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PubMed2005

Peripubertal anxiety profile can predict predisposition to spatial memory impairments following chronic stress.

We tested the hypothesis that peripubertal anxiety levels are predictive of the detrimental effects of chronic stress on hippocampal-dependent spatial memory. The anxiety levels of peripubertal male Sprague-Dawley rats (43 days old) were characterized using open field and elevated plus mazes, followed by chronic restraint stress for 6 h/day/21 days beginning in young adulthood (75 days). Following chronic stress treatment, rats were tested on the spatial Y-maze using two inter-trial interval levels of difficulty (4 h: 1 day post-chronic stress; 1 min: 2 days post-chronic stress). As expected, all groups displayed intact spatial memory in the less difficult 1 min version of the Y-maze. However, in the 4 h version of the Y-maze, chronically stressed high anxiety rats showed impaired spatial memory, while chronically stressed low anxiety and control (low and high anxiety) rats displayed intact spatial memory. Moreover, a month after chronic stress ended, high anxiety rats had significantly higher basal corticosterone levels than low anxiety rats (control and stress). These results indicate that peripubertal anxiety and chronic stress interact to influence hippocampal-dependent spatial memory in adulthood.

Age Factors↗

PubMed1985

Spatial memory of children and adults assessed in the radial maze.

To assess the development of accurate spatial memory and its relationship to organized search strategies, children (18-71 months old) and college students searched for rewards hidden at the ends of the arms of an eight-arm radial maze. Subjects made their first four choices in random order selected by the experimenter (forced choice) or in whatever order they wished (free choice). In some conditions, a retention interval was imposed between arm choices 4 and 5, followed by a resumption of the task. With free choice, accuracy of spatial memory increased linearly with age, and the proportion of tests on which the child entered four adjacent arms in sequence during the first four choices, a measure of organized searching, also increased linearly with age. Disrupting this sequential search strategy (forced choice) reduced accuracy for both children and college students, although the reduction with college students was small. Delays had minimal effects for children who met criterion at 0-delay and for college students. Although response patterns seem unimportant in accurate spatial memory in rats, systematic search strategies mature together with, and probably contribute to, the improvement of spatial memory with age in humans.

Adolescent↗

PubMed1993

Spatial memory in amnesia: evidence from Korsakoff patients.

Two experiments are reported which investigated a hypothesised disproportionate deficit in amnesic spatial memory. Korsakoff amnesic memory for the locations of objects or words placed on a grid was compared to control memory which had been attenuated by longer delays before testing. The effects of incidental versus intentional encoding of the locations were compared. No significant evidence of a disproportionate spatial memory deficit in Korsakoff amnesia was found, intentional instructions did not improve Korsakoff amnesic spatial memory scores, and there was no significant evidence of a trade-off of item memory and location memory specific to the Korsakoff amnesic group. Rather, intentional instructions significantly reduced item memory in both Korsakoff amnesics and normal controls, while having no effect on spatial memory. When location was scored by lenient criteria, there was no significant difference between groups for this measure, nor for recall and recognition memory for these items. Thus Korsakoff amnesic memory was very similar to that of control memory attenuated by longer delays before testing. The Korsakoff amnesic subjects' memory therefore differed quantitatively rather than qualitatively from that of control subjects' memory.

Adult↗

PubMed2004

Estrogen and progesterone improve scopolamine-induced impairment of spatial memory.

This study was conducted to investigate the effects of estrogen and progesterone on spatial memory in ovariectomized female rats, specifically, on memory impaired by the cholinergic antagonist scopolamine. Forty-one female rats were divided into five groups: ovariectomized (OVX), estrogen-treated after ovariectomy (OE), progesterone-treated after ovariectomy (OP), estrogen-progesterone-treated after ovariectomy (OEP), and the sham control group (Control). The animals were trained on an eight-arm radial maze with four arms baited to assess both working and reference memory performances. The OE and OEP groups showed significant improvement in the ability to perform a spatial memory task over the OVX group (P<0.05). Spatial memory in the OP group did not differ from that in the OVX group. After thirty-two trials were conducted and all rats learned the eight-radial maze task, scopolamine hydrobromide (0.2 mg/kg i.p.) was administered prior to retesting. After scopolamine injection, the OVX group showed an increased number of working memory errors, reference memory errors than the other groups (P<0.05). The OE, OEP and OP groups showed significant improvement in spatial impairment induced by scopolamine. These findings suggest progesterone alone or in combination with estrogen, improved scopolamine-induced impairment of working memory and reference memory as effectively as estrogen supplementation.

