Emory University, Department of Psychology, 36 Eagle Row, Atlanta, GA, 30322, USA.
University of Utah, Department of Psychology, 380 S 1530 E Beh S 502, Salt Lake City, UT, 84112, USA.
Neuropsychologia. 2024 Apr 15;196:108842. doi: 10.1016/j.neuropsychologia.2024.108842. Epub 2024 Feb 28.
FMRI studies of autobiographical memory (AM) retrieval typically ask subjects to retrieve memories silently to avoid speech-related motion artifacts. Recently, some fMRI studies have started to use overt (spoken) retrieval to probe moment-to-moment retrieved content. However, the extent to which the overt retrieval method alters fMRI activations during retrieval is unknown. Here we examined this question by eliciting unrehearsed AMs during fMRI scanning either overtly or silently, in the same subjects, in different runs. Differences between retrieval modality (silent vs. narrated) included greater activation for silent retrieval in the anterior hippocampus, left angular gyrus, PCC, and superior PFC, and greater activation for narrated retrieval in speech production regions, posterior hippocampus, and the DLPFC. To probe temporal dynamics, we divided each retrieval period into an initial search phase and a later elaboration phase. The activations during the search and elaboration phases were broadly similar regardless of modality, and these activations were in line with previous fMRI studies of AM temporal dynamics employing silent retrieval. For both retrieval modalities, search activated the hippocampus, mPFC, ACC, and PCC, and elaboration activated the left DLPFC and middle temporal gyri. To examine content-specific reactivation during retrieval, the timecourse of narrated memory content was transcribed and modeled. We observed dynamic activation associated with object content in the lateral occipital complex, and activation associated with scene content in the retrosplenial cortex. The current findings show that both silent and narrated AMs activate a broadly similar memory network, with some key differences, and add to current knowledge regarding the content-specific dynamics of AM retrieval. However, these observed differences between retrieval modality suggest that studies using overt retrieval should carefully consider this method's possible effects on cognitive and neural processing.
功能磁共振成像（fMRI）研究通常要求被试者在进行自传体记忆（AM）检索时进行默读以避免与言语相关的运动伪影。最近，一些 fMRI 研究已经开始使用显性（口语）检索来探测瞬间的检索内容。然而，显性检索方法在检索过程中改变 fMRI 激活的程度尚不清楚。在这里，我们通过在相同的被试者、不同的运行中，在 fMRI 扫描期间通过显性或默认知觉来诱发未经排练的 AM，来研究这个问题。检索方式（默读与讲述）之间的差异包括：在安静检索中，前海马体、左角回、后扣带回和上额前皮质的激活程度更高，而在讲述检索中，言语产生区域、后海马体和背外侧前额叶皮质的激活程度更高。为了探测时间动态，我们将每个检索期分为初始搜索阶段和后期细化阶段。无论模态如何，搜索和细化阶段的激活都非常相似，这些激活与使用静默检索的 AM 时间动态的先前 fMRI 研究一致。对于两种检索方式，搜索都激活了海马体、mPFC、ACC 和 PCC，细化则激活了左背外侧前额叶皮质和中颞回。为了在检索期间检查内容特异性再激活，我们转录并模拟了讲述记忆内容的时间历程。我们观察到与外侧枕叶复合体中的物体内容相关的动态激活，以及与后扣带回皮层中的场景内容相关的激活。目前的发现表明，沉默和讲述的 AM 都激活了一个广泛相似的记忆网络，存在一些关键差异，并为 AM 检索的内容特异性动态提供了新的认识。然而，检索方式之间的这些观察到的差异表明，使用显性检索的研究应仔细考虑该方法对认知和神经处理可能产生的影响。
