Certain brain injuries can cause people to lose the ability to visually recognize objects. Now neuroscientists from Carnegie Mellon University and Princeton University examined the brain of a person with object agnosia, a deficit in the ability to recognize objects that does not include damage to the eyes or a general loss in intelligence, and have uncovered the neural mechanisms of object recognition.
The results have described the functional neuroanatomy of object agnosia and suggested that damage to the part of the brain critical for object recognition can have a widespread impact on remote parts of the cortex.
“One of the persisting controversies in the field of visual neuroscience concerns the regions of cortex that subserve the human ability to recognize objects as efficiently and accurately as we do, and it's been an elusive topic until now,” said Marlene Behrmann, professor of psychology at CMU and a renowned expert in using brain imaging to study the visual perception system.
To gain new insight into the neural basis of object recognition, the research team used neuroimaging and behavioural investigations to study visual and object-selective responses in the cortex of healthy controls and a participant called SM who, following selective brain damage to the right hemisphere of the brain, exhibited object agnosia.
The researchers discovered that the functional organization of the 'lower' visual cortex, where the image from the retina is initially processed, was similar in SM and control subjects. However, SM exhibited decreased object-selective responses in the brain tissue in and around the brain lesion, and in more distant cortical areas that are also known to be involved in object recognition. Unexpectedly, the decrease in object-selective responses was also observed in corresponding locations of SM's structurally intact left hemisphere.
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