Several lines of evidence suggest that initial acquisition of learned behavior
involves multiple memory systems. In particular, lesions of the hippocampus impair the
acquisition of cognitive or relational memory, but do not impair the acquisition of
stimulus-response habits. Extinction behavior also involves new learning, and therefore
it is possible that multiple forms of memory may also underlie extinction.
We examined this hypothesis by training rats in a task in which extinction
behavior could putatively be acquired by either a cognitive or habit memory system.
Adult male Long-Evans rats were initially trained to run in a straight alley maze for food
reward. Following training they were placed into one of two extinction conditions. In
one condition rats were allowed to run to an empty goal box (i.e. response extinction). In
a second condition rats were placed into an empty goal box without making a running
response (i.e. latent or non-response extinction). Prior to each daily session of extinction
training, rats received intra-hippocampal infusions of either the local anesthetic
bupivacaine (0.75% solution/0.5 ul), or saline.
Rats receiving saline infusions displayed extinction behavior in both the response
and non-response conditions. In contrast, rats receiving intra-hippocampal infusions ofbupivacaine extinguished normally in the response condition, but did not display nonresponse
extinction. This latent extinction effect was enhanced by decreasing the amount
of time between the last extinction trial and the probe trial. Additionally, administering
extinction training and probe trials in different contexts did not appear to prevent latent
extinction, however large variability may be masking this effect. The new context
administered during extinction prevented latent extinction in some animals, but not
others. These findings suggest that, similar to initial acquisition, the learning that occurs
during extinction also involves multiple memory systems. Specifically, the hippocampus
may selectively mediate extinction under conditions in which new stimulus-response
learning is prevented.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/2384 |
| Date | 29 August 2005 |
| Creators | Gabriele, Amanda |
| Contributors | Packard, Mark G. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 301780 bytes, electronic, application/pdf, born digital |
Page generated in 0.0026 seconds