bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hippocampal conjunctive encoding, storage, and recall: Avoiding a trade‐off
Authors: O'Reilly Randall C. , McClelland James L. 
Published: May 2005

AbstractThe hippocampus and related structures are thought to be capable of (1) representing cortical activity in a way that minimizes overlap of the representations assigned to different cortical patterns (pattern separation); and (2) modifying synaptic connections so that these representations can later be reinstated from partial or noisy versions of the cortical activity pattern that was present at the time of storage (pattern completion). We point out that there is a trade‐off between pattern separation and completion and propose that the unique anatomical and physiological properties of the hippocampus might serve to minimize this trade‐off. We use analytical methods to determine quantitative estimates of both separation and completion for specified parameterized models of the hippocampus. These estimates are then used to evaluate the role of various properties and of the hippocampus, such as the activity levels seen in different hippocampal regions, synaptic potentiation and depression, the multi‐layer connectivity of the system, and the relatively focused and strong mossy fiber projections. This analysis is focused on the feedforward pathways from the entorhinal cortex (EC) to the dentate gyrus (DG) and region CA3. Among our results are the following: (1) Hebbian synaptic modification (LTP) facilitates completion but reduces separation, unless the strengths of synapses from inactive presynaptic units to active postsynaptic units are reduced (LTD). (2) Multiple layers, as in EC to DG to CA3, allow the compounding of pattern separation, but not pattern completion. (3) The variance of the input signal carried by the mossy fibers is important for separation, not the raw strength, which may explain why the mossy fiber inputs are few and relatively strong, rather than many and relatively weak like the other hippocampal pathways. (4) The EC projects to CA3 both directly and indirectly via the DG, which suggests that the two‐stage pathway may dominate during pattern separation and the one‐stage pathway may dominate during completion; methods the hippocampus may use to enhance this effect are discussed. © 1994 Wiley‐Liss, Inc.
Long‐lasting effects of partial hippocampal kindling on hippocampal physiology and function
Authors: Stan Leung L. , Zhao DiChen , Shen BiXia 
Published: May 2005

AbstractThe objective of this project was to study the behavioral and physiological effects at 6–9 weeks after evoking 15 afterdischarges (ADs) in hippocampal CA1 (partial hippocampal kindling). Rats were trained on the open radial arm maze (RAM) with all eight arms baited, kindled, and then tested again on the RAM, followed by in vitro recordings at 8–9 weeks after kindling. Partial kindling was manifested by an increase in hippocampal AD duration. Enhancement of the commissural basal dendritic excitatory postsynaptic potential (EPSP) was observed for at least 1 day after the ADs kindled rats performed worse than control rats during the 1st but not during the 7th or 8th week after kindling. Rats that were slow in acquiring the RAM showed more RAM errors after kindling than those that showed fast acquisition. At 8–9 weeks after kindling, as shown by field potential recording in the hippocampal slice in vitro, kindled rats showed an increase in paired‐pulse facilitation (PPF) of the EPSP in CA1 but a decreased PPF of the perforant path to dentate gyrus EPSP; no change in the PPF of the population spike was found in CA1 or DG. In a second group of rats that were not run on the RAM, at 6 weeks after kindling, PPF of the population EPSP and population spike were enhanced in the kindled rats compared to the control rats in CA1, but not in DG or CA3 in vitro (at 1.5, 2, or 4 times threshold intensity). In conclusion, partial hippocampal kindling induced persistent physiological effects for up to 8–9 weeks, and it is suggested that the normalization of the paired‐pulse population spike response in CA1 and DG at more than 6 weeks after kindling may be accompanied by a recovery of RAM performance. © 1994 Wiley‐Liss, Inc.
Dentate gyrus destruction and spatial learning impairment after corticosteroid removal in young and middle‐aged rats
Authors: Conrad Cheryl D. , Roy Edward J. 
Published: May 2005

