RT Journal Article
SR Electronic
T1 Developmental Changes in Hippocampal Associative Coding
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 4238
OP 4247
DO 10.1523/JNEUROSCI.3145-14.2015
VO 35
IS 10
A1 Mary E. Goldsberry
A1 Jangjin Kim
A1 John H. Freeman
YR 2015
UL http://www.jneurosci.org/content/35/10/4238.abstract
AB Behavioral analyses of the ontogeny of memory have shown that hippocampus-dependent learning emerges relatively late in postnatal development compared with simple associative learning. Maturation of hippocampal mnemonic mechanisms has been hypothesized to underlie the development of the later emerging learning processes. However, the role of hippocampal maturation in learning has not been examined directly. The goal of the present study was to examine developmental changes in hippocampal neuronal coding during acquisition of a hippocampus-dependent learning task. We recorded activity from CA1 pyramidal cells in rat pups while they were trained on trace eyeblink conditioning. Trace eyeblink conditioning is a Pavlovian conditioning task that involves the association of a conditioned stimulus (CS) with an unconditioned stimulus over a stimulus-free trace interval. The inclusion of the trace interval is what makes the task hippocampus dependent. In the present study, rats were trained at 21–23, 24–26, and 31–33 d of age. Previous research from our laboratory and others shows that trace conditioning begins to emerge during the third postnatal week. The results indicate that hippocampal neurons show a substantial increase in responsiveness to task-relevant events during development. Moreover, there is an age-related increase in the proportion of neurons that respond to a combination of trial events (e.g., CS and trace). Our findings indicate that the developmental emergence of hippocampally mediated learning is related to increases in the strength and complexity of CA1 associative coding.