Reuter Françoise, Del Cul Antoine, Audoin Bertrand, Malikova Irina, Naccache Lionel, Ranjeva Jean Philippe, Lyon-Caen Olivier, Ali Chérif André, Cohen Laurent, Dehaene Stanislas, Pelletier Jean
Centre de Résonance Magnétique Biologique et Médicale (CRMBM) UMR CNRS 6612, Faculté de Médecine, Université de la Méditerranée, Marseille, France.
Neuropsychologia. 2007 Sep 20;45(12):2683-91. doi: 10.1016/j.neuropsychologia.2007.04.010. Epub 2007 Apr 19.
Periventricular white matter damage affecting large bundles connecting distant cortical areas may constitute the main neuronal mechanism for the deficit of controlled information processing observed in patients with early multiple sclerosis (MS). Visual backward masking has been demonstrated to affect late stages of conscious perception involving long-range interactions between visual perceptual areas and higher level integrative cortices while leaving intact early feed-forward visual processing and even complex processing such as object recognition or semantic processing. We therefore hypothesized that patients with early MS would have an elevated masking threshold, because of an impairment of conscious perception whereas subliminal processing of masked stimuli would be preserved. Twenty-two patients with early MS and 22 normal controls performed two backward-masking experiments. We used Arabic digits as stimuli and varied quasi-continuously the temporal interval with a subsequent mask, thus allowing us to progressively "unmask" the stimuli. We finely quantified the visibility of the masked stimuli using both objective and subjective measures, thus obtaining accurate estimates of the threshold duration for access to consciousness. We also studied the priming effect caused by the variably masked numbers on a comparison task performed on a subsequently presented and highly visible target number. The threshold for access to consciousness of masked stimuli was elevated in MS patients compared to controls, whereas non-conscious processing of these stimuli, as measured by priming, was preserved. These findings suggest that conscious access to masked stimuli depends on the integrity of large-scale cortical integrative processes, which involve long-distance white matter projections, and are impaired due to diffuse demyelinating injury in patients with early MS.
脑室周围白质损伤影响连接远距离皮质区域的大神经束，可能是早期多发性硬化症（MS）患者所观察到的受控信息处理缺陷的主要神经元机制。视觉后向掩蔽已被证明会影响有意识感知的后期阶段，这涉及视觉感知区域与高级整合皮质之间的长程相互作用，而早期的前馈视觉处理甚至诸如物体识别或语义处理等复杂处理则不受影响。因此，我们假设早期MS患者由于有意识感知受损，其掩蔽阈值会升高，而被掩蔽刺激的阈下处理将得以保留。22名早期MS患者和22名正常对照者进行了两项后向掩蔽实验。我们使用阿拉伯数字作为刺激，并随后用掩蔽物准连续地改变时间间隔，从而使我们能够逐渐“解除”刺激的掩蔽。我们使用客观和主观测量方法精确量化被掩蔽刺激的可见性，从而获得进入意识的阈值持续时间的准确估计。我们还研究了在随后呈现的高度可见目标数字上执行的比较任务中，可变掩蔽数字所引起的启动效应。与对照组相比，MS患者中被掩蔽刺激进入意识的阈值升高，而通过启动测量的这些刺激的无意识处理则得以保留。这些发现表明，对被掩蔽刺激的有意识访问取决于大规模皮质整合过程的完整性，这些过程涉及长距离白质投射，并且由于早期MS患者的弥漫性脱髓鞘损伤而受损。
