Abstract
IntroductionThe prefrontal cortex (PFC) plays a crucial role in cognition, particularly in executive functions. Cortical reactivity measured with Transcranial Magnetic Stimulation combined with Electroencephalography (TMS-EEG) is altered in pathological conditions, and it may also be a marker of cognitive status in middle-aged adults. In this study, we investigated the associations between cognitive measures and TMS evoked EEG reactivity and explored whether the effects of this relationship were related to neurofilament light chain levels (NfL), a marker of neuroaxonal damage.MethodsFifty two healthy middle-aged adults (41–65 years) from the Barcelona Brain Health Initiative cohort underwent TMS-EEG, a comprehensive neuropsychological assessment, and a blood test for NfL levels. Global and Local Mean-Field Power (GMFP/LMFP), two measures of cortical reactivity, were quantified after left prefrontal cortex (L-PFC) stimulation, and cognition was set as the outcome of the regression analysis. The left inferior parietal lobe (L-IPL) was used as a control stimulation condition.ResultsLocal reactivity was significantly associated with working memory and reasoning only after L-PFC stimulation. No associations were found between NfL and cognition. These specific associations were independent of the status of neuroaxonal damage indexed by the NfL biomarker and remained after adjusting for age, biological sex, and education.ConclusionOur results demonstrate that TMS evoked EEG reactivity at the L-PFC, but not the L-IPL, is related to the cognitive status of middle-aged individuals and independent of NfL levels, and may become a valuable biomarker of frontal lobe-associated cognitive function.
Highlights
The prefrontal cortex (PFC) plays a crucial role in cognition, in executive functions
As these functions are significantly affected during aging, the role of the PFC has been extensively studied, and it has been shown that greater PFC activity is associated with better cognition (Eyler et al, 2011; Fernandez-Ruiz et al, 2018) and that preservation of PFC activity contributes to the maintenance of cognitive abilities (Morcom and Henson, 2018; Vidal-Piñeiro et al, 2019)
The goal of this study was to explore the relationship between cognition and local and global cortical reactivity after PFC stimulation using Transcranial Magnetic Stimulation combined with Electroencephalography (TMS-EEG) in healthy middleaged adults
Summary
The prefrontal cortex (PFC) plays a crucial role in cognition, in executive functions. The characterization of cognitive performance and cognitive profiles is typically carried out through specific domains referring to different processes and abilities within the global term “cognition” (Harvey, 2019), such as attention, episodic memory, working memory, reasoning, fluid intelligence, language, cognitive flexibility, visuospatial skills, and processing speed These cognitive domains have been related to specific anatomic areas and brain networks (Wu et al, 2020), and amongst them, the prefrontal cortex (PFC) plays a central role. In a hierarchical model of the neurophysiology of the cortex, the PFC constitutes the highest area of cortical representations (as opposed to lower cortical structures such as sensory and motor areas) dedicated to the integration and execution of higher-order executive functions (Fuster, 2001; Breukelaar et al, 2018) As these functions are significantly affected during aging, the role of the PFC has been extensively studied, and it has been shown that greater PFC activity is associated with better cognition (Eyler et al, 2011; Fernandez-Ruiz et al, 2018) and that preservation of PFC activity contributes to the maintenance of cognitive abilities (Morcom and Henson, 2018; Vidal-Piñeiro et al, 2019)
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