Journal article
Neurophysiological Substrates of Context Conditioning in Hermissenda Suggest a Temporally Invariant Form of Activity-Dependent Neuronal Facilitation
Neurobiology of learning and memory, Vol.72(2), pp.95-117
09/1999
DOI: 10.1006/nlme.1998.3890
PMID: 10438650
Abstract
The neurophysiological basis for context conditioning is conceptually problematic because neurophysiological descriptions of activity-dependent (associative) forms of neuronal plasticity uniformly assume that a specific temporal relationship between signals is necessary for memory induction. In the present experiments, this problem is addressed empirically by presenting, as a temporally diffuse contextual signal, a stimulus that results in known neural modifications following punctate (temporally contiguous) pairings with an aversive unconditioned stimulus. Hermissenda were trained to discriminate between adjoining contexts that were distinguished only in that one was lit and one was dark. Thirty unsignaled rotations were presented during each of three 15-min sessions in one of the two (lit or dark) contexts. Prior to training, animals displayed a slight preference for the lit context. After exposure to unsignaled rotation, animal's preferences shifted strongly to the dark context if unsignaled rotations were presented in the light, and tended (nonsignificantly) to the lit context if unsignaled rotations were presented in the dark. The B photoreceptors of the Hermissenda eye undergo several forms of activity-dependent facilitation (e.g., an increase in neuronal input resistance and evoked spike frequency) following pairings of punctate light (CS) and presynaptic vestibular stimulation (US). Similar facilitation in the B photoreceptor was observed following in vitro training that mimicked context conditioning in which presynaptic vestibular stimulation was presented repetitively during a continuous 7.5-min light. Subsequently, Ca2+-imaging experiments were conducted with Fura-2AM. It was determined that intracellular Ca2+, the CS-induced second messenger critical for the induction of activity-dependent facilitation, was elevated in the B photoreceptor throughout the 7.5-min light presentation. These results indicate that activity-dependent facilitation within similar neural structures can underlie learning about both temporally diffuse contextual stimuli and temporally punctate CS-US pairings. These results suggest that a common mechanism may underlie learning about diffuse contextual stimuli as well as punctate-conditioned stimuli, provided that the stimuli are processed similarly in each type of conditioning arrangement. Consequently, the expression of different responses to contextual and discrete stimuli are likely to reflect a higher property of the neural network, and do not necessarily arise from unique underlying mechanisms.
Details
- Title: Subtitle
- Neurophysiological Substrates of Context Conditioning in Hermissenda Suggest a Temporally Invariant Form of Activity-Dependent Neuronal Facilitation
- Creators
- Andrew C. Talk - Rutgers, The State University of New JerseyIsabel A. Muzzio - Rutgers, The State University of New JerseyLouis D. Matzel - Rutgers, The State University of New Jersey
- Resource Type
- Journal article
- Publication Details
- Neurobiology of learning and memory, Vol.72(2), pp.95-117
- DOI
- 10.1006/nlme.1998.3890
- PMID
- 10438650
- NLM abbreviation
- Neurobiol Learn Mem
- ISSN
- 1074-7427
- eISSN
- 1095-9564
- Publisher
- Elsevier Inc
- Language
- English
- Date published
- 09/1999
- Academic Unit
- Psychological and Brain Sciences; Iowa Neuroscience Institute
- Record Identifier
- 9984295024802771
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