Delayed Matching-to-sample Performance Research Articles

Effect of repeated administration of Δ9-tetrahydrocannabinol on delayed matching-to-sample performance in rats

In the present study we examined the effect of repeated exposure to Δ 9-tetrahydrocannabinol (THC) at a dose of 10 mg/kg (once a day for 4 days) 24 h after administration, on delayed matching-to-sample (DMTS) performance in rats using a three-lever operant apparatus. Although DMTS performance was not changed on the 1st day, it was impaired on the 2nd day. The impairment was potentiated in dependence of repeated administration. After withdrawal of THC, the impairment of DMTS performance gradually disappeared. On the 10th day after withdrawal, readministration of 10 mg/kg THC resulted in marked impairment of DMTS performance at 24 h after administration. Furthermore, a single administration of 1.0 mg/kg THC 30 min prior to the session, the dose at which a single administration did not cause impairment of DMTS performance in vehicle-treated rats, significantly decreased the number of reinforcements in the test trial. In conclusion, the present study demonstrated that repeated THC administration impaired DMTS performance under the condition of 24 h after administration, and that behavioral sensitization to this impairment developed. Furthermore, the suppressive state of lever-pressing induced by repeated THC administration may be a useful animal model for amotivational syndrome in humans.

Triazolam in Alzheimer's disease: Pilot study on sleep and memory effects

We examined the effects on sleep and memory of a nighttime dose of triazolam, 0.125 mg, in seven subjects with Alzheimer's disease (AD) who were reported by caregivers to be frequently up at night. Subjects were admitted to an intermediate care hospital ward for the 8-day ABA design protocol (placebo baseline-drug-placebo washout). Drug or placebo was given each evening at 2100 h. Sleep was assessed with a wrist-worn activity monitor. Memory was evaluated using a computerized delayed-matching-to-sample (DMTS) task administered at 0800 and 2130 h. Triazolam had no significant effects on total sleep time at night, latency to sleep onset, number of arousals, or time asleep during the day. DMTS performance was significantly worse at night compared to morning during baseline, but there were no significant drug effects. Our results suggest the standard geriatric dose of triazolam, 0.125 mg, may not be an effective hypnotic in AD patients with disrupted sleep, but neither does it substantially worsen the recent memory deficits of AD.

Improvement in performance of a delayed matching-to-sample task by monkeys following ABT-418: a novel cholinergic channel activator for memory enhancement.

ABT-418, a newly characterized centrally acting cholinergic channel activator (ChCA), was evaluated for its ability to improve performance in a delayed matching-to-sample (DMTS) task by mature macaques well trained in the task. Previous studies in rodents have indicated that ABT-418 shares the memory/cognitive enhancing actions of nicotine, but without many of nicotine's dose-limiting side effects. As DMTS provides a measure both of general cognitive function (the matching concept) and of recent memory, it was hypothesized that some doses of ABT-418 would enhance the monkeys' ability to correctly perform the DMTS task. Intramuscular administration of ABT-418 significantly enhanced DMTS performance at low (2-32.4 nmol/kg) doses. In fact, the drug was slightly more potent that nicotine in this regard, and all eight animals tested in this study exhibited enhanced performance at one or more doses. ABT-418 produced the greatest improvement in DMTS performance at the longest delay interval. In animals repeatedly tested with their individualized "Best Dose", DMTS performance increased on average by 10.1 +/- 3.5 percentage points correct, which was equivalent to an increase of 16.2% over baseline performance. ABT-418 did not significantly affect response times, i.e., latencies to make a choice between stimuli, or latencies to initiate new trials. Whereas nicotine enhanced DMTS performance both on the day of administration and on the following day (in the absence of drug), ABT-418-induced enhanced performance was detected only on the day of administration. Finally, single daily administration of the individualized best dose in three monkeys over a period of 8 days generally maintained enhancement of DMTS performance. Thus, the data were not consistent with the development of significant tolerance to the drug's mnemonic actions. In contrast to nicotine, no overt toxicity or side effects to acute or repeated administration of the drug were noted. Thus, ABT-418 represents a prototype of a new class of nicotinic agonists designed for the potential treatment of human dementias having a low profile of toxicity.