AbstractWe investigated the functional and behavioral implications of chronic corticosteroid removal in young and middle‐aged rats. Prepubertal and 13‐month‐old rats were adrenalectomized (ADX) or sham operated (SHAM). The young ADX rats were divided further into three groups: ADX with no hormone replacement, ADX given corticosterone chronically, (chCORT), and ADX given corticosterone acutely at the time of Morris water maze testing (acCORT). All rats were run on the Morris water maze 12 weeks after surgery. They were then sacrificed and the brains were removed for histological analysis.The results showed that prolonged corticosteroid absence caused major damage to the dentate gyrus and learning impairment on the Morris water maze. The chCORT rats had little dentate gyrus cell loss and were as efficient as the controls in Morris water maze performance, whereas the acCORT rats had dentate gyrus cell loss and were impaired in the spatial acquisition task. Furthermore, exogenously administered corticosterone had an interactive effect on ADX rats. Water maze performance was improved in dentate gyrus damaged rats (acCORT) compared to ADX rats not given corticosterone, whereas ADX rats with very little dentate gyrus damage (chCORT) did not exhibit better water maze performance relative to controls. Middle‐aged ADX rats lost cells only in the dorsal blade of the dentate gyrus but they did not show a learning impairment in the Morris water maze relative to the middle‐aged controls. These results indicate that corticosteroids are trophic for the dentate gyrus, that mature granule cells are less affected by adrenalectomy, that corticosteroid absence is responsible for some water maze impairment in ADX rats, but that in addition to corticosteroid absence, a substantial amount of dentate gyrus damage is necessary to impair spatial learning. © 1995 Wiley‐Liss, Inc.
Activation of somatostatin‐synthesizing neurons in the hippocampal formation through kindling‐induced seizures
Authors: Pretel S. , Applegate C. D. , Piekut D. T. 
Published: May 2005

AbstractThe present study was designed to determine if and to what extent somatostatin (SST) synthesizing neurons of the hippocampal formation are activated during seizures, elicited through kindling of the perforant pathway. Tissue was used and analyzed from animals which had experienced a single afterdischarge, or a stage 3 or stage 5 seizure. The protein expression of the oncogene c‐fos in activated, depolarizing neurons was utilized to identify seizure‐activated SST‐synthesizing neurons. Combined immunocytochemical and in situ hybridization methods were used to identify these double‐labeled, Fos protein, and SST mRNA‐containing neurons. The results were quantified and compared across seizure stages. The resulting data demonstrate that at every stage of seizure development, a majority of SST‐synthesizing neurons is activated, but that these activated SST mRNA‐containing neurons represent only a minority of all seizure‐activated, Fos‐expressing neurons in the hippocampal formation. The data further reveal a numerical hierarchy in which the majority of double‐labeled neurons is present in the hilus of the dentate, followed by the stratum oriens of CA1. It is concluded that SST‐synthesizing neurons represent an integral component of the kindling activated neuronal network and, since the SST synthesizing neurons represent the minority of all seizure‐activated neurons in the hippocampal formation, that this neuronal network is likely to be of considerable neurochemical complexity. & 1995 Wiley‐Liss, Inc.
Intracellular correlates of hippocampal theta rhythm in identified pyramidal cells, granule cells, and basket cells
Authors: Ylinen Aarne , Soltész Iván , Bragin Anatol , Penttonen Markku , Sik Attila , Buzsáki György 
Published: May 2005

AbstractThe cellular‐synaptic generation of rhythmic slow activity (RSA or theta) in the hippocampus has been investigated by intracellular recording from principal cells and basket cells in anesthetized rats. In addition, the voltage‐, coherence‐, and phase versus depth profiles were examined by simultaneously recording field activity at 16 sites in the intact rat, during urethane anesthesia, and after bilateral entorhinal cortex lesion. In the extracellular experiments the large peak of theta at the hippocampal fissure was attenuated by urethane anesthesia and abolished by entorhinal cortex lesion. The phase versus depth profiles were similar during urethane anesthesia and following entorhinal cortex lesion but distinctly different in the intact, awake rat. These observations suggest that dendritic currents underlying theta in the awake rat may not be revealed under urethane anesthesia.The frequency of theta‐related membrane potential oscillation was voltage‐independent in pyramidal neurons, granule cells, and basket cells. On the other hand, the phase and amplitude of intracellular theta were voltage‐dependent in all three cell types with an almost complete phase reversal at chloride equilibrium potential in pyramidal cells and basket cells. At strong depolarization levels (less than 30 mV) pyramidal cells emitted calcium spike oscillations, phase‐locked to theta. Basket cells possessed the most regular membrane oscillations of the three cell types. All neurons of this study were verified by intracellular injection of biocytin. The observations provide direct evidence that theta‐related rhythmic hyperpolarization of principal cells is brought about by the rhythmically discharging basket neurons. Furthermore, the finding that basket cells were also paced by rhythmic inhibitory postsynaptic potentials during theta suggest that they were periodically hyperpolarized by their GABAergic septal afferents. & 1995 Wiley‐Liss, Inc.
Information acquired by the hippocampus interferes with acquisition of the amygdala‐based conditioned‐cue preference in the rat
Authors: McDonald Robert J. , White Norman M. 
Published: May 2005

