Quantitative relations between BOLD responses, cortical energetics and impulse firing across cortical depth

Area of Science:

• Neuroimaging
• Biophysics
• Computational Neuroscience

Background:

• The blood oxygen level-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI) reflects neural activity through changes in cerebral blood flow (CBF) and oxygen metabolism.
• Advances in high-resolution fMRI enable studying the BOLD response across cortical depths, necessitating refined theoretical models.

Purpose of the Study:

• To develop a quantitative model of the BOLD signal that incorporates venous blood drainage between cortical layers.
• To adapt existing theories relating BOLD signal to neural activity to account for laminar BOLD responses.

Main Methods:

• Adaptation of a previous theoretical framework for BOLD signal modeling.
• Inclusion of a parameter for venous blood draining between cortical layers.
• Development of three-layer and multi-layer model versions for transient and sustained neural inputs, respectively.

Main Results:

• The quantitative model successfully integrates neural activity with laminar blood flow dynamics.
• Both transient and sustained neural input models accurately predict a range of experimental BOLD signal observations.
• The model accounts for complex phenomena such as negative BOLD signals.

Conclusions:

• The developed model provides a more comprehensive understanding of the BOLD signal's dependence on neural activity and microvascular physiology.
• Incorporating laminar venous drainage is crucial for accurately modeling depth-dependent BOLD responses in fMRI.
• This refined modeling approach has implications for interpreting high-resolution fMRI data and understanding brain function.