Quantifying muscle activity in non-ambulatory children with spastic cerebral palsy before and after selective dorsal rhizotomy

Cerebral palsy is a condition that results in varying degrees of functional deficits. The goal of this study was to develop an objective measure of muscle activity during a prescribed voluntary motor task in non-ambulatory children with spastic cerebral palsy. While performing a simultaneous hip/knee flexion task from the supine position, followed by return to the starting position, electromyographic and kinematic data were obtained from the right leg of eight children before and after selective dorsal rhizotomy and compared with eight age-matched controls. The electromyographic and kinematic data were combined to determine for each muscle of interest (tibialis anterior, soleus, vastus lateralis, biceps femoris) the percentage of the movement cycle for which the muscle was acting concentrically, eccentrically, isometrically or was considered inactive. Averaged over the four muscles, isometric activity decreased by 38% post-op and the time the muscles were inactive increased by 37% following surgery. The percentages of concentric and eccentric activity did not differ significantly between pre- and post-op conditions. Post-operatively, the percentage muscle activity patterns of the children with cerebral palsy more closely resembled that of the control children: averaged across all muscles and contraction types, the difference between the control children and the children with cerebral palsy was reduced by 50% following surgery. This measurement technique indicates promise as a method for quantifying muscle activity during voluntary motor tasks in non-ambulatory children with cerebral palsy.

Prosodic correlates of stress in babbling: an acoustical study

Prelinguistic babbling often seems remarkably speech-like, not because it has recognizable words but because it seems to have adult-like prosody. To quantify this impression, we compared disyllabic sequences from five infants and five adults in terms of the use of frequency, intensity, and duration to mark stress. Significantly larger values for the three acoustic variables were observed on stressed than on unstressed syllables independent of syllable position for both groups. Adults showed the correlates of utterance final syllables--lower f0, lower intensity, and longer duration; infants showed only decrease in intensity. Ratios for stressed to unstressed syllables and participation of the three variables in stress production in individual disyllables were highly similar in both groups. No bias toward the English lexical trochaic stress pattern was observed. We conclude that infants in English environments produce adult-like stress patterns before they produce lexical items, which specify stress. Acoustic and perceptual analyses are used to explore stress marking by prelinguistic infants in an English language environment. Results show that infants employ the three acoustic correlates of stress in individual syllables in a manner largely similar to that of adult speakers, although they do not show second-syllable declination effects or an English language trochaic stress bias.

On the origin of internal structure of word forms

This study shows that a corpus of proto-word forms shares four sequential sound patterns with words of modern languages and the first words of infants. Three of the patterns involve intrasyllabic consonant-vowel (CV) co-occurrence: labial (lip) consonants with central vowels, coronal (tongue front) consonants with front vowels, and dorsal (tongue back) consonants with back vowels. The fourth pattern is an intersyllabic preference for initiating words with a labial consonant-vowel-coronal consonant sequence (LC). The CV effects may be primarily biomechanically motivated. The LC effect may be self-organizational, with multivariate causality. The findings support the hypothesis that these four patterns were basic to the origin of words.

Deriving speech from nonspeech: a view from ontogeny

A comparison of babbling and early speech, word patterns of languages, and, in one instance, a protolanguage corpus, reveals three basic movement patterns: (1) a 'Frame' provided by the cycles of mandibular oscillation underlying the basic mouth close-open alternation of speech; this Frame appears in relatively 'pure' form in the tendency for labial consonants to co-occur with central vowels; (2) two other intracyclical consonant-vowel (CV) co-occurrence patterns sharing the alternation: coronal consonants with front vowels and dorsal consonants with back vowels; (3) an intercyclical tendency towards a labial consonant-vowel-coronal consonant (LC) sequence preference for word initiation. The first two patterns were derived from oral movement capabilities which predated speech. The Frame (1) may have evolved from ingestive cyclicities (e.g. chewing). The intracyclical consonant-vowel (CV) co-occurrence patterns involving tongue position constraints common to consonants and vowels (2) may result from the basic biomechanical property of inertia. The third pattern (LC) was a self-organizational result of pressures for interfacing cognition with action - a result which must have numerous analogs in other domains of movement organization.

