Brain-behavior relationships in aphasia studied by positron emission tomography

Area of Science:

• Neuroscience
• Medical Imaging
• Neurology

Background:

• Positron emission tomography (PET) is a powerful tool for investigating human brain physiology and chemistry.
• PET enables the study of cerebral blood flow, oxygen, and glucose metabolism.
• Aphasia, a neurobehavioral disorder, serves as a model for understanding brain function and dysfunction.

Purpose of the Study:

• To investigate glucose metabolism in aphasic patients using PET.
• To explore the relationship between structural brain damage and remote metabolic changes.
• To determine if metabolic alterations in undamaged brain regions correlate with aphasia severity and presentation.

Main Methods:

• Application of Positron Emission Tomography (PET) to assess cerebral glucose metabolism.
• Utilizing aphasia as a model to study neurobehavioral changes.
• Correlation of metabolic data with structural lesion location and extent.

Main Results:

• Cerebral glucose metabolic changes in aphasic patients frequently involve brain regions not structurally damaged.
• Remote metabolic effects are predictable based on the location and extent of structural lesions.
• All right-handed aphasic patients with left hemisphere lesions showed temporoparietal metabolic abnormalities.
• Metabolic abnormalities in undamaged left prefrontal lobe, basal ganglia, and thalamus were variable.
• Frontal metabolic changes correlated with variations in clinical aphasic syndromes.

Conclusions:

• Structural brain lesions in aphasia induce remote metabolic changes in functionally connected, yet undamaged, brain regions.
• The extent and location of these remote metabolic alterations are predictable.
• Clinical variations in aphasia syndromes may stem from functional differences in the prefrontal cortex, rather than solely from direct structural damage.