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PubMed1999

Subtypes of central nicotinic receptors involved in learning and memory.

AIM: To observe the effects of different subtypes of central nicotinic receptor on learning and memory. METHODS: Passive avoidance response, including step-down avoidance and step-through avoidance in mice and long-term potentiation (LTP) in rat hippocampal slices. RESULTS: Hexamethonium (C6) 7 micrograms/mouse and kappa-bungarotoxin (kappa-BTX) 0.6 microgram/mouse inhibited the acquisition of avoidance conditioning in mice, and kappa-BTX yielded this effect with a dose-response relationship. kappa-BTX 1 mumol.L-1 suppressed the induction of LTP (P < 0.05), but not normal synaptic transmission and maintenance of LTP in rat hippocampal slices. CONCLUSION: The subtypes of central nicotinic receptor sensitive to kappa-BTX play an important role in learning and memory.

Animals↗
PubMed1997

Nitric oxide is involved in the formation of learning and memory in rats: studies using passive avoidance response and Morris water maze task.

The study was designed to test whether blockade of endogenous NO production affects learning and memory formation in rats. The rats received an intracerebroventricular (i.c.v.) injection of the inhibitor of nitric oxide synthase, N omega-nitro-L-arginine (NAME), 30 min before each training, and were then tested in the one-trial passive avoidance response and Morris water maze task, respectively. The results showed that: (1) among four concentrations of drug used, only doses higher than 3 mumol of i.c.v. NAME impaired learning and memory formation significantly (p < 0.05) in both test models; (2) in Morris water maze task, the animals treated with highest dose of NAME (5 mumol) failed to learn while those treated with lower doses succeeded; (3) in Morris water maze task, the i.c.v. NAME, even in higher doses, did not affect the capacity of finding a visible platform. It is suggested that NO is involved in learning and memory formation by potentiating or facilitating mainly the acquisition process.

Animals↗
PubMed2003

Possible role of intramembrane receptor-receptor interactions in memory and learning via formation of long-lived heteromeric complexes: focus on motor learning in the basal ganglia.

Learning in neuronal networks occurs by instructions to the neurons to change their synaptic weights (i.e., efficacies). According to the present model a molecular mechanism that can contribute to change synaptic weights may be represented by multiple interactions between membrane receptors forming aggregates (receptor mosaics) via oligomerization at both pre- and post-synaptic level. These assemblies of receptors together with inter alia single receptors, adapter proteins, G-proteins and ion channels form the membrane bound part of a complex three-dimensional (3D) molecular circuit, the cytoplasmic part of which consists especially of protein kinases, protein phosphatases and phosphoproteins. It is suggested that this molecular circuit has the capability to learn and store information. Thus, engram formation will depend on the resetting of 3D molecular circuits via the formation of new receptor mosaics capable of addressing the transduction of the chemical messages impinging on the cell membrane to certain sets of G-proteins. Short-term memory occurs by a transient stabilization of the receptor mosaics producing the appropriate change in the synaptic weight. Engram consolidation (long-term memory) may involve intracellular signals that translocate to the nucleus to cause the activation of immediate early genes and subsequent formation of postulated adapter proteins which stabilize the receptor mosaics with the formation of long-lived heteromeric receptor complexes. The receptor mosaic hypothesis of the engram formation has been formulated in agreement with the Hebbian rule and gives a novel molecular basis for it by postulating that the pre-synaptic activity change in transmitter and modulator release reorganizes the receptor mosaics at post-synaptic level and subsequently at pre-synaptic level with the formation of novel 3D molecular circuits leading to a different integration of chemical signals impinging on pre- and post-synaptic membranes hence leading to a new value of the synaptic weight. Engram retrieval is brought about by the scanning of the target networks by the highly divergent arousal systems. Hence, a continuous reverberating process occurs both at the level of the neural networks as well as at the level of the 3D molecular circuits within each neuron of the network until the appropriate tuning of the synaptic weights is obtained and, subsequently, the reappearance of the engram occurs. Learning and memory in the basal ganglia is discussed in the frame of the present hypothesis. It is proposed that formation of long-term memories (consolidated receptor mosaics) in the plasma membranes of the striosomal GABA neurons may play a major role in the motivational learning of motor skills of relevance for survival. In conclusion, long-lived heteromeric receptor complexes of high order may be crucial for learning, memory and retrieval processes, where extensive reciprocal feedback loops give rise to coherent synchronized neural activity (binding) essential for a sophisticated information handling by the central nervous system.