Analysis of Variance↗

PubMed2003

Seizure-induced changes in place cell physiology: relationship to spatial memory.

Status epilepticus (SE) is a frequent neurological emergency associated with a significant risk of morbidity in survivors. Impairment of hippocampal-specific memory is a common and serious deficit occurring in many of the survivors. However, the pathophysiological basis of cognitive deficits after SE is not clear. To directly address the cellular concomitants of spatial memory impairment, we recorded the activity of place cells from CA1 in freely moving rats subjected to SE during early development and compared this activity to that in control rats. Place cells discharge rapidly only when the rat's head is in a cell-specific part of the environment called the "firing field." This firing field remains stable over time. Normal place cell function seems to be essential for stable spatial memory for the environment. We, therefore, compared place cell firing patterns with visual-spatial memory in the water maze in SE and control rats. Compared with controls, place cells from the SE rats were less precise and less stable. Concordantly, the water maze performance was also impaired. There was a close relationship between precision and stability of place cells and water maze performance. In contrast, a single, acute, chemically induced seizure produced cessation of place cell activity and spatial memory impairment in water maze performance that reversed within 24 hr. These results strongly bolster the idea that there is a relationship between abnormal place cells and spatial memory. Our findings also suggest that the defects in place cell and spatial memory after SE and acute chemically induced seizures result from different processes.

Action Potentials↗

PubMed2002

Individual differences in spatial memory among aged rats are related to hippocampal PKCgamma immunoreactivity.

We reported previously that the extent of spatial memory impairment among aged rats was correlated positively with levels of protein kinase Cgamma in hippocampal homogenates measured by quantitative Western blotting (Colombo et al., 1997). In the current study, immunocytochemistry was used to test whether the relationship between elevated PKC-gamma and memory impairment among aged rats could be localized further within regions of the hippocampus. Six- and 24-month-old male Long-Evans rats were first trained in the water maze on a standard place-learning task and then trained 2 weeks later on a transfer task designed for rapid acquisition. In comparison with young rats, aged rats with impaired spatial memory had increased PKCgamma-immunoreactivity (PKCgamma-ir) in CA1 of the hippocampus, but not the dentate gyrus. In addition, PKCgamma-ir in CA1 was correlated positively with spatial memory impairment among aged rats on the standard place-learning and the transfer training tasks. The current results are consistent with our previous report of PKCgamma in hippocampal homogenates, and show further that the relationships between PKCgamma-ir and memory impairments among aged rats are most evident in area CA1. Thus age-related impairments of spatial memory, as well as deficits in the flexible use of previously acquired information, may result from dysregulation of PKCgamma.

Aging↗

PubMed1999

Support for a bimodal role for type II adrenal steroid receptors in spatial memory.

We investigated the effects of acute adrenal steroid treatment on spatial memory using the Y-maze and employing adrenal steroid receptor antagonists and agonists. For receptor activation, adrenalectomized rats were injected 2 h prior to their first Y-maze trial with sesame oil (adrenalectomy or SHAM), stress levels of corticosterone, a Type I receptor agonist (aldosterone), or a Type II receptor agonist (RU362). For receptor inactivation, unoperated rats were injected with a Type I receptor antagonist (RU318), a Type II receptor antagonist (RU555), sesame oil, or not injected at all. The findings indicated that spatial memory was impaired when the Type II receptors were blocked (RU555) or highly occupied (corticosterone or RU362) and normal for the other treatment conditions. These data suggest that the Type II receptors may be responsible for the inverted U-shaped relationship between spatial memory and corticosterone levels reported by others.

Adrenalectomy↗

PubMed2005

Histidine enhances carbamazepine action against seizures and improves spatial memory deficits induced by chronic transauricular kindling in rats.

