Source Of Sensory Input Research Articles

Position sense at the human elbow joint measured by arm matching or pointing.

Position sense at the human elbow joint has traditionally been measured in blindfolded subjects using a forearm matching task. Here we compare position errors in a matching task with errors generated when the subject uses a pointer to indicate the position of a hidden arm. Evidence from muscle vibration during forearm matching supports a role for muscle spindles in position sense. We have recently shown using vibration, as well as muscle conditioning, which takes advantage of muscle's thixotropic property, that position errors generated in a forearm pointing task were not consistent with a role by muscle spindles. In the present study we have used a form of muscle conditioning, where elbow muscles are co-contracted at the test angle, to further explore differences in position sense measured by matching and pointing. For fourteen subjects, in a matching task where the reference arm had elbow flexor and extensor muscles contracted at the test angle and the indicator arm had its flexors conditioned at 90°, matching errors lay in the direction of flexion by 6.2°. After the same conditioning of the reference arm and extension conditioning of the indicator at 0°, matching errors lay in the direction of extension (5.7°). These errors were consistent with predictions based on a role by muscle spindles in determining forearm matching outcomes. In the pointing task subjects moved a pointer to align it with the perceived position of the hidden arm. After conditioning of the reference arm as before, pointing errors all lay in a more extended direction than the actual position of the arm by 2.9°-7.3°, a distribution not consistent with a role by muscle spindles. We propose that in pointing muscle spindles do not play the major role in signalling limb position that they do in matching, but that other sources of sensory input should be given consideration, including afferents from skin and joint.

From cat to man: basic aspects of locomotion relevant to motor rehabilitation of SCI

On the assumption that locomotion is partly produced by a central pattern generator (CPG) in the spinal cord of both cat and man, it is essential to learn more about how such a CPG is controlled by sensory input produced during gait. For the cat there is evidence that load receptor input both from extensor muscles and from cutaneous receptors from the foot, is able to reinforce the ongoing extensor activity in the stance phase and delay the ensuing swing phase. Original data on electrical stimulation of nerves in walking premammillary cats with one hindlimb fixed, support the notion that this type of load afferent input acts directly on the CPG. A second potential source of sensory input on the CPG is derived from sensory signals related to hip position. One would therefore expect that hip position is a more tightly controlled variable than the position of other joints. This was investigated by measuring these angles under conditions of constrained gait (crouch). It was found that cats indeed maintained the maximum excursions of hip flexion and extension within stricter limits than the corresponding angles at other joints. Finally, experiments on hip joint denervation show that there is very little effect on step cycle parameters, thereby supporting the idea that the important hip signal is unlikely to be derived from hip joint afferents. It is suggested that procedures aimed at activating the locomotor CPG in SCI patients could benefit from the use of periodic stimulation of ankle muscle load afferents and hip flexor stretch receptors.

Convergence of multiple sensory inputs onto neurons in the dorsolateral medulla in cats.

The dorsolateral medulla, including the nucleus reticularis parvicellularis, the cuneate nucleus, and the external cuneate nucleus, is an integrative region for a variety of sensory inputs. The purpose of this study was to determine whether individual neurons respond to a variety of different sensory modalities. To this end, responses of 40 neurons in the dorsolateral medulla to multiple sources of sensory input were assessed in cats anesthetized with alpha-chloralose. Neurons were located in the nucleus reticularis parvicellularis (24 cells, 60%), the cuneate nucleus (10 cells, 25%), and the external cuneate nucleus (6 cells, 15%). All neurons were tested for responses to: electrical stimulation of afferents coursing through the left stellate ganglion and afferents in the left cervical vagus nerve, and somatic, auditory, and visual stimulation. No neurons responded to all five stimuli. Three cells (7.5%) responded to four stimuli, 11 (27.5%) responded to three stimuli, 10 (25.0%) responded to two stimuli, and 15 (37.5%) responded to only a single stimulus. The remaining cell was unresponsive to any stimulus. As a group, neurons in the nucleus reticularis parvicellularis received input from the greatest number of sensory modalities, and cuneate nucleus neurons received input predominantly from somatosensory afferents. External cuneate nucleus neurons displayed response profiles intermediate between nucleus reticularis parvicellularis and cuneate nucleus. In addition, eight neurons (20% of the total) were sensitive to changes in blood pressure. Results of the present study support the hypothesis that neurons in the nucleus reticularis parvicellularis receive convergent inputs from different sensory modalities.2+ behaviors.

