Multisensory Perceptual Training in the Elderly
| Status: | Recruiting |
|---|---|
| Healthy: | No |
| Age Range: | 20 - 75 |
| Updated: | 4/17/2018 |
| Start Date: | November 1, 2017 |
| End Date: | October 31, 2020 |
| Contact: | Fang Jiang, Ph.D |
| Email: | fangj@unr.edu |
| Phone: | 775-682-8606 |
Aging impacts our unisensory perceptual abilities as well as our ability to correctly combine
signals from multiple sensory modalities to obtain a coherent percept of external events.
Elderly individuals show greater difficulty determining the temporal order of audiovisual
events, and possess a broadened temporal binding window (TBW) during which stimuli from
different modalities are likely to be integrated into a single perceptual entity. Recent
studies demonstrate that the TBW can be reduced following multisensory perceptual learning,
however, the mechanisms at work remain poorly understood. Using an adaptive training
paradigm, the goal of this proposed project is to examine how multisensory temporal
processing can be enhanced in the elderly. Specifically, the investigators will measure the
effect of multisensory perceptual learning on audiovisual temporal functions and its transfer
to unisensory temporal tasks. Combining behavioral and EEG measures, the investigators will
assess whether multisensory perceptual learning in the elderly changes only within the
unisensory processes or reflects additional cross-modal processes. Furthermore, the
investigators will characterize socioeconomic and health-related factors that contribute to
age-related deficiencies in multisensory temporal processing and identify potential training
outcomes for elderly subpopulations that are at greater risk. This work will provide insights
into the brain mechanisms underlying multisensory perception and learning in the elderly.
signals from multiple sensory modalities to obtain a coherent percept of external events.
Elderly individuals show greater difficulty determining the temporal order of audiovisual
events, and possess a broadened temporal binding window (TBW) during which stimuli from
different modalities are likely to be integrated into a single perceptual entity. Recent
studies demonstrate that the TBW can be reduced following multisensory perceptual learning,
however, the mechanisms at work remain poorly understood. Using an adaptive training
paradigm, the goal of this proposed project is to examine how multisensory temporal
processing can be enhanced in the elderly. Specifically, the investigators will measure the
effect of multisensory perceptual learning on audiovisual temporal functions and its transfer
to unisensory temporal tasks. Combining behavioral and EEG measures, the investigators will
assess whether multisensory perceptual learning in the elderly changes only within the
unisensory processes or reflects additional cross-modal processes. Furthermore, the
investigators will characterize socioeconomic and health-related factors that contribute to
age-related deficiencies in multisensory temporal processing and identify potential training
outcomes for elderly subpopulations that are at greater risk. This work will provide insights
into the brain mechanisms underlying multisensory perception and learning in the elderly.
The investigators will examine the training effects in the elderly by comparing the
behavioral and EEG measures before and after training. The investigators will include 20
young participants and use their baseline as target performance for training in the elderly.
40 elderly participants will be randomly assigned to one of the two training groups and will
be asked to undergo 5 days of active or passive training (see Table 1). Upon each day of
training, the temporal order judgment (TOJ) task will be given pre- and post-training.
Additionally, prior to the first day of training and at the end of the 5-day training,
participants will perform the audiovisual temporal recalibration testing, auditory and visual
TOJ tasks, as well as the EEG recording. Follow-up behavioral and EEG assessments will be
carried out 7 days after training to examine the persistence of training effects. Changes in
the multisensory temporal binding window induced by active training are shown to be stable
for at least one week in young adults.
Stimulus presentation. Visual and auditory stimuli will be generated using MATLAB and the
psychophysics toolbox. In behavioral and EEG experiments, visual and auditory stimuli will be
delivered via Display++ system and an AudioFile stimulus processor, respectively (Cambridge
Research Systems). The use of these two devices allows for precise control of stimulus
timing.
Active training. The investigators will use adaptive training tailored to each individual's
thresholds. Specifically, a two-alternative forced-choice TOJ task will be used, where
participants will be presented with an auditory beep (1000 Hz pure tone presented at 75 dB)
and a visual flash (a white circle presented on grey background) with varying stimulus onset
asynchronies (SOAs) and will be asked to judge the temporal order of the stimulus pair. On
each training day, the investigators will establish the range of SOAs for individuals based
on their thresholds determined from the pre-training TOJ assessment given on the same day.
The maximum SOA will be 0.2 log units greater than their estimated threshold and will be used
for both visual leading (positive SOA) and auditory leading (negative SOA) stimuli.
Participants will be exposed to a total of 160 trials in the training phase (8 SOAs x 20
repetitions). Feedback will be provided after each response.