An embodiment perspective on the acquisition of speech perception

Understanding the potential relationships between perception and production is crucial to explanation of the nature of early speech acquisition. The 'embodiment' perspective suggests that mental activity in general cannot be understood outside of the context of body activities. Indeed, universal motor factors seem to be more responsible for the distribution of early production preferences regarding consonant place and manner, and use of the vowel space than the often considerable cross-language differences in input available to the perceptual system. However, there is evidence for a perceptual basis to the establishment of a language-appropriate balance of oral-to-nasal output by the beginning of babbling, illustrating the necessary contribution of 'extrinsic' perceptual information to acquisition. In terms of representations, at least one assumption that segmental units underlying either perception or production in early phases of acquisition may be inappropriate. Our work on production has shown that the dominant early organizational structure is a relatively unitary open-close 'frame' produced by mandibular oscillation. Consideration of the role of 'intrinsic' (self-produced) perceptual information suggests that this frame may be an important basis for perceptual as well as production organization.

Obesity and osteoarthritis of the knee: hypotheses concerning the relationship between ground reaction forces and quadriceps fatigue in long-duration walking

The principal risk factors of osteoarthritis of the knee are: age, obesity and gender. It is hypothesized that long-duration walking (e. g. 20 min) in the elderly obese will lead to quadriceps fatigue. Changes in the gait pattern due to fatigue will lead to altered knee kinematics at heelstrike and consequently decreased shock absorption. This scenario will result in an increased rate of loading and possibly an increase in the overall magnitude of peak ground reaction forces, both of which could cause articular cartilage degeneration. Obese females are at an overall higher risk of developing osteoarthritis than males. This gender discrepancy may be explained by the fact that females have a higher percentage of body fat content (lower proportion of lean mass) that may increase the rate of quadriceps fatigue. These biomechanical hypotheses can be examined by studying continuous periods of walking in which ground reaction forces, knee kinematics and electromyography data are recorded.

The motor core of speech: a comparison of serial organization patterns in infants and languages

Comparison of serial organization of infant babbling and early speech with that of 10 languages reveals four movement-related design features reflecting a deep evolutionary heritage: (1) the cyclical consonant-vowel alternation underlying the syllable, a "Frame" for speech consisting of mandibular oscillation, possibly evolving from ingestive cyclicities (e.g., chewing) via visuofacial communicative cyclicities (e.g., lipsmacks); (2) three intracyclical consonant-vowel co-occurrence preferences reflecting basic biomechanical constraints-coronal consonants-front vowels, dorsal consonants-back vowels, and labial consonants-central vowels; (3) a developmental progression from above-chance to below-chance levels of intercyclical consonant repetition; (4) an ease-related labial consonant-vowel-coronal consonant sequence preference for word initiation. These design features presumably result from self-organizational responses to selection pressures, primarily determined by motor factors. No explanation for these design features is available from Universal Grammar, and, except for feature 3, perceptual-motor learning seems to have only a limited causal role in acquisition of any design feature.

Characterization of the calcaneal fat pad in diabetic and non-diabetic patients using magnetic resonance imaging

It is well known that diabetic patients have a high incidence of foot ulceration. The purpose of this study was to determine whether magnetic resonance (MR) imaging can detect changes in the composition of the calcaneal fat pad in diabetic feet. MR data were collected in vitro from amputated specimens (eight from diabetic patients and eight from non-diabetic patients) as well as in vivo from age-matched diabetic and control subjects (four subjects each group.) Three types of images were acquired: spin lattice (T1), spin-spin (T2), and magnetization transfer (MT). The in vitro results showed statistically significant differences in the T1, T2, and MT parameters between the two disease groups. The same trends were shown in the study of live subjects but the differences were not statistically significant. The differences are believed to arise from changes in the composition of the tissues as a result of the progression of diabetes.

A biomechanical evaluation of one-stage vs two-stage bilateral knee arthroplasty patients

In this study the functional abilities of eight one-stage bilateral total knee replacement (TKR) patients were compared to five two-stage bilateral TKR and nine control subjects. The TKR individuals were an average of 62 months post-operative. Based on gait analysis, ground reaction force profiles during walking and isometric knee strength assessment, the one-stage individuals did not differ significantly from the control subjects. The two-stage individuals had significantly less knee range of motion during gait and smaller vertical ground reaction forces during the braking phase than the control and one-stage individuals. To compare left and right sides, a symmetry index was computed and there were no significant differences among the three groups. Based on the variables tested in this biomechanical evaluation it can be concluded that for individuals facing bilateral knee replacement a one-stage procedure can result in functional capabilities at least comparable to a two-stage procedure.