AIM: To investigate whether histidine can enhance the anticonvulsant efficacy of carbamazepine (CBZ) and simultaneously improve the spatial memory impairment induced by transauricular kindled seizures in Sprague-Dawley rats. METHODS: Chronic transauricular kindling was induced by repeated application of initially subconvulsive electrical stimulation through ear-clip electrodes once every 24 h until the occurrence of 3 consecutive clonic-tonic seizures. An 8-arm radial maze (4 arms baited) was used to measure spatial memory, and histamine and gamma-amino-butyric acid levels were measured by high performance liquid chromatography (HPLC). RESULTS: Chronic transauricular kindling produced a significant impairment of spatial memory and a marked decrease in histamine content in the hypothalamus, the brainstem, and the hippocampus. Injection of histidine (1000 mg/kg or 1500 mg/kg, ip) significantly inhibited transauricular kindled seizures. Injection of histidine at lower doses (200 mg/kg or 500 mg/kg, ip) had no appreciable anticonvulsant effect when administered alone, whereas it significantly potentiated the protective effects of CBZ against kindled seizures. CBZ had no ameliorative effect on memory deficit, but, in contrast, histidine (200 mg/kg or 500 mg/kg, ip) alone or co-administered with CBZ significantly ameliorated the memory deficits induced by the seizures. CONCLUSION: Chronic transauricular kindling is a very useful animal model for evaluating memory deficits associated with epilepsy, and histidine has both a potentiate effect on the anticonvulsant efficacy of CBZ and an ameliorative effect on the spatial memory deficits induced in this model. Histidine at a specific dosage range might serve as a beneficial adjuvant for the clinical treatment of epilepsy, especially when accompanied by impaired spatial memory.

Animals↗

PubMed2005

Vestibular loss causes hippocampal atrophy and impaired spatial memory in humans.

The human hippocampal formation plays a crucial role in various aspects of memory processing. Most literature on the human hippocampus stresses its non-spatial memory functions, but older work in rodents and some other species emphasized the role of the hippocampus in spatial learning and memory as well. A few human studies also point to a direct relation between hippocampal size, navigation and spatial memory. Conversely, the importance of the vestibular system for navigation and spatial memory was until now convincingly demonstrated only in animals. Using magnetic resonance imaging volumetry, we found that patients (n = 10) with acquired chronic bilateral vestibular loss (BVL) develop a significant selective atrophy of the hippocampus (16.9% decrease relative to controls). When tested with a virtual variant (on a PC) of the Morris water task these patients exhibited significant spatial memory and navigation deficits that closely matched the pattern of hippocampal atrophy. These spatial memory deficits were not associated with general memory deficits. The current data on BVL patients and bilateral hippocampal atrophy revive the idea that a major--and probably phylogenetically ancient--function of the archicortical hippocampal tissue is still evident in spatial aspects of memory processing for navigation. Furthermore, these data demonstrate for the first time in humans that spatial navigation critically depends on preserved vestibular function, even when the subjects are stationary, e.g. without any actual vestibular or somatosensory stimulation.

Adult↗

PubMed1998

Individual differences in spatial memory and striatal ChAT activity among young and aged rats.

Individual differences in spatial memory among young and aged rats were assessed using memory tasks related to integrity of the hippocampus and the neostriatum. Relationships were then examined between measures of spatial memory and regional choline acetyltransferase (ChAT) activity, a marker for cholinergic integrity. Twenty-four-month-old Long-Evans rats were impaired in comparisons with 6-month-old rats on measures of place learning, working memory, reference memory, and perseveration in water-maze tasks. Aged rats that were impaired on one measure of memory, however, were not necessarily impaired on other measures. ChAT activity in the ventromedial and dorsolateral neostriatum of aged rats was significantly reduced in comparisons with young rats whereas no difference was found in the hippocampus. Aged rats with the most ChAT activity in the anterior ventromedial neostriatum performed best on the place-learning and reference memory tasks but also made the most perseverative errors on the working memory task. In addition, young and aged rats with the most ChAT activity in the anterior dorsolateral neostriatum were those with the least accurate working memory. No relationships were found between ChAT activity in the hippocampus and spatial memory. Thus age-related memory impairment has components that can be segregated by measuring relationships between cholinergic integrity in subregions of the anterior neostriatum and memory tasks with different strategic requirements.

Aging↗

PubMed1999

Differential spatial memory impairment after right temporal lobectomy demonstrated using temporal titration.

In this study a temporal titration method to explore the extent to which spatial memory is differentially impaired following right temporal lobectomy was employed. The spatial and non-spatial memory of 19 left and 19 right temporal lobectomy (TL) patients was compared with that of 16 normal controls. The subjects studied an array of 16 toy objects and were subsequently tested for object recall, object recognition and memory for the location of the objects. By systematically varying the retention intervals for each group, it was possible to match all three groups on object recall at sub-ceiling levels. When memory for the position of the objects was assessed at equivalent delays, the right TL group revealed disrupted spatial memory, compared with both left TL and control groups (P < 0.05). MRI was used to quantify the extent of temporal lobe resection in the two groups and a significant correlation between hippocampal removal and both recall of spatial location and object name recall in the right TL group only was shown. These data support the notion of a selective (but not exclusive) spatial memory impairment associated with right temporal lobe damage that is related to the integrity of the hippocampal functioning.