Animals↗
PubMed2006

[Effect of lidocaine on the impairment of learning and memory function and central cholinergic system after transient global cerebral ischemia in mice].

OBJECTIVE: To evaluate the effects of lidocaine on the impairments of learning and memorial function and central cholinergic system after transient global cerebral ischemia in mice of different apolipoprotein E genotypes. METHODS: Transient global ischemia was induced by bilateral common carotid arteries occlusion (BCCAO) for 17 minutes. Healthy male C57BL/6J wild-type mice (C57 mice) and apolipoprotein E knockout mice (ApoE mice) were randomly divided into six groups: C57 control group (sham operation, neither BCCAO was performed nor pharmacologic intervention was given), C57 ischemia group (BCCAO for 17 minutes was performed and normal saline was given intraperitoneally), C57 lidocaine group (BCCAO for 17 minutes was performed and lidocaine was given intraperitoneally), ApoE control group (the same procedure as that of C57 control group), ApoE ischemia group (the same procedure as that of C57 ischemia group), ApoE lidocaine group (the same procedure as that of C57 lidocaine group). The mice were allowed to recover for 7 days. Morris water maze test were performed from the 8th postoperative day. Mice were tested four times daily for 5 consecutive days. The latency periods were recorded and the percentages of effective search strategies were calculated. On the 12th postoperative day after Morris water maze test, mice were decapitated under anesthesia. The cerebral cortex and hippocampus were removed quickly. The activities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) as well as the binding activity of muscarinic receptor (M receptor) were assayed. RESULTS: (1) The latency periods were significantly longer in the ischemia groups than in the corresponding control groups (P<0.05 or 0.01). They were also significantly longer in C57 lidocaine group than in C57 ischemia group [on the 3rd day of test, (74.1+/-32.7)s vs (49.2+/-19.5)s] (P<0.05). However, they were significantly shorter in apoE lidocaine group than in apoE ischemia group [from the 3rd to the 5th days of test, (40.7+/-27.7)s vs (84.7+/-26.8)s, (31.2+/-19.2)s vs (72.1+/-33.0)s, and (28.0+/-22.1)s vs (60.8+/-26.9)s, respectively] (P<0.05 or 0.01). When compared between two strains, they were significantly longer in apoE ischemia group than in C57 ischemia group (P<0.05 or 0.01). However, they were significantly shorter in apoE lidocaine group than in C57 lidocaine group (P<0.01). (2) The percentages of effective search strategies were significantly lower in the ischemia groups than in the corresponding control groups (P<0.01). They were also significantly lower in C57 lidocaine group than in C57 ischemia group [from the 3rd to the 5th days of test, (18.2+/-11.7)% vs (41.7+/-17.7)%, (22.7+/-20.8)% vs (55.6+/-20.8)%, and (29.6+/-27.0)% vs (66.7+/-21.7)%, respectively] (P<0.01). However, they were significantly higher in apoE lidocaine group than in apoE ischemia group [from the 3rd to the 5th days of test, (41.7+/-25.8)% vs (15.6+/-12.9)%, 8.3+/-20.4)% vs (18.8+/-11.6)%, and (66.7+/-30.3)% vs (28.1+/-20.9)%, respectively] (P<0.01). When compared between two strains, they were significantly lower in apoE ischemia group than in C57 ischemia group (P<0.01). However, they were significantly higher in apoE lidocaine group than in C57 lidocaine group (P<0.01). (3) The parameters of central cholinergic system were significantly lower in the ischemia groups than in the corresponding control groups (P<0.05 or 0.01). They were also significantly lower in C57 lidocaine group than in C57 ischemia group [the activities of AChE of cerebral cortex and hippocampus, (0.44+/-0.09) U/mg protein vs (0.57+/-0.08) U/mg protein, and (0.73+/-0.21) U/mg protein vs (1.08+/-0.27) U/mg protein, respectively; the activities of ChAT of hippocampus, (80.60+/-6.55) pmol/mg protein/min vs (93.66+/-11.15) pmol/mg protein/min; and the binding activities of M receptor of cerebral cortex and hippocampus, (6.03+/-0.74) pmol/mg protein vs (7.49+/-0.48) pmol/mg protein, and (7.56+/-0.92) pmol/mg protein vs (10.65+/-3.35) pmol/mg protein, respectively] (P< 0.05 or 0.01). However, they were significantly higher in ApoE lidocaine group than in ApoE ischemia group [the activities of ChAT of cerebral cortex and hippocampus, (66.99+/-7.55) pmol/mg protein/min vs (46.23+/-4.96) pmol/mg protein/min, and (116.46+/-24.05) pmol/mg protein/min vs (92.08+/-16.33) pmol/mg protein/min, respectively] (P<0.05 or 0.01). When compared between two strains, they were significantly higher in ApoE lidocaine group than in C57 lidocaine group (P< 0.05 or 0.01). CONCLUSION: Transient global cerebral ischemia caused significant brain damages in both strains of mice, which were represented by decline of learning and memorial function and damage of the central cholinergic system. Compared with the C57 mice, the ApoE mice had enhanced susceptibility to global cerebral ischemic injury as shown by more severe decline of the learning and memorial function. In the C57 mice, lidocaine significantly worsened the ischemic brain damage. In the ApoE mice, however, lidocaine significantly alleviated the ischemic cerebral results.

