Rationale and protocol of the ENGAGE study: a double-blind randomized controlled preference trial using a comprehensive cohort design to measure the effect of a cognitive and leisure-based intervention in older adults with a memory complaint.

BACKGROUND: Leisure activities can be both enjoyable and cognitively stimulating, and participation in such activities has been associated with reduced age-related cognitive decline. Thus, integrating stimulating leisure activities in cognitive training programs may represent a powerful and innovative approach to promote cognition in older adults at risk of dementia. The ENGAGE study is a randomized controlled, double-blind preference trial with a comprehensive cohort design that will test the efficacy and long-term impact of an intervention that combines cognitive training and cognitively stimulating leisure activities. METHODS: One hundred and forty-four older adults with a memory complaint will be recruited in Montreal and Toronto. A particular effort will be made to reach persons with low cognitive reserve. Participants will be randomly assigned to one of two conditions: cognitive + leisure training (ENGAGE-MUSIC/SPANISH) or active control (ENGAGE-DISCOVERY). The ENGAGE-MUSIC/SPANISH training will include teaching of mnemonic and attentional control strategies, casual videogames selected to train attention, and classes in music or Spanish as a second language. The ENGAGE-DISCOVERY condition will comprise psychoeducation on cognition and the brain, low-stimulating casual videogames and documentary viewing with discussions. To retain the leisure aspect of the activities, participants will be allowed to exclude either music or Spanish at study entry if they strongly dislike one of these activities. Participants randomized to ENGAGE-MUSIC/SPANISH who did not exclude any activity will be assigned to music or Spanish based on a second random assignment. Training will be provided in 24 2-h sessions over 4 months. Outcomes will be measured at baseline, at 4-month follow-up, and at 24-month follow-up. The primary outcome will be cognitive performance on a composite measure of episodic memory (delayed recall scores for words and face-name associations) measured at baseline and at the 4-month follow-up. Secondary outcomes will include a composite measure of attention (speed of processing, inhibition, dual tasking, and shifting), psychological health, activities of daily living, and brain structure and function and long-term maintenance measured at the 24-month follow-up. Information on cognitive reserve proxies (education and lifestyle questionnaires), sex and genotype (apolipoprotein (Apo)E4, brain-derived neurotrophic factor (BDNF), and catechol-O-methyltransferase (COMT)) will be collected and considered as moderators of training efficacy. DISCUSSION: This study will test whether a program combining cognitive training with stimulating leisure activities can increase cognition and reduce cognitive decline in persons at risk of dementia. TRIAL REGISTRATION: NCT03271190 . Registered on 5 September 2017.

Willet M. Hays, great benefactor to plant breeding and the founder of our association.

Willet M. Hays was a great benefactor to plant breeding and the founder of the American Genetic Association (AGA). We commemorate the AGA's centennial. We mined university archives, U.S. Department of Agriculture (USDA) yearbooks, plant breeding textbooks, scientific periodicals, and descendants for information. Willet Hays first recognized the individual plant as the unit of selection and started systematic pure-line selection and progeny tests in 1888. He developed useful plant breeding methods. He selected superior flax (Linum usitatissimum L.), wheat (Triticum vulgare L.), corn (Zea mays L.), barley (Hordeum vulgare L.), and oat (Avena sativa L.) varieties, and discovered Grimm alfalfa (Medicago sativa L.); all became commercially important. He initiated branch stations for better performance testing. Willet Hays befriended colleagues in other universities, in federal stations, in a London conference, and in Europe. He gathered and spread the scientific plant breeding gospel. He also improved rural roads and initiated animal breeding records and agricultural economics records. He started the AGA in 1903, serving as secretary for 10 years. He became assistant secretary of agriculture in 1904. He introduced the project system for agricultural research. He authored or coauthored the Nelson Amendment, the Smith-Lever Act, the Smith-Hughes Act, and the protocol leading to the United Nations Food and Agriculture Organization-all involved teaching agricultural practices that improved the world.

Effect of chest wall vibration on the canine diaphragm during breathing.

