Alpha modulation in younger and older adults during distracted encoding

To successfully encode information into long-term memory, we need top-down control to focus our attention on target stimuli. This attentional focus is achieved by the modulation of sensory neuronal excitability through alpha power. Failure to modulate alpha power and to inhibit distracting information has been reported in older adults during attention and working memory tasks. Given that alpha power during encoding can predict subsequent memory performance, aberrant oscillatory modulations might play a role in age-related memory deficits. However, it is unknown whether there are age-related differences in memory performance or alpha modulation when encoding targets with distraction. Here we show that both older and younger adults are able to encode targets paired with distractors and that the level of alpha power modulation during encoding predicted recognition success. Even though older adults showed signs of higher distractibility, this did not harm their episodic memory for target information. Also, we demonstrate that older adults only modulated alpha power during high distraction, both by enhancing target processing and inhibiting distractor processing. These results indicate that both younger and older adults are able to employ the same inhibitory control mechanisms successfully, but that older adults fail to call upon these when distraction is minimal. The findings of this study give us more insight into the mechanisms involved in memory encoding across the lifespan.若要将信息成功编码至长时记忆（long-term memory），需借助自上而下的认知控制，将注意力聚焦于目标刺激物。该注意力聚焦可通过阿尔法功率（alpha power）调节感觉神经元兴奋性得以实现。已有研究证实，老年人在完成注意力与工作记忆（working memory）任务时，无法有效调节阿尔法功率并抑制分心信息。鉴于编码阶段的阿尔法功率可预测后续记忆表现，异常的节律调节或与年龄相关的记忆缺损存在关联。然而，在存在分心物的目标编码过程中，记忆表现或阿尔法功率调节是否存在年龄相关差异，目前仍不明确。本研究表明，青年与老年成年人均可对伴随分心物的目标进行编码，且编码阶段的阿尔法功率调节水平可预测后续再认成绩。尽管老年人表现出更高的分心易感性，但这并未损害其对目标信息的情景记忆（episodic memory）。此外，本研究还证实，老年人仅在高分心条件下调节阿尔法功率，具体表现为增强目标加工并抑制分心物加工。上述结果显示，青年与老年成年人均可成功运用相同的抑制控制机制，但老年人在分心程度较低时无法激活此类机制。本研究的发现有助于深入理解全生命周期中记忆编码所涉及的神经机制。