Social Context Affects Response to an Acute Stressor in Captive Red Crossbills, Loxia curvirostra

Sociality relies upon mechanisms that permit group living through a balance of costs and benefits. However, it is not fully known how specific social contexts influence behavioral and physiological outcomes, and more broadly, how responses to social situations contribute to social organization. A recent experiment investigating the relationship between social cues and migratory behavior in a social songbird, the red crossbill (Loxia curvirostra), found that doubly-housed birds experienced mass loss after movement to a novel environment and being paired next to a neighbor, whereas singly-housed birds did not. In order to explain the difference in observed changes in mass between treatment groups, we tested two non-mutually exclusive hypotheses – one which proposes a disruption in the dominance hierarchy of doubly-housed birds, and the other, which proposes that previously isolated singly-housed birds experienced a social buffering effect from gaining a neighbor. Analysis of food intake and activity data did not provide any statistically significant support for either hypothesis. From this, we concluded that there may be an underlying interaction between social context and stress physiology which is not reflected by a change in food intake or activity, creating a discrepancy in stress response between social treatments.Key Words: stress buffering, social context, dominance, red crossbil

立位における上肢運動時の腰部多裂筋深層線維および浅層線維の筋反応時間の検討

Based on the current literature, it remains unclear whether electromyographic onset of the deep fibers of the multifidus (DM) is dependent on the direction of shoulder movement and the position of the center of foot pressure (CFP). In the present study, we re-examined the electromyographic onset of the DM during shoulder flexion and extension and investigated the influence of the CFP position before arm movement. Intramuscular and surface electrodes recorded the electromyographic onset of the DM, superficial fibers of the multifidus (SM), rectus abdominis, and anterior and posterior deltoid. Eleven healthy participants performed rapid, unilateral shoulder flexion and extension in response to audio stimuli at three CFP positions: quiet standing, extreme forward leaning, and extreme backward leaning. It was found that the electromyographic onset of the DM and SM relative to the deltoid was dependent on the direction of arm movement. Additionally, of all electromyographic onsets recorded, only that of the DM occurred earlier in the extreme forward leaning position than in the extreme backward leaning position during shoulder flexion. These results suggest that the electromyographic onset of DM was influenced by the biomechanical disturbance such as shoulder movement and CFP position.首都大学東京, 2015-09-30, 博士（理学療法学）, 甲第619号首都大学東

Difference in the electromyographic onset of the deep and superficial multifidus during shoulder movement while standing.

Based on the current literature, it remains unclear whether electromyographic onset of the deep fibers of the multifidus (DM) is dependent on the direction of shoulder movement and the position of the center of foot pressure (CFP). In the present study, we re-examined the electromyographic onset of the DM during shoulder flexion and extension and investigated the influence of the CFP position before arm movement. Intramuscular and surface electrodes recorded the electromyographic onset of the DM, superficial fibers of the multifidus (SM), rectus abdominis, and anterior and posterior deltoid. Eleven healthy participants performed rapid, unilateral shoulder flexion and extension in response to audio stimuli at three CFP positions: quiet standing, extreme forward leaning, and extreme backward leaning. It was found that the electromyographic onset of the DM and SM relative to the deltoid was dependent on the direction of arm movement. Additionally, of all electromyographic onsets recorded, only that of the DM occurred earlier in the extreme forward leaning position than in the extreme backward leaning position during shoulder flexion. These results suggest that the electromyographic onset of DM was influenced by the biomechanical disturbance such as shoulder movement and CFP position

Two-way repeated measures analysis of variance for comparisons between the direction of shoulder arm movement and the center of foot pressure (CFP) position while standing in each muscle.

<p>DM, Deep fibers of lumbar multifidus; SM, Superficial fibers of lumbar multifidus; RA, Rectus abdominis</p><p>Two-way repeated measures analysis of variance for comparisons between the direction of shoulder arm movement and the center of foot pressure (CFP) position while standing in each muscle.</p

Raw electromyographic data for shoulder movements in three standing positions (QS, EFL, and EBL).

<p>The left panels show data for shoulder flexion, and right panels show data for shoulder extension. Panels show electromyographic data for anterior or posterior deltoid as focal muscle, deep (DM) and superficial (SM) fibers of lumbar multifidus and rectus abdominis (RA). The dashed vertical lines represent the EMG onset of deltoid, and the arrows represent the EMG onset of each muscle.</p

The center of foot pressure position in the anteroposterior direction (% foot length [%FL]) during quiet standing (QS), extreme forward leaning (EFL), and extreme backward leaning (EBL).

<p>Data are shown as mean ± SEM.</p><p>*The %FL of QS, EFL, and EBL were significantly different (all comparisons, <i>P</i> < 0.01)</p><p>The center of foot pressure position in the anteroposterior direction (% foot length [%FL]) during quiet standing (QS), extreme forward leaning (EFL), and extreme backward leaning (EBL).</p

Mean+SEM (ms) EMG onset of each trunk muscle relative to that of the deltoid.

<p>Data during flexion (open squares) and extension (close squares) are shown. The dashed vertical line represents the APA phase or CPA phase. APA, Anticipatory postural adjustments; CPA, Compensatory postural adjustments; DM, Deep fibers of the lumbar multifidus; SM, Superficial fibers of the lumbar multifidus; RA, Rectus abdominis; Flex, Arm flexion; Ext, Arm extension; QS, Quiet standing; EFL, Extreme forward leaning; EBL, Extreme backward leaning; EMG, Electromyography.</p