Multi-electrode stimulation in somatosensory cortex increases probability of detection

Abstract

Brain machine interfaces (BMIs) that decode control signals from motor cortex have developed tremendously in the past decade, but virtually all rely exclusively on vision to provide feedback. There is now increasing interest in developing an afferent interface to replace natural somatosensation, much as the cochlear implant has done for the sense of hearing. Preliminary experiments toward a somatosensory neuroprosthesis have mostly addressed the sense of touch, but proprioception, the sense of limb position and movement, is also critical for the control of movement. However, proprioceptive areas of cortex lack the precise somatotopy of tactile areas. We showed previously that there is only a weak tendency for neighboring neurons in area 2 to signal similar directions of hand movement. Consequently, stimulation with the relatively large currents used in many studies is likely to activate a rather heterogeneous set of neurons. Here, we have compared the effect of single-electrode stimulation at sub-threshold levels to the effect of stimulating as many as seven electrodes in combination. We found a mean enhancement in the sensitivity to the stimulus (d′) of 0.17 for pairs compared to individual electrodes (an increase of roughly 30%), and an increase of 2.5 for groups of seven electrodes (260%). We propose that a proprioceptive interface made up of several hundred electrodes may yield safer, more effective sensation than a BMI using fewer electrodes and larger currents.

Behavioral assessment of sensitivity to intracortical microstimulation of primate somatosensory cortex

“…That two discriminable increments of amplitude are achievable between threshold and the maximum amplitude tested (100 μA) severely limits the ability to convey sensory information by modulating amplitude. The dynamic range might also be improved by delivering more biomimetic stimulation patterns (39,41) or by delivering stimulation through multiple electrodes simultaneously (20,42), both of which are liable to result in higher sensitivity.…”

“…In one study investigating detection of ICMS of S1 (targeting primarily area 2), detection thresholds were found to range from 5 to 40 μA (20). In primary visual cortex, detection thresholds typically range from 5 to 15 μA, and thresholds have been found to be relatively consistent across visual areas (21).…”

Headers and Payloads Inside of Nervous System as Like as Digital Communication Protocols ?

“…The recording capabilities may be affected by biocompatibility with the patient [22], [23] y [24], traumatic nerve damage at electrode insertion [25], a bad mechanical adjustment due to the rigid electrode structure [26], tissue softness [27], non-penetration to fascicle [28], and the forces by the immobilization of the transcutaneous connection cables have been subjects treated in many publications in the last years [29], [30] y [31].…”

“…The Figure 3, register = 2, shows its headers values. The recording has 32 Messages with payloads longitudes of 3,6,8,9,10,12,13,15,17,18,24,25,35,36,37,39,42,54,59, 77, with a respectively occurrence of 4, 1, 1, 3, 1, 1, 2, 3, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1 y 2. See Figure 4, register = 2.…”

Toward a Proprioceptive Neural Interface that Mimics Natural Cortical Activity

“…ICMS has been shown to evoke detectable percepts from a variety of cortical areas, including human visual cortex (Bak et al 1990; Schmidt et al 1996), rat (Otto et al 2005a; Koivuniemi and Otto 2012) and cat (Wang et al 2012) auditory cortex, rat barrel fields (Talwar et al 2002; Houweling and Brecht 2008; Venkatraman and Carmena 2011; Bari et al 2013; Thomson et al 2013), and monkey somatosensory cortex (O’Doherty et al 2009; Zaaimi et al 2013; Dadarlat et al 2015; Kim et al 2015b). There is currently tremendous interest in using this stimulation to replace natural sensation when it has been lost.…”