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Biomedical subjects

J H Abbs

Publications and source records attributed to J H Abbs.

At least 19 recordsLinked to original sources
PubMed1992

Dysarthria associated with focal unilateral upper motor neuron lesion.

Speech motor changes in six patients with focal unilateral upper motor neuron (UUMN) lesions were characterised using a variety of techniques including listener judgements, speech acoustic analyses, electromyographic and strength measures. Listener judgements of speech understand-ability, intelligibility and dysarthric features indicated mild dysarthria. Diadochokinesis, electromyographic and strength measures corroborated these observations. The findings of this study delineate the characteristics of the dysarthria associated with unilateral upper motor neuron lesions and have important implications for identifying potential upper motor neuron components of other neurogenic disorders of speech and language.

Aged↗
PubMed1991

Influences of object weight and instruction on grip force adjustments.

This study investigated the influence of object weight and instructions on grip force responses in humans. Using a precision grip, subjects lifted a small instrumented test object to a predetermined height. Prior to each set of 40 trials, subjects were verbally instructed to either "hold" or "let go" of the object in response to any change in weight. Unpredictably on some trials (less than 20%), a sudden sustained increase (load) or decrease (unload) in vertical load was applied to the object. Grip responses to these induced weight changes were evaluated by measuring grip force, object position, and associated electromyographic (EMG) activity. Grip force changes for a load were over three times greater than those for an unload. Such asymmetry may reflect everyday grasp and manipulation in a gravity-influenced world. Grip force adjustments to loads following "hold" instructions were on the average somewhat larger than those following "let go" instructions, but there was no influence of instructions on responses to unloads. These findings contrast with more robust influences of verbal instruction on automatic postural and proximal upper limb responses and also may suggest that grip force adjustments are influenced to a greater extent by intrinsic task variables than by extrinsic volitional intent. Such organization appears tailored to functional task requirements in natural environmental contexts.

Adult↗
PubMed1991

Kinaesthetic acuity of stutterers and non-stutterers for oral and non-oral movements.

Six adult stutterers and six normal speakers were instructed to make the smallest possible movements of the jaw, lower lip, tongue and right index finger, both with and without continuous visual feedback. In the non-visual (kinaesthetic) condition, the stutterers showed significantly larger minimal displacements (MDs) than did the non-stutterers for oral but not for finger movements. However, movements made in the presence of visual feedback were consistently smaller for all subjects than those made without, and no differences in MD were found between the stutterers and the non-stutterers when visual feedback was provided. The results suggested the presence of a sensorimotor deficit among at least some adult stutterers that is confined to oral movements. Given the importance of somatic sensory feedback during speech production, these observed orosensory deficiencies among stutterers may provide important insights into causal factors which contribute to the breakdowns in stutterers' speech.

Adult↗
PubMed1991

Influence of speaking rate on the upper lip, lower lip, and jaw peak velocity sequencing during bilabial closing movements.

Upper lip, lower lip, and jaw movements were recorded in five adult speakers for repeated sequences of the utterance [bae] at different speech rates. The results failed to confirm several earlier reports of an invariant upper lip, lower lip, jaw peak velocity sequencing pattern for bilabial closures. While the earlier reported sequence was the most frequent, a wide variety of different sequences was also commonly observed. In addition, significant intersubject differences in sequencing were found. The present results thus do not support the earlier hypothesis that oral closure gestures reflect aspects of a centrally generated pattern of motor output during speech.

Adult↗
PubMed1991

Finger movement responses of cutaneous mechanoreceptors in the dorsal skin of the human hand.

1. The movement sensitivity of dorsal skin mechanoreceptors in the human hand was studied by the use of single afferent recording techniques. 2. Units were classified as slowly (SA) and fast adapting (FA) and further characterized by thresholds to vertical indentation and by receptive-field sizes. Whereas SA units were evenly distributed within the supply area of the superficial branch of the radial nerve. FA units were usually situated near joints. 3. The proportion of different receptor types (32% SAI, 32% SAII, 28% FAI, 8% FAII; n = 107) compared favorably with previous electrophysiological and anatomic data, arguing for minimal sampling bias. The majority of the skin mechanoreceptive units were SA, largely due to a relative scarcity of FAII [Pacinian corpuscles (PC)] units. 4. A large majority (92%) of the afferents responded to active hand or finger movements. Responses in all unit types were consistent with observed movement-induced deformations of their receptive fields. 5. FAI units responded bidirectionally, albeit usually with somewhat higher discharge frequencies for finger flexion, which in most cases were associated with skin stretch. FAI units showed meager responses to remote stimuli, typically responding to one or, at the most, two adjacent joints. 6. SA units typically showed simple directional responses to joint movements with an increased discharge during flexion and a reduced discharge during extension. Joint movement that influenced the skin within the receptive field of SA units elicited graded responses even if the field, as assessed by perpendicular indentations, was minute. This finding suggests that definition of cutaneous receptive fields by classical perpendicular indentations may be inappropriate for the receptors in the hairy, nonglabrous skin. 7. The interpretation of the data from these recordings suggests that cutaneous mechanoreceptors in the dorsal skin can provide the CNS with detailed kinematic information, at least for movements of the hand.