Is there a "trochaic bias" in early word learning? Evidence from infant production in English and French

Studies of speech perception and segmentation in the prelinguistic period, early word production, and patterns of function word omission in early syntax have all recently emphasized the role of the trochaic accentual pattern in English, sometimes positing a universal trochaic bias. We make use of perceptual and acoustic analyses of words and babble from 9 children acquiring English and 5 acquiring French in the late single-word period (13-20 months) to provide a direct test for the existence of such a bias. Neither English nor French infant vocalizations were exclusively trochaic. The iambic productions of American infants were traced to the presence of iambic phrases in the input. Differences between English and French in the acoustic realization of accent in infant vocalizations were also traceable to adult patterns. However, the almost bipolar distribution of trochaic and iambic patterns in the data from English-learning infants was ultimately traceable to the integration of prosodic and segmental patterning in individual child word production templates, themselves arguably the product of an earlier acting articulatory filter.

Inhaled nitric oxide versus conventional therapy: effect on oxygenation in ARDS

A randomized, controlled clinical trial was performed with patients with acute respiratory distress syndrome (ARDS) to compare the effect of conventional therapy or inhaled nitric oxide (iNO) on oxygenation. Patients were randomized to either conventional therapy or conventional therapy plus iNO for 72 h. We tested the following hypotheses: (1) that iNO would improve oxygenation during the 72 h after randomization, as compared with conventional therapy; and (2) that iNO would increase the likelihood that patients would improve to the extent that the FI(O2) could be decreased by > or = 0.15 within 72 h after randomization. There were two major findings. First, That iNO as compared with conventional therapy increased Pa(O2)/FI(O2) at 1 h, 12 h, and possibly 24 h. Beyond 24 h, the two groups had an equivalent improvement in Pa(O2)/FI(O2). Second, that patients treated with iNO therapy were no more likely to improve so that they could be managed with a persistent decrease in FI(O2) > or = 0.15 during the 72 h following randomization (11 of 20 patients with iNO versus 9 of 20 patients with conventional therapy, p = 0.55). In patients with severe ARDS, our results indicate that iNO does not lead to a sustained improvement in oxygenation as compared with conventional therapy.

Nasalization of vowels in nasal environments in babbling: evidence for frame dominance

An emerging concept for the characterization of the form of babbling and early speech is 'frame dominance': most of the variance arises from a frame provided by open-close mandibular oscillation. In contrast, the tongue - the most versatile articulator in adults - plays only a minor role in intersegmental and even intersyllabic changes. The contribution of another articulator - the soft palate - to time-domain changes in babbling was evaluated in an acoustic analysis of 433 consonant-vowel-consonant sequences produced by 3 infants. Strong nasal effects on vowels in symmetrical consonantal environment were observed in the form of a lower frequency first formant region in low vowels and a lower frequency second formant region in front vowels. These results, the first of which also occurs in adults, were complemented by perceptual tendencies for transcribers to transcribe more mid vowels relative to low vowels and more central vowels relative to front vowels in nasal environments. Thus the soft palate is like the tongue in making only minor contributions to time-domain changes in babbling, and this is considered to be additional evidence for the frame dominance conception.

Early prediction of prolonged ventilator dependence in thermally injured patients

BACKGROUND

Recent studies suggest that when prolonged ventilator dependence (PVD) can be predicted in trauma or intensive care unit patients, early tracheostomy may reduce hospital stay and improve utilization of resources. This study was performed to develop criteria predictive of PVD (> 14 days) in burn patients.

METHODS

We reviewed burn patients aged > or =16 years admitted between 1990 and 1994 who required ventilator support for > or =3 days. Using the variables full-thickness burn size, age, inhalation injury, and worst PaO2/FiO2 on ventilator day 3, an equation predicting PVD was created using logistic regression. The equation was tested by applying it to 1995 patients.

RESULTS

When a probability of >0.5 was considered predictive of PVD, the equation correctly predicted PVD in 82% of 1990 to 1994 patients (n = 110) and 90% of 1995 patients (n = 29).

CONCLUSION

PVD in burn patients can be predicted using objective variables in the early postburn period. Predictions can be used to select patients for prospective studies of early tracheostomy.