AbstractWhite and McDonald (1993, Behav Brain Res 55:269–281) previously reported that animals with amygdala lesions failed to acquire a conditioned‐cue preference (CCP) based on spatial cues, but that animals with fornix lesions exhibited larger CCPs of this type than normal animals. The present experments focused on the hippocampal interference with amygdala‐based CCP learning inferred from this finding. In experiment 1 we tested the hypothesis that this interference was due to the acquistion of information about the maze and its environment during a 10 min period of free exploration of the maze before the start of CCP training, hitherto given to all animals in these experiments. Normal animals that were not preexposed to the maze and animals that were preexposed to similar maze in a different room both exhibited larger CCPs than animals that were preexposed to the same maze in the same room as CCP training and testing. This suggests that normal animals acquire context‐specific information during the preexposure period and that this may be the cause of the hippocampus‐based interference with the amygdala‐mediated CCP. In experiment 2 we attempted to determine if the information thought to be acquired by the hippocampal memory system interferes with acquistion or expression of the CCP. As previously demonstrated, animals that received fornix lesions before preexposure (i.e., before the start of the experiment) exhibited larger than normal CCPs. Animals that received fornix lesions after preexposure but before CCP training and animals that received fornix lesions after CCP training but before testing both exhibited normal CCPs. These findings suggest that a hippocampally mediated process acts via a pathway that does not involve the fornix to inhibit either acquistion or expression, or both, of the CCP. These results imply the existence of some form of competition for behavioral control among neural systems that may be specialized for acquiring different types of information about the same situations. © 1995 Wiley‐Liss, Inc.
Evidence for physiological growth of hippocampal mossy fiber collaterals in the guinea pig during puberty and adulthood
Authors: Wolfer David P. , Lipp Hans‐Peter 
Published: May 2005

AbstractBy means of Timm's procedure and computer‐assisted morphometry, the left and right hippocampi of 69 hybrid guinea pigs from nine age levels (P5, P10, P20, P40, P80, P160, P320, and P610, and P1100) were analyzed for postnatal growth of recurrent hippocampal mossy fiber collaterals (RMFC) terminating below, within, and above the dentate granule cell layer. Postnatal growth of RMFCs showed, in both sexes, a first peak at P40, with stainable mossy fiber boutons covering the cell bodies of large neurones, some of which were reminiscent of basket cells. No significant changes of the density of mossy fiber collaterals were noticed from P40 to P160. At P320 a remarkable expansion of RMFCs was noted in a few animals, and by P610 all animals showed highly proliferated RMFCs which densely covered cell bodies and dendrites of target cells. The oldest group (P1100) showed an equal or slightly lowered density of RMFCs.We conclude that the growth of recurrent mossy fiber collaterals occurs in two spurts. The first completes just before sexual maturity. The second spurt occurs in the mid‐life period, between P160 and P610. © 1995 Wiley‐Liss, Inc.
AMPA‐selective glutamate receptor subtype immunoreactivity in the hippocampal formation of patients with Alzheimer's disease
Authors: Ikonomovic Milos D. , Sheffield Roxanne , Armstrong David M. 
Published: May 2005

