Short-term Memory Trace Research Articles

Cortical auditory dysfunction in children with oral clefts: relation with cleft type

Objective: Up to 46% of individuals with oral clefts suffer from language-learning disabilities. The degree of these disabilities varies according to cleft type. The pathogenesis of cognitive malfunctioning or its relationship with cleft type is not known. We investigated persistence of auditory short-term memory (STM) that is implicitly involved in language-specific perception in children with clefts, grouped using fine-graded cleft classification.Methods: Cortical evoked potentials were recorded in 78 children with non-syndromic oral clefts and in 32 healthy peers. A mismatch negativity (MMN) potential that indexes preattentive detection of change in auditory input was obtained in response to tone sounds. In order to test durability of short-term memory traces, sounds were presented with three stimulation rates.Results: With slowest stimulation, MMN amplitudes were reduced in cleft children as compared to the healthy peers (P<0.00065). Only cleft-lip children did not significantly differ from controls. Among isolated palatal clefts, the more posteriorly delimited the cleft was, the smaller was the amplitude of MMN. MMNs of smallest amplitudes were obtained in the subgroup of complete unilateral cleft of lip and palate.Conclusions: Reduced MMN amplitudes, found in cleft children, imply deficiency in auditory STM trace maintenance. This dysfunction is likely to contribute to their language and learning disabilities. The MMN diminution with shorter/more posterior clefts suggests that differences in auditory cortex function are one of the underlying mechanisms of the cleft type-malcogniton association.

Functional interaction between entorhinal cortex and basolateral amygdala during trace conditioning of odor aversion in the rat.

In rats, conditioned odor aversion (COA) occurs only if the time interval separating the odor from the subsequent intoxication is very short suggesting that the memory trace of the odor is subject to rapid decay. Recent results from our laboratory have found that lesion of the entorhinal cortex (EC), and activation of the basolateral nucleus of the amygdala (BLA) rendered COA tolerant to long interstimulus interval. The present study examined whether the odor memory trace depends on the interaction between the EC and the BLA. Rats lesioned in the EC received infusions of muscimol (a GABA(A) receptor agonist) into the BLA immediately after the odor presentation during acquisition of COA. Injection of muscimol into BLA prevented tolerance of COA to long interstimulus interval induced by EC lesions. This suggests that EC modulates the short-term memory trace of the odor by controlling the GABAergic activity of the BLA during acquisition of COA.

INVARIANT FACE AND OBJECT RECOGNITION IN THE VISUAL SYSTEM

Neurophysiological evidence is described, showing that some neurons in the macaque temporal cortical visual areas have responses that are invariant with respect to the position, size and view of faces and objects, and that these neurons show rapid processing and rapid learning. A theory is then described of how such invariant representations may be produced in a hierarchically organized set of visual cortical areas with convergent connectivity. The theory proposes that neurons in these visual areas use a modified Hebb synaptic modification rule with a short-term memory trace to capture whatever can be captured at each stage that is invariant about objects as the object changes in retinal position, size, rotation and view. Simulations are then described which explore the operation of the architecture. The simulations show that such a processing system can build invariant representations of objects. © 1977 Elsevier Science Ltd. All Rights Reserved.

Short-term reverberant memory model of hippocampal field CA3.

Synaptic plasticity mechanisms for associative learning require near-simultaneous pairs of inputs to target cells. Sensory cues encountered behaviorally, however, are typically staggered in time, implying the need for active short-term memory traces of antecedent cues. The dense recurrent connectivity within regions of hippocampal field CA3 is suggestive of the kind of re-entrant network that could subserve this kind of "holding" memory. Consequently, we have investigated whether an abstract model of this region incorporating its major anatomical and physiological features could function as a reverberatory memory network. The continuous-time model describes the behavior of highly connected groups of CA3 pyramidal cells, or "patches," in response to brief, rhythmic, sensory stimulation. Time constants for excitatory and inhibitory postsynaptic potentials and axonal transmission delays for local and distal connections were estimated from empirical data. When the inhibitory units in these patches were connected to an oscillator intended to model the theta wave activity of the medial septum, the network entered reverberatory states and maintained second-long memory traces of the cortical input, after which it lost its coherent behavior. Noise analysis indicated that the network's operation was moderately resistant to random fluctuations proportional to patch activity. These results suggest that field CA3 could function as a holding memory that assists the integration of disjoint stimuli found in innumerable associative tasks, and that the duration of its coherent operation might determine the temporal limits in their performance.

