Object, face and body representations in the human brain

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The goal of this research is to understand how we see what we see: how does the brain analyze the light coming through the retina of the eye to produce a world full of objects, people and things? During the past year we have focused on the effect of position changes on visual object recognition. It is typically assumed that visual object recognition is independent of position in the visual field, that our ability to recognize an object is unaffected by changes in the position of that object. Indeed, some models of object recognition propose that the brain produces an abstract visual representation of an object that is independent of its specific position or size, for example, which is then available to interact with semantic or conceptual knowledge. However, a review of the current behavioral literature found little support for this view. To investigate the role of position in object recognition, we have initiated an extensive series of behavioral experiments. Our initial results show that changes in position do have a large impact on object recognition and suggest that the brain may contain multiple representations of objects at different positions in the visual field. To confirm these results we are now conducting functional magnetic resonance imaging (fMRI) experiments to see how changes in position affect the neural representations of objects in the brain and whether the task the participant is performing modulates the nature of these representations. We have also started to investigate how we recognize different body parts (our own and others). Previous fMRI studies have identified a region of the brain that responds more when people view body parts (e.g. legs, arms, feet) than when they view objects (e.g. chair, car, hammer). Although it has been suggested that this brain region may be important for our ability to recognize bodies, no study has shown that this region can discriminate between different body parts. We are now conducting fMRI experiments to investigate brain activity in this brain region while participants view images of different body parts in different positions in the visual field taken from perspectives corresponding either to a view of their own body or to a view of someone elses body. Elucidating how the brain enables us to recognize objects, faces and bodies will provide important insights into the nature of our internal representations of the world around us.