The headshake enhances oculomotor response to galvanic vestibular stimulation in healthy subjects

• Published in: Clinical neurophysiology Vol. 161; pp. 10 - 16
• Main Authors: Striteska, Maja, Kremlacek, Jan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2024
• Subjects: Adult; Electric Stimulation - methods; Electrical Vestibular Stimulation; Electrically Induced Nystagmus; Electrically Induced Oculomotor Response; Eye Movements - physiology; Female; Galvanic Vestibular Stimulation; Head Movements - physiology; Headshaking Induced Nystagmus; Healthy Volunteers; Humans; Male; Middle Aged; Neurology; Nystagmus, Physiologic - physiology; Reflex, Vestibulo-Ocular - physiology; Transcranial Direct Current Stimulation; Velocity Storage; Vestibule, Labyrinth - physiology; Young Adult; Galvanic Vestibular Stimulation; Transcranial Direct Current Stimulation; HSN; Electrical Vestibular Stimulation; GVS; tDCS; Velocity Storage; Electrically Induced Oculomotor Response; SPV; Electrically Induced Nystagmus; Headshaking Induced Nystagmus; VS; slow phase velocity
• ISSN: 1388-2457; 1872-8952; 1872-8952
• DOI: 10.1016/j.clinph.2024.02.018

•Headshake enhances galvanic vestibular stimulation (GVS)-induced nystagmus in healthy participants.•GVS-assisted headshake helps to identify nystagmus response, which can be weak or absent during the head-still position.•The procedure reflects the integrity, conductivity, and excitability of vestibular afferents. To investigate whether a headshake applied during galvanic vestibular stimulation (GVS) can enhance GVS-induced nystagmus in healthy subjects. In nineteen healthy participants, we evaluated an average slow-phase velocity (aSPV) of nystagmus in a head-still and after the headshake conditions, with/out the bitemporal 2 mA GVS. The GVS was applied also with polarity congruent (supporting) or incongruent (suppressing) to any preexisting spontaneous nystagmus. The orientation of GVS-induced nystagmus depended on GVS polarity. In the head-still condition, the GVS-induced nystagmus in 14 subjects (74%) for congruent and in 12 subjects (63%) for incongruent GVS. During headshake, we recorded nystagmus in 16 subjects (84%) for congruent and 15 subjects (79%) for incongruent GVS. The aSPV of congruent GVS-induced nystagmus was higher (p = 0.0003) by 1.33 (SE 0.26) deg/s for headshake compared to head-still condition. The aSPV of incongruent GVS also induced higher nystagmus (p = 0.0014) by 1.24 (SE 0.28) deg/s for the headshake condition. Our study adds a new principle to the knowledge of the central processing of a GVS response in healthy subjects. The GVS-safety profile of current up to 2 mA was sufficient to elicit a significant GVS nystagmus response in a head-still position in 63% and after a headshake in 79%. Compared to the GVS head-still condition, a headshake enhanced the GVS-induced nystagmus more than twice. The headshake helps to identify GVS-induced nystagmus, which can be weak or absent during the head-still condition.