Aging Impairs Temporal Sensitivity, but not Perceptual Synchrony, Across Modalities

Abstract

Encoding the temporal properties of external signals that comprise multimodal events is a major factor guiding everyday experience. However, during the natural aging process, impairments to sensory processing can profoundly affect multimodal temporal perception. Various mechanisms can contribute to temporal perception, and thus it is imperative to understand how each can be affected by age. In the current study, using three different temporal order judgement tasks (unisensory, multisensory, and sensorimotor), we investigated the effects of age on two separate temporal processes: synchronization and integration of multiple signals. These two processes rely on different aspects of temporal information, either the temporal alignment of processed signals or the integration/segregation of signals arising from different modalities, respectively. Results showed that the ability to integrate/segregate multiple signals decreased with age regardless of the task, and that the magnitude of such impairment correlated across tasks, suggesting a widespread mechanism affected by age. In contrast, perceptual synchrony remained stable with age, revealing a distinct intact mechanism. Overall, results from this study suggest that aging has differential effects on temporal processing, and general impairments with aging may impact global temporal sensitivity while context-dependent processes remain unaffected.

Figure 1.. Experimental designs.

Panel A shows the experimental set-up used for all three tasks. The speaker used to present auditory cues was located in a central location relative to the observer and display. The fixation cross and visual stimulus were presented in the center of the screen for the audiovisual and visuomotor tasks while the two visual stimuli were presented peripheral to the fixation cross in the visual task. The time-course of the audiovisual TOJ task is shown in panel B. After 500 ms, the fixation cross disappeared to signal the start of the trial. During each trial a puretone auditory stimulus (As) and a visual stimulus (Vs) appeared on the screen at variable temporal delays (SOAs). Panel C shows the time-course of the visuomotor task. Participants were asked to make a keypress (Kp) immediately following the fixation cross’s disappearance. A visual stimulus (Vs) also appeared on the screen following the cross at variable temporal delays and participants then judged the temporal order. For the visual task (panel D), a visual stimulus flashed on the far right and on the far left of the fixation cross at variable asynchronies.. The fixation cross remained on the screen throughout the trial.

Figure 2.. Increased JND, not PSS, values for older adults across tasks.

Older adults (light grey bars) demonstrated significantly higher temporal order thresholds (top row) for the audiovisual (left panel), visuomotor (middle panel), and visual (right panel) TOJ tasks as compared to young (black bars) and middle-aged adults (dark grey bars). There was no difference in PSS measures (bottom row) across age groups.

Figure 3.. Significant relationships between JND values from all 3 tasks.

Simple linear regression models were fit to individual JND data from the audiovisual and visuomotor (left panel), the visual and audiovisual (middle panel), and the visual and visuomotor (right panel) conditions revealing positive associations between all tasks tested.

Figure 4.. Distinct synchronization processes for unisensory, multisensory, and sensorimotor frameworks.

Simple linear regression models were fit to individual PSS data from the audiovisual and visuomotor (left panel), the visual and audiovisual (middle panel), and the visual and visuomotor (right panel) conditions revealing no significant associations.