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Neuroscience and Biobehavioral Reviews Nov 2018What any sensory neuron knows about the world is one of the cardinal questions in Neuroscience. Information from the sensory periphery travels across synaptically... (Review)
Review
What any sensory neuron knows about the world is one of the cardinal questions in Neuroscience. Information from the sensory periphery travels across synaptically coupled neurons as each neuron encodes information by varying the rate and timing of its action potentials (spikes). Spatiotemporally correlated changes in this spiking regimen across neuronal populations are the neural basis of sensory representations. In the somatosensory cortex, however, spiking of individual (or pairs of) cortical neurons is only minimally informative about the world. Recent studies showed that one solution neurons implement to counteract this information loss is adapting their rate of information transfer to the ongoing synaptic activity by changing the membrane potential at which spike is generated. Here we first introduce the principles of information flow from the sensory periphery to the primary sensory cortex in a model sensory (whisker) system, and subsequently discuss how the adaptive spike threshold gates the intracellular information transfer from the somatic post-synaptic potential to action potentials, controlling the information content of communication across somatosensory cortical neurons.
Topics: Action Potentials; Animals; Cell Communication; Information Theory; Neurons; Perception; Somatosensory Cortex; Vibrissae
PubMed: 30227142
DOI: 10.1016/j.neubiorev.2018.09.007 -
Current Biology : CB Feb 2015Eyes may be 'the window to the soul' in humans, but whiskers provide a better path to the inner lives of rodents. The brain has remarkable abilities to focus its limited...
Eyes may be 'the window to the soul' in humans, but whiskers provide a better path to the inner lives of rodents. The brain has remarkable abilities to focus its limited resources on information that matters, while ignoring a cacophony of distractions. While inspecting a visual scene, primates foveate to multiple salient locations, for example mouths and eyes in images of people, and ignore the rest. Similar processes have now been observed and studied in rodents in the context of whisker-based tactile sensation. Rodents use their mechanosensitive whiskers for a diverse range of tactile behaviors such as navigation, object recognition and social interactions. These animals move their whiskers in a purposive manner to locations of interest. The shapes of whiskers, as well as their movements, are exquisitely adapted for tactile exploration in the dark tight burrows where many rodents live. By studying whisker movements during tactile behaviors, we can learn about the tactile information available to rodents through their whiskers and how rodents direct their attention. In this primer, we focus on how the whisker movements of rats and mice are providing clues about the logic of active sensation and the underlying neural mechanisms.
Topics: Animals; Behavior, Animal; Mechanoreceptors; Recognition, Psychology; Rodentia; Social Behavior; Spatial Navigation; Touch Perception; Vibrissae
PubMed: 25689904
DOI: 10.1016/j.cub.2015.01.008 -
Nature Sep 2022Central oscillators are primordial neural circuits that generate and control rhythmic movements. Mechanistic understanding of these circuits requires genetic...
Central oscillators are primordial neural circuits that generate and control rhythmic movements. Mechanistic understanding of these circuits requires genetic identification of the oscillator neurons and their synaptic connections to enable targeted electrophysiological recording and causal manipulation during behaviours. However, such targeting remains a challenge with mammalian systems. Here we delimit the oscillator circuit that drives rhythmic whisking-a motor action that is central to foraging and active sensing in rodents. We found that the whisking oscillator consists of parvalbumin-expressing inhibitory neurons located in the vibrissa intermediate reticular nucleus (vIRt) in the brainstem. vIRt neurons receive descending excitatory inputs and form recurrent inhibitory connections among themselves. Silencing vIRt neurons eliminated rhythmic whisking and resulted in sustained vibrissae protraction. In vivo recording of opto-tagged vIRt neurons in awake mice showed that these cells spike tonically when animals are at rest, and transition to rhythmic bursting at the onset of whisking, suggesting that rhythm generation is probably the result of network dynamics, as opposed to intrinsic cellular properties. Notably, ablating inhibitory synaptic inputs to vIRt neurons quenched their rhythmic bursting, impaired the tonic-to-bursting transition and abolished regular whisking. Thus, the whisking oscillator is an all-inhibitory network and recurrent synaptic inhibition has a key role in its rhythmogenesis.
Topics: Animals; Brain Stem; Mice; Movement; Neural Inhibition; Neural Pathways; Neurons; Parvalbumins; Periodicity; Rest; Synapses; Vibrissae; Wakefulness
PubMed: 36045290
DOI: 10.1038/s41586-022-05144-8 -
Nature Reviews. Neuroscience Sep 2019Tactile sensory information from facial whiskers provides nocturnal tunnel-dwelling rodents, including mice and rats, with important spatial and textural information... (Review)
Review
Tactile sensory information from facial whiskers provides nocturnal tunnel-dwelling rodents, including mice and rats, with important spatial and textural information about their immediate surroundings. Whiskers are moved back and forth to scan the environment (whisking), and touch signals from each whisker evoke sparse patterns of neuronal activity in whisker-related primary somatosensory cortex (wS1; barrel cortex). Whisking is accompanied by desynchronized brain states and cell-type-specific changes in spontaneous and evoked neuronal activity. Tactile information, including object texture and location, appears to be computed in wS1 through integration of motor and sensory signals. wS1 also directly controls whisker movements and contributes to learned, whisker-dependent, goal-directed behaviours. The cell-type-specific neuronal circuitry in wS1 that contributes to whisker sensory perception is beginning to be defined.