Word-frequency effects on short-term memory tasks: evidence for a redintegration process in immediate serial recall.

Four experiments investigated the mechanisms responsible for the advantage enjoyed by high-frequency words in short-term memory tasks. Experiment 1 demonstrated effects of word frequency on memory span that were independent of differences in speech rate. Experiments 2 and 3 showed that word frequency has an increasing effect on serial recall across serial positions, but Experiment 4 showed that this effect was abolished for backward recall. A model that includes a redintegration process that operates to "clean up" decayed short-term memory traces is proposed, and the multinomial processing tree model described by R. Schweickert (1993) is used to provide a quantitative fit to data from Experiments 2, 3, and 4.

Neuronal activity in posterior parietal area 7a during the delay periods of a spatial memory task.

1. Neuronal activity was recorded from area 7a of monkeys performing a delayed match-to-sample task requiring release of a behavioral key when a visual stimulus appeared at a remembered spatial location. 2. Activity in the delay periods was significantly elevated in 28% of 405 neurons studied and could be classified as either sustained or anticipatory in nature. 3. Sustained activity was characterized by maintained or slowly decreasing discharge rates that were typically greater when the preceding stimulus was at a location that evoked a strong response. Sustained activity was terminated when a subsequent stimulus appeared at another location. 4. Anticipatory activity was characterized by accelerating discharge rates that were ordinarily greater after a stimulus at a location that evoked a weak response. Anticipatory activity was often associated with facilitated responses to the next stimulus. 5. These data demonstrate that a population of neurons in area 7a is active during the delay periods of a spatial memory task that does not require a behavioral response directed toward the location of the stimulus. This activity could represent a short-term memory trace for the spatial location of the preceding stimulus.

The separability of space and time: Dimensional interaction in the memory trace

The speeded-classification paradigm, adapted from the study of perceptual interactions, was used to examine interactions among features of the short-term memory trace. In each of four experiments, a trial began with the presentation of a pair of stimuli, each member of which occurred either first or second in time and above or below a fixation point. One of the two stimuli was then presented again, and the task was to classify its prior temporal (Experiments 1 and 3) or spatial (Experiments 2 and 4) position. The main question of interest asked whether subjects could selectively attend to one of these occurrence dimensions while ignoring irrelevant variation along the other. The results suggested that whereas subjects can selectively ignore temporal or spatial variation when no recall of the irrelevant dimensions value is required, they suffer interference when values on both dimensions must be remembered. The obtained patterns of interference are consistent with postperceptual interactions of the spatial and temporal components of the memory trace.

Alzheimer's dementia produces a loss of discrimination but no increase in rate of memory decay in delayed matching to sample

Patients diagnosed with senile dementia of the Alzheimer type (SDAT) were compared with control subjects on a computerized delayed matching to sample task. Performance was assessed with a measure of discriminability at zero delay and a measure of rate of forgetting—these are the two parameters of an exponential function derived from extensive animal testing. The SDAT group showed significantly poorer discriminability at zero delay than controls but equivalent rates of forgetting over a 32-sec delay. These data suggest that SDAT may have little effect on the decay rate of the short term (or ‘primary’) memory trace and may instead affect encoding, initial storage or retrieval mechanisms. The effects of SDAT on this task are consistent with previous results with anticholinergic agents in rats.