Convergence of sympathetic, vagal, and other sensory inputs onto neurons in feline ventrolateral medulla

Responses of 80 neurons in rostral and caudal ventrolateral medulla to multiple sources of sensory input were assessed in cats anesthetized with alpha-chloralose. Sixty-one of eighty-one neurons (76%) were excited by stimulation of the stellate ganglion, and one neuron exhibited inhibition followed by excitation. In response to vagal stimulation, 12% of the neurons were excited and 29% inhibited. Vagal stimulation reduced the responses of 13 of 39 (33%) neurons to sympathetic stimulation. Overall, one-third of the neurons responded to both sympathetic and vagal stimulation. There was no difference in proportion of responsive neurons in rostral versus caudal ventrolateral reticular formation. Cells were also tested for auditory, visual, and natural somatic stimuli. Ten percent of the neurons responded to all five stimuli, and another 25% responded to four stimuli. Twelve percent of neurons were unresponsive to any stimulus. Twenty cells were tested for responses to changes in blood pressure elicited with phenylephrine and nitroglycerin. Seven neurons were inhibited by increases or excited by decreases in pressure, four had the opposite responses, and nine were unresponsive. In general, blood pressure-sensitive cells exhibited comparable convergence of other inputs as the overall cell population. However, three times as many pressure-insensitive neurons received vagal input as did pressure sensitive neurons. In conclusion, neurons in the ventrolateral medulla, including the vasopressor and vasodepressor regions, receive and integrate convergent input from multiple sensory origins. Since the regions of the reticular formation studied are functionally heterogeneous, the precise functions of these neurons are not known.

The DARPA image understanding benchmark for parallel computers

Abstract This paper describes a new effort to evaluate parallel architectures applied to knowledge-based machine vision. Previous vision benchmarks have considered only execution times for isolated vision-related tasks, or a very simple image processing scenario. However, the performance of an image interpretation system depends upon a wide range of operations on different levels of representations, from processing arrays of pixels, through manipulation of extracted image events, to symbolic processing of stored models. Vision is also characterized by both bottom-up (image-based) and top-down (model-directed) processing. Thus, the costs of interactions between tasks, input and output, and system overhead must be taken into consideration. Therefore, this new benchmark addresses the issue of system performance on an integrated set of tasks. The Integrated Image Understanding Benchmark consists of a model-based object recognition problem, given two sources of sensory input, intensity and range data, and a database of candidate models. The models consist of configurations of rectangular surfaces, floating in space, viewed under orthographic projection, with the presence of both noise and spurious nonmodel surfaces. A partially ordered sequence of operations that solves the problem is specified along with a recommended algorithmic method for each step. In addition to reporting the total time and the final solution, timings are requested for each component operation, and intermediate results are output as a check on accuracy. Other factors such as programming time, language, code size, and machine configurations are reported. As a result, the benchmark can be used to gain insight into processor strengths and weaknesses and may thus help to guide the development of the next generation of parallel vision architectures. In addition to discussing the development and specification of the new benchmark, this paper presents the results from running the benchmark on the Connection Machine, Warp, Image Understanding Architecture, Associative String Processor, Alliant FX-80, and Sequent Symmetry. The results are discussed and compared through a measurement of relative effort, which factors out the effects of differing technologies.

