Excitability at the motoneuron pool and motor cortex is specifically modulated in lengthening compared to isometric contractions

Excitability at the motoneuron pool and motor cortex is specifically modulated in lengthening compared to isometric contractions. J Neurophysiol 101: 2030–2040, 2009. First published January 28, 2008; doi:10.1152/jn.91104.2008. Neural control of muscle contraction seems to be unique during muscle lengthening. The present study aimed to determine the specific sites of modulatory control for lengthening compared with isometric contractions. We used stimulation of the motor cortex and corticospinal tract to observe changes at the spinal and cortical levels. Motor-evoked potentials (MEPs) and cervicomedullary MEPs (CMEPs) were evoked in biceps brachii and brachioradialis during maximal and submaximal lengthening and isometric contractions at the same elbow angle. Sizes of CMEPs and MEPs were lower in lengthening contractions for both muscles (by 28 and 16%, respectively; P 0.01), but MEP-to-CMEP ratios increased (by 21%; P 0.05). These results indicate reduced excitability at the spinal level but enhanced motor cortical excitability for lengthening compared with isometric muscle contractions.

Convergent validity of two visual motor integration tests

Background: Occupational therapists often assess visual motor integration (VMI) skills. It is, therefore, imperative that therapists use VMI tests with robust measurement properties.

Objective: This study examined the convergent validity of two VMI tests used to assess children, adolescents and adults.

Method: Three groups of healthy participants (n = 153) completed the Beery-Buktenica Developmental Test of Visual-Motor Integration (DTVMI) and the Full Range Test of Visual Motor Integration (FRTVMI). Seventy-three children aged 5-10 years (37 males and 36 females; mean age 7.5 years, SD = 2.20), 19 adolescents aged 11-17 years (8 males and 11 females; 13.1 years, SD = 2.16), and 61 adults (18 males and 43 females; mean age 31.82 years, SD = 11.20) completed the DTVMI and the FRTVMI. Spearman rho correlation coefficients were used to investigate whether each pair of the VMI test scores for each of the three participant age groups were associated.

Results: The Spearman rho correlation coefficients between all three versions of the DTVMI and FRTVMI were statistically significant. For the child group, the correlation coefficient was rho = 0.70 (p<0.000), while the correlation between the VMI scores obtained by the adolescent group on the two tests was rho = 0.77 (p<0.000). For the adult participant group, the correlation coefficient between the DTVMI and the FRTVMI was rho = 0.70 (p<0.000).

Conclusion: The VMI scores obtained by the three participant age groups on the DTVMI and the FRTVMI were all significantly correlated with each other. Overall, the DTVMI and the FRTVMI exhibited large levels of convergent validity with each other, indicating that the two tests appear to measure similar visual-motor integration constructs.

The reliability of two visual motor integration tests used with children

Occupational therapists often assess the visual motor integration (VMI) skills of children and young people. It is important that therapists use tools with strong psychometric properties. This study aims to examine the reliability of 2 VMI tests. Ninety-two children between the ages of 5 and 17 years (response rate of 31%) completed 2 VMI tests: the Developmental Test of Visual Motor Integration (DTVMI) and the Full Range Test of Visual Motor Integration (FRTVMI). Cronbach's alpha coefficient was used to examine the internal consistency of the 2 VMI tests whereas Spearman's rho correlation was used to evaluate the test–retest reliability, intrarater reliability, and interrater reliability of the 2 VMI tests. The Cronbach's alpha coefficient for the DTVMI was .82 and .72 for the FRTVMI. The test–retest reliability coefficient was .73 (p = .000) for the DTVMI and .49 (p = .05) for the FRTVMI. The interrater correlation was significant for both the DTVMI at .94 (p = .000) and FRTVMI at .68 (p = .001). The DTVMI intrarater reliability correlation result was .90 (p = .000) and the FRTVMI at .85 (p = .000). Overall, the DTVMI exhibited a higher level of reliability than the FRTVMI. Both VMI tests appear to exhibit reasonable levels of reliability and are recommended for use with children and young people.