Adaptation, Physiological↗
PubMed1991

Task-dependent variations in parkinsonian motor impairments.

Studies of visually-guided arm movements in patients with Parkinson's disease (PD) have suggested a relationship between slowness of movement and a reduction in the ratio of movement amplitude and peak velocity. Recent studies indicate, however, that PD impairments may be different for well-learned, natural movements performed without visual guidance, or movements associated with sequential motor behaviours such as speech. To address this issue, PD subjects and age/sex-matched controls were compared on the performance of three tasks, all of which required lowering the jaw: (1) single, rapid, visually-guided movements; (2) equivalent movements associated with a single speech syllable (inherently without visual guidance), and (3) well-learned speech movements produced in a natural sequence. PD subjects manifested similar deficits for visually-guided jaw lowering as those previously reported for arm movements, namely reduced velocity/amplitude ratios and increased movement durations. By contrast, analogous jaw movements during the sequential speech tasks were unimpaired on these measures. These results suggest that PD motor impairments are influenced by a variety of factors, including the degree to which tasks are familiar and natural, and the availability of visual information.

Adult↗
PubMed1990

Musculotopic organization of the facial motor nucleus in Macaca fascicularis: a morphometric and retrograde tracing study with cholera toxin B-HRP.

Morphometric and retrograde tracing methods were used to determine the location and number of motoneurons innervating individual facial muscles in Macaca fascicularis. Intramuscular injections of the cholera toxin B subunit-horseradish peroxidase conjugate produced discrete labeling patterns in the ipsilateral facial motor nucleus with good definition of somata and their processes. The facial nucleus extended rostrocaudally in the pons for about 2 mm, varying in shape and cross-sectional area along this axis. Motoneurons were clustered in subnuclei, but their boundaries were not sharp and they were not segregated by fiber bundles. The length, number, and area of subnuclei varied with rostrocaudal location. Retrograde labeling patterns revealed that individual muscles were innervated by longitudinal columns of motoneurons with each muscle region represented at all rostrocaudal levels of its column. The columns began at different rostrocaudal levels and varied in length. Columns for closely related muscles, such as the orbicularis oris and mentalis of the lower lip, tended to overlap, whereas columns for disparate muscles, such as the perioral and orbital, did not overlap. The dendritic processes of most motoneurons branched extensively among several different columns or subnuclei. Some dendrites extended outside of the nucleus into the surrounding tegmentum. Mean soma diameter (10.4-42.2 microns) was distributed unimodally, reflecting the absence of gamma motoneurons and lack of muscle spindles in the facial muscles. Large and small motoneurons were found in all regions of the nucleus, but the largest ones were located caudally and innervated muscles of the upper and lower lip. The perioral muscles also had more neurons, longer columns, and a lower cell density than the other muscle groups examined. These features may reflect the functions of the perioral muscles in facial expression and vocalization.

Animals↗
PubMed1990

Uniform frequency of parkinsonian resting tremor in the lips, jaw, tongue, and index finger.

Parkinsonian resting tremor was examined in the lips, jaw, tongue, and index finger using electromyography (EMG) and displacement transduction. Long-term spectral averaging of tremor movement and EMG signals revealed that resting tremor frequencies were remarkably uniform across these orofacial and hand structures within the same parkinsonian subjects. However, marked variability in tremor spectral amplitude across structures and subtle moment-to-moment variations in tremor period, amplitude, and waveform shape were also observed. Although these observations argue for a central source of tremor, it appears that interactive central and/or peripheral neural circuitry may yield variations in tremor characteristics.

Aged↗
PubMed1990

Sensorimotor contributions of the basal ganglia: recent advances.

