Structural and Functional Connectivity Predict the Effects of Direct Brain Stimulation on Memory.

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Intracranial stimulation shows potential for memory enhancement, but outcomes are inconsistent across individuals and sites.
• Variability in response may stem from differences in stimulation target network embedding.

Purpose of the Study:

• To investigate if the structural and functional network embedding of intracranial stimulation targets predicts memory enhancement variability.
• To determine the role of network connectivity in optimizing closed-loop stimulation for memory improvement.

Main Methods:

• Analyzed intracranial EEG data from 50 epilepsy patients undergoing verbal memory tasks during left temporal cortex stimulation.
• Used diffusion tractography and functional connectivity to assess network embedding of stimulation sites.
• Employed closed-loop and random stimulation paradigms, correlating memory enhancement with network properties.

Main Results:

• Closed-loop stimulation during detected low-encoding states improved recall; random stimulation did not.
• Greater memory enhancement correlated with stronger structural coupling to fronto-temporo-parietal networks.
• Structure-function congruence predicted closed-loop memory benefit (Spearman ρ = 0.58, P < 0.0001).

Conclusions:

• Reliable, stimulation-driven memory enhancement depends on the structural network embedding of the stimulation target.
• Optimizing stimulation target's structural integration and timing is crucial for individualized memory improvement.
• Findings support a network-based rationale for precision-guided neuromodulation.