Event-related brain potentials and discrimination of steady-state vowels within and between phoneme categories: A preliminary study

The mismatch negativity (MMN), a component of the human auditory event-related brain potential, is elicited by a physically deviant stimulus in a sequence of homogeneo. “standard”, stimuli. MMN reflects an automatic discrimination process between the sensory input and the short-term memory trace left by the previous stimuli. These memory traces might form the neurophysiological basis of auditory sensory memory, the echoic memory. The purpose of the study was to determine whether the automatic discrimination process of vowels, as reflected in MMN, and the discrimination performance (measured as percentage of correct responses, d's, and RTs) with the same stimuli show effects of categorical perception. According to the results the study failed to show any statistically significant neurophysiological and behavioral effects of categorical perception on vowels. However, a consistent trend toward faster reaction times and better discrimination performance in phoneme boundary conditions than in phoneme center co...

Effect of Lead Intake on Extinction of Short-Term Memory Trace (CTA) in Rats

Abstract The effect of lead acetate on the extinction of conditioned taste aversion (CTA—short-term memory trace) was studied in albino rats. Three groups of animals of both sexes weighing between 150 and 200 g and 2 to 3 months old were selected and maintained with a staple diet under uniform husbandry conditions. The CTA was induced by 30-min saccharin (0.1%) drinking followed 30 min later by poisoning (lithium chloride 25 mg/100 g body weight). Retention trials were done 1 to 5 days later by offering the animal saccharin again; in Group 1 (n = 20) only one trial was done, whereas in Groups 2 (n = 22) and 3 (n = 22) regular trials were done in between 1 to 7 days. Only Groups 1 and 3 were exposed to lead (2500 μg/kg) a day before each extinction trial, and saccharin was injected per os by mouth if their consumption of fluid was inadequate. The extinction of CTA for saccharin in unexposed rats lasted about 2 weeks. Lead had no effect on the water consumption of CTA-trained animals. Lead retarded extinction of CTA by a month during saccharin trials.

Trace decay and the priming of short-term memory in long-delay taste aversion learning: Disruptive effects of novel exteroceptive stimulation

A variation of Kalat and Rozin's two-presentation paradigm was used to test the hypothesis that the first, as opposed to the second, presentation of a flavor conditioned stimulus (CS) constitutes the functional CS in two-presentation experiments involving moderate interflavor intervals (IFIs), and results in flavor aversions that are a function of the primary, as opposed to the secondary, conditioned stimulus-unconditioned stimulus (CS-US) interval. Contrary to the hypothesis, it was shown in Experiment 1 that holding the primary CS-US interval constant at 4 hr for each of three groups, while decreasing the secondary CS-US interval (i.e., the interval between the second flavor presentation and the illness) from 3.75 hr to 2.5 hr to .5 hr, resulted in the flavor aversion increasing as the secondary CS-US interval decreased. However, the aversion acquired by the group with a 0.5 hr secondary CS-US interval was also found to be significantly weaker than that acquired by a single-presentation 0.5 hr control group. In Experiment 2 it was demonstrated that animals exposed to novel exteroceptive stimulation (NES) immediately prior to a second flavor presentation that preceded the US by 0.5 hr acquired an aversion as strong as that acquired by a 0.5-hr control group. In Experiment 3 it was demonstrated that, in the absence of a second flavor presentation, animals exposed to novel exteroceptive stimulation 0.5 hr prior to the US acquired a weaker flavor aversion than did animals not exposed to novel exteroceptive stimulation during the 4-hr flavor CS-illness US interval. The contrasting effects of novel exteroceptive stimulation observed in Experiments 2 and 3 were replicated in Experiment 4. The results suggest, consistent with the trace-decay hypothesis and Wagner's (1976) general model of stimulus processing, that exposure to novel exteroceptive stimulation disrupts continued processing of the short-term memory (STM) trace of the initial presentation of a flavor CS, and hence minimizes stimulus preexposure effects attributable to the priming of STM.

Icon thresholds in paranoid and non-paranoid schizophrenics.

