Excitability changes at brainstem and cortical levels in blind subjects

Area of Science:

• Neuroscience
• Electrophysiology
• Sensory Processing

Background:

• The trigemino-facial system plays a crucial role in facial sensation and motor control.
• Blindness can potentially lead to neuroplastic changes in sensory and motor pathways.
• Electrophysiological methods offer insights into neural pathway function and excitability.

Purpose of the Study:

• To investigate potential alterations in the trigemino-facial system of blind individuals.
• To examine motor cortex excitability using transcranial magnetic stimulation (TMS) in blind subjects.
• To explore abnormal interactions between the cortex and brainstem in the context of blindness.

Main Methods:

• Blink reflex recovery and facial F waves were assessed in 20 blind subjects (BS) and 13 controls (CoS).
• Paired electrical stimulation was used to study blink reflex recovery at various interstimulus intervals (ISIs).
• Transcranial magnetic stimulation (TMS) evaluated motor cortex excitability, including silent periods and paired magnetic stimuli.

Main Results:

• Blind subjects showed significantly reduced blink reflex recovery at longer ISIs (400 and 500 ms) compared to controls.
• Facial F wave amplitudes and F/M ratios were elevated in the blind group.
• Reduced early intracortical inhibition was observed in the motor cortex of blind subjects during TMS studies.

Conclusions:

• Reduced blink reflex recovery in blind individuals may involve cerebellar-brainstem pathway alterations.
• Diminished intracortical inhibition in motor cortices suggests altered cortical excitability.
• Facial F wave findings indicate that altered excitability impacts facial motor neurons in blind individuals.