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  • 1
    Electronic Resource
    Electronic Resource
    Septo-hippocampal connections and the hippocampal theta rhythm (1979)
    Springer
    Experimental brain research 37 (1979), S. 49-63 
    Details
    ISSN: 1432-1106
    Keywords: Septum ; Hippocampus ; Theta ; Cholinesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recordings were made of spontaneous hippocampal theta activity in free-moving rats, before and after a variety of lesions. Three recording sites were used to monitor activity in the dorsal hippocampus, the ventral hippocampus, or close to the site of the hippocampal flexure. Electrolytic lesions were made in the medial septal area or the dorso-lateral septal area; surgical transections were made of the fimbria or dorso-medial area of the fornix. Following lesions restricted to the medial septal area, theta was abolished throughout the hippocampus; after lesions restricted to the dorso-lateral septal area theta was retained. Fimbria lesions abolished theta in the ventral, but not the dorsal hippocampus; dorso-medial fornix lesions abolished it in the dorsal, but not the ventral, hippocampus. In some subjects the hippocampal formation was subsequently stained for cholinesterase: cholinesterase staining loss was generally associated with theta loss, but this was not clear at the flexure recording site. It was confirmed that theta is dependent upon the integrity of the medial septal area. It was concluded that damage to hippocampal afferents from the septum does abolish theta, while damaging the feedback efferents does not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01474253
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of intrahippocampal ibotenate on resistance to extinction after continuous or partial reinforcement (1986)
    Springer
    Experimental brain research 61 (1986), S. 519-530 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampus ; Subiculum ; Partial reinforcement extinction effect ; Partial reinforcement acquisition effect ; Entorhinal cortex ; botenate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracerebral injections of ibotenate were used to produce, in rats, extensive cell loss in the hippocampus and dentate gyrus (complete hippocampal, CH), in the CH plus subiculum (SUB + CH), or in the subiculum plus entorhinal cortex (SUB + EC). These rats and sham-operated controls were trained to run in a straight alley for food reward delivered on a continuous (CR) or partial (PR) reinforcement schedule. In controls PR training gave rise to the well-known partial reinforcement extinction effect (PREE), i.e., greater resistance to extinction than that observed in CR-trained animals. Previous work had shown that large aspiration lesions of the hippocampal formation eliminate the PREE by increasing resistance to extinction in CR-trained animals and decreasing resistance to extinction in PR-trained animals. In the present experiments the PREE survived CH lesions, which increased resistance to extinction in both CR and PR training conditions; these effects were observed in the start and run (but not goal) sections of the alley. In contrast, subicular cell loss (in both SUB + CH and SUB + EC groups) abolished the PREE (but in the goal section only) by increasing resistance to extinction in the CR condition and decreasing resistance to extinction in the PR condition. In addition, some of the effects of PR training on start and run speeds during acquisition were altered by the CH and SUB + CH lesions. These results confirm previous data showing that the hippocampal formation plays a role in mediating the behavioural effects of PR training, but require modification of the model previously proposed to account for these data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237577
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  • 3
    Electronic Resource
    Electronic Resource
    Fornix-fimbria section and the partial reinforcement extinction effect (1985)
    Springer
    Experimental brain research 58 (1985), S. 435-439 
    Details
    ISSN: 1432-1106
    Keywords: Fornix-fimbria ; Partial reinforcement ; Resistance to extinction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were trained to run in an alley for food reward given on every trial (continuous reinforcement, CR) or on a random 50% of trials (partial reinforcement, PR) and were then extinguished. Sham-operated controls showed the normal partial reinforcement extinction effect (PREE), in that PR-trained animals were significantly more resistant to extinction than CR-trained animals. The PREE was significantly reduced by lesions of the fornix-fimbria. The reduction was largely a consequence of a reduction in resistance to extinction in PR-trained rats with fimbria-fornix lesions. These results are discussed in the light of other experiments that have studied disconnections in the septo-hippocampal system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235860
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  • 4
    Electronic Resource
    Electronic Resource
