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Seeing only the right half of the forest but cutting down all the trees?

Nature volume 394, pages 75–78 (1998)Cite this article

Abstract

Unilateral neglect following damage to the right hemisphere of the brain can be characterized by failure of the global attentional mechanisms of the right hemisphere to direct the local detail processors of the left hemisphere towards the contralesional left hemispace. This is suggested by patients who recognize the global form of the left side of shapes (the forest) but fail to cancel out its local details (the trees)1. Here we report the opposite behavioural dissociation in a patient (Q.M.) with damage to the right hemisphere of the brain. Q.M. detected local details (such as the tail of a dog) on the left or right side of visual shapes, regardless of whether these details belonged to predefined target shapes (a dog in this case) or to distractor shapes differing on the opposite side (a dog with a swan's neck and head, for example). Psychological testing showed an abnormal tendency of this patient to respond to local features, but perfect accuracy in interpreting global features when the local features could not interfere in global processing. The results indicate that the left hemisphere can integrate multiple local features simultaneously but loses global awareness as soon as local features individually compete for response selection. However, awareness of the whole is not necessary for the sequential processing of the parts.

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Figure 1: NMR scans of patient Q.M. Scans were taken at a, 5 days, and b, 15 days post-stroke.
Figure 2: Cancellation tasks.
Figure 3: Bias towards local processing in patient Q.M.
Figure 4: Processing of local and global visual features in the neglected space.

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Acknowledgements

We thank Q.M. for her collaboration, L. Pizzamiglio, G. Vallar and G. Antonucci for suggestions, C. Montagna, E. Catani and B. Fane for text revision, and G. Paganelli and his team for help in the radiological examination of Q.M. This work was supported by a grant from the Centro Residenziale IRCCS S. Lucia.

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Authors and Affiliations

  1. Centro Ricerche di Neuropsicologia, IRCCS S. Lucia, Via Ardeatina 306, 00179, Roma, Italy

    Fabrizio Doricchi & Chiara Incoccia

  2. Istituto di Psicologia Luigi Meschieri, Universita' degli Studi di Urbino, Via Saffi 15, 61029, Urbino, Italy

    Fabrizio Doricchi

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  1. Fabrizio Doricchi
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  2. Chiara Incoccia
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Correspondence to Fabrizio Doricchi.

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Doricchi, F., Incoccia, C. Seeing only the right half of the forest but cutting down all the trees?. Nature 394, 75–78 (1998). https://doi.org/10.1038/27913

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