I Do Not See It, But My Brain Knows What It Means

Main Category: Neurology / Neuroscience
Article Date: 01 Jun 2008 - 1:00 PDT

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Patients suffering from "hemineglect" cannot attend to, and hence cannot see, things presented to their left side. However, sometimes these ignored stimuli may be processed without awareness. In a paper published in the May 2008 issue of Cortex, Jerome Sackur and colleagues at Unite de Neuroimagerie Cognitive, Paris, France, reported that unconscious processing in hemineglect is not limited to low level features of the stimuli.

The research was carried out on 4 right-handed female patients (40-56 years old), suffering from left unilateral neglect secondary to right hemispheric stroke and 14 neurologically normal, right handed patients (6 females, 9 males, 19-32 years old). An additional group of 4 neurologically normal age-matched control subjects was separately tested on the main experiment.

By analyzing the results of their experiment, the authors showed that the brain may extract the meaning of symbols that the patient has not consciously perceived. Thus, digits or number words presented on the left side were not detected by hemineglect patients, but still their numerical value influenced the way these patients performed on a numerical task presented shortly thereafter.

"This study demonstrates that in hemineglect the left part of the world is not a ''blind'' region: in a way, patients read and understand unconsciously what is there" says Dr. Sackur, coordinator of the study. "However, the patients cannot make conscious use of this information".

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The article is "Semantic processing of neglected numbers" by Jerome Sackur, Lionel Naccache, Pascale Pradat-Diehl, Philippe Azouvi, Dominique Mazevet, Rose Katz, Laurent Cohen and Stanislas Dehaene, and it appears in Cortex, Volume 44, Issue 6, 2008, pp 673-682, published by Elsevier Masson, in Italy.

About Cortex

Cortex is an international journal devoted to the study of cognition and of the relationship between the nervous system and mental processes, particularly as these are reflected in the behaviour of patients with acquired brain lesions, normal volunteers, children with typical and atypical development, and in the activation of brain regions and systems as recorded by functional neuroimaging techniques. It was founded in 1964 by Ennio De Renzi. The Editor in-chief of Cortex is Sergio Della Sala, Professor of Human Cognitive Neuroscience at the University of Edinburgh. Cortex is available online at http://www.sciencedirect.com/science/journal/00109452

About Elsevier

Elsevier is a world-leading publisher of scientific, technical and medical information products and services. Working in partnership with the global science and health communities, Elsevier's 7,000 employees in over 70 offices worldwide publish more than 2,000 journals and 1,900 new books per year, in addition to offering a suite of innovative electronic products, such as ScienceDirect (http://www.sciencedirect.com/), MD Consult (http://www.mdconsult.com/), Scopus (http://www.info.scopus.com/), bibliographic databases, and online reference works.

Elsevier (http://www.elsevier.com/) is a global business headquartered in Amsterdam, The Netherlands and has offices worldwide. Elsevier is part of Reed Elsevier Group plc (http://www.reedelsevier.com/), a world-leading publisher and information provider. Operating in the science and medical, legal, education and business-to-business sectors, Reed Elsevier provides high-quality and flexible information solutions to users, with increasing emphasis on the Internet as a means of delivery. Reed Elsevier's ticker symbols are REN (Euronext Amsterdam), REL (London Stock Exchange), RUK and ENL (New York Stock Exchange).

Source: Valeria Brancolini
Elsevier

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