Topics: Animals; Mice; Nerve Net; Rats; Rodentia; Sensorimotor Cortex; Signal Transduction; Somatosensory Cortex; Touch; Vibrissae
PubMed: 31367018
DOI: 10.1038/s41583-019-0200-y -
Anatomical Record (Hoboken, N.J. : 2007) Aug 2019Insufficient recovery after injury of a peripheral motor nerve is due to (1) inappropriate pathfinding as a result of axonal regrowth to inappropriate targets, (2)... (Review)
Review
Insufficient recovery after injury of a peripheral motor nerve is due to (1) inappropriate pathfinding as a result of axonal regrowth to inappropriate targets, (2) excessive collateral axonal branching at the lesion site, and (3) polyinnervation of the neuromuscular junctions (NMJs). The rat facial nerve model is often used because of its simple and reliable readout to measure recovery of function (vibrissal whisking). Over the last decades scientists have concentrated their efforts to combat mostly NMJ polyinnervation, because it turned out to be very difficult to reduce collateral axonal branching and impossible to navigate thousands of axons toward the original fascicles. In the past, several groups of scientists concentrated their efforts to reduce the activity-dependent polyinnervation of NMJs by electrical stimulation of the muscles (square 0.1 msec pulses at 5 Hz). The results showed no recovery of functions and a severe reduction in the number of innervated NMJs to approximately one fifth of those observed in intact animals. More recent experiments, however, have shown that motor recovery improved significantly following mechanical stimulation of the denervated facial muscles (vibrissal and orbicularis oculi) and that restored functions could invariably be linked to reduced polyinnervation at the NMJ while the number of innervated NMJ remained the same. These results suggest that clinically feasible and effective therapies could be developed and tested in the near future. Anat Rec, 302:1287-1303, 2019. © 2019 Wiley Periodicals, Inc.
Topics: Animals; Disease Models, Animal; Facial Muscles; Facial Nerve; Facial Nerve Injuries; Humans; Muscle Denervation; Nerve Regeneration; Rats; Recovery of Function; Vibrissae
PubMed: 30950181
DOI: 10.1002/ar.24123 -
Current Opinion in Neurobiology Oct 2016We describe recent advances in quantifying the three-dimensional (3D) geometry and mechanics of whisking. Careful delineation of relevant 3D reference frames reveals... (Review)
Review
We describe recent advances in quantifying the three-dimensional (3D) geometry and mechanics of whisking. Careful delineation of relevant 3D reference frames reveals important geometric and mechanical distinctions between the localization problem ('where' is an object) and the feature extraction problem ('what' is an object). Head-centered and resting-whisker reference frames lend themselves to quantifying temporal and kinematic cues used for object localization. The whisking-centered reference frame lends itself to quantifying the contact mechanics likely associated with feature extraction. We offer the 'windowed sampling' hypothesis for active sensing: that rats can estimate an object's spatial features by integrating mechanical information across whiskers during brief (25-60ms) windows of 'haptic enclosure' with the whiskers, a motion that resembles a hand grasp.
Topics: Animals; Cues; Mechanical Phenomena; Touch; Touch Perception; Vibrissae
PubMed: 27632212
DOI: 10.1016/j.conb.2016.08.001 -
Current Opinion in Neurobiology Apr 2012Sniffing and whisking are two rhythmic orofacial motor activities that enable rodents to localize and track objects in their environment. They have related temporal... (Review)
Review
Sniffing and whisking are two rhythmic orofacial motor activities that enable rodents to localize and track objects in their environment. They have related temporal dynamics, possibly as a result of both shared musculature and shared sensory tasks. Sniffing and whisking also constitute the overt expression of an animal's anticipation of a reward. Yet, the neuronal mechanisms that underlie the control of these behaviors have not been established. Here, we review the similarities between sniffing and whisking and suggest that such similarities indicate a mechanistic link between these two rhythmic exploratory behaviors.