    Cytotoxic lesions of the retrohippocampal region attenuate latent inhibition but spare the partial reinforcement extinction effect (1997)
    Springer
    Experimental brain research 115 (1997), S. 247-256 
    Details
    ISSN: 1432-1106
    Keywords: Key words Entorhinal cortex ; Subiculum ; Retrohippocampus ; Latent inhibition ; Partial reinforcement extinction effect ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Experiment 1 assessed the effect of cytotoxic retrohippocampal (entorhinal and extra-subicular cortices) lesions on the development of latent inhibition (LI) using an off-the-baseline, between-subjects, conditioned emotional response paradigm. Sham-operated controls and unoperated rats that had been pre-exposed to a light stimulus prior to light-shock pairings showed less conditioned suppression towards the light stimulus than the nonpre-exposed animals, thus demonstrating LI. However, LI was not evident in rats with retrohippocampal lesions. In experiment 2, the same animals were trained to run in an straight runway for food. Half of the animals were trained under a 50% partial reinforcement schedule (i.e. they were rewarded randomly on half of the acquisition trials) and the other half were trained under a continuous reinforcement schedule (i.e. they were rewarded on every acquisition trial). When tested in extinction, animals trained on the partial reinforcement schedule showed greater persistence than animals trained on continuous reinforcement, thus demonstrating the partial reinforcement extinction effect (PREE). Rats with retrohippocampal lesions showed a PREE that was at least as clear as that seen in the sham-operated controls and in the unoperated animals. It is concluded that cytotoxic lesions of the retrohippocampal region selectively led to an abolition of LI, but spared the PREE. The present study thus provided evidence against the hypothesis that LI and the PREE share a common neural substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005694
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  • 5
    Electronic Resource
    Electronic Resource
    Potentiation of amphetamine-induced locomotor activity following NMDA-induced retrohippocampal neuronal loss in the rat (1995)
    Springer
    Experimental brain research 106 (1995), S. 356-364 
    Details
    ISSN: 1432-1106
    Keywords: Retrohippocampal cortex ; Locomotion ; Amphetamine ; Ventral striatum ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present experiment assessed the locomotor response to a low dose (1 mg/kg) of systemic gemd-amphetamine in rats with cytotoxic lesions of the retrohippocampus (entorhinal and extra-subicular cortices), compared with vehicle-operated shams and unoperated controls. Under spontaneous and saline conditions, both the sham and the lesioned animals were more active than unoperated controls, and they did not differ from each other. Systemic gemd-amphetamine produced increased locomotion in all groups, but this effect was potentiated in animals with retrohippocampal lesions; two control groups did not differ from each other in their response to the drug. The present results are consistent with the suggestion that cell loss within the retrohippocampal region could affect the functional response of nucleus accumbens to amphetamine. The results are discussed in terms of the interaction between the retrohippocampus and nucleus accumbens in the control of mesolimbic dopamine release and the possible implications for schizophrenia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241131
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of hippocampectomy and of fimbria section upon the partial reinforcement extinction effect in rats (1980)
    Springer
    Experimental brain research 38 (1980), S. 273-283 
    Details
    ISSN: 1432-1106
    Keywords: Partial reinforcement extinction effect ; Hippocampectomy ; Fimbria ; Extinction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were trained to run in an alley for food reward given on every trial (continuous reinforcement, CR) or on a random 50% of trials (partial reinforcement, PR) and were then extinguished. Sham-operated controls showed the usual partial reinforcement extinction effect (PREE), i.e., PR-trained animals were more resistant to extinction than CR-trained animals. The PREE was abolished by hippocampectomy, which increased resistance to extinction in CR-trained rats and decreased it in PR-trained rats. Bilateral fimbria section had no effect on resistance to extinction in either condition. These results are discussed in the light of theories of hippocampal function and the anatomy of septohippocampal connections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236646
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  • 7
    Electronic Resource
    Electronic Resource
    Resistance to extinction after schedules of partial delay or partial reinforcement in rats with hippocampal lesions (1985)
    Springer
