This is an application to renew an ADAMHA Research Scientist Development Award (Level II). The goal of the proposed research is to understand basic processes for formation of perceptual images. The specific example to be studied is the fusion of different stimulus dimensions into the sonar images perceived by the echolocating bat, Eptesicus fuscus. Research conducted during the first term of the RSDA has discovered an unusually accessible instance of image fusion in the way this bat processes echoes of its frequency-modulated (FM) sonar signals. The bat perceives the distance to targets, or target range, from the delay of echoes, encoding echo delay by the timing of neural discharges evoked by echoes. This discharge timing then is transformed into a topographic """"""""target range"""""""" map in the auditory cortex. The bat perceives the shape of targets in terms of the distribution of parts of the target along the target-range axis. The echoes reflected by different parts of the target overlap when they arrive at the bat's ears, creating a single complex echo whose spectrum represents target shape. The bat encodes the echo spectrum in terms of the distribution of neural activity across the frequency axis of tonotopic maps in its auditory system. The target range map has an echo delay axis, and the bat actually perceives images in terms of delay. The bat transposes information about target shape into its equivalent in terms of the delay separation of echo components to perceive the target's structure along a psychological range scale. The convergence of delay and frequency information onto a computed range scale is a concrete example of image fusion. The proposed research consists of behavioral, physiological, and acoustic experiment to determine how the bat accomplishes fusion of range and shape into whole images. The development of a theoretical understanding that can link behavioral and physiological observations is a crucial aspect of the proposal. Large steps have been made during the first RSDA term, and the present proposal is to enable the candidate to strengthen our conceptual understanding of perception through the example of echolocation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Research Scientist Development Award - Research (K02)
Project #
5K02MH000521-08
Application #
3069912
Study Section
Research Scientist Development Review Committee (MHK)
Project Start
1990-08-01
Project End
1995-07-31
Budget Start
1992-08-01
Budget End
1993-07-31
Support Year
8
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Brown University
Department
Type
Schools of Arts and Sciences
DUNS #
001785542
City
Providence
State
RI
Country
United States
Zip Code
02912
Saillant, Prestor A; Simmons, James A; Bouffard, Frederick H et al. (2007) Biosonar signals impinging on the target during interception by big brown bats, Eptesicus fuscus. J Acoust Soc Am 121:3001-10
Simmons, James A; Neretti, Nicola; Intrator, Nathan et al. (2004) Delay accuracy in bat sonar is related to the reciprocal of normalized echo bandwidth, or Q. Proc Natl Acad Sci U S A 101:3638-43
Simmons, J A; Ferragamo, M J; Sanderson, M I (2003) Echo delay versus spectral cues for temporal hyperacuity in the big brown bat, Eptesicus fuscus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 189:693-702
Simmons, James A; Wotton, Janine M; Ferragamo, Michael J et al. (2002) Transformation of external-ear spectral cues into perceived delays by the big brown bat, Eptesicus fuscus. J Acoust Soc Am 111:2771-82
Wotton, J M; Simmons, J A (2000) Spectral cues and perception of the vertical position of targets by the big brown bat, Eptesicus fuscus. J Acoust Soc Am 107:1034-41
Simmons, J A; Ferragamo, M J; Moss, C F (1998) Echo-delay resolution in sonar images of the big brown bat, Eptesicus fuscus. Proc Natl Acad Sci U S A 95:12647-52
Ferragamo, M J; Haresign, T; Simmons, J A (1998) Frequency tuning, latencies, and responses to frequency-modulated sweeps in the inferior colliculus of the echolocating bat, Eptesicus fuscus. J Comp Physiol A 182:65-79
Wotton, J M; Haresign, T; Ferragamo, M J et al. (1996) Sound source elevation and external ear cues influence the discrimination of spectral notches by the big brown bat, Eptesicus fuscus. J Acoust Soc Am 100:1764-76
Simmons, J A; Dear, S P; Ferragamo, M J et al. (1996) Representation of perceptual dimensions of insect prey during terminal pursuit by echolocating bats. Biol Bull 191:109-21
Wotton, J M; Haresign, T; Simmons, J A (1995) Spatially dependent acoustic cues generated by the external ear of the big brown bat, Eptesicus fuscus. J Acoust Soc Am 98:1423-45

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