Sensory control of target acquisition

Recent research has expanded our understanding of how the nervous system uses visual and kinesthetic input to move the arm to a target. In this review, we present data to show how the nervous system can rapidly use sensory input to control impending or ongoing motor activity. We contrast visual control with kinesthetic control to show how these two sources of sensory input are used to control parameters of motor command such as amplitude and direction, to trigger the motor commands, and then to correct errors in trajectory. Despite many differences in the organization of the visual and the kinesthetic sensory systems, the nervous system appears to process these two types of sensory input similarly.

Qualitative Differences Between Shuttle On-Orbit and Transition Control

Two separate reaction control system digital autopilots evolved from one original Space Shuttle orbital autopilot concept. A computer overload forced this evolution. Part of the overload problem was due to unique performance requirements imposed on the reaction control system during each of several different flight regimes. The two resultant reaction control system digital autopilots yield different effector responses because they rely on different sources of sensory input and they process data differently. This paper describes the evolution of the two and illustrates their behavioral differences. The transition autopilot, used in orbital insertion and deorbit, is sensitive to Orbiter flexure due to its feedthrough character. The on-orbit autopilot is sensitive to transient rate control degradation from large disturbances due to feed-forward rate estimation. Simulation results and flight data are used to illustrate performance differences between the two autopilots under various conditions. These include computer failures where electronic stringing and procedural reconfiguration differences affect autopilot behavior.

Proprioceptive Control of the Bilaterally Organized Rhythmic Activity of the Oesophageal Neuronal Network in the Cape Lobster Jasus Lalandii

ABSTRACT In the lobster Jasus lalandii the activity of the oesophageal nervous system (monitored through the firing of its main motor neuron, OD1) is modulated by a pair of proprioceptors, the posterior stomach receptors (PSRs). The in vitro preparation used consisted of the oesophageal nervous system, the suboesophageal ganglion and the two PSRs, which provide the only source of sensory input. Stimulation of a PSR activates only the oesophageal oscillator located in the ipsilateral commissural ganglion. When spike conduction is blocked in the ipsilateral connective, the stimulation of a PSR activates the contralateral oesophageal oscillator. Inputs from each PSR project to the different parts of the distributed oesophageal network (in the two commissural ganglia and the oesophageal ganglion), but at a given time only one of the PSRs’ projections is effective. The relative efficacy of the PSRs’ projections is controlled by the oesophageal motor network itself and requires that the superior oesophageal nerves be intact (sons). The PSRs’ inputs are integrated in the suboesophageal ganglion before reaching the oesophageal network. However, this premotor step is not involved in the control of the unilaterality of PSRs’ effects. The PSRs are stimulated by at least two different rhythmical muscular sequences of the foregut (the gastric mill sequence and the cardiac sac sequence) and provide a source of rhythmical inputs to the CNS. The oesophageal nervous system exhibits a periodically varying sensitivity to the PSRs’ inputs, which is illustrated by a phase-response curve. Each oesophageal oscillator can be entrained by the rhythmical PSRs’ inputs over a range of period. This range includes the period of the spontaneous gastric rhythm. It is proposed that the PSRs enable the oesophageal and the gastric mill rhythms to be coordinated through a peripheral loop. The participation of PSRs in the coordination of different motor sequences of the foregut is discussed.

Sensory perception in overdenture patients

The discussion of overdentures has been confined to their capacity to use abutment teeth to improve neuromuscular control of mandibular movement. Use of overdentures has been favored often because of their mechanical advantages, but seldom because of the sensory role of the retained abutment teeth. Even though the retained teeth may be periodontally diseased, they still may provide sufficient support for the transmission of masticatory pressures and sufficient periodontal ligament receptors to initiate a jaw opening reflex. Whereas conflicting evidence shows that the periodontal nerve receptors play a role in mandibular positional sensibility (proprioception), pressure perception by the periodontal ligament remains a primary stimulus for the jaw opening reflex. Additional investigations will be essential to a complete understanding of the role of the periodontal ligament receptors. However, recognition of the importance of the periodontal ligament receptors to the overdenture patient as a source of sensory input is vital.