We live in a rich visual environment populated by many different kinds of objects. Categorisation of these objects is important for determining our actions towards them. Previous studies have shown that the human brain contains regions that respond selectively to images from a certain object category. The two most well-known category-selective regions are the fusiform face area (FFA), which responds selectively to faces, and the parahippocampal place area (PPA), which responds selectively to places. Previous studies averaged responses of these regions across individual objects, and therefore left open to what extent category selectivity holds for individual objects.
An fMRI study recently published in the Journal of Neuroscience, led by Cognition and Brain Sciences researchers Marieke Mur and Nikolaus Kriegeskorte, addresses this outstanding question. Activation of category-selective regions was measured while participants viewed images of individual objects from a wide range of categories, including faces and places. Single-image analysis showed that (1) category-selective regions might respond more strongly to every single member of their preferred category than to any non-member, (2) activation of category-selective regions drops off in a step-like fashion at the category boundary, indicating that the category boundary has a special status, and (3) activation of category-selective regions is graded within and outside the preferred category.
These findings support the idea that the brain emphasizes category distinctions relevant for behaviour, while still distinguishing individual objects. These findings enhance our understanding of the basic principles of object recognition in the human brain and serve as a starting point for future brain research in patient groups that show deficits in object recognition, including persons with prosopagnosia and semantic dementia.