Startle stimuli reduce the internal model control in discrete movements.

Area of Science:

• Neuroscience
• Motor Control
• Human Movement Science

Background:

• Movement control relies heavily on internal models for predicting and compensating for forces.
• Learned motor skills, like reaching, are executed smoothly via these internal models.
• Startling acoustic stimuli (SAS) can probe the preparatory state of planned movements.

Purpose of the Study:

• To investigate whether SAS influences the magnitude of motor adaptation after-effects.
• To determine if SAS can reveal aspects of learned preparatory control.

Main Methods:

• Participants performed a motor adaptation task involving a robot-applied force field.
• Movements were initiated either by a standard cue or by a SAS presented at varying times before the cue.
• The magnitude of after-effects following force field removal was measured.

Main Results:

• SAS significantly reduced the magnitude of motor after-effects in all subjects.
• The timing of SAS presentation did not further modulate the reduction in after-effects.
• Reduced after-effects suggest partial reliance on learned preparatory control even under startling conditions.

Conclusions:

• Startling acoustic stimuli can reveal the presence of learned preparatory control in motor tasks.
• These findings suggest that the internal model of movement is not fully overridden by a startle response.
• Understanding startle effects on motor control has implications for high-performance activities like piloting and sports.