Velnacrine maleate improves delayed matching performance by aged monkeys.

Velnacrine maleate is a novel, orally active acetylcholinesterase inhibitor of the acridine class with a longer duration of action than physostigmine. Velnacrine has shown efficacy in the treatment of Alzheimer's disease and in improving both normal and experimentally impaired mnemonic function in animals and humans. To characterize this action further, the present study evaluated velnacrine for its ability to ameliorate the decline in short-term memory associated with aging in non-human primates at two time points after velnacrine administration: (1) 30 min and (2) 24 h. Initially, doses of 1, 2, 4, and 6 mg/kg, PO (free base corrected) were administered once to each of six aged (25-40 years), memory-impaired macaques that had been trained to perform a delayed matching-to-sample (DMTS) paradigm. The dose associated with the greatest improvement in session performance was administered three more times to the same individual. Four of the six monkeys showed improved DMTS performance during the repeated best dose phase (phase 2). Almost all of the improvement occurred during long-delay trials. Compared to placebo trials, velnacrine induced a significant improvement of long delay DMTS (58.0-66.7%, 13.4% of the placebo value). Long delay DMTS remained significantly improved during the test session conducted 24 h following velnacrine administration. Pharmacokinetic analysis following administration of 4 or 6 mg/kg velnacrine to three aged monkeys revealed peak plasma concentrations ranging from 27 to 166 ng/ml, 30-60 min after dosing. Six hours after dosing velnacrine plasma levels decreased to 5.1-11.8 ng/ml; and 24 h after dosing velnacrine plasma levels were less than the limit of quantitation (5 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Isoarecolone-induced enhancement of delayed matching to sample performance in monkeys: role of nicotinic receptors.

Nicotine enhances memory performance in young and aged monkeys performing a version of the delayed matching to sample (DMTS) task. However, the beneficial actions of nicotine are often limited by debilitating side effects. Isoarecolone is a piperidine derivative with nicotine-like activity, but having a slightly different profile of behavioral actions in rodents. In young monkeys, isoarecolone produced a dose-dependent enhancement of the DMTS task on the same day of testing, with a trend towards enhanced performance in animals tested 24 h after administration. Isoarecolone was about 1500-fold less potent than nicotine in enhancing DMTS performance. The ability of isoarecolone to enhance DMTS performance was well correlated with its ability to interact with cortical nicotinic receptors in vitro.

Tyrosine reverses a cold-induced working memory deficit in humans

Acute exposure to cold stress has been shown to impair short-term, or working, memory, which may be related to reduction in, or disruption of, sustained release of brain catecholamines. Administering a supplemental dose of the catecholamine precursor tyrosine may alleviate cold stress-induced memory impairments by preventing cold-induced deficits in brain catecholamine levels. The present experiment determined whether administration of tyrosine would prevent a cold-induced working memory deficit, using a computer-based delayed matching-to-sample (DMTS) memory task. Eight male volunteers performed the DMTS task for 30 min at an ambient temperature of either 4°C (cold) or 22°C following a 30-min preexposure period and 2 h after ingesting 150 mg/kg of L-tyrosine or placebo. Subjects demonstrated a decline in matching accuracy on the DMTS task as delay interval increased, such that matching accuracy following a 16-s delay between sample and comparison stimuli was lower than that following a delay of 2 or 8 s. Consistent with previous research, and relative to 22°C exposure sessions, matching accuracy during 4°C exposure sessions was reduced significantly following placebo administration, which is attributed to the effect of cold exposure on short-term, or working, memory. Administration of tyrosine significantly improved matching accuracy at the longest delay interval most affected by cold exposure, such that matching accuracy in the cold following tyrosine was at the same level as matching accuracy following placebo or tyrosine administration at 22°C. Tyrosine administered prior to 22°C exposure had no effect on DMTS performance. Plasma norepinephrine levels and diastolic and systolic blood pressure were significantly elevated just prior to performing the DMTS task and following 30 min of acute cold exposure, indicating that the cold exposure produced a typical stress response. Tyrosine was effective in protecting against the effects of cold stress on DMTS performance, possibly by preventing cold stress-induced reduction in brain catecholamine levels.