Acetylcholinesterase↗
PubMed1997

Human temporal lobe potentials in verbal learning and memory processes.

Animal experiments and lesion studies have shown the importance of temporal lobe structures for language and memory. We recorded intracranial cognitive potentials from the human lateral and medial temporal lobe in 26 patients with temporal lobe epilepsy undergoing presurgical evaluation, using a word- and a picture-recognition paradigm. Neuropsychological testing included word fluency, verbal reasoning, sustained attention and a verbal learning memory test (VLMT), which was an adapted version of the Rey auditory verbal learning test. Word-specific N400-potentials elicited in the middle temporal gyrus of the dominant left hemisphere (LTL-N400) predicted immediate recall performance after learning, whereas N400s, elicited by words but not pictures in the left anterior medial temporal lobe (AMTL-N400), predicted delayed recall. The number of words that were learned but forgotten after a 30-min delay correlated only with N400s elicited by words in the left anterior medial temporal lobe. Thus, intracranial recordings indicated that different electrophysiological responses in different temporal lobe structures were linked to memory scores from specific neuropsychological tests.

Adolescent↗
PubMedDate not supplied

Chronic, severe hypertension does not impair spatial learning and memory in Sprague-Dawley rats.

This study tested the hypothesis that long-term hypertension impairs spatial learning and memory in rats. In 6-wk-old Sprague-Dawley rats, chronic hypertension was induced by placing one of three sizes of stainless steel clips around the descending aorta (above the renal artery), resulting in a 20-80-mm Hg increase of arterial pressure in all arteries above the clip, that is, the upper trunk and head. Ten months later, the rats were tested for 5 d in a repeated-acquisition water maze task, and on the fifth day, they were tested in a probe trial; that is, there was no escape platform present. At the end of the testing period, the nonsurgical and sham control groups had similar final escape latencies (16 +/- 4 sec and 23 +/- 9 sec, respectively) that were not significantly different from those of the three hypertensive groups. Rats with mild hypertension (140-160 mm Hg) had a final escape latency of 25 +/- 6 sec, whereas severely hypertensive rats (170-199 mm Hg) had a final escape latency of 21 +/- 7 sec and extremely hypertensive rats (>200 Hg) had a final escape latency of 19 +/- 5 sec. All five groups also displayed a similar preference for the correct quadrant in the probe trial. Together, these data suggest that sustained, severe hypertension for over 10 mo is not sufficient to impair spatial learning and memory deficits in otherwise normal rats.

Animals↗
PubMed2001

Evidence that Ames dwarf mice age differently from their normal siblings in behavioral and learning and memory parameters.

There is strong evidence supporting the deleterious effects of aging on learning and memory and behavioral parameters in normal mice. However, little is known about the Ames dwarf mouse, which has a Prop-1 gene mutation resulting in deficiencies in growth hormone, thyroid-stimulating hormone, and prolactin. These mice are much smaller and live significantly longer than their normal siblings. Using the elevated plus-maze, locomotor activity meters, and an inhibitory avoidance learning task, the present study compared Ames dwarf mice to their normal siblings. Results showed that Ames dwarf mice did not experience an age-related decline in locomotor activity when compared to their young counterparts. Furthermore, old dwarf mice did not differ from the young groups in inhibitory avoidance retention, while old normal animals performed more poorly than both young groups on this test. Elevated plus-maze behavior did not differ in the old normal versus dwarf groups, but the old groups did differ from the young. Results indicate that both old groups experienced a significant decline in anxiety with age. Taken together, these results indicate that multiple hormone deficiencies resulting from a lack of primary pituitary function have beneficial effects on cognitive function and locomotor behavior in advanced age. In fact, the Ames dwarf mouse may provide a model for studies of delayed mental as well as physical aging.

