There’s an interesting article in January’s Journal of Cognitive Neuroscience about a brain injured patient who has a curious form of simultanagnosia – the inability to perceive more than one object at once.
In this case, he also seemed unable to report more than one attribute, like colour or name, at a time, while looking at the object.
Simultanagnosia: When a Rose Is Not Red.
J Cogn Neurosci. 2008, 20 (1), 36-48
Coslett HB, Lie G.
Information regarding object identity (“what”) and spatial location (“where/how to”) is largely segregated in visual processing. Under most circumstances, however, object identity and location are linked. We report data from a simultanagnosic patient (K.E.) with bilateral posterior parietal infarcts who was unable to “see” more than one object in an array despite relatively preserved object processing and normal preattentive processing. K.E. also demonstrated a finding that has not, to our knowledge, been reported: He was unable to report more than one attribute of a single object. For example, he was unable to name the color of the ink in which words were written despite naming the word correctly. Several experiments demonstrated, however, that perceptual attributes that he was unable to report influenced his performance. We suggest that binding of object identity and location is a limited-capacity operation that is essential for conscious awareness for which the posterior parietal lobe is crucial.
This is particularly interesting because it relates to a key question in understanding consciousness, known as the ‘binding problem‘.
The brain deals with different parts of perception (for example movement, colour, light-dark differences) in different parts of the brain, yet when we perceive an object, it all seems to be integrated into one conscious experience.
For example, our experience of an object’s colour and movement never seem to be ‘out of synch’. How this happens is the essence of the binding problem.
This case report is of someone whose brain injury seems to prevent ‘binding’.
Looking at what brain injured patients can no longer do and matching this with the damaged areas can give us a clue to how the brain works because “you don’t know what you’ve got ’till it’s gone”.
Strictly speaking, this is called the transparency assumption in cognitive neuropsychology but I call it the Joni Mitchell principle as the quote is a song lyric of hers (I got this from a student essay I once marked so thank you insightful mystery student!).
In this case, the patient suffered damage to both sides of the back of the parietal lobes because of a stroke (“bilateral posterior parietal infarcts”), suggesting the parietal lobes might be key in binding perceptual elements for consciousness.
Unfortunately, I can’t get to the full-text of the paper yet, so I’m not sure what insights the authors themselves have offered. Still, a fascinating case.
Link to PubMed abstract.