Effects of auditory and visual interference on auditory-visual delayed matching-to-sample in monkeys (Macaca fascicularis).

Two monkeys were trained on an auditory-visual (AV) delayed matching-to-sample (DMS) task with auditory cues serving as sample stimuli and visual cues serving as comparison stimuli. To determine whether the monkeys were remembering auditory or visual information during the delay period, auditory and visual interference were presented following the sample stimulus. Auditory interference had little effect on AV DMS performance. In contrast, visual interference severely impaired AV DMS performance, indicating that the monkeys were remembering visual information during the delay period. This finding may reflect a predisposition of monkeys toward remembering information via their dominant visual modality.

Effects of auditory and visual interference on auditory-visual delayed matching to sample in monkeys (Macaca fascicularis).

Two monkeys were trained on an auditory-visual (AV) delayed matching-to-sample (DMS) task with auditory cues serving as sample stimuli and visual cues serving as comparison stimuli. To determine whether the monkeys were remembering auditory or visual information during the delay period, auditory and visual interference were presented following the sample stimulus. Auditory interference had little effect on AV DMS performance. In contrast, visual interference severely impaired AV DMS performance, indicating that the monkeys were remembering visual information during the delay period. This finding may reflect a predisposition of monkeys toward remembering information via their dominant visual modality.

Forgetting in rats following medial septum or mammillary body damage.

This study examined the effects of medial septal (MS) and mammillary body (MB) radio-frequency lesions in an automated delayed-matching-to-sample (DMTS) procedure using lever-position stimuli and rats. Memory performance pre- and postsurgery was assessed with a negative exponential decay function fitted to bias-free measures of recognition. Part 1 showed that MS, but not MB or sham-control surgery, impaired DMTS performance. This impairment in the MS group was best characterized as an increase in the rate of forgetting. Part 2 examined the interaction between MS and MB lesion effects and proactive interference arising from responses made on the previous DMTS trial. The results indicated that proactive interference effects were similar for all groups. These results provide further support for the critical role of the MS region in memory function but indicate that damage to this brain region does not disrupt memory function through a heightened sensitivity to proactive interference.

Verbal Self-Reports as a Function of Speed, Accuracy, and Reinforcement of the Reported Performance

Undergraduates reported about their performance on a delayed matching-to-sample (DMTS) task in which monetary reinforcers depended on both speed and accuracy. They made the reports by pressing “Yes” or “No” buttons to answer computer- presented queries about the speed, accuracy, or reinforcement of their performance on the just-completed DMTS trial. Reports about accuracy were positively, but not strongly, correlated with actual performance. Reports about speed were consistently biased in favor of affirmative reports, with subjects reporting that their DMTS responses were fast enough to earn reinforcement, regardless of actual response speed. Reports about reinforcement showed substantial intersubject variability. Manipulating the interval between DMTS performance and the self-report (from 3 s to 27 s) had no systematic influence on the correspondence between reports and performance, regardless of whether a distractor task was required during the interval. These results are inconsistent with an hypothesis that individuals performing speeded choice tasks directly monitor both speed and accuracy. The experiment illustrates the viability of studying verbal self-reports as operant behavior under discriminative control of some, but possibly not all, aspects of the reported performance.

Crossmodal short-term memory of haptic and visual information

Rhesus monkeys were trained on a within-subjects design to assess whether they could perform concurrently visual-to-haptic (V-H) and haptic-to-visual (H-V) crossmodal delayed matching-to-sample (DMS). A parametric analysis was conducted of the effect of delay between presentation and re-presentation of the test discriminanda (three-dimensional geometric objects). The results indicate that (a) monkeys are capable of concurrent V-H and H-V crossmodal matching of objects by shape, size, and texture; (b) monkeys acquire faster and perform better crossmodal matching in the V-H direction than in the H-V direction; (c) as they learn to perform DMS with successive object pairs, monkeys transfer some—procedural—knowledge from the use of one pair to the use of the next; and (d) in the monkey, crossmodal short-term memory, as measured by DMS performance, has a temporal decline.

