Peiffer Ann M, Hugenschmidt Christina E, Maldjian Joseph A, Casanova Ramon, Srikanth Ryali, Hayasaka Satoru, Burdette Jonathan H, Kraft Robert A, Laurienti Paul J
Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Hum Brain Mapp. 2009 Jan;30(1):228-40. doi: 10.1002/hbm.20497.
Even the healthiest older adults experience changes in cognitive and sensory function. Studies show that older adults have reduced neural responses to sensory information. However, it is well known that sensory systems do not act in isolation but function cooperatively to either enhance or suppress neural responses to individual environmental stimuli. Very little research has been dedicated to understanding how aging affects the interactions between sensory systems, especially cross-modal deactivations or the ability of one sensory system (e.g., audition) to suppress the neural responses in another sensory system cortex (e.g., vision). Such cross-modal interactions have been implicated in attentional shifts between sensory modalities and could account for increased distractibility in older adults. To assess age-related changes in cross-modal deactivations, functional MRI studies were performed in 61 adults between 18 and 80 years old during simple auditory and visual discrimination tasks. Results within visual cortex confirmed previous findings of decreased responses to visual stimuli for older adults. Age-related changes in the visual cortical response to auditory stimuli were, however, much more complex and suggested an alteration with age in the functional interactions between the senses. Ventral visual cortical regions exhibited cross-modal deactivations in younger but not older adults, whereas more dorsal aspects of visual cortex were suppressed in older but not younger adults. These differences in deactivation also remained after adjusting for age-related reductions in brain volume of sensory cortex. Thus, functional differences in cortical activity between older and younger adults cannot solely be accounted for by differences in gray matter volume.
即使是最健康的老年人也会经历认知和感觉功能的变化。研究表明，老年人对感觉信息的神经反应会减弱。然而，众所周知，感觉系统并非孤立运作，而是协同发挥作用，以增强或抑制对单个环境刺激的神经反应。很少有研究致力于了解衰老如何影响感觉系统之间的相互作用，特别是跨模态失活，即一个感觉系统（如听觉）抑制另一个感觉系统皮层（如视觉）中神经反应的能力。这种跨模态相互作用与感觉模态之间的注意力转移有关，可能是老年人注意力分散增加的原因。为了评估跨模态失活中与年龄相关的变化，在61名18至80岁的成年人进行简单听觉和视觉辨别任务期间，进行了功能磁共振成像研究。视觉皮层内的结果证实了先前关于老年人对视觉刺激反应降低的发现。然而，视觉皮层对听觉刺激的与年龄相关的变化要复杂得多，表明随着年龄增长，感觉之间的功能相互作用发生了改变。腹侧视觉皮层区域在年轻人而非老年人中表现出跨模态失活，而视觉皮层更靠背侧的区域在老年人而非年轻人中受到抑制。在调整了与年龄相关的感觉皮层脑容量减少后，这些失活差异仍然存在。因此，老年人和年轻人之间皮层活动的功能差异不能仅仅由灰质体积差异来解释。