Recent work in information processing points to two processes being active when a stimulus produces a short-term memory trace, the icon. Previous work in schizophrenia seems to have blurred this important distinction and as a result the processing of the icon has been confused with the strength of icon. The present paper reviews current work with this distinction in mind and presents data on the icon strength of acute paranoid and non-paranoid schizophrenics, chronic schizophrenics, and two control groups as determined by the method of stimulus exposure time. Results indicate no difference in temporal recognition thresholds between schizophrenics and controls, strongly suggesting that the schizophrenia deficit resides in the encoding process.

Reward improves working memory of rats in the radial maze

The effect of reward on the formation and retention of short-term memory traces was examined in the radial maze. In Experiment 1, overtrained rats (n=12) made fewer errors (0.45 errors/trial) in an empty than in a baited 12-arm maze (1.19 errors/trial). In Experiment 2, two-min interval between the first six and second six choices only slightly increased error incidence in rewarded trials (1.33 errors/trial), but significantly deteriorated performance in non-rewarded trials (2.48 errors/trial). In Experiment 3, restricting the reward and non-reward conditions to the first six (R-N) or last six (N-R) choices of a trial only slightly impaired performance (about 1.5 errors/trial). In Experiment 4, rats were rewarded or non-rewarded in the first six choices made in maze A or in the second six choices performed in the similar maze B. The performances in the second six choices were close to chance in the AN-BN and AR-BN conditions (2.58 errors/trial) and intermediate in the AR-BR and AN-BR conditions (1.91 and 2.04 errors/trial, respectively). The positive effect of reward was not eliminated by the change of apparatus and cannot be due, therefore, to more intense scent marking. It is concluded that anticipated or accomplished consummatory activity improves efficiency of the working memory.

Memories and engrams: a clinical viewpoint.

Memory research is based on the assumption that a more or less permanent trace of previous experience, an “engram”, is being laid down somewhere in the brain and memory research is still “the search of the engram”. However, the clinician engaged in memory research has to be aware of the fact that he is dealing with memories and behavioural change, but not with engrams. Nevertheless, clinicopathological studies as well as the introduction of animal experiments into memory research using stimulation ablation and chemical methods have led to some progress in the search of the engram. The parallelism of the clinical observations and the experimental studies seems to indicate that one has to differentiate two kinds of memory trace, a short term trace which under normal conditions becomes consolidated into a permanent trace, while pathologically, the consolidation process does not take place. There are reasons to believe that the short term trace may be initiated or even maintained for a short time electrophysiologically by reverberating circuits in certain cell assemblies. This may set into action changes at the synapses probably by means of cholinergic and/or adrenergic enzyme systems. The mode of action of the electrophysiological and biochemical changes underlying short term retention, however, is only poorly understood and this also applies to the biochemical changes which are assumed to take place during the consolidation process and which eventually form the basis of the permanent engram. The clinicopathological findings seem to indicate that the short term memory traces of human experiences, which are always multisensorial, are distributed over the various relevant neocortical areas. The specific partial short term memory traces are integrated at first by the factor of temporal contiguity and form the basis of short term personal memories which characterize the memory function in clouded states and in chronic amnestic syndromes. The cortex seems also to be responsible for the consolidation of the “partial memories” while a bilaterally intact limbic system is necessary for the integration of the short term memory traces into consolidated long term engrams of “personal memories”.

Analysis of Y-maze learning in mice using cycloheximide

1. Experiments in mice with Cycloheximide (CXM) helped to elucidate some of the underlying mechanisms involved in learning and memory. 2. It appeared that there were consolidation processes occurring whereby short-term memory (STM) was converted into a long-term memory (LTM) trace. 3. The STM traces were unaffected by CXM and therefore did not appear to involve protein synthesis in the neurones. These STM traces under conditions of CXM injection had a viable period of approx 3 hr. 4. Under normal circumstances STM traces were consolidated directly into LTM traces providing an adequate protein synthesis level was present. 5. For this consolidation to occur a necessary level of arousal in the mice was also required. 6. Evidence is presented to suggest that protein synthesis may be involved in consolidation processes by increasing the levels of NA in the brain.