High-frequency mechanical vibration of the ribcage reduces dyspnoea in patients with chronic obstructive pulmonary disease, and the suggestion has been made that this effect might be related to a decrease in central respiratory drive resulting from an increase in afferent inputs from intercostal muscles. In the present studies, the effects of ribcage vibration on central respiratory drive have been assessed without the confounding influence of conscious reactions. The electromyographic (EMG) activity of the diaphragm and the changes in pleural (Ppl) and abdominal (Pab) pressure were measured in six anaesthetized, spontaneously-breathing dogs while the rostral, the middle, or the caudal portion of the ribcage was vibrated at intervals during inspiration. The EMG activity of the external and parasternal intercostals was also measured. Ribcage vibration consistently elicited a marked increase in the inspiratory EMG activity recorded from the external intercostals, thus indicating that the procedure did activate intercostal muscle spindles. However, no alteration in diaphragmatic or parasternal intercostal EMG activity was seen in any animal. Transdiaphragmatic pressure and the relationship between deltaPab and deltaPpl during inspiration were also unaltered. The authors conclude that ribcage vibration and, with it, stimulation of external intercostal muscle spindles has no significant influence on phrenic motoneurones or on medullary inspiratory neurones. It is unlikely, therefore, that the beneficial effect of the procedure on dyspnoea results from a specific reduction in central respiratory drive.

Germplasm Ownership: Related Corn Inbreds.

Corn (Zea mays L.) germplasm ownership methods are unwieldy and limit progress. Agronomic performance in hybrids better identifies inbreds for distinctness, i.e., independent varieties (IVs) or for dependency, i.e. essentially derived varieties (EDVs) than do molecular methods alone. Our objectives were to assess hybrid agronomic performance of some popular, closely related inbreds on the basis of molecular methods, and to offer thoughts on developing inbreds and on germplasm ownership. Significant agronomic differences were detected between the following: two hybrids in the same genetic group on the basis of 21 isozymic loci; two closely related inbreds (B73 and LH119) with 88.6% (62/70) RFLP (restriction fragment length polymorphism) similarity; and two closely related inbreds (Mo17 and LH51) with 88.2% (60/68) RFLP similarity. We suggest raising dependency standards for patenting inbreds to 90% or more, allowing the right to use and also paying a small royalty for only 5 yr on EDVs to the owner of the IV, and maintaining a research exemption to provide elite inbreds for developing new inbreds and experimental hybrids to all breeders. This will help maintain genetic gain for corn grain yield and serve the common good.

[The pneumology department]. / Le Service de Pneumologie.

The department of pneumology of the Erasme hospital exists since 25 years. The basic clinical activities include pulmonary function testing (7,500 patients per year), endoscopy, including interventional endoscopy (1,500 patients per year), thoracic oncology, allergology, rehabilitation and aid to smoking cessation. The following expertise fields have been largely developed: lung transplantation, treatment of cystic fibrosis in collaboration with the children's hospital Reine Fabiola, occupational.

Contribution of spindle reflexes to post-inspiratory activity in the canine external intercostal muscles.

1. The external intercostal muscles have greater post-inspiratory activity than the parasternal intercostal muscles and are more abundantly supplied with muscle spindles. In the present study, the hypothesis was tested that spindle afferent inputs play a major role in determining this activity. 2. The electrical activity of the external and parasternal intercostal muscles in the rostral interspaces was recorded in anaesthetized spontaneously breathing dogs, and the ribs were manipulated so as to alter their normal caudal displacement and the normal lengthening of the muscles in early expiration. 3. Post-inspiratory activity in the external intercostal muscles showed a reflex decrease when the caudal motion of the ribs and the lengthening of the muscles was impeded, and it showed a reflex increase when the rate of caudal rib motion and muscle lengthening was increased. In contrast, the small post-inspiratory activity in the parasternal intercostal muscles remained unchanged. 4. When the two ribs making up the interspace investigated were locked to keep muscle length constant, post-inspiratory activity in the external intercostal muscles was reduced and no longer responded to cranial rib manipulation. 5. These observations confirm that afferent inputs from muscle receptors, presumably muscle spindles, are a primary determinant of post-inspiratory activity in the canine external intercostal muscles. In anaesthetized animals, the contribution of central control mechanisms to this activity is small.

Response of the canine internal intercostal muscles to chest wall vibration.