Topics: Animals; Behavior, Animal; Exploratory Behavior; Rodentia; Vibrissae
PubMed: 22177596
DOI: 10.1016/j.conb.2011.11.013 -
Neuroscience Jan 2018A fundamental question in the investigation of any sensory system is what physical signals drive its sensory neurons during natural behavior. Surprisingly, in the... (Review)
Review
A fundamental question in the investigation of any sensory system is what physical signals drive its sensory neurons during natural behavior. Surprisingly, in the whisker system, it is only recently that answers to this question have emerged. Here, we review the key developments, focussing mainly on the first stage of the ascending pathway - the primary whisker afferents (PWAs). We first consider a biomechanical framework, which describes the fundamental mechanical forces acting on the whiskers during active sensation. We then discuss technical progress that has allowed such mechanical variables to be estimated in awake, behaving animals. We discuss past electrophysiological evidence concerning how PWAs function and reinterpret it within the biomechanical framework. Finally, we consider recent studies of PWAs in awake, behaving animals and compare the results to related studies of the cortex. We argue that understanding 'what the whiskers tell the brain' sheds valuable light on the computational functions of downstream neural circuits, in particular, the barrel cortex.
Topics: Afferent Pathways; Animals; Biomechanical Phenomena; Somatosensory Cortex; Touch Perception; Trigeminal Ganglion; Vibrissae
PubMed: 28843998
DOI: 10.1016/j.neuroscience.2017.08.005 -
Anatomical Record (Hoboken, N.J. : 2007) Feb 2021In whisking rodents, the mystacial pad is supplied with vibrissae and contains a collagenous skeleton that is a part of the snout fascia. The collagenous skeleton is...
In whisking rodents, the mystacial pad is supplied with vibrissae and contains a collagenous skeleton that is a part of the snout fascia. The collagenous skeleton is composed of three interconnected layers: superficial, deep spongy mesh and subcapsular fibrous mat. We found that the first two layers contain diverse fascial structures, such as sheets of subcutaneous connective tissue, tendons, ligaments and follicular capsules which transmit muscle efforts to vibrissae and are thus involved in whisking. Subcapsular fibrous mat is built of oriented rostro-caudal wavy fibrils. It maintains spatial arrangement of whisker follicles, provides a quick response to deformation and connects entire mystacial pad to the skull. To move vibrissae, the forces of intrinsic muscles are applied directly to the capsules of the vibrissa follicles, whereas the forces of extrinsic muscles are applied to other parts of the collagenous skeleton, which transmit the forces to the capsules. According to the spatial distribution and anchoring sites of the muscles and fascia, extrinsic muscles provide vibrissa protraction or retraction by pulling the superficial layer of the collagenous skeleton rostral or caudal, respectively. Vibrissae can be also retracted when the efforts of extrinsic muscles are applied to the subcapsular fibrous mat. When the muscles relax, fascial structures return the vibrissae to their resting position. The deep spongy layer encompasses vibrissal follicles providing a uniform distribution of stresses and strains during whisking. In the mystacial pad, fascia is a dominant type of tissue that maintains the integrity of the vibrissa motor plant, translates muscular momentum to the vibrissae, and plays a role in vibrissae movements.
Topics: Animals; Facial Muscles; Mice; Mice, Inbred C57BL; Movement; Muscle Fibers, Skeletal; Rats; Rats, Wistar; Vibrissae
PubMed: 32374069
DOI: 10.1002/ar.24409 -
Sensors (Basel, Switzerland) Apr 2022Whisker sensors are a class of tactile sensors that have recently attracted attention. Inspired by mammals' whiskers known as mystacial vibrissae, they have displayed... (Review)
Review
Whisker sensors are a class of tactile sensors that have recently attracted attention. Inspired by mammals' whiskers known as mystacial vibrissae, they have displayed tremendous potential in a variety of applications e.g., robotics, underwater vehicles, minimally invasive surgeries, and leak detection. This paper provides a supplement to the recent tactile sensing techniques' designs of whiskers that only sense at their base, as well as the materials employed, and manufacturing techniques. The article delves into the technical specifications of these sensors, such as the resolution, measurement range, sensitivity, durability, and recovery time, which determine their performance. The sensors' sensitivity varies depending on the measured physical quantity; for example, the pressure sensors had an intermediate sensitivity of 58%/Pa and a response time of around 90 ms, whereas the force sensors that function based on piezoelectric effects exhibited good linearity in the measurements with a resolution of 3 µN and sensitivity of 0.1682 mV/µN. Some sensors were used to perform spatial mapping and the identification of the geometry and roughness of objects with a reported resolution of 25 nm. The durability and recovery time showed a wide range of values, with the maximum durability being 10,000 cycles and the shortest recovery time being 5 ms. Furthermore, the paper examines the fabrication of whiskers at the micro- and nanoscales, as well as their contributions to mechanical and thermal behavior. The commonly used manufacturing techniques of 3D printing, PDMS casting, and screen printing were used in addition to several micro and nanofabrication techniques such as photolithography, etching, and chemical vapor deposition. Lastly, the paper discusses the main potential applications of these sensors and potential research gaps in this field. In particular, the operation of whisker sensors under high temperatures or high pressure requires further investigation, as does the design of sensors to explore larger topologies.
Topics: Animals; Mammals; Printing, Three-Dimensional; Robotics; Touch; Vibrissae
PubMed: 35408319
DOI: 10.3390/s22072705