Visual learning and retention examined with reversible cold lesions of the anterior temporal lobe

Learning and retention of visual discriminations and delayed match-to-sample (DMS) performance were examined in monkeys while cooling the anterior temporal lobe. Four cryodes were bilaterally implanted on the dura overlying the anterior temporal cortex, an anterior pair covered the temporal pole (TP) and a posterior pair covered the anterior inferior temporal cortex (AIT). The visual discriminations were examined under 4 different test combinations of cooling and not cooling the anterior temporal lobe. Learning deficits were produced by cooling either TP or AIT. Once learned, there was no difficulty recalling discriminations under cooling or control conditions for either TP or AIT. There was a deficit during cooling in the recall of discriminations that had been learned prior to cooling TP or AIT. The animals were then trained and tested on a DMS task at a 0-s and 10-s delay. They performed at chance when either TP or AIT was cooled in the 0-s delay. Only TP was cooled at the 10-s delay and it also resulted in chance performance. The cold lesions demonstrated that the anterior temporal cortex, i.e. TP and AIT, has an important role in the processes of learning and, to a lesser extent, retention of visual information. The results also support previous findings regarding the participation of this area in DMS performance. The findings were discussed in relation to the amnesic syndrome.

A method for examining short-term retention of haptic cues in monkeys

Tasks used to examine short-term memory (STM) in animals have almost exclusively required retention of visual cues. To determine if haptic information can be retained, three rhesus monkeys were trained to perform, using only haptic cues, a simultaneous (SMS) and a delayed matching-to-sample (DMS) task. On each trial, the monkeys felt and responded to a sample stimulus on a centrally located manipulandum. They were then presented two comparison stimuli located on both sides of the central manipulandum. A response matching the comparison stimulus with the sample stimulus was reinforced. In SMS a mean of 2,725 trials was required to reach a criterion of 90% correct. As in DMS performance for visual cues, in haptic DMS the monkeys were capable of above-chance responding at retention intervals of greater than 1 min. This haptic DMS task should be useful for testing STM models, for examining the physiological basis of STM, and for examining drug effects.

Short-term memory in the pigeon using a modified autoshaping paradigm

Most investigations of short-term memory in the pigeon have employed the delayed matching-to-sample (DMTS) paradigm. Generally, the limits of retention in these studies have been 15-20 sec. In the present experiment, pigeons were tested with a visual short-term memory task that is based upon autoshaping. On some trials, the birds were shown a horizontal line for 5 sec, followed by a variable retention interval, a 5-sec green stimulus, and, finally, a 4-sec food presentation. On other trials, a 5-sec vertical line was followed by a variable retention interval, a 5-sec green stimulus, and no food. Response latencies and rates to the green stimulus were recorded as measures of retention. Horizontal trials generated higher rates and shorter latencies to green than did vertical trials. In contrast to DMTS performance, discrimination was maintained with no significant decrement at retention intervals up to 20 sec. Possible reasons for this discrepancy and the potential usefulness of this paradigm as a memory task are discussed.

Disruption of delayed matching to sample

Two pigeons were exposed to a 3-sec delayed matching-to-sample (DMTS) procedure. Following acquisition, reinforcement for sample responding was presented during the delay interval. After baseline recovery, a blackout procedure was instituted during the delay interval. Both procedures reduced the accuracy of responding on the DMTS task. Accuracy was below that seen in baseline sessions. In addition, reductions in sample-specific behaviors were obtained with both procedures. The data support and extend the notion that sample-specific behaviors mediate accurate DMTS performance.