In the last decade, a great deal of research has been aimed at ascertaining the manner in which the basal ganglia (BG) contribute to the control of movement. The formation of workable hypotheses, however, has been limited by the great variety of putative roles reported in the literature. Reported functions have often been in direct conflict. Recent developments, however, provide new perspectives from which to view seemingly discordant functions. Data reviewed in this article suggest a distinct anatomical topography within the BG, allowing for highly specialized subfunctions. In parallel, BG cellular activity has been found primarily in association with specific sensory and task-related dimensions relevant to particular movements. The multiple sensorimotor contributions of the BG therefore are not contradictory, but represent BG contributions within different functional contexts. These multiple roles of the BG offer particular clinical insights.

Basal Ganglia↗
PubMed1989

Sensorimotor characteristics of speech motor sequences.

The present experiment focused on the characteristics of sequential speech movements. Subjects generated two successive lip and jaw closing movements associated with the two 'p's' in 'sapapple'. By selectively manipulating the lower lip perturbation it was possible to discern the role of somatic sensory interactions with the presumed sequential movement programming. Lower lip perturbation duration was manipulated to yield two different load conditions. In the Load On (LN) condition, the perturbation remained on for both closing movements. In the Load On/Off (LNF) condition, the perturbation was removed at variable times prior to the second closing movement. Analyses focused on comparing the EMG and resulting kinematic changes for the second "p" closure across the two load conditions relative to the normal control (no load) condition. The second "p" closure was differentially affected by the load conditions resulting in changes in the upper and lower lip compensations. Upper lip changes reflected consistent load duration differences; however, the magnitude of the lower lip EMG and kinematic adjustments did not mirror those of the upper lip. In contrast to the differential upper lip/lower lip changes observed for the magnitude adjustments, timing adjustments were similar for both upper lip and lower lip suggesting a separation between the specification of magnitude and timing of speech movements. Differential load effects were also observed for the timing of the second closing movements. For the LN condition, the onset of muscle activity and subsequent movement occurred earlier (re: control); for the LNF condition, load removal delayed the onset of muscle activity and the subsequent movement (re: control). Further, the opening movement preceding the second closing movement was modified for both load conditions suggesting that all movements in the sequence, not just closing movements, can be modified. The present results suggest that the programming of speech movement sequences is a dynamic process involving scaling and timing of motor commands relying on various degrees of sensory interaction. The apparent separation in the magnitude and timing specification of the movement sequences suggests the parallel influences of different neural systems. The consequence of this control scheme is that specification of movement parameters for sequential motor acts is a flexible real-time sensorimotor process interacting with less-flexible well-established central motor relations. Further, motor program for speech may reflect certain generalized movement actions (e.g., oral opening, oral closing) rather than individual words, syllables, or other linguistic categories programmed on a movement-to-movement basis.

Adult↗
PubMed1989

Parkinsonian deficits in serial multiarticulate movements for speech.

Unlike the single joint arm movements so commonly the focus of Parkinson's disease (PD) studies, orofacial movements for speech are well-learned, complex motor sequences generated without visual guidance. The present study of upper lip, lower lip, and jaw movements during speech in PD was thus aimed at determining whether (1) PD speech kinematic deficits are comparable to those often observed in simpler limb movements; (2) coordination for multimovement actions such as speech is aberrant in PD, as recently claimed; and (3) the component muscle groups involved in this behaviour manifest uniform deficits. Results indicated that despite reduced amplitudes of jaw and upper lip displacement in PD subjects, all three of these oral movements were of normal duration. Secondly, PD lower lip movements manifested no deficits and bradykinesia (reduced velocity) was only found in movements of the jaw. Finally, there was an indication of movement coordination aberrations in these parkinsonian subjects. Overall, these results not only suggest a difference between orofacial and limb movement impairments in PD, but also document the need to broaden our perspectives on this movement disorder by examining a wider range of functional motor tasks.

Aged↗
PubMed1989

Neuronal RNA in nucleus ambiguus and nucleus hypoglossus of patients with amyotrophic lateral sclerosis.

To establish objectively the involvement of neurons in the medulla oblongata in patients with amyotrophic lateral sclerosis (ALS), ribonucleic acid (RNA) content was determined in neurons of the hypoglossal nucleus and the nucleus ambiguus. Neurons from those two nuclei showed a significant loss of RNA content in patients with ALS; only 57% and 38% of the normal RNA content was found in hypoglossal and ambiguus neurons, respectively. This marked loss of neuronal RNA suggests changes in functional states of neurons, which may contribute to fasciculations in the tongue and difficulties in swallowing often associated with ALS.

Adult↗
PubMed1988

Kinematic variability of grasp movements as a function of practice and movement speed.

