Anodal block permits directional vagus nerve stimulation

Area of Science:

• Neuroscience
• Bioelectronic Medicine
• Autonomic Physiology

Background:

• Vagus nerve stimulation (VNS) is a therapeutic modality for brain and peripheral organ disorders.
• Selective activation of vagal fibers is crucial for maximizing VNS efficacy and minimizing side effects.
• Anodal block (ABL) is a technique for achieving directional nerve activation, but its application in VNS is not well-established.

Purpose of the Study:

• To investigate the efficacy of anodal block (ABL) in achieving directional vagus nerve stimulation (VNS).
• To determine if ABL can enable selective activation of afferent or efferent vagal fibers for functional effects.
• To establish physiological markers for distinguishing afferent and efferent VNS responses.

Main Methods:

• Vagus nerve stimulation (VNS) with bipolar electrodes of varying polarities and locations (left/right).
• Physiological measurements including stimulus-elicited changes in breathing rate (ΔBR) for afferent and heart rate (ΔHR) for efferent activity.
• Analysis of stimulus-evoked compound nerve potentials to confirm fiber activation patterns.

Main Results:

• VNS polarity influenced functional responses: cathode cephalad polarity favored afferent (ΔBR) responses, while cathode caudad favored efferent (ΔHR) responses.
• VNS laterality also affected responses: left VNS showed a greater afferent pattern, and right VNS showed a greater efferent pattern.
• Compound nerve potential analysis supported that these functional differences are attributable to anodal block (ABL) of specific fiber types.

Conclusions:

• Anodal block (ABL) is a viable mechanism for achieving directional vagus nerve stimulation (VNS).
• Polarity and laterality of VNS can be manipulated to preferentially activate afferent or efferent vagal fibers.
• This directional control holds potential for optimizing VNS therapies and understanding autonomic circuit function.