Task-dependent Activity and Connectivity Predict Episodic Memory Network-based Responses to Brain Stimulation in Healthy Aging

• Main Authors: Dídac Vidal-Piñeiro, Pablo Martin-Trias, Eider M. Arenaza-Urquijo, Roser Sala-Llonch, Imma C. Clemente, Isaias Mena-Sánchez, Núria Bargalló, Carles Falcón, Álvaro Pascual-Leone, David Bartrés-Faz
• Format: Article
• Language: English
• Published: Elsevier 2014-03-01
• Series: Brain Stimulation
• Subjects: Transcranial magnetic stimulation; Functional magnetic resonance imaging; Level of processing; Episodic memory; Aging
• Online Access: http://www.sciencedirect.com/science/article/pii/S1935861X14000035

Background: Transcranial magnetic stimulation (TMS) can affect episodic memory, one of the main cognitive hallmarks of aging, but the mechanisms of action remain unclear. Objectives: To evaluate the behavioral and functional impact of excitatory TMS in a group of healthy elders. Methods: We applied a paradigm of repetitive TMS – intermittent theta-burst stimulation – over left inferior frontal gyrus in healthy elders (n = 24) and evaluated its impact on the performance of an episodic memory task with two levels of processing and the associated brain activity as captured by a pre and post fMRI scans. Results: In the post-TMS fMRI we found TMS-related activity increases in left prefrontal and cerebellum-occipital areas specifically during deep encoding but not during shallow encoding or at rest. Furthermore, we found a task-dependent change in connectivity during the encoding task between cerebellum-occipital areas and the TMS-targeted left inferior frontal region. This connectivity change correlated with the TMS effects over brain networks. Conclusions: The results suggest that the aged brain responds to brain stimulation in a state-dependent manner as engaged by different tasks components and that TMS effect is related to inter-individual connectivity changes measures. These findings reveal fundamental insights into brain network dynamics in aging and the capacity to probe them with combined behavioral and stimulation approaches.