Sources Of Sensory Information Research Articles

Chapter 23 Abnormal postural control associated with peripheral vestibular disorders

The development of a systematic approach to the diagnosis and management of ataxias of vestibular origin depends critically on the elucidation of the complex sensory and motor interactions involved in human postural control. In this paper, the results of studies of both sensory and motor control of posture in adults and children with peripheral vestibular deficits are summarized and reviewed. In studies of the sensory organization of postural control, normal subjects and patients with peripheral vestibular deficits were exposed to unreliable information from their support surface and/or visual surround during quiet stance. While normal adults and children were able to maintain balance under these conditions, the majority of children and adults with peripheral vestibular deficits showed one or both of the following abnormalities: (1)Vestibular loss patients were unable to maintain equilibrium when forced to rely on vestibular information for postural control. (2)Vestibular distortion patients were unable to select an accurate source of sensory information when exposed to sensory conflicts during quiet stance. Preliminary results of studies of motor coordination in these patients also suggest that vestibular loss patients rely almost exclusively on ankle sway to control posture, even during balance tasks which require hip movements to maintain equilibrium. In contrast, some vestibular distortion patients appear to rely on hip motions, even when not required to do so to maintain balance. The results of these studies are discussed in terms of the implications for both sensory and motor aspects of postural control in patients with ataxias of vestibular origin.

Illusory contours from inducers defined solely by spatiotemporal correlation.

Vivid and perceptually salient subjective contours are perceived when inducing (two-dimensional) objects that move and change form so as to "simulate" the presence of an occluding shape are defined solely by (the differences in) temporal correlation in random-dot cinematograms. These effects suggest that subjective contours are due to mechanisms not directly tied to a single source of sensory information, and challenge accounts based on low-level brightness-domain computations.

Functional recovery from lesions in the escape system of the cockroach

1. The cellular basis of the behavioral correction of the cockroach's turning response was studied. 2. Intracellular recordings from cockroaches whose left cercus was ablated were obtained from the left and right giant interneurons (GI's) both before and after the period of behavioral recovery. 3. Five of the seven identified left GI's (no.'s 1, 2, 3, 5, and 6) significantly enhanced their responses to wind (Fig. 1 and 2). The other two (no.'s 4 and 7) did not change significantly (Fig. 2). 4. GI's 1, 2, 3, and 6 recovered about 25% of their normal responses. Their normal characteristic directional curves were well restored (Fig. 3). 5. The major, and possibly the only, source of sensory information to the recovered GI's was the right cercus (Fig. 4). 6. The responses of all the right GI's but one (no. 4) did not change (Fig. 5). Thus the normal left/ right balance of GI activity was partially restored. 7. The number of action potentials in the GI's after the period of behavioral recovery is sufficient to produce turning behavior similar to that of day 30 animals (Figs. 6 and 7). 8. The response latency of axons in the left connective relative to those in the right connective was also greatly improved (Fig. 8). Both the restoration of the balance between the number of action potentials in the left and the right connectives, and the improvement in the relative latency may cooperate in producing the behavioral recovery. 9. Synaptic events that could underlie these physiological changes are discussed.

The vibrissal pad as a source of sensory information for the oculomotor system of the cat.

Responses from lateral rectus, medial rectus and retractor bulbi nerves were obtained following electrical stimulation of the vibrissal pad of the cat. Discharges in afferent fibres dissected from the infraorbital nerve were recorded during movements of the vibrissae and following electrical stimulation of the vibrissal pad. Both stimuli activated the same population of A alpha fibers. Intracellular records were obtained from lateral rectus motoneurones identified antidromically in the principal abducens nucleus and from retractor bulbi motoneurones similarly identified in the accessory abducens nucleus. EPSPs (3 mV) were recorded in lateral rectus motoneurones following electrical stimulation of the ipsilateral vibrissal pad at a latency of 3.5 ms. Large-amplitude disynaptic EPSPs (15 mV) were recorded in retractor bulbi motoneurones following the same vibrissal stimulation. The synaptic excitation evoked in both lateral rectus and retractor bulbi motoneurones through stimulation of the ipsilateral vibrissal pad induced an early retraction followed by an abduction of the eye ball. The hypothesis is that the vibrissal message might complement other sensory modalities in the generation of patterned eye movements.

