As they age, many individuals can struggle to remember recent events or what they meant to say next during a conversation, while also frequently losing or misplacing objects. In some cases, cognitive tests detect these memory impairments. In others, people notice and report a decline even though their test scores remain within the normal range.
The term mild cognitive impairment (MCI) refers to measurable difficulties with memory or other thinking skills in people who remain largely independent in daily life. Subjective cognitive decline (SCD), on the other hand, is a perceived decline despite normal performance on standard cognitive tests. Understanding the neural underpinnings of both could potentially help researchers develop and test interventions for cognitive decline.
Researchers at the Affiliated Brain Hospital of Nanjing Medical University, Nanjing University and other institutions recently compared brain scans and memory test scores using data collected from more than 1,000 people. Their paper, published in Translational Psychiatry, suggests that different areas of cortical thinning in people with MCI could map to a shared memory network, while the same pattern was not statistically significant in people with SCD.
Linking patterns of thinning to a memory network
The researchers analyzed data from 1,312 people across three independent cohorts, including brain scans and scores on tests assessing episodic memory, the ability to recall specific events or experiences. They used structural magnetic resonance imaging (MRI) to measure cortical thickness and a reference map based on resting-state functional MRI (fMRI) to estimate how activity in different brain regions typically varies together.
When they analyzed the structural scans, the team specifically looked at the thickness of each participant’s cerebral cortex. This allowed them to identify regions whose thickness was linked to episodic memory scores.
“First, single-subject key atrophy maps were constructed by comparing cortical thickness with cognitively normal groups and retaining regions showing significant thickness-memory correlations,” wrote Anxing Huang, Keke Jiang and their colleagues in their paper. “Second, these maps served as seeds for functional connectivity analysis in a large normative connectome, generating atrophy networks weighted by atrophy extent. Third, group-level comparisons identified impaired networks in MCI and SCD, and methodological reliability was further validated against a memory network derived from patients with focal brain lesions.”
The team found that areas of cortical thinning varied from person to person. In most participants with MCI, however, these areas mapped to a common network associated with episodic memory.
The team did not find statistically significant evidence of the same shared network pattern in participants with SCD. Yet this does not necessarily mean that those participants had no cortical thinning or other brain changes.
Huang, Jiang and their colleagues also carried out another experiment involving 25 participants with MCI and 13 with SCD. The experiment used a four-week course of repetitive transcranial magnetic stimulation (rTMS). This is a technique that delivers repeated magnetic pulses through a coil placed against the scalp.
The researchers found that the rTMS intervention was linked to changes in the functional connectivity of people with MCI. Specifically, after stimulation, signals from regions within the identified network varied more closely together.
“Despite substantial individual-level heterogeneity, atrophied regions in most MCI patients were functionally connected to a common episodic memory-associated impaired network,” wrote the authors. “This phenomenon was not significant in SCD patients. Both lesion-memory network mapping and cross-dataset validation confirmed consistency across cohorts. Critically, rTMS can modulate the impaired network in MCI patients, primarily reflected by enhanced functional connectivity within this network.”
Guiding future research and therapeutic interventions
The team’s findings suggest that the difficulties in remembering past events experienced by people with MCI could be associated with cortical thinning linked to the same neural network. In addition, the researchers showed that for people with MCI, functional connectivity within this network increased after rTMS.
“This study developed a robust weighted key atrophy network mapping method, localizing common episodic memory-associated impaired networks in MCI/SCD,” wrote the authors. “Modulation of this impaired network may serve as a potential therapeutic strategy to delay MCI progression.”
The researchers did not yet establish whether the changes observed in scans translate into better memory or slower cognitive decline. In the future, their results could inspire more studies examining the neural network they identified and the possible effects of stimulating it on the episodic memory of people with MCI. https://medicalxpress.com/news/2026-11-brain-imaging-uncovers-memory-network.html
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