The initial decrease in 7T-BOLD signals detected by hyperalignment contains information to decode facial expressions.

Area of Science:

• Neuroimaging
• Cognitive Neuroscience
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• The blood oxygenation level-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI) traditionally relies on positive hemodynamic responses.
• The initial dip in the BOLD signal, reflecting primary neuronal activity, is increasingly recognized for its potential but remains less understood.
• Ultra-high field (7T) fMRI offers enhanced sensitivity to detect subtle BOLD signal changes, including the initial dip.

Purpose of the Study:

• To investigate the information content of the initial BOLD signal decrease regarding task events and cognitive processes.
• To assess the utility of multivoxel pattern analysis (MVPA) on early BOLD signals, beyond traditional peak responses.
• To explore the application of inter-individual functional alignment (hyper-alignment) for analyzing early BOLD signal patterns.

Main Methods:

• Applied a signal-based functional inter-individual alignment algorithm (hyper-alignment) to 7T-BOLD fMRI data.
• Utilized multivoxel pattern analysis (MVPA) to decode information from BOLD signal patterns during a facial expression discrimination task.
• Focused analysis on the early phase of the BOLD response, approximately 2 seconds post-stimulus onset.

Main Results:

• Achieved significant beyond-chance MVPA decoding accuracy in the bilateral amygdala at 2 seconds after face onset.
• Confirmed that the voxels contributing to this early decoding accuracy exhibited a decreasing hemodynamic response (initial dip).
• Demonstrated that the initial decrease in 7T-BOLD signals carries substantial information about task events.

Conclusions:

• The initial decrease in 7T-BOLD signals contains richer information about task events and cognitive processes than previously assumed.
• MVPA applied to early BOLD signal dips, facilitated by hyper-alignment, can effectively decode cognitive information.
• This study highlights the importance of analyzing the early phase of the BOLD response for a more comprehensive understanding of neural activity.