Mapping movement, mood, motivation and mentation in the subthalamic nucleus

Area of Science:

• Neuroscience
• Neurology
• Neurosurgery

Background:

• The subthalamic nucleus (STN) plays a crucial role in motor control.
• Variability in motor and non-motor responses to STN deep brain stimulation (DBS) in Parkinson's disease (PD) may be linked to the precise anatomical location of stimulation.
• Previous studies used 3D statistical methods to analyze DBS effects, but parameters were patient-specific.

Purpose of the Study:

• To investigate the relationship between the anatomical location of STN DBS contacts and acute motor and non-motor effects in PD patients.
• To determine if standardized DBS parameters and blind contact selection influence the observed functional outcomes.
• To provide functional evidence for anatomically derived models of STN function.

Main Methods:

• A study involving 74 individuals with PD undergoing STN DBS.
• Standardized voltage, frequency, and pulse width were used for unilateral DBS.
• Contacts were selected near dorsal and ventral STN borders, with participants tested off medication in ventral STN DBS, dorsal STN DBS, and DBS-off conditions.

Main Results:

• Both dorsal and ventral STN DBS improved motor function, with no significant effect on cognitive measures.
• Ventral STN DBS showed greater improvement in rigidity and anxiety compared to dorsal STN DBS.
• Three-dimensional analysis revealed that contact location significantly impacted hypokinesia, rigidity, and tremor, with maximal improvement from dorsal STN and zona incerta stimulation.

Conclusions:

• The precise anatomical location of STN DBS is critical for motor improvements in PD, supporting models where dorsal STN is key for motor function.
• Functional segregation within the STN is limited, as stimulation sites yielding motor improvements also showed overlap with mood improvements.
• These findings offer direct functional evidence for the anatomical organization of the STN and its role in PD.