    Experimental brain research 59 (1985), S. 273-281 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampus lesion ; Partial reinforcement ; Delay of reinforcement ; Inter-trial interval ; Inter-event interval ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two experimental procedures were employed to establish the reason why hippocampal lesions apparently block the development of tolerance for aversive events in partial reinforcement experiments, but do not do so in partial punishment experiments. Rats were trained to run in a straight alley following hippocampal lesions (HC), cortical control lesions (CC) or sham operations (SO), and resistance to extinction was assessed following differing acquisition conditions. In Experiment 1 a 4–8 min inter-trial interval (ITI) was used. Either every acquisition trial was rewarded immediately (Continuous Reinforcement, CR), or only a randomly selected half of the trials were immediately rewarded, the reward being delayed for thirty seconds on the other trials (Partial Delay, PD). This delay procedure produced increased resistance to extinction in rats in all lesion groups. In Experiment 2 the ITI was reduced to a few seconds, and rats were trained either on a CR schedule, or on a schedule in which only half the trials were rewarded (Partial Reinforcement, PR). This form of partial reinforcement procedure also produced increased resistance to extinction in rats in all lesion groups. It thus appears that hippocampal lesions only prevent the development of resistance to aversive events when the interval between aversive and subsequent appetitive events exceeds some minimum value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230907
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of pre- and postweaning rearing conditions on latent inhibition and partial reinforcement extinction effect in male rats
    Amsterdam : Elsevier
    Behavioral and Neural Biology 53 (1990), S. 189-204 
    Details
    ISSN: 0163-1047
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Psychology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0163-1047(90)90407-W
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  • 9
    Electronic Resource
    Electronic Resource
    Discrimination of response-contingent and response-independent shock by rats: Effects of medial and lateral septal lesions and chlordiazepoxide
    Amsterdam : Elsevier
    Behavioral and Neural Biology 35 (1982), S. 121-138 
    Details
    ISSN: 0163-1047
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Psychology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0163-1047(82)91143-8
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of NMDA-induced retrohippocampal lesions on performance of four spatial memory tasks known to be sensitive to hippocampal damage in the rat (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Four separate cohorts of rats were employed to examine the effects of cytotoxic retrohippocampal lesions in four spatial memory tasks which are known to be sensitive to direct hippocampal damage and/or fornix-fimbria lesions in the rat. Selective retrohippocampal lesions were made by means of multiple intracerebral infusions of NMDA centred on the entorhinal cortex bilaterally. Cell damage typically extended from the lateral entorhinal area to the distal ventral subiculum. Experiment 1 demonstrated that retrohippocampal lesions spared the acquisition of a reference memory task in the Morris water maze, in which the animals learned to escape from the water by swimming to a submerged platform in a fixed location. In the subsequent transfer test, when the escape platform was removed, rats with retrohippocampal lesions tended to spend less time searching in the appropriate quadrant compared to controls. Experiment 2 demonstrated that the lesions also spared the acquisition of a working memory version of the water maze task in which the location of the escape platform was varied between days. In experiment 3, both reference and working memory were assessed using an eight-arm radial maze in which the same four arms were constantly baited between trials. In the initial acquisition, reference memory but not working memory was affected by the lesions. During subsequent reversal learning in which previously baited arms were now no longer baited and vice versa, lesioned animals made significantly more reference memory errors as well as working memory errors. In experiment 4, spatial working memory was assessed in a delayed matching-to-position task conducted in a two-lever operant chamber. There was no evidence for any impairment in rats with retrohippocampal lesions in this task. The present study demonstrated that unlike direct hippocampal damage, retrohippocampal cell loss did not lead to a general impairment in spatial learning, implying that the integrity of the retrohippocampus and/or its interconnection with the hippocampal formation is not critical for normal hippocampal-dependent spatial learning and memory. This outcome is surprising for a number of current hippocampal theories, and suggests that other cortical as well as subcortical inputs to the hippocampus might be of more importance, and further raises the question regarding the functional significance of the retrohippocampal region.Introduction
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1999.00413.x
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