In the first funding period we investigated the encoding of time in visual cortical areas V4 and V1 during steady fixation and during eye movements. We could show that, surprisingly, brief temporal intervals (<100ms) as defined by pairs of flashes of light were encoded with high accuracy not only during steady fixation, but also during saccades and smooth pursuit.

While vision is the dominant sense in primates, interaction with the physical world is multisensory. Hence, in the second funding period, we aim to go one step further and investigate the neural and behavioural interaction of brief visual and auditory stimuli. Numerous studies in monkeys and humans have revealed cross-modal modulatory influences already at the level of the primary visual cortex, area V1. In our own work, we could show spatially congruent visual and auditory responses in macaque area VIP. How visual and auditory signals interact at the neural level, however, is barely understood. 

In the first two work packages, we will determine the neural interaction of brief visual and auditory stimuli in macaque areas V1 and VIP. A comparison of response properties between the two areas will allow determining how the visual cortical hierarchy shapes bi-modal interaction.

From human psychophysics it is known that when a single brief visual flash is accompanied by two auditory blips, it is frequently perceived incorrectly as two flashes. The neural basis of this perceptual phenomenon is far from being understood. In a third work package, we aim to train monkeys to indicate the perceived number of visual flashes, while task irrelevant auditory stimuli are presented. In case monkeys would also reveal a sound-induced visual illusion, we aim to correlate on a trial-by-trial basis neural activity with the monkey’s behaviour.

In summary, we expect an improved understanding of the neural and behavioural interactions of visual and auditory stimuli in primates.

Bremmer et al. (2016) Decoding target distance and saccade amplitude from population activity in the macaque lateral intraparietal area (LIP). Frontiers in Integrative Neuroscience, dx.doi.org/10.3389/fnint.2016.00030.

Dowiasch et al. (2016) Neural correlate of spatial (mis-)localization during smooth eye movements. European Journal of Neuroscience, DOI: 10.1111/ejn.13276. Dataset made publicly accessible at: https://doi.org/10.12751/g-node.m9hpkr