Although high-frequency mechanical vibration of the rib cage reduces dyspnea, its effects on the respiratory muscles are largely unknown. We have previously shown that in anesthetized dogs, vibrating the rib cage during inspiration elicits a marked increase in the inspiratory electromyographic (EMG) activity recorded from the external intercostal muscles but does not affect tidal volume (VT). In the present studies, we have tested the hypothesis that the maintenance of VT results from the concomitant contraction of the internal interosseous (expiratory) intercostals. When the rib cage was vibrated (40 Hz) during hyperventilation-induced apnea, a prominent activity was recorded from the external intercostals but no activity was recorded from the internal intercostals, including when the muscles were lengthened by passive inflation. The internal intercostals remained also silent when vibration was applied during spontaneous inspiration, and the phasic expiratory EMG activity recorded from them was unaltered when vibration was applied during expiration. Thus, the internal interosseous intercostals in dogs are much less sensitive to vibration than the external intercostals, and they do not interfere with the action of these latter during rib cage vibration. This lack of sensitivity might be the result of a reflex inhibition of the muscle spindle afferents by afferents from external intercostal muscle spindles.

Respiratory effects of the external and internal intercostal muscles in humans.

The current conventional view of intercostal muscle actions is based on the theory of Hamberger (1749) and maintains that as a result of the orientation of the muscle fibres, the external intercostals have an inspiratory action on the lung and the internal interosseous intercostals have an expiratory action. Recent studies in dogs, however, have shown that this notion is only approximate. In the present studies, the respiratory actions of the human external and internal intercostal muscles were evaluated by applying the Maxwell reciprocity theorem. Thus the orientation of the muscle fibres relative to the ribs and the masses of the muscles were first assessed in cadavers. Five healthy individuals were then placed in a computed tomographic scanner to determine the geometry of the ribs and their precise transformation during passive inflation to total lung capacity. The fractional changes in length of lines with the orientation of the muscle fibres were then computed to obtain the mechanical advantages of the muscles. These values were finally multiplied by muscle mass and maximum active stress (3.0 kg cm-2) to evaluate the potential effects of the muscles on the lung. The external intercostal in the dorsal half of the second interspace was found to have a large inspiratory effect. However, this effect decreases rapidly in the caudal direction, in particular in the ventral portion of the ribcage. As a result, it is reversed into an expiratory effect in the ventral half of the sixth and eighth interspaces. The internal intercostals in the ventral half of the sixth and eighth interspaces have a large expiratory effect, but this effect decreases dorsally and cranially. The total pressure generated by all the external intercostals during a maximum contraction would be -15 cmH2O, and that generated by all the internal interosseous intercostals would be +40 cmH2O. These pressure changes are substantially greater than those induced by the parasternal intercostal and triangularis sterni muscles, respectively.

Heterogeneity of metabolic activity in the canine parasternal intercostals during breathing.

In the dog, the inspiratory mechanical advantage of the parasternal intercostals shows a marked spatial heterogeneity, whereas the expiratory mechanical advantage of the triangularis sterni is relatively uniform. The contribution of a particular respiratory muscle to lung volume expansion during breathing, however, depends both on the mechanical advantage of the muscle and on its neural input. To evaluate the distribution of neural input across the canine parasternal intercostals and triangularis sterni, we have examined the distribution of metabolic activity among these muscles in seven spontaneously breathing animals by measuring the uptake of the glucose tracer analog [(18)F]fluorodeoxyglucose (FDG). FDG uptake in any given parasternal intercostal was greatest in the medial bundles and decreased rapidly toward the costochondral junctions. In addition, FDG uptake in the medial parasternal bundles increased from the first to the second interspace, plateaued in the second through fifth interspaces, and then decreased progressively toward the eighth interspace. In contrast, uptake in the triangularis sterni showed no significant rostrocaudal gradient. These results overall strengthen the idea that the spatial distribution of neural input within a particular set of respiratory muscles is closely matched with the spatial distribution of mechanical advantage.

The effect of divided attention on memory for items and their context.

Memory for context, in comparison to memory for items, is a more demanding task and requires more attentional resources. We examined differences between item and context memory using divided attention at encoding and retrieval. Participants were presented with word lists and were instructed to learn the items (i.e., words), the intrinsic context (i.e., the colour of the cards on which each word was presented), and the extrinsic context (i.e., the temporal order of the words). Among 72 young adults, in comparison to conditions of full attention, divided attention applied at encoding only or retrieval only resulted in equally lower performance on all memory tasks; in contrast, divided attention applied at both encoding and retrieval resulted in lower performance only on memory for temporal order. The findings support the idea that memory for temporal order requires greater attentional resources and strategic processing than memory for items.

