Physical methods for interacting with neural circuits
Neural interfaces bring physical stimulation, biological measurement and device engineering together. Our research investigates how electrical, magnetic and acoustic approaches can influence neural activity, and how recording methods can characterise the resulting response. The emphasis is on the relationship between the applied physical stimulus, the tissue through which it acts and the neural signals that can be measured. Modelling and experiments address different parts of this relationship, from fields and material properties to network activity and physiological responses.
Work on magnetic stimulation includes modelling electrical conduction in anisotropic brain tissue using information from diffusion imaging. Studies of vagus nerve stimulation examine links between peripheral receptors, brainstem pathways and autonomic regulation. These lines of research show why the location, timing and physical mechanism of stimulation matter: the same broad intervention category can engage different structures and processes depending on how it is implemented.
Wireless interfaces and adaptive stimulation
Device-oriented projects investigate miniaturised interfaces that combine neural recording with stimulation. Wireless microdevices, engineered nanomaterials and nanoelectronics provide complementary routes for coupling to neural tissue. Research examines the physical mechanisms by which these systems sense or actuate, together with the experimental methods needed to assess their operation in biological settings. Integrated approaches also combine electrophysiological recording with functional ultrasound imaging and focused ultrasound stimulation.
Adaptive control connects recorded activity to the choice of subsequent stimulation. Neuromorphic learning and computational models are investigated as components of this feedback process, with attention to the information available from the recording system and the constraints imposed by the interface. Experimental testing, imaging and physiological analysis support the interpretation of device behaviour and tissue response. This theme therefore links the physics of stimulation with neural measurement and control, while keeping the contribution of each technology explicit.
Research resources
Profiles by research interest
Publications
2023
Brain stimulation
BACKGROUND: The autonomic response to transcutaneous auricular vagus nerve stimulation (taVNS) has been linked to the engagement of brainstem circuitry modulating autonomic outflow. However, the physiological mechanisms supporting such efferent vagal responses are not well understood, particularly in humans. HYPOTHESIS: We present a paradigm for estimating d…Read the full abstractCollapse abstract
BACKGROUND: The autonomic response to transcutaneous auricular vagus nerve stimulation (taVNS) has been linked to the engagement of brainstem circuitry modulating autonomic outflow. However, the physiological mechanisms supporting such efferent vagal responses are not well understood, particularly in humans. HYPOTHESIS: We present a paradigm for estimating directional brain-heart interactions in response to taVNS. We propose that our approach is able to identify causal links between the activity of brainstem nuclei involved in autonomic control and cardiovagal outflow. METHODS: We adopt an approach based on a recent reformulation of Granger causality that includes permutation-based, nonparametric statistics. The method is applied to ultrahigh field (7T) functional magnetic resonance imaging (fMRI) data collected on healthy subjects during taVNS. RESULTS: Our framework identified taVNS-evoked functional brainstem responses with superior sensitivity compared to prior conventional approaches, confirming causal links between taVNS stimulation and fMRI response in the nucleus tractus solitarii (NTS). Furthermore, our causal approach elucidated potential mechanisms by which information is relayed between brainstem nuclei and cardiovagal, i.e., high-frequency heart rate variability, in response to taVNS. Our findings revealed that key brainstem nuclei, known from animal models to be involved in cardiovascular control, exert a causal influence on taVNS-induced cardiovagal outflow in humans. CONCLUSION: Our causal approach allowed us to noninvasively evaluate directional interactions between fMRI BOLD signals from brainstem nuclei and cardiovagal outflow.