, dissociated by hemispheric localization, are implicated following passive avoidance training in the chick. In the present study, we trained black Australorp-white Leghorn chicks on a color discrimination avoidance task. Diphenyleneiodonium chloride (1 microM) or N-propyl-l-arginine (50 microM) was administered into either the left or right hemisphere of the chick brain in an attempt to differentiate the effects of inhibiting eNOS or nNOS, respectively. The memory loss previously observed following administration of diphenyleneiodonium chloride between 10 and 20 min posttraining was found to be lateralized to the right hemisphere, although administration of this agent into the left hemisphere around the time of training was also amnestic. In contrast, N-propyl-l-arginine caused memory loss only when administered to the left hemisphere around the time of training. These findings suggest that activation of both eNOS and nNOS isoforms may be essential for long-term memory consolidation of this task. Further, these two periods of activity are defined temporally and by hemisphere localization, although confirmation with more selective inhibitors when they become available is advised.     

Inhibition of guanylate cyclase and protein kinase G impairs retention for the passive avoidance task in the day-old chick

Nitric oxide (NO) is a highly labile chemical messenger which has previously been implicated in memory processes in a variety of learning paradigms and species. However, there is only limited evidence to suggest which enzymes are acted upon by NO during the formation of memory. The present study investigates the role of guanylate cyclase (GC) and protein kinase G (PKG) in a form of passive avoidance learning known to be dependent on nitric oxide activity. It was determined that in vivo pharmacological inhibition of GC using either 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one or 6-anilino-5,8-quinolinedione resulted in two transitory memory retention deficits centred around 40 and 120 min posttraining, respectively. In contrast, inhibition of PKG with N-[2-(methylamino)ehtyl]-5-isoquinoline-sulfornamide hydrochloride (H-8) resulted in a single temporary retention loss centered at 120 min posttraining. These temporary retention losses appear to be specific to memory since they were dose-dependent and could not be explained by nonspecific performance effects. Further, these results suggest that these agents inhibit memory retrieval rather than formation, since memory is subsequently available. The current findings indicate that guanylyl cyclase mediates two memory retrieval processes, the latter of which appears to be PKG-dependent. In contrast, since inhibition of NO results in a permanent retention loss, it is suggested that NO is required for memory formation through GC-independent processes.     

Pharmaco-behavioural evidence indicating a complex role for ryanodine receptor calcium release channels in memory processing for a passive avoidance task

Calcium signalling is an important process underlying neuronal function and consequently behaviour. The release of calcium from intracellular stores via the ryanodine receptor calcium release (RyR) channel has been implicated in both synaptic plasticity and to a limited extent in memory processing. While past investigations have suggested a role for RyR channels in long-term memory, the present study suggests their action is more complex. Using a single trial passive avoidance task developed for the day-old chick, it is proposed that RyR channels are necessary both prior to the expression of long-term memory and also in retrieval processes. Specifically, 5 mM dantrolene (a specific RyR channel blocker) resulted in a persistent retention loss from 40 min post-training while 10 nM dantrolene produced a transient retention loss centred at 40 min post-training. We speculate that in the context of memory formation, RyR channels may be activated by nitric oxide and in the context of memory retrieval may lead to the activation of large conductance calcium-activated potassium BK(Ca) channels which, when blocked by 50 nM iberiotoxin, also demonstrated a transient retention loss centred at 40 min post-training.     

Training the removal of negative information from working memory: A preliminary investigation of a working memory bias modification task

Rumination in depressed adults is associated with a bias toward retaining negative information in working memory. We developed a task designed to modify this cognitive bias by having subjects repeatedly practice removing negative words from working memory, thereby enabling them to retain positive and neutral words. To assess the efficacy of this task, we recruited 60 adults who reported elevated repetitive negative thought (RNT) and randomly assigned them to receive a single administration of either the working memory bias modification (WMBM) task or a control task. Subjects in the WMBM condition exhibited greater reduction in proactive interference for negative information than did those in the control condition. These results suggest that the WMBM task reduces biased retention of negative information in working memory and, thus, may be useful in investigating the possible causal role of this cognitive bias in RNT or depression.     

Visuospatial working memory and the construction of a spatial situation model in listening comprehension: An examination using a spatial tapping task

Cognitive Processing - The present study investigated how visuospatial working memory (VSWM) is involved in the construction of a spatial situation model for spatial passages presented auditorily....     

Investigating the time course of tactile reflexive attention using a non-spatial discrimination task

Peripheral cues are thought to facilitate responses to stimuli presented at the same location because they lead to exogenous attention shifts. Facilitation has been observed in numerous studies of visual and auditory attention, but there have been only four demonstrations of tactile facilitation, all in studies with potential confounds. Three studies used a spatial (finger versus thumb) discrimination task, where the cue could have provided a spatial framework that might have assisted the discrimination of subsequent targets presented on the same side as the cue. The final study circumvented this problem by using a non-spatial discrimination; however, the cues were informative and interspersed with visual cues which may have affected the attentional effects observed. In the current study, therefore, we used a non-spatial tactile frequency discrimination task following a non-informative tactile white noise cue. When the target was presented 150 ms after the cue, we observed faster discrimination responses to targets presented on the same side compared to the opposite side as the cue; by 1000 ms, responses were significantly faster to targets presented on the opposite side to the cue. Thus, we demonstrated that tactile attentional facilitation can be observed in a non-spatial discrimination task, under unimodal conditions and with entirely non-predictive cues. Furthermore, we provide the first demonstration of significant tactile facilitation and tactile inhibition of return within a single experiment.     

Attentional orienting and awareness: evidence from a discrimination task

We used several cue–target SOAs (100, 500, 1000 ms) and three different degrees of cue predictability (Non-predictive-50%, Predictive-75%, Counter-predictive-25%), to investigate the role of awareness of cue–target predictability on cueing effects. A group of participants received instructions about the informative value of the cue, while another group did not receive such instructions. Participants were able to extract the predictive value of a spatially peripheral cue and use it to orient attention, whether or not specific instructions about the predictive value of the cue were given, and no matter their ability to correctly report it in a post-test questionnaire. In the non-predictive block, bad estimators who received no instructions showed regular cueing effects, while good estimators exhibited smaller and non-significant facilitatory effects at the short SOA and an absence of significant IOR at longer SOAs. However, for the instructions group, the pattern of results reversed.     

Structure in semantic memory: A probabilistic approach using a continuous response task

In the continuous response (CR) task, the subject is given the name of a familiar category and must respond with category examples within a fixed time limit. The response sequence and the interresponse times are the measured variables. A general model is proposed for performance in the CR task. The time taken to generate a response is identified with the shortest search time from among a set of simultaneous search processes. Each response has a generation probability that is a function of the parameters governing the search process durations. Data involving the category states in the United States are used to test the model. The model accounts for the performance of nearly all individuals in these data.This article is based on a dissertation completed at the University of California-Berkeley in partial fullfillment of the requirements for the Ph.D. degree in psychology. Portions of the article were presented at the joint meeting of the Psychometric and Classification Societies (June 1984) and at the meeting of the Society for Mathematical Psychology (August 1984). The authors wish to thank Barbara Mellers, Juliet Schaffer, Steve Palmer, and Eleanor Rosch for helpful comments.