Response of the rabbit diaphragm to tendon vibration.

To evaluate the potential role of diaphragmatic muscle spindles in the act of breathing, we have recorded the electromyograms of the diaphragm and the external intercostal muscle in the third interspace during high-frequency mechanical vibration (50 Hz) of the central tendon in eight anesthetized, spontaneously breathing rabbits. Vibration induced a consistent, clear-cut increase in the inspiratory activity recorded from the external intercostal, thus indicating that the mechanical stimulus applied to the diaphragm was strong enough to trigger muscle spindles at distant sites. However, vibration did not elicit any alteration in costal or crural diaphragmatic activity in any animal. Similarly, when vibration was applied during hyperventilation-induced apnea, activity was recorded in the external intercostal but not in the diaphragm. These observations support the traditional view that the diaphragm is poorly endowed with muscle spindles and that these play little or no significant role in the act of breathing.

Atheroemboli to the brain: size threshold for causing acute neuronal cell death.

OBJECTIVE: The objective of this study was to investigate the dilemma posed by the observations that carotid angioplasty dislodges significant numbers of plaque fragments but is reported to have a low rate of neurologic consequences. We examined the fragments released by ex vivo carotid angioplasty. The smaller and most numerous were separated by size and injected into rats to determine the tolerance of the brain to microemboli. METHODS: Ex vivo angioplasty was performed on a total of 20 human carotid plaques removed en bloc. Plaques were placed within polytetrafluoroethylene grafts, and three manipulations were performed: guide wire insertion, 3.5- or 4.0-mm balloon angioplasty, and 5-mm angioplasty with or without a Palmaz stent. After each manipulation, the lumen was flushed, effluent was collected, and fragments were counted under 100x magnification. Using 200-microm and 500-microm micropore mesh, we separated fragments by size into two groups: (1) less than 200 microm and (2) 200 to 500 microm. We then injected rats with saline alone (Group A), with 100 fragments less than 200 microm (Group B), or with 100 fragments 200 to 500 microm (Group C). Animals were euthanized at 1, 3, and 7 days, and brain sections were examined for cell viability and expression of HSP- 72. RESULTS: The total number of fragments dislodged from the plaques varied from 30 to 553. The mean number of fragments released with each manipulation was as follows: guide wire passage, 24; initial balloon angioplasty, 97; second balloon angioplasty, 68; and second angioplasty plus stent, 172. Sixteen of the 20 plaques dislodged fragments that were 1 mm or more in greatest dimension. There was no evidence of brain ischemia in Group A at any time. Group B also showed no injury at 1 or 3 days. However, injection of 200- to 500-microm fragments (Group C) caused a scattered pattern of neuronal cell death. At 7 days, brain sections from both Group B and Group C animals had a scattered pattern of ischemic neurons. There were no classic wedge-shaped infarctions. DISCUSSION: The brain appears to have a surprising tolerance for microembolization in the acute setting. Thus, carotid angioplasty may dislodge plaque fragments, but there may still be a low incidence of stroke. However, even small plaque fragments, less than 200 microm, may cause neuronal ischemia at later time points. Periprocedural microemboli could cause subtle neurologic dysfunction in late follow-up.

Normative data for clustering and switching on verbal fluency tasks.

Normative data for clustering and switching on verbal fluency tasks are provided. Four hundred and eleven healthy adults between the ages of 18 and 91 were given tests of phonemic fluency (FAS or CFL) and semantic fluency (Animals and Supermarket). Raw scores were corrected for demographic (i.e., age, education, and sex) and test (i.e., fluency form) variables that were determined to make sizable contributions to fluency performance. These normative data should be useful for clinicians and researchers in determining the nature of the fluency impairment in any given individual.

Regional differences in serotonergic input to canine parasternal intercostal motoneurons.

