Smania N, Martini M C, Gambina G, Tomelleri G, Palamara A, Natale E, Marzi C A
Rehabilitation Center, Policlinico Borgo Roma, Verona, Italy.
Brain. 1998 Sep;121 ( Pt 9):1759-70. doi: 10.1093/brain/121.9.1759.
We studied the visual field distribution of speed and accuracy of manual responses to small brief light flashes, in patients with left hemineglect or extinction resulting from right hemisphere vascular lesions and in brain-damaged and healthy control subjects. All patients with right hemisphere lesions showed a greater impairment in both the speed of response and the detection rate in the contralesional than in the ipsilesional hemifield. This interfield difference increased with the eccentricity of stimulus presentation and was especially pronounced in neglect patients who showed a paradoxical increase in speed of response and detection rate at increasingly larger eccentricities in the ipsilesional hemifield. We hypothesize that both the contralesional slowing down and the ipsilesional speeding up of the response depends upon an exaggerated gradient of attention towards the ipsilesional hemifield. To assess whether these abnormalities concern automatic or controlled attentional processes, in a second experiment, we manipulated the predictability of the side of the stimulus presentation by using blocked rather than randomized stimulus presentations. This resulted in a speeding up of responses in both hemifields thus showing that the patients were able to focus attention to the side of stimulus presentation voluntarily. However, there was no modification of the contra-ipsilesional differences which, therefore, are likely to be related to abnormal automatic processes rather than controlled attention.
我们研究了右半球血管病变导致左侧半侧忽视或消退的患者以及脑损伤和健康对照受试者对短暂小闪光手动反应的速度和准确性的视野分布。所有右半球病变患者在对侧半视野的反应速度和检测率方面的损伤均大于同侧半视野。这种视野间差异随刺激呈现的偏心度增加而增大，在忽视患者中尤为明显，这些患者在同侧半视野中，随着偏心度越来越大，反应速度和检测率出现了反常的增加。我们假设，对侧反应减慢和同侧反应加速均取决于对同侧半视野注意力的过度梯度。为了评估这些异常是否涉及自动或受控的注意力过程，在第二个实验中，我们通过使用分块而非随机的刺激呈现方式来操纵刺激呈现侧的可预测性。这导致两个半视野的反应均加快，从而表明患者能够自愿将注意力集中在刺激呈现侧。然而，对侧与同侧的差异没有改变，因此，这些差异可能与异常的自动过程而非受控注意力有关。
