An investigation of changes in motor and memory networks in patients with transient ischemic attack

1510 

Abstract Submission 

Truc Chu^1,2, Seonjin Lee^1,2, Il-Young Jung³, Youngkyu Song⁴, Hyun Ah Kim⁵, Anh Nguyen^1,2, Jong Wook Shin⁶, Sungho Tak^1,2

¹Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, Chungcheongbuk, Korea, Republic of, ²Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, Chungcheongnam, Korea, Republic of, ³Department of Rehabilitation Medicine, Chungnam National University Sejong Hospital, Sejong, Chungcheongnam, Korea, Republic of, ⁴Bio-Chemical Analysis Team, Korea Basic Science Institute, Cheongju, Chungcheongbuk, Korea, Republic of, ⁵Department of Rehabilitation Medicine, Chungnam National University Hospital, Daejeon, Chungcheongnam, Korea, Republic of, ⁶Department of Neurology, Chungnam National University Sejong Hospital, Sejong, Chungcheongnam, Korea, Republic of

Truc Chu  
Research Center for Bioconvergence Analysis, Korea Basic Science Institute|Graduate School of Analytical Science and Technology, Chungnam National University
Cheongju, Chungcheongbuk, Korea, Republic of|Daejeon, Chungcheongnam, Korea, Republic of

Seonjin Lee  
Research Center for Bioconvergence Analysis, Korea Basic Science Institute|Graduate School of Analytical Science and Technology, Chungnam National University
Cheongju, Chungcheongbuk, Korea, Republic of|Daejeon, Chungcheongnam, Korea, Republic of

Il-Young Jung  
Department of Rehabilitation Medicine, Chungnam National University Sejong Hospital
Sejong, Chungcheongnam, Korea, Republic of

Youngkyu Song, Dr.  
Bio-Chemical Analysis Team, Korea Basic Science Institute
Cheongju, Chungcheongbuk, Korea, Republic of

Hyun Ah Kim  
Department of Rehabilitation Medicine, Chungnam National University Hospital
Daejeon, Chungcheongnam, Korea, Republic of

Anh Nguyen  
Research Center for Bioconvergence Analysis, Korea Basic Science Institute|Graduate School of Analytical Science and Technology, Chungnam National University
Cheongju, Chungcheongbuk, Korea, Republic of|Daejeon, Chungcheongnam, Korea, Republic of

Jong Wook Shin, Dr.  
Department of Neurology, Chungnam National University Sejong Hospital
Sejong, Chungcheongnam, Korea, Republic of

Sungho Tak, Dr.  
Research Center for Bioconvergence Analysis, Korea Basic Science Institute|Graduate School of Analytical Science and Technology, Chungnam National University
Cheongju, Chungcheongbuk, Korea, Republic of|Daejeon, Chungcheongnam, Korea, Republic of

Transient ischemic attack (TIA) is a temporary episode of neurological dysfunction resulting from focal brain ischemia. Although TIA symptoms are transient, patients with TIA have a high risk of stroke and persistent impairments in various motor and cognitive functions (Coull et al., 2004). This study aims to explore the changes in task-residual effective connectivity of TIA during motor and working memory tasks. Additionally, this study seeks to associate these altered connectivity of patients with TIA with the risk of stroke.

This study involved 15 patients with TIA and 28 age-matched healthy subjects (HC). The subjects underwent scanning using a 7T MRI system while performing motor and working memory experiments. During the motor task, the subjects performed right or left fist-closing movements synchronized with a 1Hz visual cue. In the working memory assessment, subjects performed the n-back task, involving 0-, 1-, and 2-back conditions. We applied spectral dynamic causal modeling (DCM) (Razi et al., 2015) to task-residual BOLD time series, to estimate effective connectivity among regions of interest (ROI). Specifically, based on the general linear model (GLM) results across all participants, ROIs for motor task included the primary motor cortex (M1), premotor cortex (PMC), supplementary motor area (SMA), and inferior parietal lobule (IPL). The ROIs for the n-back task comprised various regions such as the prefrontal cortex (PFC), parietal cortex (PAR), and cingulate cortex (CC). The task-residual time series within the ROIs were obtained by regressing out the task-related signal and systemic confounds from the fMRI signal. The parameters of effective connectivity were then estimated from the task-residual time series using spectral DCM.

Compared to HC, stronger excitatory connections from the left PMC to the ipsilateral M1 were observed in patients with TIA, during both right- and left-hand movement. Moreover, during right-hand movement, patients with TIA exhibited a stronger excitatory influence from the contralateral M1 to the ipsilateral M1. Regarding the SMA region, the effective connectivity to the SMA was decreased in patients with TIA, compared with HC during both right- and left-hand movement. Regarding the PMC regions, patients with TIA had higher suppressive influence to the PMC during right hand movement than HC. These results were shown in Figure 1. During the n-back task, patients with TIA exhibited higher connectivity strength compared to the HC group, as shown in Figure 2. Specifically, patients with TIA consistently showed increased effective connectivity among the ROIs of the PAR and CC in both hemispheres, in contrast to the HC group. Moreover, there was a reduction in connectivity to the right PFC in patients with TIA.

This study showed that while performing fist-closing movements according to the visual stimuli of flickering circles, patients with TIA had greater connections to the ipsilateral M1 and lower connections to the SMA and PMC than the HC (Chu et al., 2023). These results may reflect the disruptions in the information processing (visual cue to action) and controls of voluntary movement, and decreased efficiency of primary motor function M1 in patients with TIA. We also found that patients with TIA had higher excitatory connections between the PAR and CC, and lower connections toward the right PFC during working memory task, compared with HC. It has been shown that the PAR is involved in the storing and retrieving information, and the CC plays a role in performance adjustment during working memory task (Owen et al., 2005). Therefore, although further investigation may be required, these results suggest that patients with TIA would have an increased recruitment of interaction between the storing-retrieving information and its adjustment for supporting the short-term memory function, and the reduced neural capacity of information controls.

Neurodegenerative/ Late Life (eg. Parkinson’s, Alzheimer’s) ²

Working Memory

Connectivity (eg. functional, effective, structural) ¹

fMRI Connectivity and Network Modeling

Visuo-Motor Functions

Computational Neuroscience

FUNCTIONAL MRI

HIGH FIELD MR

Other - effective connectivity; transient ischemic attack; motor processing; working memory; task-residual fMRI response; spectral dynamic causal modelling