There is a mediolateral gradient in activation of the parasternal intercostal (PI) muscle during inspiration. In the present study, we tested the hypotheses that serotonergic [5-hydroxytryptamine (5-HT)] input from descending central drive and/or intrinsic size-related properties of PI motoneurons leads to the differential activation of PI muscles. In dogs, PI motoneurons innervating the medial and lateral regions of the PI muscles at the T(3)-T(5) interspaces were retrogradely labeled by intramuscular injection of cholera toxin B subunit. After a 10-day survival period, PI motoneurons and 5-HT terminals were visualized by using immunohistochemistry and confocal imaging. There were no differences in motoneuron morphology among motoneurons innervating the medial and lateral regions of the PI muscle. However, the number of 5-HT terminals and the 5-HT terminal density (normalized for surface area) were greater in motoneurons innervating the medial region of the PI muscle compared with the lateral region. These results suggest that differences in distribution of 5-HT input may contribute to regional differences in PI muscle activation during inspiration and that differences in PI motoneuron recruitment do not relate to size.

Interaction between left and right intercostal muscles in airway pressure generation.

The interactions between the different rib cage inspiratory muscles in the generation of pleural pressure remain largely unknown. In the present study, we have assessed in dogs the interactions between the parasternal intercostals and the interosseous intercostals situated on the right and left sides of the sternum. For each set of muscles, the changes in airway opening pressure (DeltaPao) obtained during separate right and left activation were added, and the calculated values (predicted DeltaPao) were then compared with the DeltaPao values obtained during symmetric, bilateral activation (measured DeltaPao). When the parasternal intercostals in one or two interspaces were activated, the measured DeltaPao was commonly greater than the predicted value. The difference, however, was only 10%. When the interosseous intercostals were activated, the measured DeltaPao was nearly equal to the predicted value. These observations strengthen our previous conclusion that the pressure changes produced by the rib cage inspiratory muscles are essentially additive. As a corollary, the rib cage can be considered as a linear elastic structure over a wide range of distortion.

Abdominal muscle strength in patients with tetraplegia.

The abdominal muscles are completely paralyzed after traumatic transection of the cervical cord. To assess the residual pressure-generating capacity of these muscles, we first measured the changes in gastric pressure (DeltaPga) during paired bilateral stimulation of the lower thoracic nerve roots in eight chronic patients with C5-C7 tetraplegia and eight matched unaffected subjects in the seated posture. Stimulations were applied with a 90-mm circular magnetic coil positioned at the level of T10 and connected to a Magstim 250 stimulator. During relaxation at FRC, DeltaPga during maximal stimulation averaged (mean +/- SE) 76.0 +/- 11.7 cm H(2)O in the control subjects, whereas in the patients it was only 29.9 +/- 3.7 cm H(2)O (p = 0.002). Stimulations were next applied during the course of a forced expiration. All patients consistently demonstrated an abrupt increase in esophageal pressure (22.7 +/- 4.5 cm H(2)O), and six of them also showed an increase in expiratory flow. The cumulative thickness of the four abdominal muscles, as measured with an ultrasound probe, was 34% smaller in the patients than in the control subjects and correlated positively with maximal DeltaPga. We conclude that in patients with tetraplegia, muscle atrophy causes a marked reduction in abdominal muscle strength. However, magnetic stimulation of the abdominal muscles elicits increases in intrathoracic pressure that are greater than those required to initiate dynamic airway compression; it might, therefore, improve the clearing of airway secretions.

The canine parasternal and external intercostal muscles drive the ribs differently.

1. In the dog, the elevation of the ribs during inspiration results from the combined actions of the parasternal and external intercostal muscles. In the present studies, the hypothesis was tested that co-ordinated activity among these two sets of muscles reduces the distortion of the rib cage. 2. During spontaneous inspiration before or after section of the phrenic nerves, the ribs moved cranially and outward in the same way as they did during passive inflation. However, whereas the sternum moved cranially during passive inflation, it was displaced caudally during spontaneous inspiration. 3. When the parasternal intercostal muscles were selectively denervated, both the sternum and the ribs moved cranially, but the rib outward displacement was markedly reduced. In contrast, when the external intercostals were excised and the parasternal intercostals were left intact, the sternum continued to move caudally and the outward displacement of the ribs was augmented relative to their cranial displacement. 4. These observations establish that the external intercostal muscles drive the ribs primarily in the cranial direction, whereas the parasternal intercostals drive the ribs both cranially and outward. They also indicate, in agreement with the hypothesis, that co-ordinated activity among these two sets of muscles displaces the ribs on their relaxation curve. 5. However, this co-ordinated activity also displaces the sternum caudally. Although this distortion requires an additional energy expenditure, it enhances the outward component of rib displacement which is more effective with respect to lung expansion.

