Leonard E. Jarrard

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An overview of lesion experiments concerned with the involvement of the hippocampus in learning and memory in the rat is presented. Multiple injections of small amounts of ibotenic acid were used to selectively remove the hippocampus (dentate gyrus, hilar cells, CA1-CA3 pyramidal cells). Similar selective, axon-sparing ibotenate lesions of hippocampus were(More)
Procedures are described for lesioning two components of the hippocampal formation (hippocampus, subiculum) using multiple injections of small amounts of ibotenic acid (IBO). The resulting loss of cells is more selective and limited than can be obtained with conventional techniques. Thus, problems associated with damage to adjacent areas, fibers-of-passage,(More)
Experiment 1 investigated the effects of catecholaminergic deafferentation or cell body lesions of the amygdala on fear conditioning to explicit and contextual cues. Bilateral infusions of quinolinic acid mainly damaged neurons within the basolateral region of the amygdala. 6-Hydroxydopamine infusions at the same coordinates resulted in an 86% depletion of(More)
Kainic acid (KA) lesions were used to study the effects of damage to the CA3 cell field and subiculum on performance of complex place and cue tasks. In Experiment 1, neuroanatomical techniques were employed to determine the selectivity of the lesions. In a within-subjects design, rats in Experiment 2 were trained before the operations to run on an eight-arm(More)
Damage to either the fimbria-fornix or to the hippocampus can produce a deficit in spatial behavior and change in locomotor activity but the extent to which the two kinds of damage are comparable is not known. Here we contrasted the effects of cathodal sections of the fimbria-fornix with ibotenic acid lesions of the cells of the hippocampus (Ammon's horn(More)
Although there is a good deal of evidence that animals require the hippocampus for learning place responses, animals with damage to the afferent and efferent fibers coursing through the fimbria-fornix have been shown to acquire a place response. This finding suggests either that the cells of the hippocampus proper (CA1-4 and dentate gyrus), via their(More)
According to configural association (CAS) theory (Sutherland & Rudy, 1989), an intact hippocampus is required for rats to solve learning problems that are based on "configural" processes. This theory identifies the negative patterning discrimination as a critical example of this type of problem. Rudy and Sutherland (1989) reported disruption of negative(More)
The behavioral effects of interrupting the axons that pass in the fimbria and dorsal fornix were compared with the effects of selective removal of the cells that comprise the hippocampus with ibotenic acid. Starting 4.5 months after surgery, lesioned and control rats were (i) trained in both the Morris water maze and the eight-arm radial maze using(More)
The effects of ibotenate lesions of the hippocampus (HIPP) or hippocampus plus collateral damage to extrahippocampal structures (HCX) were investigated in rats trained to criterion on spatial versions of either a delayed-match (DMS) or delayed-nonmatch-to-sample (DNMS) task. After recovery from surgery, animals were retrained at "0" sec delays, then(More)
Rats were given injections of ibotenic acid that made lesions of neurons throughout the hippocampus (CHC), or restricted to area CA3 (CA3), or to the subiculum (SUB), and were trained to lever press on a differential reinforcement of low rates (DRL) schedule. Their performance efficiency was compared with that of sham-operated (SO) rats in three(More)