Wednesday, April 2, 2025
4/2/2025
Neural basis of precedence-type sound localization processes - Project Summary This research project aims to study the neural basis of the precedence-type sound localization processes, including the Franssen effect. This central computation is key to understanding the normal function of auditory perception and is a priority area in NIH's hearing research. The precedence phenomena play a critical role in speech-in-noise, dichotic, and temporal processing, in addition to source location and echo identification. Illusions such as these are distortions in perception that provide insights into the workings of the auditory system. The basic precedence effect consists of two ‘identical’ tone bursts are presented with various timing relations from separate loudspeakers situated on either side; the listener perceives a single ‘fused’ sound as coming from the speaker that broadcasted the leading sound. The Franssen effect is an illusion where the listener incorrectly perceives the sound as coming from a loudspeaker that broadcasts a leading short-duration sound pulse with a fast amplitude rise and slow decay. This happens despite most of the sound originating from a contralaterally placed lagging loudspeaker producing long-duration sound with a slow onset. The proposed research takes advantage of the natural preference of a species of gray treefrogs (Hyla versicolor) for slow-rise, long-duration (SR-LD) sound pulses that represent those used to elicit FE illusions. In choice tests, H. versicolor females strongly prefer SR-LD sound pulses over the fast-rise, short-duration (FR-SD) pulses of their sister species Hyla chrysoscelis and approach the transducer broadcasting the former. In aim 1, we plan to conduct behavioral experiments that take advantage of this natural preference. We hypothesize that subjects will erroneously approach a loudspeaker broadcasting FR-SD pulses when they precede SR-LD pulses form an orthogonally placed loudspeaker. In aim 2, we propose to make extracellular recordings from single neurons in the anuran inferior colliculus (ICan) to stimuli that elicit FE. We hypothesize that FR-SD pulses from a contralateral loudspeaker suppress neurons selective to SR-LD stimuli. To understand the temporal integration of binaural excitatory and inhibitory inputs to the ICan, we propose, in aim 3, to examine the role of inhibition in FE. We seek to utilize a constellation of techniques, including in vivo whole-cell recordings and analytical methods for estimating inhibition elicited in SR-LD selective neurons by preceding ipsilateral FR-SD stimulus.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).