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Potentiation of amygdaloid and hippocampal auditory‐evoked potentials in a discriminatory fear‐conditioning task in mice as a function of tone pattern and context
Author(s) -
Tang Jianrong,
Wagner Stefanie,
Schachner Melitta,
Dityatev Alexander,
Wotjak Carsten T.
Publication year - 2003
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2003.02758.x
Subject(s) - fear conditioning , amygdala , neuroscience , long term potentiation , conditioning , psychology , auditory cortex , hippocampal formation , classical conditioning , stimulus (psychology) , startle response , freezing behavior , medicine , cognitive psychology , statistics , receptor , mathematics
According to the local memory storage hypothesis, information about the tone–shock association in an auditory fear‐conditioning paradigm is stored in synapses within the lateral amygdala. Thus, fear‐conditioning‐induced potentiation of auditory‐evoked potentials in response to a conditioned stimulus (CS+, a series of short lasting tones; patterned tone) has been interpreted as an in vivo correlate of amygdaloid synaptic plasticity. Here, we re‐examine the specificity of potentiation of auditory‐evoked potentials in terms of (i) local confinement to the lateral amygdala, (ii) parameters of CS+ and (iii) influence of context, using a discriminatory fear‐conditioning paradigm. Adult male C57BL/6J mice were implanted with recording electrodes aimed at the lateral amygdala, the CA1 region of the hippocampus and the neck muscles for simultaneous recordings of auditory‐evoked potentials and startle responses. In a neutral context, auditory‐evoked potentials within lateral amygdala and CA1 as well as startle and freezing responses to the CS+ were significantly potentiated following conditioning, as compared with pre‐conditioning values and responses to a neutral stimulus (CSn; tone of different frequency). Potentiation was only evident if CS+ was presented as a uniform series but not if presented mixed with CSn. Accordingly, mice failed to show intensified freezing to a patterned tone if a single lasting tone of the same frequency served as CS+. Both CA1 and lateral amygdala auditory‐evoked potentials were potentiated in response to CSn if presented in the conditioning context. These findings demonstrate that (i) potentiation of auditory‐evoked potentials is not restricted to the lateral amygdala, (ii) both tone frequency and pattern of tone presentation are essential for proper CS+ recognition and (iii) contextual memory leads to a general potentiation of auditory‐evoked potentials.