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Biological and bionic hands: natural neural coding and artificial perception.

Bensmaia SJ - Philos. Trans. R. Soc. Lond., B, Biol. Sci. (2015)

Bottom Line: For upper-limb neuroprostheses to be clinically viable, they must therefore provide for the restoration of touch and proprioception.I focus on biomimetic approaches to sensory restoration, which leverage our current understanding about how information about grasped objects is encoded in the brain of intact individuals.I argue that not only can sensory neuroscience inform the development of sensory neuroprostheses, but also that the converse is true: stimulating the brain offers an exceptional opportunity to causally interrogate neural circuits and test hypotheses about natural neural coding.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA sliman@uchicago.edu.

ABSTRACT
The first decade and a half of the twenty-first century brought about two major innovations in neuroprosthetics: the development of anthropomorphic robotic limbs that replicate much of the function of a native human arm and the refinement of algorithms that decode intended movements from brain activity. However, skilled manipulation of objects requires somatosensory feedback, for which vision is a poor substitute. For upper-limb neuroprostheses to be clinically viable, they must therefore provide for the restoration of touch and proprioception. In this review, I discuss efforts to elicit meaningful tactile sensations through stimulation of neurons in somatosensory cortex. I focus on biomimetic approaches to sensory restoration, which leverage our current understanding about how information about grasped objects is encoded in the brain of intact individuals. I argue that not only can sensory neuroscience inform the development of sensory neuroprostheses, but also that the converse is true: stimulating the brain offers an exceptional opportunity to causally interrogate neural circuits and test hypotheses about natural neural coding.

No MeSH data available.


(a) Neuronal activation evoked over a 4 × 4 mm patch of cortex by indentations delivered to the tip of the little finger at four amplitudes. As the amplitude increases, the firing rate increases and the area of activated neurons also increases. (b) Psychometric equivalence functions that map electrical amplitude onto mechanical amplitude such that the ICMS and the corresponding poke are of equal perceptual magnitude (each curve corresponds to one electrode/skin location pair; different colours denote different animals; reproduced from [10]). (c) Animals perform identically on a pressure discrimination task whether pokes are delivered to their native finger (blue) or to a prosthetic one (red). The standard amplitude for these experiments was 150 µm (reproduced from [10]).
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RSTB20140209F3: (a) Neuronal activation evoked over a 4 × 4 mm patch of cortex by indentations delivered to the tip of the little finger at four amplitudes. As the amplitude increases, the firing rate increases and the area of activated neurons also increases. (b) Psychometric equivalence functions that map electrical amplitude onto mechanical amplitude such that the ICMS and the corresponding poke are of equal perceptual magnitude (each curve corresponds to one electrode/skin location pair; different colours denote different animals; reproduced from [10]). (c) Animals perform identically on a pressure discrimination task whether pokes are delivered to their native finger (blue) or to a prosthetic one (red). The standard amplitude for these experiments was 150 µm (reproduced from [10]).

Mentions: When we grasp an object, we minimally need to know not only which fingers are in contact with it, but also how much pressure we are exerting on it. We need to apply just enough pressure so that the object does not slip from our grasp when we pick it up but not so much that we crush it. Tactile signals convey very precise information about contact pressure [32]. In primary somatosensory cortex, an increase in pressure results not only in an increase in the activity of the neurons that are most sensitive to the skin location at which it is applied (neurons in the hotzone of activation) but also in the recruitment of nearby neurons (figure 3a). A biomimetic approach to conveying information about contact pressure would then be to modulate both the firing rate of the neurons in the hotzone and the volume of neurons activated in responses to changes in skin pressure. It turns out that we can achieve both of these changes in neuronal activity by modulating the ICMS amplitude [16,23]. Indeed, increases in current amplitude will result in stronger depolarization of nearby neurons, thereby increasing the strength of their response, and in greater current spread, leading to the recruitment of more distant neurons.Figure 3.


