Date of Degree
PhD (Doctor of Philosophy)
Freeman, John H.
First Committee Member
Second Committee Member
Johnson, Alan K.
Third Committee Member
Fourth Committee Member
Research concerning the development of learning and memory suggests that there are multiple memory systems. These systems differ in complexity, underlying neural substrates, and consequently, their developmental emergence. Pavlovian conditioning, and specifically eyeblink conditioning (EBC), allows researchers to investigate both simple and complex forms of learning and memory early in development. Delay EBC, which is considered a relatively simple form of learning, involves the association of a conditioned stimulus (CS) with an unconditioned stimulus (US). Research from our laboratory suggests that the emergence of delay EBC is dependent on the development of sensory input to the pontine nucleus. Trace EBC, a more complex form of learning, involves the association of a CS with a US over a stimulus-free trace interval. Due to its relatively late emergence, the developmental time course of trace EBC has been traditionally regarded as independent of sensory system development. Rather, it is the involvement of late-developing structures such as the hippocampus which is considered the principle limiting factor in the emergence of trace EBC.
The current collection of studies investigates the developmental emergence of delay and trace conditioning. We found that both delay and trace conditioning are facilitated by using an early-developing somatosensory CS. This suggests that the sensory system development plays a role in even late-developing trace EBC. Moreover, hippocampal CA1 neuronal activity shows increased responsiveness in even very young animals when trained with an early-developing somatosensory CS compared to those trained with a tone CS. Combined, these data suggest that both hippocampal and sensory system development may play key roles in the developmental emergence of learning.
Research concerning the development of learning and memory suggests that there are multiple memory systems. These systems differ in complexity, underlying neural substrates, and consequently, their developmental emergence. Simpler forms of learning emerge early in development and are believed to be heavily dependent on sensory system development. More complex forms of learning depend on the circuitry involved in simple forms and additionally require the involvement of late-developing structures such as the hippocampus. Due to their late development, the emergence of complex forms of learning is generally believed to be independent of sensory system development. Indeed, it is this late development of the hippocampus which is currently believed to be the principle limiting factor in the development of complex forms of learning.
The current collection of studies investigates the developmental emergence of both simple and complex forms of learning. We found that using an earlier-developing sensory modality facilitates both simple and complex forms of learning. This would suggest that sensory system development is continuing to play a crucial role, even in late-developing complex forms of learning. Moreover, when we examined the activity of hippocampal neurons during complex learning tasks we found that they were more responsive when using an early-developing sensory modality. This would suggest that hippocampal function is more mature than originally believed. Therefore, both sensory system and hippocampal development are important contributing factors to the developmental emergence of simple and complex forms of learning.
development, eyeblink conditioning, hippocampus, learning, sensory development
ix, 111 pages
Includes bibliographical references (pages 103-111).
Copyright © 2016 Mary Goldsberry-Troyer
Goldsberry-Troyer, Mary. "Sensory system contributions to the development of trace and delay eyeblink conditioning." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.