EPISODIC MEMORY IN MILD COGNITIVE IMPAIRMENT INVERSELY CORRELATES WITH THE PATIENT CONTRIBUTION TO CEREBRAL BLOOD FLOW NETWORK MODULARITY

Abstract

Listen

Translate article

Cerebral blood flow (CBF) SPECT is an interesting methodology to study connectivity in mild cognitive impairment (MCI) as it is a neuroimaging biomarker of neuronal injury of MCI due to Alzheimer disease (AD) and accessible worldwide. In this context, connectivity is a concept grounded on a group-based correlation network whose topology is analyzed using graph theory [Melie-García et al., 2103]. However, topological metrics derived from the CBF correlation (CBFcorr) network cannot be used to support diagnosis and prognosis individually. Recently, methods to extract the individual patient contribution to the metrics of a group-based correlation network were published [Saggar et al., 2015] but not yet applied to MCI . To clarify whether this approach could be useful for MCI, we investigated whether the episodic memory of amnestic MCI patients correlates with individual patient contributions to topological metrics of the group-based CBFcorrnetwork. We first investigated topological metrics of the CBFcorrnetwork constructed using 24 amnestic MCI patients, by comparing with one corresponding to 26 controls. We focused on the global network modularity which seems to be more sensitive to the AD process compared with more used metrics [Pereira et al., 2016]. We also analyzed the global and mean local efficiencies that are typically used as metrics of network integration and segregation, respectively. Metrics that showed significant differences were then used for the individual patient contribution analysis. This latter analysis was performed by extracting the patient contribution to a metric for the network constructed using healthy controls plus the patient. The Rey Complex Figure test was used for episodic memory assessment. The global network modularity was increased while global efficiency decreased in the MCI network compared with the control network. Most important, only the individual patient contribution to the global network modularity showed a significant negative correlation with episodic memory as shown in the figure.