**1. Introduction**

#### **1.1 Anatomy**

Proprioception was first described by Sir Charles Bell in 1830s as sixth sense coming from Latin word proprius meaning "one's own" and perception "perceiving one's own self" [1]. Proprioception is generally defined as either the sense of position or the motion of the limbs and body in the absence of vision [2]. Limb position is a static sense, whereas limb motion is a dynamic sense [3]. It is described as the most important sensorial modality for the internal representation of body map providing static and dynamic proprioceptive systems [4].

Proprioception is a complex system having both conscious and unconscious components involving peripheral and central pathways. The proprioceptive sensations arise from the deeper tissues. The main receptors are muscle spindles, tendons, Ruffini endings in joint capsules ligaments and Pacinian corpuscles reacting pressure, tension, stretching or contraction. The cutaneous receptors of the skin also contribute to joint position and motion sense especially at digits, elbow and knee. The term kinesthesia is generally used to describe the conscious awareness of the body or limb position in space [1, 5–7]. Conscious proprioceptive impulses elongate along large and myelinated fibers from the peripheral nerves into the dorsal root ganglion of spinal cord (first order neurons) and then via the medial division of the posterior root, via posterior white columns of fasciculi gracilis and cuneatus and ascend to the nuclei gracilis and cuneatus in the lower medulla. Axons of the second-order neuron decussate as internal arcuate fibers (second order neurons), and then ascend in the medial lemniscus to the contralateral somatosensory region of thalamus (**Figure 1**) [2, 5].

**Figure 1.**

*Neuroanatomic pathway adopted from DeJong's the neurologic examination.*

The main pathway for proprioceptive information is via the dorsal column medial lemniscal, posterior and anterior spinocerebellar tracts and spinoreticular tracts [6, 7].

There is a high density of complex spindles in deeper cervical muscles particularly in the intermediate columns, acting as neck prorioceptive receptors. This system is important for head and neck position sense together with the high density muscle spindles of sub-occipital triange. The density of muscle spindles is higher in the upper cervical spine when compared with the lower cervial and cervicothoracic and thoraco-lumbar junctions [8]. Neck proprioception plays an important role in limb coordination and body-scheme representation [8]. Proprioceptive impulses from the head and neck are supplied by cranial nerves [5].

Contralateral primary and secondary sensorimotor cortex, supplementary motor area and bilateral inferior parietal lobes and basal ganglia (especially nigrostriatal pathways, striatal neurons and putamen) are involved in processing proprioceptive information during passive movement [9, 10]. The cerebellum contributes to proprioception only during movement [3]. Especially deep medial fastigial nucleus of cerebellum converges vestibular and neck proprioceptive sensory signals describing body's movement in space [11, 12].

#### **1.2 Proprioception and motor control**

The sensorimotor system, defined as the sensory, motor, and central integration, is a crucial and intricate component of the motor control system [13]. Motor control is a complex and dynamic process based on the selective integration of sensory information from multiple sources, motor commands, and motor output [13, 14]. There are specific unique roles associated with each sensory source (i.e., somatosensory, visual, vestibular) that cannot be compensated fully with each other [14, 15]. The environment is experienced through sensory systems: exteroception (e.g., sight,

**21**

*Proprioception and Clinical Correlation DOI: http://dx.doi.org/10.5772/intechopen.95866*

motor control and considered as multifold [14].

internal forward model of motor command [21].

**1.3 Proprioception and postural control**

hearing, touch), interoception (e.g., arousal, pain, visceral sensations, muscular sensations), and proprioception (e.g., sense of position, motion, and force), which all required for successful motor control [16, 17]. During a task-oriented activity, motor adaptation, defined as a process of modifying the movement based on error feedback [18], skills are needed to cope with the changes occurring in the *external* and *internal environment* [2]. Motor adaptation is stimulated with sensorial triggers by using both feedback (reactive: adjust ongoing motor behavior) and feedforward (preparatory: pre-planning and anticipating the motor sequence from the previous experience) mechanism. Proprioceptive information, from proprioceptors found in muscle, tendon, ligament, capsule, skin, and fascial layers, plays an integral role in

The role of proprioceptive information in motor control can be divided into two categories: *external environment* (even vs. uneven ground) and *internal environment* (carrying a load on shoulders vs. hands below knuckle height). The motor programs often need to be adjusted to accommodate unexpected perturbations or changes in the *external environment*. Although the source of this information is usually associated mainly with visual input, there are many situations where proprioceptive input is the fastest and/or most accurate. Proprioception is necessary during motion execution to update feedforward commands derived from the visual image [14]. Attention to environmental constraints is also required because dealing with complex environments often requires behavioral flexibility to maintain postural balance [19]. Secondly, the central nervous system needs an updated body schema of the biomechanical and spatial properties of body parts to plan and modify *internally generated* motor commands [20]. Before and during a motor command, the motor control system must consider the current and changing positions of the respective joints to account for the complex mechanical interactions within the musculoskeletal system components [14]. Additionally, proprioception is important after movement to compare the actual movement and intended movement, besides the predicted movement derived from the efference copies (corollary discharge: copying of motor commands based on past events) of motor commands, which has an essential role in motor learning to update the

