Diminished preparatory physiological responses in frontotemporal lobar degeneration syndromes

Area of Science:

• Neuroscience
• Physiology
• Psychology

Background:

• Physiological responses are typically studied post-stimulus or upon valence revelation.
• Anticipatory responses, or 'preparation for action,' occur even without knowing stimulus valence.
• Frontotemporal lobar degeneration (FTLD) affects brain regions crucial for these preparatory responses.

Purpose of the Study:

• To investigate preparatory physiological responses in FTLD clinical subtypes.
• To identify the structural and functional neural correlates of these responses.
• To examine the relationship between preparatory responses and behavioral symptoms in FTLD.

Main Methods:

• Assessed cardiac interbeat interval decreases (heart rate increases) during an 'instruction period' in FTLD subtypes, Alzheimer's disease patients, and healthy controls.
• Evaluated behavioral symptoms (apathy, disinhibition) using caregiver reports.
• Utilized voxel-based morphometry and resting-state functional MRI to analyze brain structure and function.

Main Results:

• FTLD patients showed significantly smaller preparatory responses compared to controls and Alzheimer's disease patients.
• Behavioral variant FTD and progressive supranuclear palsy subtypes exhibited significant differences in preparatory responses.
• Smaller preparatory responses correlated with reduced volume and functional connectivity in the ventromedial prefrontal cortex and salience network.

Conclusions:

• Diminished preparatory physiological responding in FTLD may indicate impaired preparation for action.
• The ventromedial prefrontal cortex and salience network are critical for these preparatory responses.
• Damage to these circuits in FTLD may underlie clinical symptoms like disinhibition.