Adaptive and dynamic control of respiratory and motor systems during object manipulation

"Brain-breath" interactions: respiration-timing-dependent impact on functional brain networks and beyond

Breathing is a natural daily action that one cannot do without, and it sensitively and intensely changes under various situations. What if this essential act of breathing can impact our overall well-being? Recent studies have demonstrated that breathing oscillations couple with higher brain functions, i.e., perception, motor actions, and cognition. Moreover, the timing of breathing, a phase transition from exhalation to inhalation, modulates specific cortical activity and accuracy in cognitive tasks. To determine possible respiratory roles in attentional and memory processes and functional neural networks, we discussed how breathing interacts with the brain that are measured by electrophysiology and functional neuroimaging: (i) respiration-dependent modulation of mental health and cognition; (ii) respiratory rhythm generation and respiratory pontomedullary networks in the brainstem; (iii) respiration-dependent effects on specific brainstem regions and functional neural networks (e.g., glutamatergic PreBötzinger complex neurons, GABAergic parafacial neurons, adrenergic C1 neurons, parabrachial nucleus, locus coeruleus, temporoparietal junction, default-mode network, ventral attention network, and cingulo-opercular salience network); and (iv) a potential application of breathing manipulation in mental health care. These outlines and considerations of "brain-breath" interactions lead to a better understanding of the interoceptive and cognitive mechanisms that underlie brain-body interactions in health conditions and in stress-related and neuropsychiatric disorders.

Regular change in spontaneous preparative behaviour on intra-abdominal pressure and breathing during dynamic lifting

PURPOSE

Intra-abdominal pressure (IAP) and breathing behaviour are important preparative pre-lifting actions for functional stability during lifting. This study aimed to examine spontaneous changes in the peak rate of IAP development (Rate-IAP), peak IAP (Peak-IAP), the time of Rate- and Peak-IAP occurrence and respiratory volume in response to dynamic load lifting.

METHODS

Eleven healthy men performed quick dynamic deadlifting using 30, 45, 60 and 75% of the isometric maximal lifting effort (iMLE). IAP was measured using an intrarectal pressure transducer. The spontaneous respiratory volume was calculated from air flow data using pneumotachography. The lifting motion onset was determined from the hip joint motion using an electrogoniometer.

RESULTS

From 30 to 75% of the iMLE, Rate-IAP occurred early from 2 ± 28 to -179 ± 16 ms (P < 0.01), whereas Peak-IAP occurred late from 165 ± 31 to 82 ± 23 ms (P = 0.12) relative to the lifting motion onset. Rate-IAP increased from 224 ± 47 to 507 ± 69 mmHg/s (P < 0.01), whereas Peak-IAP increased from 37 ± 8 to 90 ± 11 mmHg (P < 0.01) at 30-75% of the iMLE. Rate-IAP strongly correlated with Peak-IAP at each lifting load (r = 0.94-0.97). Relative to the resting tidal volume, the inspiratory volume during pre-lifting significantly increased above 60% of the iMLE, whereas expiratory volume significantly decreased at all lifting loads.

CONCLUSIONS

Preparative pre-lifting behaviours alter IAP and breathing and are co-ordinated by the lifting load magnitude. These behaviours appear to be functionally important for dynamic lifting.

Internal models underlying fingertip force control during object manipulation in humans

Since sensory information pertaining to an object's weight and weight distribution is not available until after an object has been grasped and lifted from its support surface, skillful manipulation requires predictive scaling of fingertip forces. The predictive control is based on internal models of the object formed during prior manipulatory experience. The present study investigates the extent to which such predictive control achieved with practice of one hand can be generalized to the contralateral hand. Subjects grasped and lifted an object instrumented with force transducers. The object's center of mass (CoM) was displaced 2 cm laterally from the object's center, requiring asymmetric partitioning of tangential force development to prevent tilting. They first performed five lifts using their right hand with the CoM located on a given side with a given weight. Then the subjects translated the object the left side of the body and performed one lift with the left hand. The procedure was repeated five times with the CoM located on each side of the object and with a total object weight of 400 g and 800 g. On the last pre-translation lift, the rate of tangential force development was appropriately higher in the digit opposing the CoM (p<0.05). In contrast, following translation to the left hand, the rate of tangential force development was nearly equal in each digit (p>0.05). Nevertheless the force rates were higher in both digits for lifts with the heavier (800 g) object (p<0.05). The results suggest there is a dichotomy between the generalizability of predictive control based on the object's weight and CoM. We propose that the control may be hierarchical in nature, with parameters that can be globalized representing higher level control and those that cannot (e.g., individuated digit control) representing a lower level control.

