Spatial Cues, Task Demands, and Auditory Selective Attention

How Spatial Cues Support Communication: Interactions Between Auditory Spatial Features and Task Demands Across Cortical Networks

Understanding speech in restaurants and other noisy environments is the most common complaint from the more than 60 million Americans with hearing impairment. Succeeding in such environments requires a listener to first segregate sound sources and then selectively attend to the source of interest. This study examines how individual auditory spatial cues (interaural time differences and interaural level differences) support spatial selective attention, the cortical processes that underlie this ability, and how these processes are modulated by task demands. Participants with normal hearing and participants who use bilateral cochlear implants will perform listening tasks while brain and physiological responses are recorded (electroencephalography, functional near-infrared spectroscopy, pupillometry, and, for normal-hearing participants only, functional magnetic resonance imaging). The findings will provide new insights into the mechanisms of spatial selective attention and help guide clinical solutions for cochlear implant users, individuals with hearing impairment more generally, and older normal-hearing adults who have difficulty understanding speech in noisy environments.

Study Overview

• Status: Recruiting
• Conditions: Healthy; Hearing Loss, Bilateral; Bilateral Cochlear Implants
• Intervention / Treatment: Device: Existing bilateral cochlear implants; Other: Normal Hearing Control

Detailed Description

This study will examine the contributions of spatial cues (interaural level differences and interaural time differences) and task demands on spatial selective attention. Aim 1 will simultaneously collect functional near infrared spectroscopy (fNIRS), electroencephalography (EEG), pupillometry, and behavioral data in normal-hearing (NH) participants, while they perform tasks designed to probe various aspects of spatial selective attention. We will make every effort to include as many Aim 1 participants in Aim 2 as possible. Aim 2 will record functional magnetic resonance imaging (fMRI) during the same tasks. Aim 3 will essentially replicate Aim 1 in bilateral CI users. We will not record fMRI with CI users due to safety concerns.

Paradigm 1. The paradigm will require listeners to hold information in working memory. We will measure effects of task demands and auditory spatial cues on cognitive and sensory responses to a single stream of stimuli. Stimuli will be a set of recorded "crash" sound effects with a broadband frequency profile, ideal for spatialization (important because a main goal of ours is to compare measures when spatialization is achieved with either interaural time differences (ITDs), which dominate spatial perception in the low-frequency region, or interaural level differences (ILDs), which dominate in the high-frequency region). Taxing working memory is an important component to the paradigm because it will allow us to influence listening effort, a critical factor in our hypotheses, and because it will ensure engagement of prefrontal cortex, which we hypothesize drives lateralization of activity in auditory cortex.

Paradigm 2. The paradigm asks listeners to attend to either the Location or the Pitch of a single speech token, hold that value in memory while a diffuse noise masker is presented, and compare the remembered location or pitch to a subsequent probe token. The noise masker will ensure that listeners cannot rely on echoic memory. We will examine the effects of task demands and spatial cues on auditory cortex spatial selectivity. As with Paradigm 1 (and for the same reasons), the choice to force listeners to use working memory to perform the task was deliberate. Here, the main goal is to force listeners to have to map a perceived location to exogenous space, which is the only way to hold a location in memory. This should allow us to observe auditory cortical tuning with much more precision.

Paradigm 3. This paradigm will present listeners with an ongoing, isochronous stream of words, which can be spoken by either a male or a female, and which will be spatialized to come from either the left or right. There are two tasks. The first is to attend to a given talker (male or female), and ignore location, and the second is to attend to a given location and ignore talker. On each trial, subjects must count the number of occurrences of a particular word that match the feature that they are asked to attend. The goal here is to force participants to use either space or to use another cue (voice pitch) to perform the task.

Neuroimaging Approach 1. We will use EEG to record event-related potentials, which will allow us to observe changes in encoding and lateralization of sounds, which should increase as spatial cue quality increases. fNIRS will allow us to measure prefrontal cortical activity during task engagement, which has been linked to cognitive effort. Pupillometry will provide a more traditional, well-defined measure of overall effort. Behavior will provide an indication of the summative contributions of each factor.

Neuroimaging Approach 2. We will use fMRI to look at stimulus-induced lateralization and spatial receptive fields in auditory cortex. We will also look for particular activity in prefrontal cortex indicating recruitment of visually-biased regions, associated with spatial processing. These regions have particular importance to our hypotheses, because they are only engaged when space is required to perform an auditory task.

We propose nine experiments. Six experiments will test NH listeners, and will each leverage one of the three paradigms and one of the two neuroimaging approaches. The three additional experiments will test bilateral CI users, and we will use only neuroimaging approach 1 (fNIRS/EEG/Pupillometry), due to safety concerns regarding their medical devices and the MRI scanner.

