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PubMed2002

Cerebellar nodulectomy impairs spatial memory of vestibular and optokinetic stimulation in rabbits.

Natural vestibular and optokinetic stimulation were used to investigate the possible role of the cerebellar nodulus in the regulation and modification of reflexive eye movements in rabbits. The nodulus and folium 9d of the uvula were destroyed by surgical aspiration. Before and after nodulectomy the vertical and horizontal vestibuloocular reflexes (VVOR, HVOR) were measured during sinusoidal vestibular stimulation about the longitudinal (roll) and vertical (yaw) axes. Although the gain of the HVOR (G(HVOR) = peak eye movement velocity/peak head velocity) was not affected by the nodulectomy, the gain of the VVOR (G(VVOR)) was reduced. The gains of the vertical and horizontal optokinetic reflexes (G(VOKR), G(HOKR)) were measured during monocular, sinusoidal optokinetic stimulation (OKS) about the longitudinal and vertical axes. Following nodulectomy, there was no reduction in G(VOKR) or G(HOKR). Long-term binocular OKS was used to generate optokinetic afternystagmus, OKAN II, that lasts for hours. After OKAN II was induced, rabbits were subjected to static pitch and roll, to determine how the plane and velocity of OKAN II is influenced by a changing vestibular environment. During static pitch, OKAN II slow phase remained aligned with earth-horizontal. This was true for normal and nodulectomized rabbits. During static roll, OKAN II remained aligned with earth-horizontal in normal rabbits. During static roll in nodulectomized rabbits, OKAN II slow phase developed a centripetal vertical drift. We examined the suppression and recovery of G(VVOR) following exposure to conflicting vertical OKS for 10-30 min. This vestibular-optokinetic conflict reduced G(VVOR) in both normal and nodulectomized rabbits. The time course of recovery of G(VVOR) after conflicting OKS was the same before and after nodulectomy. In normal rabbits, the head pitch angle, at which peak OKAN II velocity occurred, corresponded to the head pitch angle maintained during long-term OKS. If the head was maintained in a "pitched-up" or "pitched-down" orientation during long-term OKS, the subsequently measured OKAN II peak velocity occurred at the same orientation. This was not true for nodulectomized rabbits, who had OKAN II peak velocities at head pitch angles independent of those maintained during long-term OKS. We conclude that the nodulus participates in the regulation of compensatory reflexive movements. The nodulus also influences "remembered" head position in space derived from previous optokinetic and vestibular stimulation.

Animals↗
PubMed1997

Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties.

According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by passive transport can be used to build a dynamic as well as a static representation of the traveled path. We found a close quantitative similarity between the present findings on distance reproduction and those obtained from active locomotion experiments in which the same paradigm was used. This resemblance suggests that the two types of navigation tasks draw on common physiological processes and extends the relevance of our results to naturally occurring path integration.

Acceleration↗
PubMed2005

Spatial memory performance 2 weeks after general anesthesia in adult rats.

We have previously demonstrated that general anesthesia with 1.2% isoflurane-70% nitrous oxide impairs acquisition of a radial arm maze task in both young and aged rats when testing begins 2 days after anesthesia and in aged rats when testing begins 2 wk later. We designed this study to examine whether postanesthesia learning impairment is persistent in young rats. Six-month-old rats were randomized to anesthesia for 2 h with 1.2% isoflurane-70% nitrous oxide, 1.8% isoflurane, or a control group that received 30% oxygen (n = 10 per group). Rats recovered for 2 wk and were then tested daily on a radial arm maze for 14 days. There were no differences between the controls and anesthesia groups in number of correct choices to first error or time to complete the maze. There was no main effect of group in terms of total number of errors (P > 0.05) but the group by day interaction was significant (P < 0.05), reflecting improved performance in the 1.2% isoflurane-70% nitrous oxide group relative to controls during the later days of testing (P < 0.005). Hence, in adult rats, previous general anesthesia is not associated with impaired learning 2 wk later. In fact, previous 1.2% isoflurane-70% nitrous oxide improves maze performance 2 wk later.

Anesthesia, General↗
PubMed1996

1-[[[5-(4-Nitrophenyl)-2-furanyl]methylene]imino]-2,4-imidazolidinedione (dantrolene), an inhibitor of intracellular Ca2+ mobilization, impairs avoidance performance and spatial memory in mice.