AbstractImmunocytochemical techniques were employed in order to examine the distribution and relative intensity of the AMPA receptor subunits GluR1 and GluR2/3 within the hippocampal formation of normal controls and Alzheimer's disease (AD) cases. Throughout our investigation we examined cases exhibiting a wide range of pathologic severity, thus allowing us to correlate our immunohistochemical data with the extent of pathology. Specifically, we investigated the distribution of these receptor subunits in hippocampal sectors that are particularly vulnerable to AD pathology (i. e., CA1 and subiculum) and compared these findings with those obtained following examination of sectors that are generally resistant to pathologic change (i. e., CA2/3, dentate gyrus). Within vulnerable sectors we observed a variable loss of GluR1 and GluR2/3 immunolabeling. The degree to which these proteins were reduced appeared to correlate with the extent of neurofibrillary pathology and cell loss. Despite the loss of labeled cells, the intensity of immunolabeling within the remaining neurons was comparable with, and in many instances even greater than, that observed in control cases. Within resistant sectors, the distribution of immunoreactive elements was comparable in both case groups yet the intensity of immunolabeling was markedly increased in AD cases, particularly in the molecular layer of the dentate gyrus and in the stratum lucidum of CA3 (i. e., the termination zones of perforant pathway and mossy fibers). In addition, within AD cases dramatic increases were observed within the supragranular and polymorphic layer of the dentate gyrus (i. e., the terminal zones of sprouting mossy fiber collaterals). The increase in GluR1 and GluR2/3 immunolabeling is hypothesized to occur in response to the deafferentation of selected glutamatergic pathways. Moreover, our data support that hippocampal plasticity is preserved, even in severe AD cases, and suggest a critical role for AMPA receptor subunits in this plasticity and in maintaining hippocampal functioning. © 1995 Wiley‐Liss, Inc.
Caffeine: Clinical and experimental effects in humans
Authors: Bruce M. S. , Lader M. H. 
Published: May 2005

AbstractThe contrast of attitudes to the psychiatric effects of caffeine between North America and Britain is highlighted. A summary of the dietary sources, pharmacology and effects of caffeine on normal subjects is given. The emphasis in normal subjects is on the acute, chronic, toxic and withdrawal effects. With this background information, a more specific evaluation of the psychiatric issues are discussed. In conclusion, the case is made for the inclusion of a specific category, in non‐dependent abuse of drugs, for caffeine.
Therapeutic drug monitoring in psychiatry—is it worthwhile?
Authors: Burgess C. D. 
Published: May 2005

AbstractAlthough many drugs used in psychiatry can be assayed in body fluids, the measurement of agents such as the tricyclic antidepressants (TCAs) and the antipsychotic agents in the therapeutic setting remains controversial. This is due to both pharmacokinetic and pharmacodynamic factors. Pharmacokinetically, neither the TCAs nor the antipsychotics meet the criteria for therapeutic drug monitoring, because they undergo extensive first‐pass metabolism to active metabolites, their mechanism of action probably involves alteration in receptor responsiveness, and at least for the TCAs protein binding is not constant. The pharmacodynamic end points in assessing depression and schizophrenia have also proved difficult to define; thus the relationship between plasma levels and clinical response has proved elusive. Lithium, alone, is suitable for therapeutic drug monitoring because it has a narrow therapeutic range, is not protein bound, is not metabolized, and there is serum level variability for the same dose. Besides this agent, plasma level measurement is unlikely to add any benefit to the patient in the clinical setting.
Plasma fluphenazine concentrations in outpatients receiving fluphenazine decanoate (Modecate)
Authors: Kimber Nigel M. , Marriott Peter F. , Norman Trevor R. , Burrows Graham D. 
Published: May 2005

AbstractPlasma fluphenazine concentrations were measured by neuroleptic radioreceptor assay in 17 outpatients receiving chronic treatment with intramuscular fluphenazine decanoate. The range of concentrations was 0.5–2.4 μg/L over the dosage range of 0.30–3.2 mg/d. Age, sex and smoking status had no influence on plasma fluphenazine concentrations, which were not correlated with dose (expressed as mg/kg/d). There was no significant correlation between plasma concentration and clinical status of the patients. No difference in plasma concentration between patients with extrapyramidal signs or tardive dyskinesia and those without signs were observed.
Transdermal scopolamine: Effects of single and repeated patches upon aspects of vision
Authors: Parrott A. C. 
Published: May 2005

