Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. Includes bibliographical references (leaves 234-241).

Dissertation (Ph.D.)--University of Toledo, 2005. / Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 128-141.

The first stage of mammalian auditory processing occurs within the dorsal and ventral divisions of the cochlear nucleus. The dorsal cochlear nucleus (DCN) is remarkable in that it shares striking similarities with the cerebellum in terms of its development, gene expression patterns, and anatomical organization. Notably, principal cells of the DCN integrate auditory nerve input with a diverse array of signals conveyed by a mossy fiber- granule cell system. Yet how the elaborate cerebellum-like circuitry of DCN contributes to early auditory processing has been a longstanding puzzle. The work in this thesis shows that, in mice, that the DCN functions to cancel responses to self-generated sounds. While the DCN and ventral cochlear nucleus (VCN) neurons respond similarly to externally-generated acoustic stimuli, sounds generated by licking behavior evoke much weaker responses in DCN than in VCN. Recordings in deafened mice revealed non- auditory signals related to licking in Purkinje-like neurons of DCN. Moreover, silencing somatosensory mossy fiber inputs revealed prominent DCN responses to sounds generated by licking, suggesting that these inputs normally function to cancel responses to self-generated sounds. Finally, I show that this cancellation is not fixed, but involves an adaptive process whereby neural responses correlated with the animal’s own behavior are gradually reduced. Together, these findings suggest that the fundamental process of distinguishing self-generated from external stimuli begins at the very first stage of mammalian auditory processing. Related adaptive filtering functions have been described for cerebellum-like sensory structures in fish and hypothesized for the mammalian cerebellum. Hence our findings also suggest that, despite their wide phylogenetic separation, different cerebellum-like structures and the cerebellum itself may all perform a similar computation.

Studies of cerebellum-like circuits in fish have demonstrated that synaptic plasticity shapes the motor corollary discharge responses of granule cells into highly-specific predictions of self- generated sensory input. However, the functional significance of such predictions, known as negative images, has not been directly tested. Here we provide evidence for improvements in neural coding and behavioral detection of prey-like stimuli due to negative images. In addition, we find that manipulating synaptic plasticity leads to specific changes in circuit output that disrupt neural coding and detection of prey-like stimuli. These results link synaptic plasticity, neural coding, and behavior and also provide a circuit-level account of how combining external sensory input with internally-generated predictions enhances sensory processing. In addition, the mammalian dorsal cochlear nucleus (DCN) integrates auditory nerve input with a diverse array of sensory and motor signals processed within circuity similar to the cerebellum. Yet how the DCN contributes to early auditory processing has been a longstanding puzzle. Using electrophysiological recordings in mice during licking behavior we show that DCN neurons are largely unaffected by self-generated sounds while remaining sensitive to external acoustic stimuli. Recordings in deafened mice, together with neural activity manipulations, indicate that self-generated sounds are cancelled by non-auditory signals conveyed by mossy fibers. In addition, DCN neurons exhibit gradual reductions in their responses to acoustic stimuli that are temporally correlated with licking. Together, these findings suggest that DCN may act as an adaptive filter for cancelling self-generated sounds. Adaptive filtering has been established previously for cerebellum-like sensory structures in fish suggesting a conserved function for such structures across vertebrates.

The study of cerebellum-like circuits allows many points of entry. These circuits are often involved in very specific systems not found in all animals (for example electrolocation in weakly electric fish) and thus can be studied with a neuroethological approach in mind. There are many cerebellum-like circuits found across the animal kingdom, and so studies of these systems allow us to make interesting comparative observations. Cerebellum-like circuits are involved in computations that touch many domains of theoretical interest - the formation of internal predictions, adaptive filtering, cancellation of self-generated sensory inputs. This latter is linked both conceptually and historically to philosophical questions about the nature of perception and the distinction between the self and the outside world. The computation thought to be performed in cerebellum-like structures is further related, especially through studies of the cerebellum, to theories of motor control and cognition. The cerebellum itself is known to be involved in much more than motor learning, its traditionally assumed function, with particularly interesting links to schizophrenia and to autism. The particular advantage of studying cerbellum-like structures is that they sit at such a rich confluence of interests while being involved in well-defined computations and being accessible at the synaptic, cellular, and circuit levels. In this thesis we present work on two cerebellum-like structures: the electrosensory lobe (ELL) of mormyrid fish and the dorsal cochlear nucleus (DCN) of mice. Recent work in ELL has shown that a temporal basis of granule cells allows the formation of predictions of the sensory consequences of a simple motor act - the electric organ discharge (EOD). Here we demonstrate that such predictions generalize between electric organ discharge rates - an ability crucial to the ethological relevance of such predictions. We develop a model of how such generalization is made possible at the circuit level. In a second section we show that the DCN is able to adaptively cancel self-generated sounds. In the conclusion we discuss some differences between DCN and ELL and suggest future studies of both structures motivated by a reading of different aspects of the machine learning literature.

Thesis (Ph.D.)--University of Melbourne, Dept. of Otolaryngology, 2005. / Typescript. Author's name on spine: B.Y. Cahyono. Includes bibliographical references (p. 185-220).

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains x, 192 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 126-139).

The cochlear nucleus (CN), as the first brain centre in the auditory system is responsible for sorting the neural signals received from the cochlea, into parallel processing streams for transmission to the assorted higher auditory nuclei. A commissural connection formed between cochlear nuclei through direct projections, thereby provides the first site in the central auditory system at which binaural information is able to influence the ascending auditory signal. This thesis investigates the nature of commissural projections and the impact of their input upon neurons of the ventral CN (VCN) through in vivo intracellular and extracellular electrophysiological recordings together with both acoustic and electrical stimulation of the contralateral CN.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 59-64).