During the execution of all motor tasks, proprioception is required to prepare, maintain, and restore the stability of both the entire body (postural equilibrium) and the segments (joint stability) [14, 15]. Postural control, defined as controlling the position of the body regarding the task in the environment, involves neural control of "postural equilibrium" and "postural orientation". Postural equilibrium consists of the coordination of sensory and motor strategies to maintain balance by controlling the body's center of mass (COM) over its base of support (BOS) to maintain postural stability during both intrinsic (self-initiated) and extrinsic (externally triggered) disturbances. The postural equilibrium controls stability during both static (i.e., quiet standing) and dynamic (i.e., walking and reaching) situations. Postural orientation involves positioning body alignment with respect to gravity, the support surface, visual environment, and other sensory reference frames [22].

Postural control is considered as a complex motor skill derived from the interaction of multiple sensorimotor processes, which are; biomechanical constraints (i.e., BOS, degrees of freedom, strength, limits of stability), movement strategies (i.e., reactive, anticipatory, voluntary), sensory strategies (i.e., sensory integration, sensory re-weighting), orientation in space (i.e., perception of visional verticality, perception of postural verticality), control of dynamics (i.e., gait, proactive), cognitive

#### *Proprioception and Clinical Correlation DOI: http://dx.doi.org/10.5772/intechopen.95866*

*Proprioception*

tracts [6, 7].

**Figure 1.**

The main pathway for proprioceptive information is via the dorsal column medial lemniscal, posterior and anterior spinocerebellar tracts and spinoreticular

There is a high density of complex spindles in deeper cervical muscles particularly in the intermediate columns, acting as neck prorioceptive receptors. This system is important for head and neck position sense together with the high density muscle spindles of sub-occipital triange. The density of muscle spindles is higher in the upper cervical spine when compared with the lower cervial and cervicothoracic and thoraco-lumbar junctions [8]. Neck proprioception plays an important role in limb coordination and body-scheme representation [8]. Proprioceptive

Contralateral primary and secondary sensorimotor cortex, supplementary motor area and bilateral inferior parietal lobes and basal ganglia (especially nigrostriatal pathways, striatal neurons and putamen) are involved in processing proprioceptive information during passive movement [9, 10]. The cerebellum contributes to proprioception only during movement [3]. Especially deep medial fastigial nucleus of cerebellum converges vestibular and neck proprioceptive sensory signals

The sensorimotor system, defined as the sensory, motor, and central integration, is a crucial and intricate component of the motor control system [13]. Motor control is a complex and dynamic process based on the selective integration of sensory information from multiple sources, motor commands, and motor output [13, 14]. There are specific unique roles associated with each sensory source (i.e., somatosensory, visual, vestibular) that cannot be compensated fully with each other [14, 15]. The environment is experienced through sensory systems: exteroception (e.g., sight,

impulses from the head and neck are supplied by cranial nerves [5].

*Neuroanatomic pathway adopted from DeJong's the neurologic examination.*

describing body's movement in space [11, 12].

**1.2 Proprioception and motor control**

**20**

hearing, touch), interoception (e.g., arousal, pain, visceral sensations, muscular sensations), and proprioception (e.g., sense of position, motion, and force), which all required for successful motor control [16, 17]. During a task-oriented activity, motor adaptation, defined as a process of modifying the movement based on error feedback [18], skills are needed to cope with the changes occurring in the *external* and *internal environment* [2]. Motor adaptation is stimulated with sensorial triggers by using both feedback (reactive: adjust ongoing motor behavior) and feedforward (preparatory: pre-planning and anticipating the motor sequence from the previous experience) mechanism. Proprioceptive information, from proprioceptors found in muscle, tendon, ligament, capsule, skin, and fascial layers, plays an integral role in motor control and considered as multifold [14].

The role of proprioceptive information in motor control can be divided into two categories: *external environment* (even vs. uneven ground) and *internal environment* (carrying a load on shoulders vs. hands below knuckle height). The motor programs often need to be adjusted to accommodate unexpected perturbations or changes in the *external environment*. Although the source of this information is usually associated mainly with visual input, there are many situations where proprioceptive input is the fastest and/or most accurate. Proprioception is necessary during motion execution to update feedforward commands derived from the visual image [14]. Attention to environmental constraints is also required because dealing with complex environments often requires behavioral flexibility to maintain postural balance [19]. Secondly, the central nervous system needs an updated body schema of the biomechanical and spatial properties of body parts to plan and modify *internally generated* motor commands [20]. Before and during a motor command, the motor control system must consider the current and changing positions of the respective joints to account for the complex mechanical interactions within the musculoskeletal system components [14]. Additionally, proprioception is important after movement to compare the actual movement and intended movement, besides the predicted movement derived from the efference copies (corollary discharge: copying of motor commands based on past events) of motor commands, which has an essential role in motor learning to update the internal forward model of motor command [21].