Increasing retention rates of disadvantaged students through a faculty development program

Efforts to recruit disadvantaged students have been increasing over the past three decades. How to retain those students once they have been recruited remains a critical issue for faculty. The authors include a Faculty Development Model presently being implemented at an inner city community college to increase faculty's expertise in enhancing the skills and abilities of students from diverse backgrounds with an emphasis on the disadvantaged student.

Effects of age, density, and geometry on the bending strength of human metatarsals

In this basic study, we investigated the relative roles of donor age, bone density, and bone geometry in determining structural strength of human metatarsals tested in a four-point bending configuration. Density measurements were made noninvasively using dual energy X-ray absorptiometry, and geometric measurements were made by digitally imaging cross-sections of specimens. Correlations between area bone mineral density and metatarsal strength were strong (r2 = 0.83, 0.81 for second and third metatarsals, respectively) and were not improved by including cross-sectional area or minimum moment of inertia in multiple regression analyses. Increased donor age was associated with decreased bending strength (r2 = 0.51 and 0.45, respectively), which was expected because increased age correlated significantly with decreased bone density (r2 = 0.69 and 0.80, respectively). These results indicate that the strength of human metatarsals generally decreases with age and that this decrease is likely attributable to decreased bone density. Moreover, the results indicate that noninvasive dual energy x-ray absorptiometry measurements of metatarsal density are useful for assessing metatarsal strength and that additional measurements of bone geometry are not required.

Production constraints on utterance-final consonant characteristics in babbling

In order to evaluate hypotheses regarding production constraints on final consonants in babbling, 721 utterance-final consonants produced by 6 infants in consonant-vowel-consonant (CVC) syllables were examined and compared with the preceding consonant in the CVC. Consistent with earlier studies, major patterns were observed for each of the three main consonantal properties--place and manner of articulation and voicing. These patterns included a strong tendency for final consonants to repeat the place of articulation of nonfinal consonants and a tendency for relatively more fricative, nasal and voiceless consonants to occur in final position than in nonfinal position. The high frequency with which final consonants shared place of articulation with the preceding consonant was considered to reflect 'frame dominance' or the tendency of a relatively constant mandibular cycle (the frame) to determine the structure of utterances with very little contribution from other active articulators. The manner and voicing effects were attributed to an overall terminal energy decrease in the vocal production system.

Use of an instrumented treadmill for real-time gait symmetry evaluation and feedback in normal and trans-tibial amputee subjects

The purpose of this research was to evaluate a newly developed system for assessing and providing feedback of gait symmetry information in real time to subjects walking on a motorised treadmill (the CCF Treadmill). The advantages of the system are that it allows the rapid collection and comparison of temporal and kinetic parameters of gait for multiple successive strides, at a constant known speed, without forcing subjects to target their footsteps. Gait asymmetries of six normal (mean age 42.7 years) and six unilateral transtibial amputee subjects (mean age 41.7, and average 6.0 years using a prosthesis) were quantified. The amputee group was the reevaluated after receiving five minutes of training with each of three different types of real-time visual feedback (RTVF). Asymmetries in the measured parameters before feedback were 4.6 times greater in the amputee population than in the normal group, and were consistent with the finding of previous authors. Significant decreases in gait asymmetry were demonstrated for all forms of feedback after amputees received feedback training. Results, however, indicated that gait asymmetries for different variables are not necessarily related, and that more work needs to be done to identify those variables for which attaining a more symmetrical gait pattern is most beneficial. Further work also needs to be done to determine the long term effects of such RTVF training. The CCF Treadmill and RTVF were shown to be potentially useful tools both for defining rehabilitation targets and for quantifying patients' progress towards those goals.

Frequency content of normal and diabetic plantar pressure profiles: implications for the selection of transducer sizes

How small do pressure transducers need to be in order to faithfully measure the plantar pressure profiles (PPPs) under normal and diabetic feet? In this study, pressures were collected from five diabetic and six non-diabetic subjects using a commercial measurement system with 25 mm2 transducers. Discrete Fourier Transform techniques were then used to determine (i) the spatial frequency content of diabetic and non-diabetic PPPs, and (ii) the effects of quadrupling the transducer area (from 5 mm x 5 mm to 10 mm x 10 mm). When the data were filtered to represent the effects of using 10 mm x 10 mm transducers, it was found that the ensuing reductions in peak pressure in the toe region (50 kPa) were significantly greater than in all other regions of the foot (p < 0.05). There was a significant correlation between pressure underestimations and measured peak pressures in the metatarsal regions. Based on data collected with 25 mm2 transducers it was concluded that transducer sizes greater than 6.36 mm x 6.18 mm (medio-lateral and antero-posterior directions) would result in sub-optimal sampling of PPPs.