Effects of the intracerebroventricular administration of 1-[[[5-(4-nitrophenyl)-2-furanyl]methylene]imino]-2,4-imidazolidinedi one (dantrolene, an inhibitor of intracellular Ca2+ mobilization) on learning/ memory were investigated in mice using step-through passive avoidance and radial-arm maze tests. In the passive avoidance test, the administration of 6 nmol of dantrolene shortened the response latency in the retention test. The number of times of acquisition training required to achieve the criterion latency (300 s) did not change in the acquisition test. Ten nmol of administration of dantrolene increased the number of times of acquisition training required to achieve the criterion latency in the acquisition test and shortened the response latency in the retention test. In the radial-arm maze tests, 20 nmol of administration of dantrolene disrupted maze-choice accuracy and increased error numbers. These results suggest that intraneuronal Ca2+ mobilization plays important roles in learning and memory.

Adenosine Diphosphate Ribose↗
PubMed1983

Pigeons' spatial memory: II. Acquisition of delayed matching of key location and transfer to new locations.

Five hungry pigeons first received delayed matching of key location training. Trials began with a "ready" stimulus (brief operation of the grain feeder). Then one (randomly chosen) of a set of four keys from a three-by-three matrix was lit briefly as the sample. After a short delay (retention interval), the sample key was lit again along with one of the other eight keys. A peck at the key that had served as the sample produced grain reinforcement, whereas a peck to the other key produced only the intertrial interval. After delayed matching of key location was learned, the remaining five key locations were introduced as samples. Four of the five birds performed at considerably above-chance levels on the novel sample trials during the first as well as subsequent sessions. These results suggest that pigeons sometimes learn the single rule-"choose the location that matches the sample." The relevance of these results to the issue of whether pigeons learn a generalized matching rule (i.e., a concept of "sameness") is discussed.

Animals↗
PubMed1998

"Subclinical" dosages of lithium and pilocarpine that do not evoke overt seizures affect long-term spatial memory but not learning in rats.

After training is an automated radial maze, 11 male rats were injected with either "subclinical" dosages of lithium and pilocarpine or saline and then tested 5 days or 4 months later. When employed as their own controls or when compared with a saline-injected reference group, the rats that had received the lithium and pilocarpine displayed memory deficits but not learning learning deficits after the longest of the two delays (effect size was 41%). These results suggest that subtle disruption in memory but not learning to criterion could be associated with "subclinical electrical seizures" or the micromorphological changes associated with this activity.

Animals↗
PubMed2003

Sign language and Chinese characters on visual-spatial memory: a literature review.

Long-term use of a sign language may enhance visual abilities. Deaf signers consistently outscore their hearing nonsigning counterparts on visual memory tests. In a similar vein, the long-term use of a logographic script, Chinese characters appears to boost visual memory. Both learning a sign language and mastering Chinese characters involve a relatively complex task of visual recognition and memory. This review of the literature suggests that daily use of either a sign language, one not based on sound, or Chinese characters, a script which maps language at the word level rather than at the phonemic level, may facilitate recall of visual forms.

Child↗
PubMed2005

Representational momentum and related displacements in spatial memory: A review of the findings.

Memory for the final location of a moving target is often displaced in the direction of target motion, and this has been referred to as representational momentum. Characteristics of the target (e.g., velocity, size, direction, and identity), display (e.g., target format, retention interval, and response method), context (landmarks, expectations, and attribution of motion source), and observer (e.g., allocation of attention, eye movements, and psychopathology) that influence the direction and magnitude of displacement are reviewed. Specific conclusions regarding numerous variables that influence displacement (e.g., presence of landmarks or surrounding context), as well as broad-based conclusions regarding displacement in general (e.g., displacement does not reflect objective physical principles, may reflect aspects of naive physics, does not solely reflect eye movements, may involve some modular processing, and reflects high-level processes) are drawn. A possible computational theory of displacement is suggested in which displacement (1) helps bridge the gap between perception and action and (2) plays a critical part in localizing stimuli in the environment.

Environment↗
PubMed2003

Motion parallax is computed in the updating of human spatial memory.