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Christopher A Brown, PhD; Phone Number: 412-670-2772; Email: cb43@usf.edu

Study Locations

• United States
  • Florida
    • Tampa, Florida, United States, 33620
      • Recruiting
      • University of South Florida, PCD Building, Room 3008A
      • Contact: Christopher A Brown, PhD; Phone Number: 412-670-2772; Email: cb43@usf.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults with normal hearing, confirmed by audiometric assessment (thresholds within 20 dB HL of normal through 8 kHz), OR adults with bilateral cochlear implants who have used their implants for at least one year
• Native speakers of American English
• Normal or corrected-to-normal vision

Exclusion Criteria:

• Known neurological disorders
• For fMRI sessions (normal-hearing participants only): contraindications to MRI scanning; cochlear implant users do not complete MRI sessions

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Bilateral Cochlear Implant Users; Adults with existing bilateral cochlear implants (implanted and using their devices for at least one year). Participants complete the discrimination and selective-attention auditory paradigms with manipulated spatial cues while combined EEG, fNIRS, and pupillometry are recorded. No fMRI is collected in this arm due to device safety concerns.	Device: Existing bilateral cochlear implants; Participants in this arm are recruited from a population who have existing bilateral cochlear implants. The implants are the participants' own clinical devices, used as clinically programmed; no investigational device or modification is provided by the study. Auditory attention tasks are presented with manipulated spatial cues (interaural time differences, interaural level differences, or HRTFs).
Other: Normal Hearing Controls; Adults with audiometrically confirmed normal hearing (thresholds within 20 dB HL of normal through 8 kHz). Participants complete three auditory attention paradigms (working memory, discrimination, selective attention) with manipulated spatial cues, under combined EEG, fNIRS, and pupillometry sessions and fMRI sessions.	Other: Normal Hearing Control; Control group recruited from the normal hearing population. Participants perform the same auditory attention tasks with manipulated spatial cues (interaural time differences, interaural level differences, or HRTFs) under EEG/fNIRS/pupillometry and fMRI.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
EEG	EEG data acquired using 32 Ag-Ag/Cl electrodes embedded in an elastic cap (Brain Products), impedances below 20 kOhms, locations per the extended 10-20 system, recorded at 5 kHz from 0.1-100 Hz. Event-related potentials (including attentional modulation of the N1) and parietal alpha lateralization are compared across spatial-cue and task-demand conditions.	2 hours
NIRS	Functional near-infrared spectroscopy collected with a montage targeting bilateral superior temporal gyrus (STG) and bilateral prefrontal cortex, using a NIRSport 2 8x8 channel system (NIRx) with long- and short-distance channel probes; 3D structural head scanning registers probe placement. Optical signals recorded at 10 Hz with an average source-detector distance of 35 mm. Oxygenated and deoxygenated hemoglobin responses are compared across conditions.	2 hours
Pupillometry	Pupil dilation from both eyes recorded with the EyeLink 1000 at a sampling rate of 1000 Hz, normalized to each participant pupillary dynamic range, as an index of listening effort across conditions.	2 hours
MRI	Data acquired on a 3 Tesla Siemens Prisma MRI scanner (64-channel head coil). High-resolution (0.8 mm iso) T1-weighted multi-echo MP-RAGE and T2-weighted SPACE images collected for cortical reconstruction (FreeSurfer); functional MRI measures stimulus-induced lateralization and spatial receptive fields in auditory cortex. Normal-hearing arm only.	2 hours
Discrimination (DISCR)	Behavioral discrimination performance for spatialized sounds. HRTFs span +/- 90 degrees, broadband ILDs span +/- 20 dB, and broadband ITDs span +/- 800 microseconds; values chosen to roughly equate perceived lateral range across cues.	2 hours

Collaborators and Investigators

• Sponsor: University of South Florida
• Collaborators: National Institute on Deafness and Other Communication Disorders (NIDCD); Carnegie Mellon University
• Investigators: Principal Investigator: Christopher A Brown, PhD, University of South Florida

Study record dates

Study Major Dates

• Study Start (Actual): October 22, 2025
• Primary Completion (Estimated): April 1, 2030
• Study Completion (Estimated): July 1, 2030

Study Registration Dates

• First Submitted: August 10, 2026
• First Submitted That Met QC Criteria: August 10, 2026
• First Posted (Actual): August 14, 2026

Study Record Updates

• Last Update Posted (Actual): August 14, 2026
• Last Update Submitted That Met QC Criteria: August 10, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: fMRI; EEG; fNIRS; cochlear implant; pupillometry; speech in noise; spatial hearing; auditory selective attention; interaural level difference; interaural time difference
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Otorhinolaryngologic Diseases; Sensation Disorders; Ear Diseases; Hearing Loss; Hearing Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Hearing Loss, Bilateral
• Other Study ID Numbers: STUDY008767; R01DC022699 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data for all primary measures (behavioral, EEG, fNIRS, pupillometry, and MRI) will be publicly shared in BIDS-compliant format, per the NIH Data Management and Sharing Plan for this award. Smaller datasets (demographics, behavioral scores) will be shared as text/CSV files via GitHub and permanently archived on Zenodo; larger neuroimaging datasets will be shared on Zenodo directly, with permanent DOIs. Custom acquisition and analysis software will also be shared via GitHub and archived on Zenodo.
• IPD Sharing Time Frame: Data supporting each publication will be shared no later than the time of publication, and retained permanently (Zenodo provides permanent archiving with DOIs).
• IPD Sharing Access Criteria: Publicly available with no access restrictions.
• IPD Sharing Supporting Information Type: ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No