Kaufman L, Curtis S, Wang J Z, Williamson S J
Department of Psychology, New York University, NY 10003.
Electroencephalogr Clin Neurophysiol. 1992 Apr;82(4):266-84. doi: 10.1016/0013-4694(92)90107-s.
The magnetoencephalogram (MEG) was used to detect regional changes in spontaneous cortical activity accompanying short-term memory search. This method was chosen because magnetic fields are detectable only within a few centimeters of the projections of their sources onto the scalp. The specific hypothesis that auditory cortex is involved in scanning memory for tones was tested by sensing the field of the magnetic counterpart to N100 (N100m) which is known to originate in auditory cortex. N100m was measured at many different positions and the spontaneous cortical rhythms in the alpha bandwidth (8-12 Hz) were measured at the same places. These rhythms were found to be suppressed while subjects scanned memory for musical tones in a Sternberg paradigm. For 3 subjects, both the MEG suppression time (ST) and reaction time (RT) increased linearly with memory set size. The correlation between ST measured over the left hemisphere and set size was significant for two subjects but not significant for the third, and the slopes of the regression lines relating ST to set size were too shallow to be related to the time required to scan memory. However, the correlation between ST of the right hemisphere and set size was highly significant for all subjects, and the slopes of the regression lines were comparable to those relating RT to set size. The electroencephalogram (EEG) recorded with midline electrodes failed to reveal a significant relationship between suppression time and set size for 2 of the subjects, thus ruling out global alpha blockage and generalized arousal as the basis for the task-related suppression duration. The electric N100, measured at Cz, decreased significantly in amplitude with set size for 2 subjects, but it increased significantly in amplitude for the third subject. In contrast, RT increased with set size for all subjects. N100m measured over the right hemisphere was similar to the behavior of N100, while N100m measured over the left hemisphere showed little change in amplitude with set size, thus establishing an asymmetry in N100 between the hemispheres. Since N100 amplitude is normally larger when attention is paid to auditory stimuli, differential attention alone cannot account for the relation between ST and set size. Furthermore, the processing negativity, which may be superimposed on N100 in selective attention tasks, was not discernible for any set size. It was also found that ST prior to the button press was not correlated with RT. Hence, the covariation of set size with ST is not attributable to preparation for a motor response.(ABSTRACT TRUNCATED AT 400 WORDS)
脑磁图（MEG）被用于检测伴随短期记忆搜索的自发皮质活动的区域变化。选择这种方法是因为磁场仅在其源投射到头皮的几厘米范围内可被检测到。通过检测与N100（N100m）对应的磁场来检验听觉皮质参与音调记忆扫描的特定假设，已知N100起源于听觉皮质。在许多不同位置测量N100m，并在相同位置测量α频段（8 - 12赫兹）的自发皮质节律。发现在受试者以斯特恩伯格范式扫描音乐音调记忆时，这些节律受到抑制。对于3名受试者，MEG抑制时间（ST）和反应时间（RT）均随记忆集大小线性增加。在两名受试者中，左半球测量的ST与记忆集大小之间的相关性显著，而第三名受试者不显著，并且将ST与记忆集大小相关的回归线斜率太浅，无法与扫描记忆所需时间相关。然而，右半球的ST与记忆集大小之间的相关性在所有受试者中都非常显著，并且回归线斜率与将RT与记忆集大小相关的斜率相当。用中线电极记录的脑电图（EEG）未能揭示2名受试者的抑制时间与记忆集大小之间的显著关系，从而排除了全局α阻断和全身性唤醒作为任务相关抑制持续时间的基础。在Cz处测量的电N100，对于2名受试者，其幅度随记忆集大小显著减小，但对于第三名受试者，其幅度显著增加。相比之下，所有受试者的RT均随记忆集大小增加。右半球测量的N100m与N100的行为相似，而左半球测量的N100m幅度随记忆集大小变化不大，从而在半球间建立了N100的不对称性。由于当关注听觉刺激时N100幅度通常较大，仅差异注意力不能解释ST与记忆集大小之间的关系。此外，在任何记忆集大小下，在选择性注意任务中可能叠加在N100上的加工负波都不可见。还发现按键前的ST与RT不相关。因此，记忆集大小与ST的协变不归因于运动反应的准备。（摘要截断于400字）
