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The neurovascular impulse response function differentially reflects intrinsic neuromodulation across cortical regions
Bradley C Rauscher1, Natalie Fomin-Thunemann2, Sreekanth Kura2
1Graduate program in Biomedical Engineering, Boston University, Boston, MA, USA.
Nature Neuroscience
|March 27, 2026
Summary
Neuromodulation impacts brain blood flow signals. Norepinephrine (NE) significantly improves models of hemodynamic responses, unlike acetylcholine (ACh), revealing potential misinterpretations in neuroimaging.
Area of Science:
- Neuroscience
- Neuroimaging
- Systems Neuroscience
Background:
- Neuromodulatory transmitters like norepinephrine (NE) and acetylcholine (ACh) possess vasoactive properties.
- The relationship between neuronal activity and hemodynamic responses (impulse response function, IRF) may be influenced by neuromodulation.
Purpose of the Study:
- To investigate the impact of neuromodulation on the impulse response function (IRF) linking neuronal activity and hemodynamics.
- To determine whether NE and ACh modulate the hemodynamic response and improve hemodynamic modeling.
Main Methods:
- Utilized optical imaging in awake mice to simultaneously measure cortical neuronal calcium (Ca2+) activity, norepinephrine (NE) and acetylcholine (ACh) levels, and cerebral hemodynamics.
- Developed and compared models of hemodynamics using Ca2+-specific IRFs (IRFCa2+) versus models incorporating both Ca2+-specific and NE-specific IRFs (IRFCa2+ and IRFNE).
Main Results:
- Modeling hemodynamics with both IRFCa2+ and IRFNE significantly improved performance compared to using IRFCa2+ alone.
- Acetylcholine (ACh) showed redundancy with Ca2+ activity and did not enhance hemodynamic estimation.
- Norepinephrine (NE) levels correlated with arousal, leading to instances of diminished hemodynamic coherence between cortical regions during high arousal, despite coherent neuronal Ca2+ activity.
Conclusions:
- Noradrenergic neuromodulation plays a crucial role in shaping the hemodynamic response to neuronal activity.
- Failure to account for NE's influence can lead to misinterpretation of hemodynamic coherence as neuronal desynchronization in neuroimaging studies.
- ACh does not appear to significantly contribute to hemodynamic estimation beyond neuronal activity itself.
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