Functional neuroanatomy of human vocalization: an H215O PET study

Area of Science:

• Neuroscience
• Comparative Psychology
• Speech Science

Background:

• Vocalization in animals is regulated by a visceromotor call system involving the periaqueductal grey (PAG) and paramedian cortical structures.
• Understanding the role of this evolutionarily older system in human phonation is crucial for comprehending speech production mechanisms.

Purpose of the Study:

• To investigate the role of phylogenetically older visceromotor systems in human phonation.
• To contrast brain activity during voiced versus unvoiced speech and analyze functional connectivity.

Main Methods:

• Positron emission tomography (PET) was used to image brain activity during voiced and unvoiced speech production.
• Functional connectivity analysis was performed on regions showing significant differences between conditions.

Main Results:

• Vocalization engaged midline structures, including the PAG and paramedian cortices, with increased and correlated activity.
• Neocortical and subcortical motor regions, such as premotor structures and basal ganglia thalamocortical circuits, showed concurrent activation and connectivity, suggesting voluntary control.
• The temporal lobe and cerebellum were selectively activated during voiced speech and functionally coupled to motor areas, indicating a role in self-monitoring and feedback regulation.

Conclusions:

• The study identifies a conserved visceromotor system in the human brainstem and cortex involved in vocalization.
• Evidence suggests that human voluntary speech control involves the integration of these older systems with neocortical motor pathways.
• Temporal lobe and cerebellar regions play a key role in the self-monitoring and feedback regulation of human phonation.