Texture perception: studies of intersensory organization using a discrepancy paradigm, and visual versus tactual psychophysics.

Three experiments were performed involving the perception of surface texture. Experiment 1 indicated that when vision and touch are presented with discrepant information concerning texture, the two senses appear to weight the information about equally. Moreover, Experiment 2 showed that using touch, vision, or touch and vision, subjects performed a texture identification task with comparable matching accuracy and precision. Experiment 3 demonstrated that using the same three modes, subjects performed a magnitude estimation task similarly, in terms of magnitude estimates of roughness, the rates of growth of perceived roughness, and response precision. The comparability of the two senses in texture-related tasks may underlie the relatively equal compromise between discrepant sources of texture information demonstrated in Experiment (modality superiority interpretation). Such a compromise is somewhat different from that commonly reported in the sensory conflict literature. The relative weighting of multiple sources of sensory information about surface texture was also considered in terms of a directed-attention interpretation of intersensory organization.

Muscle spindles in the human anterior digastric muscle

The occurrence of muscle spindles in the anterior digastric muscle in man was investigated and the fibre calibre spectrum of the corresponding nerve was determined. After removal at autopsy from five individuals of both sexes (aged 23--73), the muscles were stained with Weigert's iron hematoxylin-van Gieson stain and the nerves according to the Alzheimer - Mann - Häggqvist method. Altogether 12 spindles were found in five out of ten muscles. Only muscles from one individual were devoid of spindles. This sparsity or absence was supported by analyses of fibre calibre spectra. The small number of spindles and the fact that they do not occur in all muscles or in all individuals, suggest that they are not an essential source of sensory information.

Occurrence of a muscle spindle in the anterior digastric muscle of a monkey ( Macaca fascicularis)

The muscles from 5 monkeys were examined for spindles. One spindle only was observed, in the middle of the muscle. As spindles in this muscle are absent in various mammals, these receptors cannot be an essential source of sensory information in the anterior digastric muscle, or play a major role in mandibular function.

Prismatically induced curvature and finger-tracking pressure changes in a visual capture phenomenon

A method was developed to help elucidate the manner in which vision exerts a dominant influence over other sources of sensory information. Subjects were required to track a horizontal straight edge with their forefingers while viewing the movements of their limbs through a curve-inducing lens. FiII'ger tracking pressure changes along the edge were transduced and monitored as a function of indtfced curvature orientation (convex-down, convex-up). Findings showed that greater pressure occurred when the finger was located at the low point(s) of the apparent curvature. A trend analysis indicated that the obtained pressure profiles (passive proprioception) contained large quadratic components and were exactly opposite in orientation to the shape of the visual image and subjects' reported felt curvature of the straight edge. Results were discussed in terms of central and peripheral interpretations of visual capture. In most real-life situations, humans process visual spatial information in larger amounts and with greater acuity than any other spatial information. A likely consequence is the experimental finding that when contlicting cues regarding spatial position are encountered by a subject, the resolution is preponderantly in the direction of the visual information in spite of the true state of affairs. Empirical contirmations of the so-called dominance of vision over the other senses have been widely

First-breath response of medullary inspiratory neurones to the mechanical loading of inspiration

Experiments have been conducted to investigate whether electrical activity of medullary inspiratory neurones is altered on the first breath following mechanical loading of inspiration. The predominant effect of resistive loading was an increase in both rate and duration of neurone activity. This facilitation was completely eliminated by vagotomy suggesting that the vagi are the only source of sensory information impinging on the inspiratory neurones conveying information about the loaded breath. In the intact animal, elastic loading and tracheal occlusion elicited the following responses : 1) an extended firing time of all neurones, 2) increased rate of unit activity in one population of neurones, 3) a decreased rate of unit activity in another population of neurones. Following vagotomy the only response noted with these types of loading was a decrease in the firing rate of some neurones. A probable source of the observed inhibition are the tendon organs of the diaphragm and /or external intercostal muscles via dorsal root pathways.