Summary: An international research team has advanced understanding of the brain’s noradrenaline (NA) system and developed a new method to record rapid chemical signals from the living human brain. Their approach, adapted to standard clinical depth electrodes used in epilepsy monitoring, reveals how NA in the amygdala tracks emotional intensity and attention—findings relevant to conditions such as ADHD, anxiety, and depression.
The study stands out both for its scientific findings and for the technical breakthrough: for the first time, researchers obtained sub-second neurochemical recordings in conscious human patients using electrodes already in clinical use. This method opens a practical and scalable window into human neuromodulator dynamics that were previously accessible only in animal models.
Key Facts:
- After more than a decade of development, the team adapted electrochemical recording techniques (voltammetry) to clinical depth electrodes routinely implanted for epilepsy monitoring.
- Using this approach, they measured noradrenaline dynamics in the human amygdala and found that NA signals correlate with emotional arousal and attentional responses to unexpected stimuli.
- The method does not require specially manufactured electrodes; it can be implemented using depth electrodes already used in clinical practice, enabling broader human studies of neuromodulation.
Source: Virginia Tech
New insights into the noradrenaline system and a clinical-ready method for fast neurochemical recordings
Researchers published their results in Current Biology and showed both proof of concept and novel findings about NA function in humans. The team focused on the amygdala, a central hub for emotional processing that receives strong projections from the locus coeruleus (LC), the brainstem nucleus that generates noradrenaline and helps regulate arousal and attention.
“This study reports the first fast neurochemical recordings by voltammetry from conscious humans,” said Read Montague, co-corresponding and senior author and director of the Center for Human Neuroscience Research at Virginia Tech. Montague emphasized that the fully human implementation followed more than 11 years of development and refinement.
About the method
Voltammetry and related electrochemical techniques have delivered high-resolution measures of neuromodulator dynamics in animals for decades, but translating these methods to humans posed a major obstacle: they require electrodes placed within brain tissue. Rather than inventing a new clinical implant, the team asked a practical question: when do surgeons already place an electrode in the brain that could be used for neurochemical sensing?
By adapting voltammetric recordings to clinical depth electrodes used during epilepsy monitoring, the researchers avoided the need for exclusive carbon-fiber sensors. This adaptation allows electrochemical monitoring to piggyback on existing clinical procedures, enabling safe, direct measurement of sub-second neuromodulator fluctuations in awake patients.
About the noradrenaline system
The NA system originates in the locus coeruleus and projects broadly to cortical and subcortical regions, including the amygdala. It plays a central role in regulating arousal, attention, and the prioritization of salient or emotionally relevant stimuli. Because medications targeting NA are widely used for ADHD, depression, and anxiety, understanding real-time NA dynamics in humans is clinically important.
In the study, three patients performed a visual affective oddball task while electrodes in their amygdala recorded electrochemical estimates of NA. The task mixed neutral checkerboard images with emotionally charged images that varied in valence (positive or negative) and arousal (low or high). Noradrenaline measures rose in proportion to emotional intensity and showed particularly robust responses to unexpected, high-arousal stimuli—linking NA transients to attention and the processing of salient events.
The team also compared NA estimates with pupil dilation, a common behavioral proxy for LC-NA activity. They found that the coupling between pupil size and NA levels depended on cognitive state: pupil and NA signals were positively correlated for oddball stimuli during high-arousal conditions, but not during low-arousal states. This state-dependent coupling highlights the complexity of how neuromodulators influence behavior and physiology.
Experts not involved in the study hailed the work as a major technical and conceptual advance. Measuring neurotransmitter dynamics at sub-second timescales in humans provides a missing piece of the puzzle: electrical recordings reveal neuronal spiking, but electrochemical measures reveal how those neurons communicate through neuromodulators.
About the team
This group has a history of pioneering fast neurochemical recordings in humans. Earlier work demonstrated sub-second variations in brain chemicals in awake subjects and later explored the joint roles of dopamine and serotonin in decision-making and sensory processing using specially designed electrodes during deep brain stimulation procedures. The current study extends that legacy by showing the feasibility of using clinical depth electrodes for neuromodulator monitoring.
About this Neuroscience research news
Author: John Pastor
Source: Virginia Tech
Contact: John Pastor – Virginia Tech
Image: The image is credited to Neuroscience News
Original Research: Open access. “Noradrenaline tracks emotional modulation of attention in human amygdala” by Read Montague et al., Current Biology. DOI: 10.1016/j.cub.2023.09.074
Abstract
Noradrenaline tracks emotional modulation of attention in human amygdala
Highlights
- Sub-second neuromodulator dynamics can be measured using clinical depth electrodes.
- Noradrenaline dynamics in the human amygdala reflect attention and arousal during emotionally salient events.
- Coupling between noradrenaline signals and pupil dilation varies with cognitive and arousal states.
Summary
The noradrenaline (NA) system, centered in the locus coeruleus, is a major neuromodulatory network that shapes attention and arousal across the brain. Direct recordings of NA dynamics in humans have been limited. This study demonstrates that electrochemical estimates of sub-second NA fluctuations are obtainable with clinical depth electrodes implanted for epilepsy monitoring.
Recordings were performed in the amygdala while patients completed a visual affective oddball task designed to induce different cognitive and arousal states. NA estimates tracked emotional modulation of attention, showing stronger responses for high-arousal oddball stimuli. Pupil dilation measurements supported a state-dependent relationship between pupil dynamics and NA, with positive coupling during high arousal but not low arousal. These results provide proof of concept that neuromodulator monitoring in humans is now possible using electrodes already in standard clinical use, creating new opportunities to study brain chemistry in health and disease.