Vocal Communications and the Maintenance of Population Specific Songs in a Contact Zone

Bird song has been hypothesized to play a role in several important aspects of the biology of songbirds, including the generation of taxonomic diversity by speciation; however, the role that song plays in speciation within this group may be dependent upon the ability of populations to maintain population specific songs or calls in the face of gene flow and external cultural influences. Here, in an exploratory study, we construct a spatially explicit model of population movement to examine the consequences of secondary contact of populations singing distinct songs. We concentrate on two broad questions: 1) will population specific songs be maintained in a contact zone or will they be replaced by shared song, and 2) what spatial patterns in the distribution of songs may result from contact? We examine the effects of multiple factors including song-based mating preferences and movement probabilities, oblique versus paternal learning of song, and both cultural and genetic mutations. We find a variety of conditions under which population specific songs can be maintained, particularly when females have preferences for their population specific songs, and we document many distinct patterns of song distribution within the contact zone, including clines, banding, and mosaics

The acute motor-sensory axonal neuropathy variant of Guillain-Barré syndrome after thoracic spine surgery

Guillain-Barre syndrome (GBS) is the eponym used to describe acute inflammatory polyradiculoneuropathies, which manifest with weakness and diminished reflexes. Although the classic form of GBS is considered to be an ascending demyelinating polyneuropathy, several variants have been described in the literature, including the Miller-Fisher syndrome, acute panautonomic neuropathy, acute motor axonal neuropathy, and acute motor-sensory axonal neuropathy (AMSAN). Few cases of postoperative GBS have been documented, particularly for the AMSAN variant. The authors describe the case of a patient who developed AMSAN after thoracic spine surgery and highlight the importance of investigating new-onset weakness in the postoperative period. (DOI: 10.3171/2011.8.SPINE1159

Has the management of shoulder dislocation changed over time?

Anterior shoulder dislocation is a disabling injury affecting all ages, young and old alike. Recently, the treatment of traumatic shoulder dislocation has included immobilisation for varying periods of time followed by physiotherapy. This study is the first in this country to address the demographic data and recurrence rates of shoulder dislocation. Three hundred and eight patients (170 men and 138 women) were followed up for an average of 5.9 years. The most frequent mechanism of injury was a fall (65.66% of cases), and in 92.1% of the patients, the shoulder was reduced in the Emergency Department without the need for sedation or general anaesthesia. The overall recurrence rate in all ages was 50%, but rose to 88.9% in the 14–20-year age group. The duration of immobilisation did not affect the rate of re-dislocation of the humeral head. We believe that conventional shoulder immobilisation in a sling offers no benefits, and it would be preferable not to immobilise the shoulder at all