Respiratory pattern in awake rats : effects of motor activity and of alerting stimuli

Our aim was to assess the impact of motor activity and of arousing stimuli on respiratory rate in the awake rats. The study was performed in male adult Sprague–Dawley (SD, n = 5) and Hooded Wistar (HW, n = 5) rats instrumented for ECG telemetry. Respiratory rate was recorded using whole-body plethysmograph, with a piezoelectric sensor attached for the simultaneous assessment of motor activity. All motor activity was found to be associated with an immediate increase in respiratory rate that remained elevated for the whole duration of movement; this was reflected by: i) bimodal distribution of respiratory intervals (modes for slow peak: 336 ± 19 and 532 ± 80 ms for HW and SD, p < 0.05; modes for fast peak 128 ± 6 and 132 ± 7 ms for HW and SD, NS); and ii) a tight correlation between total movement time and total time of tachypnoea, with an R2 ranging 0.96–0.99 (n = 10, p < 0001). The extent of motor-related tachypnoea was significantly correlated with the intensity of associated movement. Mild alerting stimuli produced stereotyped tachypnoeic responses, without affecting heart rate: tapping the chamber raised respiratory rate from 117 ± 7 to 430 ± 15 cpm; sudden side move — from 134 ± 13 to 487 ± 16 cpm, and turning on lights — from 136 ± 12 to 507 ± 14 cpm (n = 10; p < 0.01 for all; no inter-strain differences). We conclude that: i) sniffing is an integral part of the generalized arousal response and does not depend on the modality of sensory stimuli; ii) tachypnoea is a sensitive index of arousal; and iii) respiratory rate is tightly correlated with motor activity.

Retroactive interference and mental practice effects on motor performance : a pilot study

This study examined the effect of similar versus dissimilar retroactive interference on the mental practice effects for performing a novel motor skill. Research has shown that mental practice of a motor task can interfere with learning and performance of the task; however, little is known about how different retroactive interference activities affect mental practice effects. 90 volunteers ages 18 to 51 years (M=26.8, SD=9.6) completed a pre-test and post-test of 10 sets of five trials of a throwing task with the non-preferred hand. In the practice phase, participants mentally practiced the throwing task and then mentally practiced a task that was similar, dissimilar, or completed an unrelated reading task. Performance for all groups improved from pre- to post-test; however, there were no differences in increases for the three groups. The findings suggest that mental practice of similar and dissimilar tasks produced no significant interference in performance.

Altered intracellular localization and valosin-containing protein (p97 VCP) interaction underlie ATP7A-related distal motor neuropathy

ATP7A is a P-type ATPase that regulates cellular copper homeostasis by activity at the trans-Golgi network (TGN) and plasma membrane (PM), with the location normally governed by intracellular copper concentration. Defects in ATP7A lead to Menkes disease or its milder variant, occipital horn syndrome or to a newly discovered condition, ATP7A-related distal motor neuropathy (DMN), for which the precise pathophysiology has been obscure. We investigated two ATP7A motor neuropathy mutations (T994I, P1386S) previously associated with abnormal intracellular trafficking. In the patients' fibroblasts, total internal reflection fluorescence microscopy indicated a shift in steady-state equilibrium of ATP7AT994I and ATP7AP1386S, with exaggerated PM localization. Transfection of Hek293T cells and NSC-34 motor neurons with the mutant alleles tagged with the Venus fluorescent protein also revealed excess PM localization. Endocytic retrieval of the mutant alleles from the PM to the TGN was impaired. Immunoprecipitation assays revealed an abnormal interaction between ATP7AT994I and p97/VCP, an ubiquitin-selective chaperone which is mutated in two autosomal dominant forms of motor neuron disease: amyotrophic lateral sclerosis and inclusion body myopathy with early-onset Paget disease and fronto-temporal dementia. Small-interfering RNA (SiRNA) knockdown of p97/VCP corrected ATP7AT994I mislocalization. Flow cytometry documented that non-permeabilized ATP7AP1386S fibroblasts bound a carboxyl-terminal ATP7A antibody, consistent with relocation of the ATP7A di-leucine endocytic retrieval signal to the extracellular surface and partially destabilized insertion of the eighth transmembrane helix. Our findings illuminate the mechanisms underlying ATP7A-related DMN and establish a link between p97/VCP and genetically distinct forms of motor neuron degeneration.