An analysis of short-term memory and conceptual behavior in three inbred strains of mice

Female mice of three inbred strains were trained in a T maze to develop a successive-reversal learning set. After obtaining the set, animals were tested at several delay intervals following a signal to reverse in order to measure the activity of the short-term memory trace. Peak performance occurred within 1 min for A/Js, 1 min for DBA/2Js, and 10 min for CBA/Js. Performance deteriorated to chance levels within 20 min for DBA/2Js, CBA/Js, and A/Js. The results indicate genetic differences in short-term memory for the mouse. Moreover, since subjects from all three strains mastered the learning set, differences in simple conceptual behavior of the three strains were not apparent.

Dual trace theory and the consolidation of long-term memory

Retention functions were determined for four Ss for recognition memory of letters at 14 different delays from 3 sec to 5 min and two levels of storage load (1 and 6 letter lists), the retention interval being filled with backward counting. Memory strength retention functions were fit extremely well by assuming that two traces, short-term memory and long-term memory, are operative in this type of memory task. Only the short-term memory trace appears to be present during the first 8 or 10 sec of the retention interval, and this short-term trace decays exponentially with a time constant in the vicinity of 10 sec. Long-term memory is subject to a consolidation process which does not begin until about 10 sec after the study period and which is substantially complete at about 30 sec after the study period. Storage load has a very large effect on the degree of acquisition (learning) for both short and long-term traces, but storage load appears to have only a moderate effect or no effect on the decay rate of the short-term trace. There is some suggestion that the duration of the consolidation phase is shortened by an increase in storage load.

The effects of chlorpromazine on one-trial passive avoidance learning in mice: further examination of pre- and post-learning administration.

Chlorpromazine in doses of 0.5 mg/kg was administered to mice 0.5, 2, or 10 min after a one-trial passive avoidance learning experience. The drug produced effects on the magnitude and rate of extinction of the learned response dependent upon the injection, time, confirming results contained in an earlier report. In a second experiment with doses of 2.0 mg/kg, the effects of further injecion times were investigated. The drug had no effect when given 240 min before learning, but produced maximal blocking of response acquisition when given 120 and 8 min before learning. Drug injections 6 and 3 min before learning were suggested as having actions on post-learning memory traces. A distinction was noted between the effects of drug injections 1 and 1.5 min after learning and this was related to an effect on a rapidly decaying short-term memory trace. Chlorpromazine had no effect when given 20 min after learning.

Chlorpromazine slows decay of visual short-term memory

The effects of chlorpromazine, scopolamine, and pentobarbital on the visual short-term memory trace were studied using Sperling’s method. Ss were classified as introverts or extraverts with the Maudsley Test, but this variable had no significant effect. Analysis of variance showed a significant difference among the drug treatments (p <.05). The mean numbers of correct responses for scopolamine, pentobarbital, and placebo, among which there was no significant difference, were pooled and found to differ significantly from the chlorpromazine mean (p <.01). It was concluded that chlorpromazine improved performance either by filtering poststimulus “noise” or by delaying the encoding process for the visual STM trace, thereby making the information available longer.

The effects of chlorpromazine on the decay and consolidation of short-term memory traces in mice.

F1 hybrids of two highly inbred strains of mice were trained in a one-trial passive avoidance learning situation. Chlorpromazine, in doses of 0.5, 2.0 and 3.5 mg/kg, was administered at one of four injections times, 10 min before and 0.5, 2 and 10 min after learning. Pre-learning drug administration completely blocked acquisition of a learned avoidance response. Post-learning drug effects were more complex, involving reduced expression of avoidance learning but less rapid extinction of the learned response. The results were related to effects of the drug on short-term memory trace decay and consolidation.