Biomedical subjects

R Maulucci

Publications and source records attributed to R Maulucci.

3 recordsLinked to original sources

PubMed1982

Development and plasticity of visual and vestibular generated eye movements.

Slow phase horizontal eye movements, elicited by the vestibulo-ocular reflex (VOR) and/or visual pursuit (VP) systems, were examined in normal children (NC, 9-16 years) and normal adults (NA). At slow frequencies of sinusoidal stimulation of the body (with the head immobilized) and/or of a visual target, the NC (9-12 years) exhibited (a) immature VP and VOR Suppression and mature VOR Enhancement in the presence of a visual image; (b) immature VOR Suppression and mature VOR Enhancement in the presence of a non-visual image of the spatial location of a visual target, an extra-retinal signal; (c) inability to augment or depress the VOR gain with a non-visual image; (d) mature VOR Suppression ratios; and (e) adjustment of VOR gain to a high value. The maturational process was featured by (a) parallel development of VP and VOR Suppression; (b) modification of the VOR gain; and (c) an increasing ability to augment or depress the VOR with a non-visual image. The observations in NC (9-12) are ascribed to a maturational lag of an extra-retinal process interacting with mature retinal and vestibular processes and, hence, suggest that both the retinal and vestibular contributions to ocular stability predate the development of an extra-retinal signal. When mature, the central nervous system utilizes both extra-retinal and retinal signals to mediate adaptive regulation of VOR gain and to preserve stable visual pursuit motion and VOR Suppression. Our findings also suggest that during tasks requiring visual-vestibular interaction, VP and VOR mechanisms appear to be indirectly rather than directly coupled.

Adolescent↗

PubMed1981

Visually triggered eye-arm movements in man.

The degree of temporal coupling and the nature of temporal ordering between the gaze (eye-head) and arm motor systems was studied in normal subjects by measuring the reaction time, RT, of each system to randomly generated visual signals presented along the horizontal meridian: (1) at two spatial locations, 15.5 degrees and 29.1 degrees, (2) to the right and left of a central fixation point, and (3) with and without room illumination. Upon detecting the visual signal, the subject was instructed to guide the arm from its rest position upon a supporting table and to extinguish the light source by touching a metal disc enclosing the stimulus "as quickly and accurately as possible." The results indicated (1) saccadic eye motion initiated gaze towards the target, (2) a change in the eccentric position of the target was associated with alteration of the eye and arm RT by a similar value; the interval between eye and the subsequent arm RT was invariant with spatial location no matter the presence or absence of room illumination, and (3) the arm RT increased when visual information of the environment was not available. It is postulated that a visual stimulus triggers a command system releasing a patterned sequence of eye-hand-arm motion; the initiation of motion in these motor systems is based upon the same retinal error calculation; however, no rigid rule can be established for the serial ordering or temporal sequencing of motion between the triggered motor systems. The temporal arrangement between head and arm with eye can be modified, at least in part, by alterations in supraspinal control of postural mechanisms and/or motoneuronal excitability of the responding muscles prior to motion.

Adolescent↗

PubMedDate not supplied

Idiopathic scoliosis and the central nervous system: a motor control problem. The Harrington lecture, 1983. Scoliosis Research Society.

An etiologic concept linking an impaired axial motor control system to the structural deformity of idiopathic scoliosis (ISc) is proposed. Postural studies reveal that during quiet stance, adaptation is marked in conditions associated with visual control of sway, particularly of lateral sway; during imposed perturbations of the body, destabilized postural reactions are pronounced in tests requiring visual-vestibular coupling. Observations of visual and/or vestibular generated eye movements indicate ocular instability among a high proportion of the ISc. Previously, the authors argued that a direct relationship exists between visual and/or vestibular functioning and a disordered axial motor system. This was attributed to an aberrant brain stem mechanism. In this presentation, however, we propose that a higher level CNS disturbance may be responsible for reports of EEG abnormalities, visuo-spatial impairment, motor adaptation, and learning deficits. Among the wide range of visual-vestibular variables studied, those representing processing of vestibular signals within the CNS yield the highest degree of correlation with the magnitude of the curve. Moreover, differences in vestibular processing between two subsets of ISc, namely ISc with (70%) and without (30%) normal academic achievement are significant. Variables referable to both vestibular and visual processing correctly classify 87% of the ISc with normal academic achievement and 100% of the ISc with a history of academic problems. The association between learning deficits, altered processing of vestibular information, and ISc suggest a unique syndrome complex, and an important role of cortical structures in the etiology of this disorder. The presence of a visuo-spatial perceptual impairment may be the common feature of ISc. In an attempt to restore perceptual dysfunction (by rearrangement), the ISc adopts a new axial and vestibular motor control strategy based upon recalibration or reinterpretation of proprioceptive signals arising from the axial musculature.

Adaptation, Physiological↗