Adult↗

PubMed2005

Amygdalar inactivation blocks stress-induced impairments in hippocampal long-term potentiation and spatial memory.

Electrolytic lesions to the amygdala, a limbic structure implicated in stress-related behaviors and memory modulation, have been shown to prevent stress-induced impairments of hippocampal long-term potentiation (LTP) and spatial memory in rats. The present study investigated the role of intrinsic amygdalar neurons in mediating stress effects on the hippocampus by microinfusing the GABA(A) receptor agonist muscimol into the amygdala and examining stress effects on Schaffer collateral/commissural-CA1 LTP and spatial memory. The critical period of the amygdalar contribution to stress effects on hippocampal functions was determined by applying muscimol either before stress or immediately after stress. Our results indicate that intra-amygdalar muscimol infusions before uncontrollable restraint-tailshock stress effectively blocked stress-induced physiological and behavioral effects. Specifically, hippocampal slices prepared from vehicle-infused stressed animals exhibited markedly impaired LTP, whereas slices obtained from muscimol-infused stressed animals demonstrated robust LTP comparable with that of unstressed animals. Correspondingly, vehicle-infused stressed animals displayed impaired spatial memory (on a hidden platform version of the Morris water maze task), whereas muscimol-infused stressed animals revealed unimpaired spatial memory. In contrast to prestress muscimol effects, however, immediate poststress infusions of muscimol into the amygdala failed to interfere with stress impairments of LTP and spatial memory. Together, these results suggest that the amygdalar neuronal activity during stress, but not shortly after stress, is essential for the emergence of stress-induced alterations in hippocampal LTP and memory.

Amygdala↗

PubMed2005

Dominance-related changes in spatial memory are associated with changes in hippocampal cell proliferation rates in mountain chickadees.

It is well established that spatial memory is dependent on the hippocampus in both mammals and birds. As memory capacity can fluctuate on a temporal basis, it is important to understand the mechanisms mediating such changes. It is known that early memory-dependent experiences in young animals result in hippocampal enlargement and in increased neurogenesis, including cell proliferation and neuron survival. It is less clear, however, whether temporal changes in spatial memory are also associated with changes in hippocampal anatomy and cell proliferation in fully grown and experienced adult animals. In a previous study, we experimentally demonstrated that socially subordinate mountain chickadees (Poecile gambeli) showed inferior spatial memory performance compared to their dominant group mates, in the absence of significant differences in baseline corticosterone levels. Here we investigated whether these differences in memory between dominant and subordinate birds were associated with changes in the hippocampus. Following memory tests, chickadees were injected with 5-bromo-2'-deoxyuridine to label dividing cells and sacrificed 2 days after the injections. We found no significant differences in volume or the total number of neurons in the hippocampal formation between dominant and subordinate chickadees, but subordinate birds had significantly lower cell proliferation rates in the ventricular zone adjacent to both the hippocampus and mesopallium compared to the dominants. Individuals, which performed better on spatial memory tests tended to have higher levels of cell proliferation. These results suggest that social status can affect cell proliferation rates in the ventricular zone and support the hypothesis that neurogenesis might be involved in memory function in adult animals.

Animals↗

PubMed2001

New excitement in cognitive space: between place cells and spatial memory.

Hippocampal principal neurons-'place cells'-exhibit location-specific firing. Recent work addresses the link between place cell activity and hippocampal memory function. New tasks that challenge spatial memory allow recording from single neurons, as well as ensembles of neurons, during memory computations, and insights into the cellular mechanisms of spatial memory are beginning to emerge.

Animals↗

PubMed2003

Ameliorative effect of NC-1900, a new AVP4-9 analog, through vasopressin V1A receptor on scopolamine-induced impairments of spatial memory in the eight-arm radial maze.