The effects of illumination on the acquisition of delayed matching-to-sample

Illumination effects during steady-state performance of discrimination tasks in animals have been well documented, whereas research on illumination effects during acquisition has been largely ignored. Exceptions to this rule are Wasserman’s (1973) autoshaping experiments and Maki’s (1979) successive discrimination experiment. The present experiment investigated the effects of illumination changes on acquisition of a conditional discrimination—delayed matching-to-sample (DMTS). Pigeons were used in a between-groups design which factorially varied house-light illumination, on or off, during the presentations of DMTS stimuli, the delay interval, and the intertrial interval (ITI). DMTS performance over five blocks of sessions was the dependent variable. The major result was the three-way interaction of sessions, the intertrial interval, and the DMTS stimuli. Constant illumination resulted in the highest discrimination ratios over the last four blocks of sessions. A constant dark condition did not differ from a condition with dark ITIs and illuminated stimulus presentations or from a condition with illuminated ITIs and dark stimulus presentations. The proffered explanation of these data emphasizes the disruptive effects of stimulus changes and Wasserman’s (1973) cue localization hypothesis. The loci of the stimulus change and cue localization effect are suggested to be either at the beginning of a trial or at the end of a trial. A pretrial account emphasizes the role of stimulus changes on the encoding of the sample stimulus, and a posttrial account emphasizes the role of stimulus changes during consolidation processing.

Codes and coding processes in pigeon short-term memory

The delayed matching-to-sample (DMTS) task was used in three experiments to investigate how pigeons code information about sample stimuli. In all experiments, each trial consisted of a signaled presentation of a sample stimulus for a fixed duration followed, after some delay, by the presentation of three comparison stimuli. After incorrect first choices, the bird was allowed a second choice between the remaining two stimuli. It was found, in Experiment 1, that the probability of a second choice error declined with increasing sample duration. This result is consistent with a gradual short-term memory encoding process but not with a simple two-state all-or-none process. In the second experiment, it was found that the distribution of first-choice errors was affected by the particular sample occurring on a trial. This result is inconsistent with a two-stage discrete state memory/attention model based on the assumption that encoding of the sample and attention to the comparison stimuli are both independent all-or-none processes. The third experiment involved symbolic DMTS, in which the sample stimuli varied along a dimension different from that along which the comparison stimuli varied. With increasing delay between sample and comparison stimulus presentations, the pigeons were more likely to confuse test stimuli than to confuse sample stimuli. The results of these experiments lead to the conclusion that pigeon DMTS performance depends on a gradual encoding process in which a representation isomorphic with the test stimuli is generated and maintained.

Strength vs. temporal-order information in delayed-matching-to-sample performance by monkeys

The usual procedure in delayed-matching-to-sample (DMTS) experiments is that the most recently presented sample stimulus is correct on choice tests. The present paper reports two experments in which the first of two samples was always correct. Theories based on trace strength, such as the Roberts and Grant trace strength competition model, predict that such a procedure will yield below chance performance, because on the average the more recently presented stimulus will have the greater trace strength. In contrast, D’Amato and others have proposed that DMTS performance is mediated by a temporal discrimination process and, since either stimulus may act as S+ in a discrimination problem, monkeys should be capable of learning to choose either the secondor the first of two sample stimuli. Performance did not exceed chance in either experiment. The generality of these results is tentatively explored.

Temporal discrimination factors in the delayed matching-to-sample task in monkeys

The temporal discrimination hypothesis (TDH) of delayed matching-to-sample (DMTS) stresses the animal’s ability to discriminate which choice-stimulus alternative has appeared most recently as sample. Thus, the emphasis is placed on discriminative processes, temporal in nature, rather than on the traditional trace or buffer storage mechanisms of short-term memory. Some of the predictions of the TDH were tested within the context of the DMTS task. Experiment I showed that the difficulty of sample-stimulus sequences could be predicted by the TDH. Experiment II showed DMTS performance to be an increasing function of the number of sample stimuli employed, a result predicted by the TDH, but not by a traditional proactive interference interpretation. The results demonstrate the importance of temporal discriminative processes in DMTS. The possibility for a simpler theoretical approach to memory, in general, is discussed.