Aging↗
PubMed2006

Regulation of CaMKII by alpha4/PP2Ac contributes to learning and memory.

Ca(2+)-dependent CaMKIIalpha activation with autophosphorylation plays an essential role in learning and memory. The regulation of CaMKIIalpha by dephosphorylation by protein phosphatase 1 (PP1) has been demonstrated. We addressed whether the protein phosphatase 2A (PP2A) that is abundant in the brain could be involved in the regulation of CaMKIIalpha. CaMKIIalpha was associated with the catalytic subunit of PP2A (PP2Ac) and alpha4, a regulator of PP2A. To investigate whether alpha4 plays an important role in the CNS, we established a neuron specific Cre transgenic mouse and a neuron specific alpha4 deficient mouse (N-alpha4 KO mouse). This N-alpha4 KO mouse showed impaired learning and memory in a water maze and also shuttle-box avoidance test. The activity of CaMKIIalpha also increased in hippocampus. An overexpression of alpha4 in the neuronal cell line demonstrated the activity of CaMKIIalpha to be regulated by alpha4. alpha4 and PP2Ac were localized in the cytoplasm but not in the postsynaptic density (PSD), thus suggesting that the dephosphorylation of CaMKIIalpha by alpha4/PP2Ac occurred in the cytoplasm. These results suggest that alpha4 and PP2A may thus play an important role in CaMKIIalpha regulation and thereby also influence learning.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Effects of BN-50730 (PAF receptor antagonist) and physostigmine (AChE inhibitor) on learning and memory in mice.

The present study was designed to investigate the effect of BN-50730, a PAF receptor antagonist, on learning and memory in mice using elevated plus-maze and to delineate the role of acetylcholine in modulating the effect of PAF receptor antagonist on learning and memory. BN-50730 administered immediately after plus-maze training on day 1 induced retrograde amnesia as indicated by a dose-dependent increase in transfer latency (TL) measured on day 2 whereas no such increase in TL was noted when BN-50730 (2.5 mg/kg, i.p.) was administered prior to plus-maze training. Physostigmine (0.5 mg/kg; 1.0 mg/kg, i.p.) administered 30 min prior to plus-maze training attenuated BN-50730-induced increase in TL measured on day 2. These results suggest that BN-50730, a PAF receptor antagonist, produced retrograde amnesia and physostigmine attenuated BN-50730-induced amnesia possibly through increased concentration of cerebral acetylcholine and a consequent increase in PAF release.

Acetylcholine↗
PubMed1998

Gene discovery in Drosophila: new insights for learning and memory.

Genetic approaches have been used to investigate increasingly complex biological systems. Here we review the current state of genetic analysis of learning and memory in the fruitfly, Drosophila melanogaster. Emerging findings support two main themes. First, discovery and manipulation of genes involved with behavioral plasticity in genetically accessible systems such as D. melanogaster enables dissection of the biochemical, cellular, anatomical, and behavioral pathways of learning and memory. Second, because core cellular mechanisms of simple forms of learning are evolutionarily conserved, biological pathways discovered in invertebrates are likely to be conserved in vertebrate systems as well.

Animals↗
PubMed1998

NC-1900, an active fragment analog of arginine vasopressin, improves learning and memory deficits induced by beta-amyloid protein in rats.

We have reported that the continuous infusion of beta-amyloid protein-(1-40) into the rat cerebral ventricle produces learning and memory deficits accompanied by dysfunction in the cholinergic and dopaminergic systems. L-Pyroglutamyl-L-asparaginyl-L-seryl-L-prolyl-L-arginylglycinamide (NC-1900), an active fragment analog of arginine vasopressin in the rat brain, is a stable peptide with a five-fold longer half-life than that of arginine vasopressin-(4-9). In the present study, we examined the effects of NC-1900 on learning and memory deficits in beta-amyloid protein-(1-40)-infused rats. The rats were injected subcutaneously with NC-1900 (0.1 and 1 ng kg(-1)) once a day throughout the period of behavioral examination. In the beta-amyloid protein-infused rats, learning and memory in water maze and passive avoidance tasks were impaired compared with these in the control rats. NC-1900 prevented the learning and memory deficits in beta-amyloid protein-infused rats. Moreover, NC-1900 tended to increase the choline acetyltransferase activity in the frontal cortex of the beta-amyloid protein-infused rats. These results suggested that NC-1900 could be useful for the treatment of patients with Alzheimer's disease.

