UBC Theses and Dissertations
Time-place learning Thorpe, Christina Marie
The ability to learn spatiotemporal characteristics of biologically significant events is advantageous for an animal and is known as time-place learning (TPL). Gallistel (1990) proposed an influential theory positing that whenever a biologically significant event occurred, a memory code was automatically formed, encoding the nature of the event, and the time and place in which it occurred. When the animal is later faced with a biological need it could consult these memory codes and determine when and where that need had been met in the past. This information could be used to guide current behaviour. Importantly, Gallistel theorized that the encoding of the spatiotemporal characteristics of an event into a tripartite code was an automatic process. Despite the appealing power and simplicity of Gallistel's theory, I have provided arguments suggesting that it has serious limitations. Perhaps the most damaging evidence against this theory is the reluctance of rats to demonstrate daily TPL (i.e., events that vary in location depending on time of day). Widman, Gordon, and Timberlake (2000) argue that for TPL to occur the response cost for incorrect decisions must be high. While this hypothesis is unable to explain the inconsistencies in TPL, it does highlight the fact that animals do not automatically store time-place-event information as a tripartite code. If they did, it would not make sense for them to ignore such information in some tasks. I have provided an alternative hypothesis that states that whenever a biologically significant event occurs two bipartite memory codes (time-event and place-event) are automatically formed. Only under some conditions, perhaps those with high response cost, do animals form tripartite codes. For this reason, rats often have difficulty learning a TPL task; although rats easily learn a place preference for those places that provide reinforcement (place-event), and easily learn a go/no-go discrimination (time-event). This thesis provides data from both the daily and interval TPL realms supporting the proposed theory of bipartite codes. Although rats do not readily learn daily TPL tasks, they do demonstrate knowledge of interval TPL under a variety of conditions designed to enhance the ecological validity of the task. The properties of interval TPL are discussed.
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