Vestibular system detects tilt, rotation, and head position

When your head stops turning, the fluid bends the sensory hair cells in the other direction. That allows us to notice changes in the speed of the turning movement (accelerating or stopping). Each of the three semicircular canals detects one of three directions of head movement:

Activation of the superior and medial vestibular nuclei during head rotation generates impulses that cross to the contralateral abducens nucleus, stimulating the lateral rectus muscle, while interneuronal projections via the MLF activate the ipsilateral oculomotor nucleus to contract the medial rectus. This bilateral coordination produces conjugate eye movements opposite to head motion, preserving visual stability through the vestibulo-ocular reflex (VOR).[8]

Locked in the bony structure of ... two otolith · organs sense linear acceleration and its gravitational equivalent, and the three semicir- cular canals sense rotational movement in space....

The vestibular system, a sensory apparatus localized bilaterally in the inner ears, detects the motion of the head and body in space [a]. It is composed of two functional parts: (1) the otolith organs (Fig. I, blue and green colored areas), and (2) the semicircular canals (Fig.

Vision is an important sensory input that is integrated into the postural control system, along with proprioceptive and vestibular information. Thus, although in healthy adults, vision cannot be totally disregarded, the integration process allows an individual to maintain balance even if exposed to conflicting visual information.

The central vestibular pathways ... Roy and Cullen, 2002; Dieterich and Brandt, 2015). The vestibulo-ocular reflex and the optokinetic reflex interact with the visual system to maintain visual and postural stability (Pettorossi et al., 1996; Kandel et al., 2000; Raphan and ...

The VOR generates compensatory eye movements of equal and opposite magnitude to head rotation, stabilizing gaze relative to space1,2. Patients with a compromised vestibular system have impaired VOR function and thus experience blurry vision, poor balance and postural control, and an increased risk of falls3–5. Under current clinical guidelines, patients with impaired VOR are often prescribed a series of gaze-stabilization exercises, whose efficacy has been demonstrated by moderate to strong evidence in previous randomized and controlled studies6–10.

However, the disturbed visual modulation of balance responses in PCA suggest that some cortical regions with visual processing capabilities do interact with the balance control system. Our imaging data implicate occipitotemporal cortices, thalamic regions such as the paracentral nuclei and pulvinar, and their reciprocal connections. There is one other curious difference between the current and previous findings. As we have shown here, the impact of vision on vestibular balance mechanisms is reduced.

Thus, while specific vestibular deficits are not always directly associated with SMD, data regarding the impact of vision on balance suggest that some patients with SMD may have an underlying balance disorder.