AbstractTransdermal scopolamine and transdermal placebo patches were administered on alternating days to 12 normal volunteer subjects. Visual near‐point values and self‐reports of blurred vision were systematically assessed 24 hours following each transdermal patch. Blurred vision was not reported following the first scopolamine patch, but became increasingly frequent following successive scopolamine patches. Six of the 12 subjects reported blurred vision by their fourth scopolamine patch. Subjects reporting blurred vision had long initial visual near‐points (i.e. were comparatively hypermetropic), whereas subjects not reporting blurred vision had short initial visual near‐points (i.e. were comparatively myopic). The visual near‐point values of the (hypermetropic) subjects who developed blurred vision became longer following each successive scopolamine patch, whereas the visual near‐point values of the (myopic) subjects not reporting blurred vision remained basically unchanged. Visual changes following scopolamine have been previously shown to be slow to develop and slow to dissipate; this slow time course probably produced the cumulative visual problems reported here.
The use of flumazenil in prevention of Diazepam dependence in the rat
Authors: Baldwin Helen A. , Hitchcott Paul K. , File Sandra E. 
Published: May 2005

AbstractRats were treated with diazepam (4 mg/kg per day) or its vehicle for 21 days. Twenty‐four hours after their last dose they were tested in the social interaction test of anxiety. Diazepam withdrawal significantly reduced the time spent in social interaction compared with controls, indicating an anxiogenic withdrawal response. The administration of a single dose of flumazenil (4 mg/kg) during chronic diazepam treatment, 7 or 14 days before testing, prevented the development of this withdrawal response. The clinical implications of these findings are discussed.
Clinical evaluation of alprazolam in patients with panic disorder: A double‐blind comparison with imipramine
Authors: Lepola U. , Heikkinen H. , Rimón R. , Riekkinen P. 
Published: May 2005

AbstractThe antipanic effect and tolerability of alprazolam and imipramine were compared during 9 weeks in 55 inpatients with panic disorder with or without agoraphobia. Both drugs decreased significantly the frequency of panic attacks, alprazolam as early as 3 weeks of treatment. The symptoms of generalized anxiety and depression decreased similarly in both groups. The tolerability of alprazolam appeared slightly better than that of imipramine. Drug‐induced anticholinergic side‐effects were more frequent in the imipramine group, whereas sedation, impotency, and myoclonic jerks appeared more often in the alprazolam group.
The effects of caffeine on two computerized tests of attention and vigilance
Authors: Frewer L. J. , Lader M. 
Published: May 2005

AbstractSingle doses of caffeine (250 mg, 500 mg) or placebo were administered double‐blind to healthy volunteer subjects (n = 12), using a fully balanced crossover design (Williams square) with 1‐week washout. Assessments were made predrug, and at 45 min and 165 min post‐drug administration. The test battery comprised physiological measures (blood pressure, heart rate and urinary volume), subjective measures of alertness, a letter cancellation task (one‐target, two‐target and four‐target versions), and two computerized measures of attention and vigilance: a rapid information processing task and a continuous attention task. Physiological variables did not alter following caffeine administration, but subjective and cognitive variables showed significant changes in the predicted direction. Thus, doserelated changes in subjective calmness and interest were observed, together with changes in performance for the letter cancellation task at low and intermediate difficulty levels. A dose‐related performance improvement was observed for the rapid information processing task. The continuous attention task was also sensitive to the effects observed for the rapid information processing task. The continuous attention task was also sensitive to the effects of caffeine. The 250 mg dose offset the decline in attention observed under placebo, and indeed facilitated performance at both post‐drug administration times. The 500 mg dose impaired performance at 45 min and improved it at the 165 min post‐administration time. Sensitivity to vigilance change was also observed within test sessions for this test, indicating that the continuous attention task was more sensitive to caffeine‐induced changes in attention than the rapid information processing task.