Biological and bionic hands: natural neural coding and artificial perception.

Bensmaia SJ - Philos. Trans. R. Soc. Lond., B, Biol. Sci. (2015)

(a) Neuronal activation evoked over a 4 × 4 mm patch of cortex by indentations delivered to the tip of the little finger at four amplitudes. As the amplitude increases, the firing rate increases and the area of activated neurons also increases. (b) Psychometric equivalence functions that map electrical amplitude onto mechanical amplitude such that the ICMS and the corresponding poke are of equal perceptual magnitude (each curve corresponds to one electrode/skin location pair; different colours denote different animals; reproduced from [10]). (c) Animals perform identically on a pressure discrimination task whether pokes are delivered to their native finger (blue) or to a prosthetic one (red). The standard amplitude for these experiments was 150 µm (reproduced from [10]).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528821&req=5

RSTB20140209F3: (a) Neuronal activation evoked over a 4 × 4 mm patch of cortex by indentations delivered to the tip of the little finger at four amplitudes. As the amplitude increases, the firing rate increases and the area of activated neurons also increases. (b) Psychometric equivalence functions that map electrical amplitude onto mechanical amplitude such that the ICMS and the corresponding poke are of equal perceptual magnitude (each curve corresponds to one electrode/skin location pair; different colours denote different animals; reproduced from [10]). (c) Animals perform identically on a pressure discrimination task whether pokes are delivered to their native finger (blue) or to a prosthetic one (red). The standard amplitude for these experiments was 150 µm (reproduced from [10]).
Mentions: When we grasp an object, we minimally need to know not only which fingers are in contact with it, but also how much pressure we are exerting on it. We need to apply just enough pressure so that the object does not slip from our grasp when we pick it up but not so much that we crush it. Tactile signals convey very precise information about contact pressure [32]. In primary somatosensory cortex, an increase in pressure results not only in an increase in the activity of the neurons that are most sensitive to the skin location at which it is applied (neurons in the hotzone of activation) but also in the recruitment of nearby neurons (figure 3a). A biomimetic approach to conveying information about contact pressure would then be to modulate both the firing rate of the neurons in the hotzone and the volume of neurons activated in responses to changes in skin pressure. It turns out that we can achieve both of these changes in neuronal activity by modulating the ICMS amplitude [16,23]. Indeed, increases in current amplitude will result in stronger depolarization of nearby neurons, thereby increasing the strength of their response, and in greater current spread, leading to the recruitment of more distant neurons.Figure 3.

Bottom Line: For upper-limb neuroprostheses to be clinically viable, they must therefore provide for the restoration of touch and proprioception.I focus on biomimetic approaches to sensory restoration, which leverage our current understanding about how information about grasped objects is encoded in the brain of intact individuals.I argue that not only can sensory neuroscience inform the development of sensory neuroprostheses, but also that the converse is true: stimulating the brain offers an exceptional opportunity to causally interrogate neural circuits and test hypotheses about natural neural coding.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA sliman@uchicago.edu.

ABSTRACT
The first decade and a half of the twenty-first century brought about two major innovations in neuroprosthetics: the development of anthropomorphic robotic limbs that replicate much of the function of a native human arm and the refinement of algorithms that decode intended movements from brain activity. However, skilled manipulation of objects requires somatosensory feedback, for which vision is a poor substitute. For upper-limb neuroprostheses to be clinically viable, they must therefore provide for the restoration of touch and proprioception. In this review, I discuss efforts to elicit meaningful tactile sensations through stimulation of neurons in somatosensory cortex. I focus on biomimetic approaches to sensory restoration, which leverage our current understanding about how information about grasped objects is encoded in the brain of intact individuals. I argue that not only can sensory neuroscience inform the development of sensory neuroprostheses, but also that the converse is true: stimulating the brain offers an exceptional opportunity to causally interrogate neural circuits and test hypotheses about natural neural coding.

No MeSH data available.