Oscillations and plastic changes in connectivity due to brain stimulation
Abstract
Brain stimulation has the potential to enhance human performance. To fully realize this potential, it is vital to develop a deeper understanding of its effects upon brain function. Converging evidence from human and animal studies suggests that stimulation - specifically Transcranial Magnetic Stimulation (TMS) - affects synaptic plasticity. We propose to determine how the plastic changes induced by TMS in large-scale networks are affected by brain oscillations, and in turn affect the oscillations that functionally connect brain areas. The rules governing synaptic change are very dependent upon timing. TMS pulses delivered to a pair of connected brain areas are envisaged to change the strength of the connection between those areas. However, they only do so when the pulses from the two distant areas are timed to converge at, or around the same time, on a common synaptic connection. Within large-scale networks, the timing of communication across networks is determined by oscillations. Hence, the delay for an event at one brain area, such as a TMS pulse, to propagate to a distant brain area - at or around the time when another pulse delivered to the distant area - is likely affected by oscillations. We hypothesize that only a short time delay may be necessary between pulses for their effects to approximately coincide and consequently alter connectivity by inducing plastic change when inter-area communication operates at a high frequency (i.e., a short time-lag between phases of high excitability). By contrast, a longer time and delay may be necessary for the TMS pulse to arrive and induce plasticity when the inter-area communication operates at a low frequency. We will test our hypothesis by determining the relationship between the delay needed to drive plastic change to alter functional connectivity between the pair of brain areas, and the underlying oscillations. We will also determine the directional specificity of the connectivity changes (i.e., unidirectional or bidirectional) to provide insight into the locus of the plasticity supporting the connectivity changes. Finally, we will test whether connectivity changes can causatively drive a change in human performance. Establishing that connectivity modifies performance is critical for any future use of stimulation to modify behaviour. Overall our project provides fundamental insight into how stimulation affects brain function. We will determine how plasticity is affected by oscillations across large scale networks, provide the insight required to tailor time-delays to target specific connections and frequencies, and will test the critical importance of connectivity change for human performance. Together these fresh insights will strengthen the use of TMS as a neuroscientific tool for fundamental discovery, and provide novel strategies for modifying human performance.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 07, 2024
- Source ID
- FA95502310608
Entities
People
- Edwin M Robertson
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Glasgow