As we move through space, stationary objects around us show motion parallax: their directions relative to us change at different rates, depending on their distance. Does the brain incorporate parallax when it updates its stored representations of space? We had subjects fixate a distant target and then we flashed lights, at different distances, onto the retinal periphery. Subjects translated sideways while keeping their gaze on the distant target, and then they looked to the remembered location of the flash. Their responses corrected almost perfectly for parallax: they turned their eyes farther for nearer targets, in the predicted nonlinear patterns. Computer simulations suggest a neural mechanism in which feedback about self-motion updates remembered locations of objects within an internal map of three-dimensional visual space.

Adult↗
PubMedDate not supplied

[Effects of central administration of beta-amyloid peptide (25-35): pathomorphological changes in the hippocampus and impairments of spatial memory].

A possible relationship between the amnesia induced by central administration of beta-amyloid (25-35) [Abeta(25-35)] and neurodegeneration in the hippocampus was studied. Male Wistar rats received a single intracerebroventricular injection of Abeta(25-35) at a dose of 15 nmol. One month after the administration, animals were trained in an eight-arm radial maze. After the training, a histopathological investigation of the hippocampus was carried out using brain slices stained with hematoxylin/eosin. Abeta(25-35) induced impairments in reference and working memory in the eight-arm radial maze. A moderate decrease in neuronal cell number was demonstrated in the CA1, but not in the CA3 subfield of the hippocampus. The number of both reference and working errors negatively correlated with the number of neurons in hippocampal CA1. The results are the first evidence for a specific relationship between neurodegeneration in the CA1 subfield of rat hippocampus and impairments of learning and memory induced by Abeta(25-35).

Amyloid beta-Peptides↗
PubMedDate not supplied

Four-arm radial open maze (FAROM) as a tool for assessing the effect of atropine in spatial memory of the rats.

Place learning behaviour for working (short term) memory and reference (long term) memory is studied with the Four-arm radial open maze (FAROM) in 18 rats divided equally in three groups. In group I, 0.5 mg of atropine was injected intra-peritoneally 30 minutes before the trial. In group II, saline and in group III Glycopyrrolate were injected instead. Twenty three hours hungry animals were tested on each day in the maze to search for food kept in one of the eight cul-de-sacs of maze. The latency i.e. the time to reach the goal cul-de-sacs, as well as the error score i.e. the number of entries in the non-goal cul-de-sacs were counted during six consecutive trials, per day. Each trial duration was 5 minutes or the time taken by the animal to search the goal compartment whichever was less. The inter-trials period was 10 min and the work was carried out for a period of 3 weeks. The results show that atropine does block effectively both the memory faculties i.e. working and reference memory and that level of memory deficit induced by atropine is related to the rate of drug uptake by the central cholinergic receptors.

Animals↗
PubMed1988

Effects of training on a spatial memory task on high affinity choline uptake in hippocampus and cortex in young adult and aged rats.

The relation of forebrain cholinergic function to learning and memory was explored by identification and characterization of a training-induced change in high-affinity choline uptake (HACU), an index of cholinergic activity. Young adult rats were trained to find an invisible escape platform in a water tank using environmental cues. After 4 d of this place-training (16 trials), hippocampal HACU was significantly reduced relative to that observed in rats trained to find a visible platform (cue-training), even when cue- and place-trained rats were yoked for swim time. These place- but not cue-trained rats showed significantly lower hippocampal HACU than did naive rats, and no effect of training was noted after only 1 d of training. Similar results were obtained in parietal cortex. These differential training effects on HACU correspond to previous reports that muscarinic blockade impairs place, but not cue, learning. A further experiment revealed that the decrease in HACU in hippocampus, but not in parietal cortex, occurred only during the acquisition phase of learning and was related to the rate of acquisition for individual animals. Hippocampal HACU in naive young and aged (24-27 months) rats did not differ, but the response of the septohippocampal cholinergic system to training was diminished in the aged rats. Old rats displayed impaired place learning and a corresponding dampening of the training-induced change in HACU. These results suggest that there is a task-specific engagement of cholinergic function in young animals that does not occur in behaviorally impaired aged animals, a finding that is consistent with a role for cholinergic dysfunction in memory impairments associated with aging.

Aging↗