Visual properties of objects affect manipulative forces and respiration differently

Previously, we demonstrated that the respiratory and motor systems responded differently following consecutive lifts of an object whose weight could be altered (lighter or heavier) without changing the object's visual properties. When the weight of the object was altered in a manner unpredictable to the subject, the motor system response reflected the previous weight of the object (light or heavy) while the respiratory system reflected responses seen when lifting the heavier object regardless of whether a lighter or heavier object was lifted previously. It is possible that the default pattern of the respiratory system was due to a lack of visual size cues, which are known to have robust affects on grasp control. To test this hypothesis, 14 seated subjects performed self-initiated alternating lifts with objects whose size and weight covaried such that the weight of the upcoming lift was known despite the weight of the object previously lifted. Following both consecutive and alternating trials, the load force was scaled to the weight of the object (e.g., the heavier the object the larger the force) while the volume was scaled only following the consecutive trials. This suggests that the load forces were developed entirely based on visual information while lung volume was not. In addition, we suggest that following the consecutive trials, the volume increased as the object's weight increased in an effort to assist with trunk stabilization by indirectly increasing intra-abdominal pressure.

Natural breath control during lifting tasks: effect of load

Anecdotal evidence suggests that people hold their breath during lifting tasks in order to increase intra-abdominal pressure (IAP) and thereby increase lumbar stability. Studies have shown that voluntary control of the breath influences IAP and that increases in IAP are related to increases in lumbar stability. However, a description of naturally occurring breath control during whole-body lifting tasks in normal healthy subjects is currently not available. Therefore, the specific aims of this study were to: (1) determine the naturally occurring breath patterns during lifting tasks in healthy subjects; (2) determine the effects of different levels of load during lifting tasks on natural breath control patterns in healthy subjects. The present study enrolled 20 healthy subjects to describe inspired volume and categories of airflow direction (inspiration, expiration, or breath hold) during two self-paced lifts of crates loaded at 5, 15, and 25% of body weight. When the breath pattern was examined across all loads there was a significant increase in the magnitude of inspired volume and the frequency of occurrence of inspiration immediately prior to lift-off. When examining the effect of load on breath patterns, there was a significant increase of inspired volume and occurrence of breath holding when lifting the heavy load compared to the medium and light loads. These results suggest that: (1) distinct patterns of natural breath control occur during lifting tasks; and (2) breath control is responsive to the timing and magnitude of load lifted.

Internal representations underlying respiration during object manipulation

We examined the presence of anticipatory control and the resulting interactions of the respiratory and motor systems during discrete object manipulation. In response to an auditory signal, subjects reached forward, grasped, and lifted an instrumented object weighing 150 or 1000 g while the breathing pattern, fingertip forces, and movements were measured. Following every block of five lifts, the object was removed from sight and replaced with the same or an alternate mass. Thus, the object's weight was predictable during the last lift of each block and unpredictable during the first lift after the transition. When the object's weight was predictable, the force application was faster and inspiratory duration and the tidal volume were reduced for the breath associated with the lift for 1000-g compared to 150-g lifts. Following the transition, when the object's weight was unpredictable, the force application reflected the weight of the object during the previous lift while the respiratory output, regardless of the preceding weight, resembled that used for 1000-g lifts. Additionally, inspiratory duration was significantly correlated with the reach duration in three of the four unpredictable lifting conditions. We conclude that these system-specific anticipatory alterations may arise from a common internal representation that was formed through past manipulatory weight experience.

Choreography of song, dance and beak movements in the zebra finch (Taeniopygia guttata)

As do many songbirds, zebra finches sing their learned songs while performing a courtship display that includes movements of the body, head and beak. The coordination of these display components was assessed by analyzing video recordings of courting males. All birds changed beak aperture frequently within a single song, and each individual’s pattern of beak movements was consistent from song to song. Birds that copied their father’s songs reproduced many of the changes in beak aperture associated with particular syllables. The acoustic consequences of opening the beak were increases in amplitude and peak frequency, but not in fundamental frequency, of song syllables. The change in peak frequency is consistent with the hypothesis that an open beak results in a shortened vocal tract and thus a higher resonance frequency. Dance movements (hops and changes in body or head position) were less frequent, and the distribution of dance movements within the song was not as strongly patterned as were changes in beak aperture, nor were the peaks in the distribution as strongly marked. However, the correlation between the positioning of dance movements within fathers’ and sons’ songs was striking, suggesting that the choreography of dance patterns is transmitted from tutor to pupil together with the song.

A QuickTime movie of a courtship display used in this study can be found at: http://www.williams.edu/Biology/ZFinch/zfdance.html.