Sensorimotor processing for balance in spinocerebellar ataxia type 6.

Area of Science:

• Neuroscience
• Human Physiology
• Motor Control

Background:

• Cerebellar degeneration can cause balance impairments.
• Investigated if these deficits stem from specific sensorimotor processing issues.
• Focused on cerebellar roles in scaling and coordinate transformation of balance responses.

Purpose of the Study:

• To determine if balance impairments in cerebellar disease (SCA6) are linked to specific sensorimotor processing deficits.
• To examine cerebellar functions in scaling and coordinate transformation of balance responses across sensory modalities.

Main Methods:

• Stimulated vestibular, visual, and proprioceptive channels independently in 16 SCA6 patients and 16 controls.
• Used galvanic vestibular stimulation, moving visual scenery, and muscle vibration.
• Assessed disease severity using the Scale for Assessment and Rating of Ataxia.

Main Results:

• SCA6 subjects exhibited faster body sway during unperturbed stance, correlating with disease severity.
• A specific sensorimotor abnormality was found in visual response scaling.
• Visually evoked postural responses were significantly larger (approx. 3x) in SCA6 patients, correlating with disease severity.

Conclusions:

• Cerebellar degeneration disrupts the scaling of postural responses to visual motion.
• This may involve disinhibition of extracerebellar visuomotor centers.
• An overactive visual channel without compensatory changes in other sensory channels likely causes balance instability in cerebellar disease.