Researchers induce “sightless vision” in volunteers

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <table border="0" cellpadding="0" cellspacing="0" width="95%" height="1"> <tr> <center> <td valign="top" width="33%" height="33"> <b> <p class="MsoNormal"><font face="Arial" size="5">Researchers induce “sightless vision” in volunteers</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">July 13, 2005<br> Courtesy University of California at San Diego<br> and World Science staff<br> </font> <b><font size="2" face="Arial"><br> Researchers report inducing temporary “blindsight” in healthy volunteers—a condition in which people think they can’t see anything, but in fact can.<br> <br> The condition occurs when a part of their brain called the primary visual cortex is deactivated. The primary visual cortex is essential for visual perception. People with damage to this region report no awareness of objects in their field of vision. <br> <br> Yet people with blindsight, which normally results from certain kinds of damage to the brain, can still “sense” these unseen objects. Pressed into taking a guess at an object’s location, for instance, they give the right answer much of the time, even though they insist they can’t see anything.<br> <br> Tony Ro and colleagues at Rice University in Houston, Texas, tested blindsight in human subjects with normal vision. Using an electromagnetic brain stimulation technique, the researchers deactivated the primary visual cortex in 12 volunteers. An object on a screen was then flashed in front of the temporarily blinded volunteers. <br> <br> In one experiment, the object was a horizontal or vertical bar; in another, colored discs were shown. Although the volunteers reported no awareness of the objects’ characteristics the majority of the time, they also guessed correctly at a level significantly higher than chance. <br> <br> The results suggest the existence of a visual pathway that bypasses the primary visual cortex and can process some characteristics unconsciously, the researchers said. They described the findings in a paper published in this week’s early online edition of the research journal Proceedings of the National Academy of Sciences.<br> <br> Some researchers say even perfectly ordinary people have some capacity for blindsight all the time. Play this game to see if you do.</font></b></p> <p class="MsoNormal"> <b><font size="2" face="Arial">* * *</font></p> </b> <p><b><font face="Arial" size="2" color="#FFFFFF">Send us a <a href="mailto:editor@world-science.net">comment</a> on this story, or <a href="mailto:?Body=http://www.world-science.net/othernews/051031_blindsightfrm.htm">send it to a friend</a></font></b> </p> <p> </center> </td> </tr> </table> </body>