One of the mysteries of how the brain processes what our eyes see is how it interprets visual objects. Benjamin de Haas published a study he did mapping the organisation of tuning functions for facial features. We informally termed this faceotopic maps. Just as retinotopic maps measure the spatial preference and selectivity for position in visual space, the idea of faceotopy is a preference for the position relative to the geometry of the face. We used bar apertures, placed either in the upper or lower visual field, through which the observers viewed a picture of faces that scrolled up or down. Thus we were able to measure the spatial preference and selectivity in face space. We indeed found map-like organisation in inferior occipital gyrus, part of the face processing network in extrastriate visual cortex. We further compared this to retinotopic maps acquired using a similar bar stimulus that traversed the visual field. The structure of these maps is similar in both conditions, particularly as far as selectivity is concerned. There is a gradient of increasing tuning width as one moves from the posterior to the anterior side of this part of cortex. For retinotopy, this increased invariance to spatial location at higher stages of the processing hierarchy is well established. However, our findings show that faceotopic organisation mirrors this relationship. Posterior parts of this brain region are fairly selective for facial features while more anterior parts respond to whole faces.
It may also be the first study with a guitar-shaped brain region… 😉
de Haas, B, Sereno, MI, & Schwarzkopf, DS (2021). Inferior occipital gyrus is organised along common gradients of spatial and face-part selectivity. Journal of Neuroscience In press.