Passive training. To control for pure practice or exposure effects, a second group of elderly
participants will undergo passive training. Participants will be exposed to an auditory beep
(1000 Hz) and a visual flash (a white circle) with varying SOAs, similarly as in the active
training group. The maximum SOA for each individual will be likewise determined by his or her
threshold from the TOJ assessment. However the participants will not be asked to perform the
TOJ task and no feedback will be provided. Instead, participants will perform an oddball task
in which they are asked to detect a dark grey circle or a high pitch beep (1500 Hz) that
occurs less frequently than the standard stimuli (i.e., a white circle or a 1000 Hz beep).
Having an oddball task in both auditory and visual modalities will ensure that participant's
attention is divided between the two modalities as required in the active training task 16.
There will be a total of 160 trials in the training phase (8 SOAs x 20 repetitions).
Behavioral assessment before and after training. The investigators will carry out a series of
behavioral studies to measure training effects on multisensory and unisensory temporal
functions using tasks such as the precision in TOJ and the temporal recalibration.
EEG assessment before and after training. The investigators will carry out a series of EEG
studies to measure training effects on electrophysiological measures such as ERP amplitude
during audiovisual temporal tasks.
behavioral and EEG measures before and after training. The investigators will include 20
young participants and use their baseline as target performance for training in the elderly.
40 elderly participants will be randomly assigned to one of the two training groups and will
be asked to undergo 5 days of active or passive training (see Table 1). Upon each day of
training, the temporal order judgment (TOJ) task will be given pre- and post-training.
Additionally, prior to the first day of training and at the end of the 5-day training,
participants will perform the audiovisual temporal recalibration testing, auditory and visual
TOJ tasks, as well as the EEG recording. Follow-up behavioral and EEG assessments will be
carried out 7 days after training to examine the persistence of training effects. Changes in
the multisensory temporal binding window induced by active training are shown to be stable
for at least one week in young adults.
Stimulus presentation. Visual and auditory stimuli will be generated using MATLAB and the
psychophysics toolbox. In behavioral and EEG experiments, visual and auditory stimuli will be
delivered via Display++ system and an AudioFile stimulus processor, respectively (Cambridge
Research Systems). The use of these two devices allows for precise control of stimulus
timing.
Active training. The investigators will use adaptive training tailored to each individual's
thresholds. Specifically, a two-alternative forced-choice TOJ task will be used, where
participants will be presented with an auditory beep (1000 Hz pure tone presented at 75 dB)
and a visual flash (a white circle presented on grey background) with varying stimulus onset
asynchronies (SOAs) and will be asked to judge the temporal order of the stimulus pair. On
each training day, the investigators will establish the range of SOAs for individuals based
on their thresholds determined from the pre-training TOJ assessment given on the same day.
The maximum SOA will be 0.2 log units greater than their estimated threshold and will be used
for both visual leading (positive SOA) and auditory leading (negative SOA) stimuli.
Participants will be exposed to a total of 160 trials in the training phase (8 SOAs x 20
repetitions). Feedback will be provided after each response.
Passive training. To control for pure practice or exposure effects, a second group of elderly
participants will undergo passive training. Participants will be exposed to an auditory beep
(1000 Hz) and a visual flash (a white circle) with varying SOAs, similarly as in the active
training group. The maximum SOA for each individual will be likewise determined by his or her
threshold from the TOJ assessment. However the participants will not be asked to perform the
TOJ task and no feedback will be provided. Instead, participants will perform an oddball task
in which they are asked to detect a dark grey circle or a high pitch beep (1500 Hz) that
occurs less frequently than the standard stimuli (i.e., a white circle or a 1000 Hz beep).
Having an oddball task in both auditory and visual modalities will ensure that participant's
attention is divided between the two modalities as required in the active training task 16.
There will be a total of 160 trials in the training phase (8 SOAs x 20 repetitions).
Behavioral assessment before and after training. The investigators will carry out a series of
behavioral studies to measure training effects on multisensory and unisensory temporal
functions using tasks such as the precision in TOJ and the temporal recalibration.
EEG assessment before and after training. The investigators will carry out a series of EEG
studies to measure training effects on electrophysiological measures such as ERP amplitude
during audiovisual temporal tasks.
Inclusion Criteria:
- Age between 65 and 75 (elderly group) and between 20 and 40 (young group)
Exclusion Criteria:
- History of epilepsy, stroke, Parkinson's disease, Alzheimer's disease, attention
deficit-hyperactivity disorder
- History of head injury with loss of consciousness, brain surgery, or psychiatric
disorders
- Early dementia or cognitive impairment
- Serious vision problems (including best-corrected binocular visual acuity worse than
20/25)
- Uncorrected hearing problems (pure tone threshold > 40 dB for 1000-2000 Hz)
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