Hippocampal lesions and discrimination performance of mice in the radial maze: Sparing or impairment depending on the representational demands of the task

Nicole Etchamendy, Aline Desmedt, Cedric Cortes-Torrea, Aline Marighetto, Robert Jaffard
Hippocampus. 2003-01-01; 13(2): 197-211
DOI: 10.1002/hipo.10055

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1. Hippocampus. 2003;13(2):197-211.

Hippocampal lesions and discrimination performance of mice in the radial maze:
sparing or impairment depending on the representational demands of the task.

Etchamendy N(1), Desmedt A, Cortes-Torrea C, Marighetto A, Jaffard R.

Author information:
(1)Laboratoire de Neurosciences Cognitives, Université de Bordeaux 1, Talence
Cedex, France.

The effects of ibotenate hippocampal lesions on discrimination performance in an
eight-arm radial maze were investigated in mice, using a three-stage paradigm in
which the only parameter that varied among stages was the way the arms were
presented. In the initial learning phase (stage 1), animals learned the valence
or reward contingency associated with six (three positive and three negative)
adjacent arms of the maze using a successive (go/no-go) discrimination procedure.
In the first test phase (stage 2), the six arms were grouped into three pairs, so
that on each trial, the subject was faced with a choice between two adjacent arms
of opposite valence (concurrent two-choice discrimination). In the second test
phase (stage 3), the subject was faced with all six arms simultaneously
(six-choice discrimination). Hippocampal-lesioned mice acquired the initial
learning phase at a near-normal rate but behaved as if they had learned nothing
when challenged with the two-choice discriminations at stage 2. In contrast, they
behaved normally when confronted with the six-choice discrimination at stage 3.
Detailed examination of within- and between-stage performance suggests that
hippocampal-lesioned mice perform as intact mice when presentation of the
discriminanda encourages the storage and use of separate representations (i.e.,
in initial learning and six-choice discrimination testing), but that they fail in
test situations that involve explicit comparisons between such separate
representations (two-choice discriminations), hence requiring the use of
relational representations.

DOI: 10.1002/hipo.10055
PMID: 12699328 [Indexed for MEDLINE]


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