Risk of falls and motor vehicle collisions in glaucoma

PURPOSE. To investigate the risk of falls and motor vehicle collisions (MVCs) in patients with glaucoma.

METHODS. The sample comprised 48 patients with glaucoma (mean visual field mean deviation [MD] in the better eye = −3.9 dB; 5.1 dB SD) and 47 age-matched normal control subjects, who were recruited from a university-based hospital eye care clinic and are enrolled in an ongoing prospective study of risk factors for falls, risk factors for MVCs, and on-road driving performance in glaucoma. Main outcome measures at baseline were previous self-reported falls and MVCs, and police-reported MVCs. Demographic and medical data were obtained. In addition, functional independence in daily living, physical activity level and balance were assessed. Clinical vision measures included visual acuity, contrast sensitivity, standard automated perimetry, useful field of view (UFOV), and stereopsis. Analyses of falls and MVCs were adjusted to account for the possible confounding effects of demographic characteristics, medications, and visual field impairment. MVC analyses were also adjusted for kilometers driven per week.

RESULTS. There were no significant differences between patients with glaucoma and control subjects with respect to number of systemic medical conditions, body mass index, functional independence, and physical activity level (P > 0.10). At baseline, 40 (83%) patients with glaucoma and 44 (94%) control subjects were driving. Compared with control subjects, patients with glaucoma were over three times more likely to have fallen in the previous year (odds ratio [OR]adjusted = 3.71; 95% CI, 1.14–12.05), over six times more likely to have been involved in one or more MVCs in the previous 5 years (ORadjusted = 6.62; 95% CI, 1.40–31.23), and more likely to have been at fault (ORadjusted = 12.44; 95% CI, 1.08–143.99). The strongest risk factor for MVCs in patients with glaucoma was impaired UFOV selective attention (ORadjusted = 10.29; 95% CI, 1.10–96.62; for selective attention >350 ms compared with ≤350 ms).

CONCLUSIONS. There is an increased risk of falls and MVCs in patients with glaucoma.

Fault detection and diagnosis of induction motors using motor current signature analysis and a hybrid FMM-CART model

In this paper, a novel approach to detect and classify comprehensive fault conditions of induction motors using a hybrid fuzzy min-max (FMM) neural network and classification and regression tree (CART) is proposed. The hybrid model, known as FMM-CART, exploits the advantages of both FMM and CART for undertaking data classification and rule extraction problems. A series of real experiments is conducted, whereby the motor current signature analysis method is applied to form a database comprising stator current signatures under different motor conditions. The signal harmonics from the power spectral density are extracted as discriminative input features for fault detection and classification with FMM-CART. A comprehensive list of induction motor fault conditions, viz., broken rotor bars, unbalanced voltages, stator winding faults, and eccentricity problems, has been successfully classified using FMM-CART with good accuracy rates. The results are comparable, if not better, than those reported in the literature. Useful explanatory rules in the form of a decision tree are also elicited from FMM-CART to analyze and understand different fault conditions of induction motors.

The behavioural response of Australian fur seals to motor boat noise

Australian fur seals breed on thirteen islands located in the Bass Strait, Australia. Land access to these islands is restricted, minimising human presence but boat access is still permissible with limitations on approach distances. Thirty-two controlled noise exposure experiments were conducted on breeding Australian fur seals to determine their behavioural response to controlled in-air motor boat noise on Kanowna Island (39&deg;10′S, 146&deg;18′E). Our results show there were significant differences in the seals' behaviour at low (64–70 dB) versus high (75–85 dB) sound levels, with seals orientating themselves towards or physically moving away from the louder boat noise at three different sound levels. Furthermore, seals responded more aggressively with one another and were more alert when they heard louder boat noise. Australian fur seals demonstrated plasticity in their vocal responses to boat noise with calls being significantly different between the various sound intensities and barks tending to get faster as the boat noise got louder. These results suggest that Australian fur seals on Kanowna Island show behavioural disturbance to high level boat noise. Consequently, it is recommended that an appropriate level of received boat sound emissions at breeding fur seal colonies be below 74 dB and that these findings be taken into account when evaluating appropriate approach distances and speed limits for boats.