Distinct neural patterns for various information in working memory: A brain connectivity study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Computational Neuroscience

Background:

• Working memory (WM) relies on complex brain networks, with the prefrontal cortex (PFC) and medial temporal lobe (MTL) as crucial nodes.
• Graph theory analysis offers a powerful framework for characterizing brain connectivity architectures.
• Understanding the distinct effective connectivity patterns between PFC and MTL during WM information processing remains an open question.

Purpose of the Study:

• To investigate frequency-specific and regionally organized brain network mechanisms underlying the processing of identity, spatial, and temporal information in WM.
• To analyze effective connectivity patterns between PFC and MTL using graph theoretical analysis.
• To predict behavioral reaction times (RT) based on identified connectivity metrics.

Main Methods:

• Analysis of intracranial EEG data from eight epilepsy patients performing a WM task involving 'what', 'where', and 'when' information.
• Application of the directed transfer function to measure effective connectivity between PFC and MTL.
• Assessment of graph theoretical metrics including degree, strength, clustering coefficient, eigenvector centrality, and betweenness centrality.

Main Results:

• Theta-band oscillations are predominantly involved in spatial and temporal WM processing, with PFC and orbitofrontal cortex (OFC) critical for spatial and temporal sequencing, respectively.
• The MTL plays a central role in spatial and spatio-temporal integration.
• Alpha band connectivity is vital for spatio-temporal decoding, while beta and high-gamma bands significantly differentiate reaction times, especially for identity and spatial information.
• The PFC exhibits extensive involvement across various graph metrics, highlighting its role in coordinating WM tasks.

Conclusions:

• WM processing of different information types involves distinct, frequency-specific network mechanisms orchestrated by the PFC and MTL.
• Graph theory analysis effectively reveals the complex interplay between brain regions and frequency bands in supporting cognitive functions.
• These findings advance the understanding of WM's neural underpinnings and the dynamic coordination of brain networks in cognitive tasks.