Response of the canine inspiratory intercostal muscles to chest wall vibration.

High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and external intercostal muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent external intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal intercostal activity was recorded in only four animals. Similarly, when the vibrator was applied to more rostral and more caudal interspaces, activity was recorded commonly from the external intercostal but only occasionally from the parasternal. The two muscles, however, showed similar changes in length. We next examined the response to vibration of the muscles in seven spontaneously breathing animals. Vibrating the rib cage during inspiration (in-phase) had no effect on parasternal intercostal inspiratory activity but induced a marked increase in neural drive to the external intercostals. For the animal group, peak external intercostal activity during the control, nonvibrated breaths averaged (mean +/- SE) 43.1 +/- 3.7% of the activity recorded during the vibrated breaths (p < 0.001). External intercostal activity during vibration also occurred earlier at the onset of inspiration and commonly carried on after the cessation of parasternal intercostal activity. Yet tidal volume was unchanged. Vibrating the rib cage during expiration (out-of-phase) did not elicit any parasternal or external intercostal activity in six animals. These observations thus indicate that the external intercostals, with their larger spindle density, are much more sensitive to chest wall vibration than the parasternal intercostals. They also suggest that the impact of this procedure on the mechanical behavior of the respiratory system is relatively small.

Component analysis of verbal fluency in patients with schizophrenia.

OBJECTIVE: Clustering and-switching components of phonemic fluency performance were compared in patients with schizophrenia and healthy normal controls. BACKGROUND: These components were selected to provide evidence for a specific anatomic locus for the breakdown of language processes or for a multiple-disease model of schizophrenia. METHOD: As part of a larger battery of neuropsychological tests, phonemic fluency tests were administered on an individual basis. On separate 60-second trials, participants were instructed to generate words beginning with the letters C, F, and L, excluding proper names and variants of the same word. Three scores were obtained for each participant: (1) number of words generated, excluding errors and repetitions; (2) mean cluster size; and (3) raw number of switches. RESULTS: The patients showed small but significant impairments in clustering and larger impairments in switching relative to normal controls. CONCLUSIONS: This pattern suggests a relatively greater deficit in functioning in the frontal lobe than in the temporal lobe. However, neither measure was able to completely discriminate patients with schizophrenia from controls. Moreover, differences in fluency performance were observed among subtypes of schizophrenia. Taken together, the findings of impaired performance for both aspects of fluency, differences between subtypes, and the failure to completely discriminate patients with schizophrenia from controls indicate that there is not a single marker of the disease, at least among these fluency variables. Instead, the current findings are more supportive of a multiple-disease model of schizophrenia.

Effects of increased ventilatory drive on motor unit firing rates in human inspiratory muscles.

This study was designed to determine whether increased neural drive increases firing rates of inspiratory motoneurons uniformly in humans. The discharge of single motor units in the diaphragm, parasternal intercostal and scalene muscles was recorded with monopolar electrodes. Ventilation was increased threefold with an external dead space. The discharge of 516 motor units was sampled in four subjects. All but 4 units increased their discharge rate during inspiration with only 46 discharging tonically during expiration. With increased dead space, discharge frequencies of diaphragmatic motor units increased from 11.0 +/- 2.7 to 17.7 +/- 3.3 Hz (mean +/- SD; p < 0.001). However, firing rates increased for parasternal intercostals from 10.0 +/- 1.6 to only 11.9 +/- 1.9 Hz (p < 0.001), and for scalenes from 8.7 +/- 1.8 to only 9.5 +/- 1.2 Hz (p < 0.05). Proportionate increases in rib cage and abdominal expansion accompanied the increased ventilation with added dead space. These results suggest that previously reported predominant increase in firing rates of diaphragmatic motor units in patients with chronic airflow limitation reflects the normal response of respiratory motor output to increased neural drive. The motoneuron pools of the parasternal intercostals and scalenes may show more prominent recruitment than frequency modulation.