Overview—Boosting sensory information

By applying a proprietary form of neurostimulation directly to target neurons in the extremities, Afferent Corporation’s technology dramatically boosts sensory information that is traveling to the spinal cord and brain. By accessing the nervous system via this unique pathway and mechanism, it is possible to impact chronic neurological dysfunction stemming from stroke, aging, and disease.

 

Background—The human nervous system

The human nervous system sends information in two directions (Figure 2):

• Efferent signaling starts in the central nervous system (brain and spinal cord) and is conveyed to the peripheral nervous system (arms and legs, for example). An example of efferent “traffic” is motor control, that is the commands from the brain to contract certain muscles.
• Afferent signaling arises in the peripheral nervous system and moves toward the central nervous system. All sensory information—sight, hearing, touch, movement—is conveyed to the brain and spinal cord as afferent signals.

As the name of the company suggests, our technology accesses the nervous system and treats neurological conditions via these afferent pathways.

Figure 2.  Neural information travels both away from and toward the brain. This “sensorimotor loop” is the means by which all coordinated movement is accomplished.

A variety of specialized neurons are involved in detecting and conveying sensory information. Among them is a specialized class of sensory neurons called mechanoreceptors. These neurons are found in skin, muscle, ligaments and tendons. They convert mechanical stimuli from the environment (e.g. touch, pressure, vibration, and limb movements) into nerve impulses that are interpreted by the central nervous system. This sensory feedback is key to coordinated movements of all kinds, and directly drives the acquisition of motor skills and reestablishing sensorimotor function following injury.

Core Technology—“Stochastic resonance” stimulation enhances sensory function

Afferent's core technology, which is based on the seminal research of James J. Collins, Ph.D., at Boston University, dramatically increases the flow of sensory information traveling from mechanoreceptors in muscles, joints, and skin to the body’s control centers. Dr. Collins’s important discovery was that certain forms of electrical or mechanical stimulation applied to mechanoreceptors increase their ability to transmit sensory information.

Based on a well-established principle termed “stochastic resonance” (SR), the stimulation essentially energizes sensory neurons so that they are predisposed to fire in response to stimuli from the environment. By increasing the sensitivity of mechanoreceptors, it is possible effectively to boost sensory information in a fashion that is concordant with normal function.

The most effective levels of stimulation (whether electrical or mechanical) are below the sensory threshold of the individual. That is, beneficial levels of this form of stimulation cannot themselves be felt.

In various forms, Afferent’s sensory enhancement technology has been tested safely in over 200 humans. Landmark studies that show benefits resulting from boosting sensory signaling, in both healthy and clinical subjects, have been published in preeminent journals such as Nature, The Lancet, Diabetes Care, and Annals of Neurology.

Early research in this field sought to demonstrate direct improvement in local sensory function (Figure 1). In a typical experiment, the subject reports when a slight tactile stimulus is felt on the fingertip. By repeatedly testing a variety of light touch stimuli, it is possible to determine the subject’s “sensory threshold,” i.e. the level at which the stimulus is just barely felt. Over many presentations of a stimulus at that level, a normal subject is expected to correctly identify the presence of the stimulus approximately 50% of the time. However, when a sub-sensory noise signal was presented at the stimulus site, subjects on average correctly identified the presence of the stimulus more than 75% of the time. In essence, the neurostimulation increased the sensitivity of the fingertip to touch.

These results have been corroborated in several similar experiments in both normal subjects and individuals suffering from sensory loss resulting from stroke, aging, and diabetes.

Figure 3.  Early research established the power of “stochastic resonance stimulation” to improve sensory function in humans. In this touch sensation experiment, very low levels of SR stimulation, or “input noise,” boosted subjects’ ability to detect light touch stimuli (from Collins et al., Nature, 1996).

Additionally, the potential of the technology to impact whole-body sensorimotor function, e.g. balance, has been extensively explored. Notably, it has been established that applying low-level SR stimulation to the plantar surface of the feet improves measures of balance in healthy young and elderly subjects, and in patients with sensory dysfunction.

Figure 4.   Early research established the power of “stochastic resonance stimulation” to improve sensory function in humans. In this touch sensation experiment, very low levels of SR stimulation, or “input noise,” boosted subjects’ ability to detect light touch stimuli.

Building from this strong foundation of scientific demonstration of effect and mechanism of action, Afferent Corporation has a unique opportunity to deploy its core platform technology against many prevalent neurological pathologies.