Amyloid beta-Peptides↗
PubMedDate not supplied

Effects of aerosol-vapor JP-8 jet fuel on the functional observational battery, and learning and memory in the rat.

To determine whether JP-8 jet fuel affects parameters of the Functional Observational Battery (FOB), visual discrimination, or spatial learning and memory, the authors exposed groups of male Fischer Brown Norway hybrid rats for 28 d to aerosol/vapor-delivered JP-8, or to JP-8 followed by 15 min of aerosolized substance P analogue, or to sham-confined fresh room air. Behavioral testing was accomplished with the U.S. Environmental Protection Agency's Functional Observational Battery. The authors used the Morris swim task to test visual and spatial learning and memory testing. The spatial test included examination of memory for the original target location following 15 d of JP-8 exposure, as well as a 3-d new target location learning paradigm implemented the day that followed the final day of exposure. Only JP-8 exposed animals had significant weight loss by the 2nd week of exposure compared with JP-8 with substance P and control rats; this finding compares with those of prior studies of JP-8 jet fuel. Rats exposed to JP-8 with or without substance P exhibited significantly greater rearing and less grooming behavior over time than did controls during Functional Observational Battery open-field testing. Exposed rats also swam significantly faster than controls during the new target location training and testing, thus supporting the increased activity noted during Functional Observational Battery testing. There were no significant differences between the exposed and control groups' performances during acquisition, retention, or learning of the new platform location in either the visual discrimination or spatial version of the Morris swim task. The data suggest that although visual discrimination and spatial learning and memory were not disrupted by JP-8 exposure, arousal indices and activity measures were distinctly different in these animals.

Administration, Inhalation↗
PubMed2001

Hippocampus-dependent learning and memory is impaired in mice lacking the Ras-guanine-nucleotide releasing factor 1 (Ras-GRF1).

Previous results have suggested that the Ras signaling pathway is involved in learning and memory. Ras is activated by nucleotide exchange factors, such as the calmodulin-activated guanine-nucleotide releasing factor 1 (Ras-GRF1). To test whether Ras-GRF1 is required for learning and memory, we inactivated the Ras-GRF1 gene in mice. These mutants performed normally in a rota-rod motor coordination task, and in two amygdala-dependent tasks (inhibitory avoidance and contextual conditioning). In contrast the mutants were impaired in three hippocampus-dependent learning tasks: contextual discrimination, the social transmission of food preferences, and the hidden-platform version of the Morris water maze. These studies indicate that Ras-GRF1 plays a role in hippocampal-dependent learning and memory.

Amygdala↗
PubMedDate not supplied

Verbal learning and memory among heterozygous fragile X females.

In this paper we report the results of a brief examination of verbal learning and memory in 20 heterozygous fragile X [fra(X)] positive females and in 2 control groups of 20 subjects each. One control group was composed of fra(X)-negative mothers (obligate carriers) and sisters of male probands with fra(X) syndrome, while the other consisted of 14 head injured and 6 learning disabled females. Intellectual functioning was assessed by means of the Wechsler scales, and learning was assessed by several different clinical memory tests. Significant differences were found between groups on measures of short-term memory and learning efficiency. Groups did not differ on measures of cued recall or delayed recall. The findings are consistent with other data and suggest the possibility that central information processing and/or specific encoding processes are defective in persons with fra(X).

Adolescent↗
PubMed2005

Expression of c-fos and c-jun proteins in the marginal division of the rat striatum during learning and memory training.

