Intaitė Monika, Koivisto Mika, Castelo-Branco Miguel
Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra, Azinhaga De Santa Comba, Celas, 3000-548 Coimbra, Portugal.
Centre for Cognitive Neuroscience, University of Turku, 20014 Turku, Finland; Department of Psychology, University of Turku, 20014 Turku, Finland.
Neuropsychologia. 2014 Apr;56:428-38. doi: 10.1016/j.neuropsychologia.2014.02.016. Epub 2014 Feb 22.
While viewing ambiguous figures, such as the Necker cube, the available perceptual interpretations alternate with one another. The role of higher level mechanisms in such reversals remains unclear. We tested whether perceptual reversals of discontinuously presented Necker cube pairs depend on working memory resources by manipulating cognitive load while recording event-related potentials (ERPs). The ERPs showed early enhancements of negativity, which were obtained in response to the first cube approximately 500 ms before perceived reversals. We found that working memory load influenced reversal-related brain responses in response to the second cube over occipital areas at the 150-300 ms post-stimulus and over central areas at P3 time window (300-500 ms), suggesting that it modulates intermediate visual processes. Interestingly, reversal rates remained unchanged by the working memory load. We propose that perceptual reversals in discontinuous presentation of ambiguous stimuli are governed by an early (well preceding pending reversals) mechanism, while the effects of load on the reversal related ERPs may reflect general top-down influences on visual processing, possibly mediated by the prefrontal cortex.
在观察诸如内克尔立方体等模糊图形时，可用的感知解释会相互交替。高级机制在这种反转中所起的作用仍不清楚。我们通过在记录事件相关电位（ERP）时操纵认知负荷，来测试不连续呈现的内克尔立方体对的感知反转是否依赖于工作记忆资源。ERP显示出早期负性增强，这是在感知到反转前约500毫秒对第一个立方体做出反应时获得的。我们发现，工作记忆负荷在刺激后150 - 300毫秒时影响枕叶区域对第二个立方体的反转相关脑反应，在P3时间窗口（300 - 500毫秒）影响中央区域的反应，这表明它调节中间视觉过程。有趣的是，反转率并未因工作记忆负荷而改变。我们提出，在模糊刺激的不连续呈现中，感知反转受一种早期（远早于即将发生的反转）机制支配，而负荷对反转相关ERP的影响可能反映了对视觉处理的一般自上而下的影响，可能由前额叶皮层介导。
