應變相關規則處理之神經機制的年齡差異

Abstract

給定的行為在大多數情況下可能是適當的，但在某些其他情況下是不合適的。同樣，一些情境可能會鼓勵某種行為，但也可能偶爾需要替代行為。我們假設老化對人類大腦功能特別影響了針對目標導向行為的特殊規則應變的選擇。年輕與老年成年人進行了功能磁共振成像（fMRI）XDPX實驗，這是一個增設XNOR規則的DPX（dot probe expectancy）任務。Cue-probe配對實例化了不同的情境和應變規則處理，方式類似於非線性邏輯表，其中一些配對更頻繁。特別是當相關便應規則出現頻率次數較少時，老年人比較年輕的成年人反應慢且不準確。皮質活動普遍於年輕人上觀察到，但在老年人上卻有限。老年人在Default Mode Network（DMN）中對較不頻繁的XNOR規則產生了較高的神經活動。這些研究結果表明，在面臨情境應變處理時，與年齡有關的主動轉變為反應處理策略。最重要的是，我們指認出了當人類大腦經歷神經功能資源的年齡相關變化時，DMN參與XNOR邏輯規則計算的角色。

A given behavior may be appropriate in most contexts but inappropriate in some other contexts. Likewise, some contexts may encourage a given behavior but might also contingently require alternative behaviors at times. We hypothesized that age effects on human brain function particularly compromises such selection of contingent rule mappings for goal-directed behavior. Young and older adults underwent a functional magnetic resonance imaging (fMRI) XDPX experiment, which was a modified DPX (dot probe expectancy) task incorporating the XNOR rule. Cue-probe pairings instantiated different contextual and contingent response rule mappings akin to a non-linear logic table with some pairings being more frequent. Older adults were slower and less accurate than younger adults for less common cue contexts particularly when the probe response rule contingency was also less frequent. Cortical activity was widespread to contextual cues in young but minimal in older adults. Older adults engaged higher neural activity in the default mode network (DMN) to the least frequent XNOR probe. These findings suggest an age-related shift from proactive to reactive processing strategies when facing contextual contingencies. Critically, we identify a novel DMN involvement in XNOR computations when the human brain undergoes age-related changes in neural functional resources.