The mechanism by which NC-1900, a new pGlu-Asn-Cys(Cys)-Pro-Arg-Gly-NH(2) (AVP(4-9)) analog, improves spatial memory in rats using an eight-arm radial maze was examined. Even at very low doses (0.2 ng/kg for s.c., 1 microg/kg for p.o., 1 fg for i.c.v.) NC-1900 improved scopolamine-induced impairment of spatial memory. NC-1900 (1 ng/kg, s.c.) also improved impairment of spatial memory induced by pirenzepine, a muscarinic(1) (M(1)) receptor antagonist, and by KN-62, a Ca2+/calmodulin (CaM)-dependent protein kinase II inhibitor. [Pmp(1), Tyr(Me)(2)]-Arg(8)-vasopressin, a vasopressin(1A) (V(1A)) receptor antagonist, and nicardipine, L-type Ca2+ blocker, but not OPC-31260, a V(2) antagonist, suppressed the effect of NC-1900 on scopolamine-induced impairment of spatial memory. A microdialysis study showed that NC-1900 did not affect acetylcholine release in the ventral hippocampus (VH) of intact rats or of scopolamine-treated rats. NC-1900 (1 microM) increased [Ca2+](i) in the VH than in the dorsal hippocampus (DH). Pretreatment with nicardipine (1 microM) and Ca2+ -free conditions inhibited the NC-1900-induced [Ca2+](i) response in the VH. Whereas co-administration of NC-1900 (1 microM) and carbachol (500 microM) increased [Ca2+](i) in the VH. Moreover, nicardipine concentration-dependently inhibited the increase in [Ca2+](i) induced by the co-administration of NC-1900 and carbachol in the VH. These results suggest that NC-1900 activates the V(1A) receptor at the postsynaptic cholinergic nerve, and causes a transient influx of intracellular Ca2+ through L-type Ca2+ channels, to interact with the M(1) receptor. The activation of these Ca2+ -dependent processes induced by NC-1900 may be involved in the positive effect of NC-1900 on scopolamine-induced impairment of spatial memory.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1991

Sex differences in spatial memory: a reanalysis of block tapping long-term memory according to the short-term memory level.

This paper analyzes the spatial memory performance of 495 subjects. Both short-term and long-term memory have been analyzed by means of the Corsi block-tapping test. We provide separate norms for the learning of a supra-span sequence according to the level of spatial short-term memory. The long-term memory of males and females was compared in groups matched for spatial short-term memory, and the gender effect was never found to be significant. This finding is discussed in relation to the nature of sex differences in spatial abilities.

Educational Status↗

PubMed2007

Kamikihi-to, a Kampo medicine, ameliorates impairment of spatial memory in rats.

The present study investigated the effects of Kamikihi-to (KKT), a Kampo medicine, on impairment of spatial memory in rats using an eight-arm radial maze task. Scopolamine (0.5 mg/kg, i.p.), a non-selective muscarinic receptor antagonist, and Delta(9)-tetrahydrocannabinol (THC; 6 mg/kg, i.p.), a principal psychoactive component of marihuana, each markedly impaired the spatial memory. KKT (1 and 3 mg/kg, p.o.) significantly improved the scopolamine-induced impairment of spatial memory. KKT (30 mg/kg, p.o.) also improved significantly the THC-induced impairment of spatial memory. Moreover, KKT (3 and 30 mg/kg, p.o.) enhanced tremors induced by oxotremorine, a muscarinic M(1) receptor agonist. Taken together these findings suggest that KKT is a useful drug for treating memory deficits.

Animals↗

PubMed1998

Experimental evidence for spatial memory in foraging wild capuchin monkeys, Cebus apella.

Obtaining convincing evidence for spatial memory of natural food sources in wild animals is hard because the observer rarely knows as much about the available food as does the animal, and the ability of the animal to detect novel food sources is usually not measured. In this study, I took advantage of the scarcity of natural fruit sources in the subtropical winter to present a wild group of brown capuchin monkeys with a large-scale array of 15 feeding platforms spaced ca 200 m apart. With this array, I could control the location, productivity and renewal schedule of the major fruit sources used by these animals. Combining an independent measurement of their detection field for these platforms with the known locations of the platforms, I calculated the expected patterns of movement among platform sites by the group under various models of 'random' foraging. These expected patterns were compared to the actual spatial movements of the group. The capuchin group moved significantly more often toward closer platforms and in straighter lines than expected by any random search model using their observed detection field of 82 m, although their behaviour did agree with such models for unrealistically large search fields of 225-350 m. I infer that the movements of this study group are likely to be guided by spatial memory. However, straight-line movement and a preference for closer platforms are in general not convincing evidence for spatial memory unless the detection field of the forager for the resources is known. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