Universidad de Granada, Spain.
Cortex. 2012 May;48(5):540-52. doi: 10.1016/j.cortex.2011.01.008. Epub 2011 Feb 3.
Signs of left unilateral neglect often occur after damage to the right hemisphere and entail a left-right imbalance in stimulus processing. Typically, neglect patients deviate rightward when bisecting lines. An underestimation of the left portion of the line and/or a right overestimation could explain this effect.
Here we dissected their respective contribution by asking participants to compare a vertical segment to a horizontal segment, either on the left or on the right. We also tested whether neglect patients exhibited the symmetry law, whereby normal participants underestimate symmetrically bisected lines as compared to asymmetrically bisected lines.
Controls and patients underestimated symmetric figures. Depending on the degree of left-right horizontal competition, neglect patients underestimated left-sided stimuli or overestimated right-sided stimuli.
We concluded that two independent deficits contribute to neglect signs: a deficit in attentional orienting to the left, which can be worsened by left hemianopia, perhaps depending on impaired functioning of right-hemisphere attentional networks, and a tendency for attention to be captured by right-sided stimuli, possibly resulting from the activity of an isolated left hemisphere. Finally, the symmetry law was preserved in neglect patients, and thus appears to be driven by pre-attentive mechanisms.
左侧单侧忽略的迹象通常发生在右半球损伤后，并导致刺激处理中的左右不平衡。通常，忽略患者在分割线时会向右偏。这种效应可以用对线条左侧的低估和/或对右侧的高估来解释。
在这里，我们通过要求参与者将垂直线段与水平线段进行比较，来分别测试左右两侧的线段，从而分解它们各自的贡献。我们还测试了忽略患者是否表现出对称性法则，即与不对称分割线相比，正常参与者会低估对称分割线。
对照组和患者都低估了对称图形。根据左右水平竞争的程度，忽略患者会低估左侧刺激或高估右侧刺激。
我们得出结论，两个独立的缺陷导致了忽略的迹象：对左侧的注意力定向缺陷，这种缺陷可能会因左侧偏盲而恶化，可能取决于右半球注意力网络功能受损，以及注意力被右侧刺激吸引的趋势，这可能是孤立的左半球活动的结果。最后，忽略患者保留了对称性法则，因此似乎是由前注意机制驱动的。
