Anatomical tract tracing of intrinsic and extrinsic connections of the midbrain superior colliculus of the echolocating bat

Brittney Boublil

Background

The anatomy and functional connections of the midbrain superior colliculus (SC) in visually-guided mammals have been well-established; however, far less is known about the SC of the echolocating bat and its role in acoustic orienting by sonar. The superficial retinal input layer of the SC of the big brown bat, Eptesicus fuscus, is sparse, which suggests that it plays a reduced role in the orienting behavior of this animal that relies heavily on hearing to guide its locomotion.13 I am now carefully mapping the anatomical organization within the subdivisions of the bat SC and its projections with other brain regions.

Approach

I am tracing the intrinsic and extrinsic anatomical connections of the mammalian SC, using both anterograde and retrograde tract tracing techniques. Using the big brown bat, I am performing unilateral injections of 1, 1’-Dioctadecyl-3, 3, 3’, 3’-tetramethylindocarbocyanine perchlorate (DiI) into the SC. I plan to visualize and quantify fluorescent labeling in target brain regions using fluorescent microscopy. This work will contribute to interpretation of the behavioral studies on the functional role of the midbrain SC in acoustic orienting by sonar.

Fig. 3. Retrograde DiI labeling of auditory cortex in the big brown bat, Eptesicus fuscus.

References

1. Griffin, D.R. (1958). Listening in the dark. New Haven: Yale UP.

2. Moss, C. F., & Sinha, S. R. (2003). Neurobiology of echolocation. CONB,13(6), 751-758.

3. Ulanovsky, N., & Moss, C. F. (2008). What the bat's voice tells the bat's brain, PNAS, 105(25), 8491-8498.

4. Surlykke, A., & Moss, C. F. (2000). Echolocation behavior of big brown bats, Eptesicus fuscus, in the field and the laboratory, JASA, 108(5), 2419- 2429.

5. Simmons, J. A. (1979). Perception of echo phase information in bat sonar, Science, 204(4399), 1336- 1338.

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9. Valentine, D. E., Sinha, S. R., & Moss, C. F. (2002). Orienting responses and vocalizations produced by microstimulation in the superior colliculus of the echolocating bat, Eptesicus fuscus. JCPA, 188(2), 89-108.

10. Wenstrup, J.J., & Suthers, R.A. (1981). Do lesions of the superior colliculus affect acoustic orientation in echolocating bats?, Physiol. & Behav. 27(5), 835-839.

11. Valentine, D.E. & Moss, C.F. (1998). Sensorimotor integration in bat sonar. In T.H. Kunz and P.A. Racey (Editors) Bats: Phylogeny, Morphology, Echolocation and Conservation Biology. Smithsonian Institution Press, Washington, D.C., 1998, 220-230.

12. Wohlgemuth, M.J., Kothari, N.B. & Moss, C.F. Midbrain Functional Organization and Dynamic Activity in the Superior Colliculus of the Echolocating Bat, Eptesicus fuscus, J. Neurosci, in press.

13. Covey, E., Hall, W.C., & Kobler, J.B. (1987). Subcortical connections of the superior colliculus in the mustache bat, Pteronotus parnellii. J. Comp. Neurol., 263(2), 179-197.

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