Early cortical processing of coherent vs. non-coherent motion stimuli in younger and older adults: An event-related...

The neurophysiological basis of vection (i.e., the illusion of self-motion) is not well understood. Preliminary evidence suggests that neural predictors of vection can be identified through event-related potentials (ERPs) and that these markers may correlate with vection intensity. The current study examined age-related differences in neurocortical activity during the early stages of sensory processing of vection-inducing stimuli. Twenty-two younger (age range: 20-35 years) and 25 older adults (age range: 65-83) observed optokinetic stimuli in two blocks, a short (∼3s) presentation block and a long (35s) presentation block. In both types of blocks, the optokinetic stimuli varied in motion coherence (coherent vs. non-coherent motion). During the short presentation block, EEG was used to measure neural activity in the form of ERPs time-locked to the onset of visual motion, whereas subjective ratings of vection intensity, duration, and onset latency were collected during the long presentation block. Vection was significantly stronger following coherent vs. non-coherent motion for both age groups. ERP analyses revealed differences between coherent and non-coherent motion at parietal-occipital electrodes around 100-150 ms (P1) and 150-230 ms (P2), with greater area under the curve (AUC) during non-coherent vs. coherent motion. Neither vection ratings nor ERPs showed significant age differences for coherent visual motion; however, age differences in ERPs were observed during the processing of non-coherent visual motion. These findings indicate that the subjective experience of vection and the neurophysiological mechanisms underlying visual processing preceding vection remain relatively stable with age. However, they also reveal age-related differences in the processing of non-coherent motion.