Relationship between Somatosensory and Motor Research

**119**

**Chapter 8**

*Hitoshi Asai*

anteroposterior direction

**1. Introduction**

**Abstract**

Functional Role of the

Somatosensory Information to

the Anteroposterior Direction

or backward while standing may contribute to the position information.

**Keywords:** somatosensory information, perception, standing positions,

The control of the standing posture in humans requires various sensory systems, including visual [1], vestibular [2, 3], plantar sole mechanoreceptor [4–8], and proprioceptive [9] systems. The central nervous system (CNS) integrates these different sensory inputs. Upright posture control was performed in various standing positions on the anteroposterior and mediolateral directions. When both arms are rapidly flexed to the front from the quiet standing (QS) posture, the postural muscles (the erector spinae, hamstrings, etc.) are activated 20–30 ms earlier than the focal muscles of the upper extremities (the anterior deltoid) [10]. This earlier activation of the postural muscles in comparison to the focal muscles was defined as the anticipatory postural control to minimize the effect of forthcoming body perturbations due to arm movement [11]. This anticipatory activation of the postural muscles during the QS position was significantly slower than that in the standing position near the most forward-leaning position [10]. Thus, because the preceding time of the earlier activation of the postural muscles varies according to the initial standing position just before arm movement, the initial standing position may be accurately perceived.

Perceive the Standing Position in

The perceptibility of standing positions in the anteroposterior direction varies according to the standing position. Standing positions with the center of foot pressure (COP) located far from the COP in the quiet standing position show lower stability, and the perceptibility was markedly higher in comparison to positions with the COP near the COP in the quiet standing position. This chapter focuses on the role of somatosensory information in the perception of standing positions in the anteroposterior direction based on our previous study, which concluded that a large change in sensory information generated from the sole of the heel and knee may provide important cues regarding the perception of standing positions with low stability. Large changes in the somatosensory information generated from pressure changes on the sole and from the upward movement of the patella leaning forward

## **Chapter 8**
