Subcortical loops through the basal ganglia

Area of Science:

• Neuroscience
• Evolutionary Biology
• Comparative Anatomy

Background:

• Cortical-basal ganglia-cortical loops are key to brain function.
• Existing models focus on neocortical involvement in these loops.
• The evolutionary origins and diversity of basal ganglia circuitry are not fully understood.

Purpose of the Study:

• To hypothesize the existence of evolutionarily older, subcortical closed-loop circuits involving the basal ganglia.
• To propose the midbrain superior colliculus as a key component of these ancient circuits.
• To explore how distinct inputs (cortical vs. subcortical) may influence basal ganglia function.

Main Methods:

• Hypothetical framework based on comparative neuroanatomy.
• Analysis of basal ganglia-brainstem sensorimotor connections.
• Theoretical modeling of input interactions (independent, cooperative, competitive).

Main Results:

• Evidence suggests a phylogenetically older closed-loop system connecting the basal ganglia with brainstem structures like the superior colliculus.
• This subcortical circuitry predates or parallels neocortical loops.
• Both cortical and subcortical inputs likely play roles in basal ganglia-mediated action selection.

Conclusions:

• The basal ganglia's role in action selection is supported by ancient subcortical circuits, not solely by neocortical pathways.
• Understanding these parallel processing streams offers insight into brain evolution and function.
• Independent and interactive processing of cortical and subcortical information is crucial for motor control.