Early spatiotemporal dynamics of navigational affordance coding in the dorsal visual cortex.

Successful navigation requires extracting navigationally relevant signals from a dynamically changing visual environment. The process by which we identify navigable routes through the environment is termed navigational affordances. Here, using a combination of functional magnetic resonance imaging, magnetoencephalography and behavioural testing we report that the extraction of such navigational affordance information likely takes place rapidly within dorsal early visual cortex before higher-level scene selective regions. Whilst we replicate prior work showing the involvement of the occipital place area in navigational affordance coding, whole-brain analyses indicate the most likely cortical locus to be dorsal early visual cortex. Analyses comparing the spatiotemporal pattern of navigational affordances suggest such information is detectable within ~110 milliseconds post stimulus onset. Finally, through varying the presentation durations of scenes, we demonstrate that navigational affordance representations are emergent, but not strong with stimulus durations as short as 33-66 milliseconds but become robust with stimulus durations >132 milliseconds. Taken together these data challenge previous views regarding the critical cortical locus for navigational affordance coding and suggest that such affordances can be extracted from very briefly presented stimuli.