Final answer:
The brain's sensitivity to horizontal or vertical imbalance stems from the vestibular system's semicircular canals, which detect angular acceleration in three dimensions. Lesions in the vestibular area of the somatosensory cortex affect the perception of vertical orientation, but overall, there is no clear evidence that the brain is more sensitive to one type of imbalance over the other.
Step-by-step explanation:
When considering the question of whether the brain is more sensitive to horizontal or vertical imbalance, it's important to understand the role of the vestibular system, which includes the semicircular canals. The horizontal canal is involved in sensing rotation around a vertical axis, such as turning the head to the left or right. The other two canals respond primarily to motions of the head that are not aligned with this horizontal plane. The brain processes input from all three canals to detect angular acceleration in three dimensions. This system helps maintain balance and provides the brain with information about the body's orientation in space.
Individuals with lesions in the vestibular areas of the somatosensory cortex may perceive vertical objects as tilted, suggesting this area contributes to the perception of both orientations. However, the available research doesn't specify a heightened sensitivity to either horizontal or vertical imbalances over the other. Instead, the vestibular system monitors changes in velocity involving any kind of rotation or movement relative to the three dimensional semicircular canals' axes.
The brain's ability to detect movement and orientation is also supported by higher processing areas, including those involved in coordinating movements (cerebellum), and perceiving dizziness (temporal cortex), among other functions. Walking in a straight line, for example, involves the integration of sensory feedback from the vestibular system and proprioceptive systems to coordinate movement and maintain balance.