Grasp movements were studied in six female subjects to determine the effects of practice and movement speed on kinematics and movement variability. Subjects performed four-joint pinch movements of the index finger and thumb, with 200 repetitions at each of three durations (100, 200, and 400 ms). As observed previously, movements of high velocity were performed with bell-shaped, single-peaked velocity profiles. In contrast, slower movements (approximately 200, 400 ms) were performed as a series of two to four submovements with multiple peaks in the associated joint angular velocity profiles. With practice, only the slowest movements (400 ms duration) showed significant reductions in variability of joint end-positions. Surprisingly, variability of finger and thumb joint end-positions did not increase with increasing movement speed as has been observed for arm pointing movements. This was apparently due to reductions in positional variability during deceleration of the movement which offset increases in positional variability during acceleration. Neither practice nor movement speed affected variability of the location of fingertip contact on the thumb, which always occurred on the thumb distal pulpar surface.

Adolescent↗
PubMed1988

Mechanoreceptive afferent activity in the infraorbital nerve in man during speech and chewing movements.

The method of microneurography was used to record activity in trigeminal cutaneous and mucosal mechanoreceptive afferents during natural orofacial behaviors such as speech gestures, chewing, licking and swallowing. Multi-unit activity and impulses in single nerve fibers were recorded from the infraorbital nerve. It appeared that these mechanoreceptors respond to contact between the lips, air pressures generated for speech sounds, and to the deformation/strain changes of the facial skin and mucosa associated with various phases of voluntary lip and jaw movements. The relatively vigorous discharge of cutaneous and mucosal afferents during natural movements of the face are consistent with the claim that mechanoreceptors found within the facial skin provide proprioceptive information on facial movements.

Action Potentials↗
PubMed1988

Central patterning of speech movements.

Previous speech kinematic studies have demonstrated systematic timing relations among the upper lip, lower lip, and jaw suggesting the operation of a central pattern generator (CPG). The present study evaluated the consistency of these timing relations following unanticipated perturbation of the lower lip. Using this approach, it was also possible to evaluate the influence of sensory information on the timing of motor output and subsequent coordination of the multiple speech movements. Perturbations were applied to the lower lip during the closing movement associated with the first "p" in "sapapple". Muscle activity and movements of the upper lip, lower lip, and jaw were obtained. Changes in movement displacement, velocity and duration, the timing and sequencing of peak velocities, EMG area, and EMG rise time were analyzed for the control and load conditions. Similar to previous perturbation results, significant magnitude compensations from the muscles and movements of the upper lip, lower lip, and jaw were observed. In contrast, movement durations and the sequencing of peak velocities were relatively unaffected by the lower lip load. The timing of peak EMG amplitude and consequently the timing of peak closing velocity for all structures (UL, LL, and J) occurred earlier relative to the preceding opening movement. These results are consistent with the interaction of phasic sensory input with centrally-driven commands resulting in a phase-advanced motor output. Further, as the timing of one structure is modified so were all the functionally-linked components thereby maintaining the necessary coordination. As in other rhythmic motor behaviors such as locomotion and chewing, there appears to be a centrally patterned framework for speech movement coordination.

Adult↗
PubMed1988

Kinematic analysis of multiple movement coordination during speech in stutterers.

This study addresses the long-standing claim that stuttering reflects an impairment in the neuromotor coordination of multiple speech movements. Upper lip (UL), lower lip (LL), and jaw (J) kinematics for nonstuttered speech behaviours in stutterers and normal speakers were examined using quantitative indices of normal multiple movement coordination reported in recent studies of gait, reaching, grasping, and speech. While two measures of coordination--dynamic movement composition and intermovement motor equivalence--did not distinguish between stutterers and normals, stutterers manifested striking differences from normal on a third measure, the sequencing of UL, LL, and J movement onsets and velocity peaks. These findings suggest that, contrary to previous hypotheses, stutterers do not manifest general problems of coordination of speech movement. Instead, stuttering appears to be associated with a specific impairment in multiple movement coordination associated with sequencing of those movements.

Adult↗
PubMed1988

Deficits in the production of grip forces in Down syndrome.

Down syndrome (DS) and control individuals were examined as to their ability to adapt grip forces to changes in the properties of lifted objects. The DS group generated substantially greater grip forces than the controls in all tests and failed to adapt normally to changes in the frictional properties of the objects. Their greater grip forces were not due to greater slipperiness of the skin of their fingers. These results are consistent with other findings of subtle deficits in DS individuals' use of somatosensory information for controlling movement and posture.

Adolescent↗