BACKGROUND: A new brain region, the marginal division (MrD), was discovered at the caudal margin of the neostriatum. The MrD was shown to be involved in learning and memory in the rat. The aim of this study was to investigate the expression of the immediate-early genes c-fos and c-jun in the MrD of the striatum during learning and memory processes in the rat, immunocytochemical and Western blot methods were used to examine Y-maze trained rats. METHODS: The rats were divided into three groups, namely the training, pseudotraining, and control groups. After Y-maze training, the expression of the immediate-early genes c-fos and c-jun in the MrD of the rats was investigated using immunocytochemical and Western blot methods. RESULTS: After one hour of Y-maze training, the expression of c-jun and c-fos proteins was significantly enhanced in the MrD; the c-jun protein, in particular, was more intensely expressed in this region than in other parts of the striatum. The expression of these two proteins in the training group was significantly higher than in the pseudotraining and control groups. In addition, positive expression was also found in the hippocampus, cingulum cortex, thalamus, and in other areas. Western blot disclosed two immunoreactive bands for the anti-c-fos antibody (47 kD and 54 kD) and two immunoreactive bands for the anti-c-jun antibody (39 kD and 54 kD). CONCLUSIONS: These results indicate that the immediate-early genes c-fos and c-jun participate in signal transduction during the learning and memory processes associated with Y-maze training in rats.

Animals↗
PubMed2004

[Effect of gastrodia elata on learning and memory impairment induced by aluminum in rats].

OBJECTIVE: In order to investigate the mechanism of the improvement of Gastrodia elata (G.E.) on learning and memory impairment of rats exposed to aluminum. METHODS: 36 SD rats, adult and healthy, were divided into 6 groups at random: 1. normal saline, 2. Al3+ 5 mg/kg, 3. Al3+ 10 mg/kg, 4. normal saline +G.E., 5. Al3+ 5 mg/kg +G.E. and 6. Al3+ 10 mg/kg +G.E. Then, they were exposed to AlCl3 by intraperitioneal injection at a dose of 0.2 ml/d, 60 d. G.E. was administered by drinking water at a dose of 0.4 g/kg body weight. RESULTS: The results of learning and memory were recorded by Step-Down Test. It was showed that compared with the normal saline group, in the group of Al3+ 5 mg/kg, the content of brain cortex aluminum and EN1 increased significantly; the latency (LT) was shortened obviously(P < 0.01); the activity of AChE decreased and the activity of MAO increased (P < 0.01). In the group of Al3+ 10 mg/kg, the content of brain cortex aluminum, EN1 and EN2 increased significantly(P < 0.01), the LT is shortened obviously (P < 0.01), the activity of AChE decreased and the activity of MAO increased (P < 0.01). Compared with the group of Al3+ 5 mg/kg, in the group of Al3+ 5 mg/kg +G.E., EN1 decreased significantly (P < 0.05); the LT is prolonged obviously(P < 0.01), the activity of AChE increased(P < 0.05) and the activity of MAO decreased (P < 0.01). Compared with the group of Al3+ 10 mg/kg, in the group of Al3+ 10 mg/kg +G.E., both EN1 and EN2 decreased significantly(P < 0.01); the LT is prolonged obviously(P < 0.01), the activity of AChE increased (P < 0.01) and the activity of MAO decreased (P < 0.01). CONCLUSION: It is suggested that G.E. might decrease the content of brain cortex aluminum of rats. However it might improve the learning and memory ability possibly through regulating the cholinergic system and the monoaminergic system.

Aluminum↗
PubMed2006

Learning-related development of context-specific neuronal responses to places and events: the hippocampal role in context processing.

Contextual information plays a key role in learning and memory. Learned information becomes associated with the context such that the context can cue the relevant memories and behaviors. An extensive literature involving experimental brain lesions has implicated the hippocampus in context processing. However, the neurophysiological mechanisms of context coding are not known. Although "context" has typically been defined in terms of the background cues, recent studies indicate that hippocampal neurons are sensitive to subtle changes in task demands, even in an unchanging environment. Thus, the context may also include non-environmental features of a learning situation. In the present study, hippocampal neuronal activity was recorded while rats learned to approach different reward locations in two contexts. Because all of the training took place in the same environment, the contexts were defined by the task demands rather than by environmental stimuli. Learning to differentiate two such contexts was associated with the development of highly context-specific neuronal firing patterns. These included different place fields in pyramidal neurons and different event (e.g., reward) responses in pyramidal and interneurons. The differential firing patterns did not develop in a control condition that did not involve a context manipulation. The context-specific firing patterns could modulate activity in extrahippocampal structures to prime context-appropriate behavioral responses and memories. These results provide direct support for a context processing role of the hippocampus and suggest that the hippocampus contributes contextual representations to episodic memories.

Action Potentials↗