Ground reaction forces during locomotion in simulated microgravity

BACKGROUND

Significant losses in bone density and mineral, primarily in the lower extremities, have been reported following exposure to weightlessness. Recent investigations suggest that mechanical influences such as bone deformation and strain rate may be critically important in stimulating new bone formation.

HYPOTHESIS

It was hypothesized that velocity, cadence, and harness design would significantly affect lower limb impact forces during treadmill exercise in simulated zero-gravity (0G).

METHODS

A ground-based hypogravity simulator was used to investigate which factors affect limb loading during tethered treadmill exercise. A fractional factorial design was used and 12 subjects were studied.

RESULTS

The results showed that running on active and passive treadmills in the simulator with a tethering force close to the maximum comfortable level produced similar magnitudes for the peak ground reaction force. It was also found that these maximum forces were significantly lower than those obtained during overground trials, even when the speeds of locomotion in the simulator were 66% greater than those in 1G. Cadence had no effect on any of the response variables. The maximum rate of force application (DFDTmax) was similar for overground running and exercise in simulated 0G, provided the "weightless" subjects ran on a motorized treadmill.

CONCLUSIONS

These findings have implications for the use of treadmill exercise as a countermeasure for hypokinetic osteoporosis. As the relationship between mechanical factors and osteogenesis becomes better understood, results from human experiments in 0G simulators will help to design in-flight exercise programs that are more closely targeted to generate appropriate mechanical stimuli.

The articulatory basis of babbling

This article evaluates the "Frames, then Content" hypothesis for speech acquisition, which states that much of the patterning of babbling is a direct result of production of syllabic "Frames" by means of rhythmic mandibular oscillation, with relatively little of the intrasyllabic and intersyllabic "Content" of the syllable-like cycles under mandible-independent control. Analysis was based on a phonetically transcribed corpus of 6,659 utterances of 6 normally developing infants obtained from one-hour weekly audio-recordings over a 4-6 month period. Intrasyllabic predictions were that front vowels would preferentially co-occur with front (alveolar) consonants, back vowels with back (velar) consonants, and central vowels with labial consonants, with the latter effect presumably resulting from mandibular oscillation alone. Intersyllabic predictions were for more variegation in tongue height for vowels than in front-back tongue movement, and for consonant manner changes to predominate over place changes (related primarily to mandibular oscillation). All 30 individual predictions from both hypotheses were confirmed, leading to a conception of the articulatory basis of babbling as "Frame Dominance."

Visual guidance to force plates does not influence ground reaction force variability

Gait analysis methods commonly require the subject to avoid visual guidance, that is, targeting, the force plate upon which a foot-strike is necessary. The putative rationale underlying the preference for not using targeting is the unsubstantiated contention that gait is altered. This study evaluated the influence of force plate targeting on the variability of ground reaction forces (GRF) in 15 normal subjects. Secondary factors of single vs multiple steps to the force plate and whether or not subjects were informed of the study's primary purpose were also examined. ANOVA main effects revealed that targeting did not significantly affect GRF variability (p > 0.05). A significant main effect of the number of steps required to reach the force plate on AP force variability was found (p = 0.002). Prior knowledge of the purpose of the study did not significantly affect GRF variability (p > 0.05). It was concluded that the variability of ground reaction forces is not significantly affected by targeting the force plate. Thus, targeting would not be expected to influence the variability of calculated kinetic variables that are subservient to GRF.

Student upward mobility: utilization of an educational support model

Hampton University School of Nursing was funded by the Teagle Foundation in 1990 for four years and later expanded for an additional year to develop, implement and evaluate an innovative Individualized Educational Support Model for licensed practical nurses (LPNs) residing in Southeastern Virginia. Project staff assigned the Teagle Initiative developed a model program for LPNs seeking the Bachelor of Science degree in nursing. The Teagle model offers opportunities for advanced placement through National League for Nursing Mobility Examinations, CLEP, ACT-PEP, and challenge examinations; tutoring by faculty and peers; counseling by project staff for academic and financial aid, and other concerns as needed; socialization with other project students and generic students; monthly stipends to assist with additional expenses incurred when the adult student returns to school and an alternative admissions criteria for the LPN who may not meet all aspects of the Hampton University admissions criteria.