Cortical responses associated with predictable and unpredictable compensatory balance reactions.

Area of Science:

• Neuroscience
• Human motor control
• Somatosensory processing

Background:

• Maintaining upright stance requires continuous sensory-motor integration.
• Cortical processing of external perturbations is crucial for balance.
• The role of predictability in cortical responses to postural challenges is not fully understood.

Purpose of the Study:

• To investigate how postural set, influenced by predictable versus unpredictable perturbations, affects cortical responses during human upright stance.
• To determine if the cortical response to external perturbations is dependent on stimulus predictability or a general state of balance control.

Main Methods:

• Participants maintained upright stance while subjected to predictable or unpredictable whole-body perturbations.
• Cortical activity was measured using electroencephalography (EEG) to identify evoked potentials.
• Balance reactions were assessed to quantify compensatory responses.

Main Results:

• Unpredictable perturbations elicited a significant large negative cortical potential (e.g., CZ: -19.9+/-5.1 microV at 98.9+/-5.5 ms).
• Predictable perturbations, despite eliciting balance reactions, did not produce this distinct cortical potential.
• The large negative potential occurred even when a surprise perturbation followed predictable ones, indicating dependence on stimulus expectation mismatch.

Conclusions:

• The evoked cortical potential is linked to the detection of unexpected events, rather than a tonic central state related to balance.
• This suggests a neural mechanism for error detection that operates independently of the sensory or motor aspects of balance reactions.
• Cortical processing of postural perturbations is sensitive to the predictive nature of the stimuli.