Heterogeneous structure in mixed-species corvid flocks in flight

Flocks of birds in flight represent a striking example of collective behaviour. Models of self-organization suggest that repeated interactions among individuals following simple rules can generate the complex patterns and coordinated movements exhibited by flocks. However, such models often assume that individuals are identical and interchangeable, and fail to account for individual differences and social relationships among group members. Here, we show that heterogeneity resulting from species differences and social structure can affect flock spatial dynamics. Using high-resolution photographs of mixed flocks of jackdaws, Corvus monedula, and rooks, Corvus frugilegus, we show that birds preferentially associated with conspecifics and that, like high-ranking members of single-species groups, the larger and more socially dominant rooks positioned themselves near the leading edge of flocks. Neighbouring birds showed closer directional alignment if they were of the same species, and neighbouring jackdaws in particular flew very close to one another. Moreover, birds of both species often flew especially close to a single same-species neighbour, probably reflecting the monogamous pair bonds that characterize these corvid social systems. Together, our findings demonstrate that the characteristics of individuals and their social systems are likely to result in preferential associations that critically influence flock structure

Water metabolism and postconcussional symptoms 5 weeks after mild head injury

Posttraumatic diabetes insipidus has been reported as a sequela to head injury. It is unknown whether subclinical types of diabetes insipidus, or other types of water metabolism disorders, occur after mild head injury (MHI) and, if so, whether they are related to the persistence of postconcussional symptoms. MHI patients (n = 38) were screened for disturbances of water metabolism by comparing plasma and urine osmolalities at about 5 weeks after the trauma. Eight patients had evidence of an increased plasma osmolality together with a relatively decreased urine osmolality after an overnight fast. The presence of this disturbance was significantly related to the persistence of postconcussional symptoms. The results suggest that subclinical disturbances of water metabolism may, among other factors, be related to the persistence of symptoms after MHI

Post-traumatic and emotional symptoms in different subgroups of patients with mild head injury

Post-concussional symptoms, such as headache, dizziness and irritability, are thought to result from the emotional stress associated with decreased cognitive performance after a head injury. A questionnaire-based investigation was carried out in 71 patients with mild head injury (MHI), using a heterogeneous item pool in order to study the interrelationships between traditional post-concussive complaints, cognitive problems, and more emotional and functional complaints. Factor analysis indicated that post-concussive symptoms loaded together with items on problems associated with decreased work performance and fatigability on a first factor, whereas psychovegetative and emotional complaints loaded together on a second factor. Two rating scales were constructed from the relevant items and were used to compare between subgroups of MHI patients and non-concussed controls. Patients with uncomplicated MHI had significantly higher scores than non-concussed subjects on the post-concussive-cognitive scale, but not on the emotional-vegetative scale. Patients with multiple head injuries or pre-existing emotional problems had higher scores on both the post-concussive-cognitive scale and the emotional-vegetative scale than MHI patients without a history of emotional problems. Reliable rating scales may be useful m multidiagnostic studies of MHI patients

Persistence of postconcussional symptoms in uncomplicated mildly head-injured patients: a prospective cohort study

We report the follow-up of 41 nonhospitalized subjects with uncomplicated mild head injury (MHI) and no premorbid compromising condition. At 3 months after the trauma 22 patients still complained of at least 1 postconcussional symptom (PCS) and 10 patients had 3 or more PCS. At 6 months 12 patients complained of at least 1 PCS, whereas 9 patients still had 3 symptoms or more. Patients with persistent PCS complained more of emotional symptoms. Results obtained with objective tests indicated that this group was characterized by a decreased performance on the Stroop Color Word Interference Test and a reduced tolerance to light and sound stimuli in comparison with patients with only few or no PCS. Persistent neurobehavioral deficits were correlated with scores on a postconcussive/cognitive rating scale, but not with scores on an emotional/vegetative scale. Although most patients may substantially recover after MHI, about 1 in 4 patients may persist with a residue of neurobehavioral deficits. Patients with persistent PCS should be evaluated in a multidiagnostic and objective way in order to gain a better understanding of the nature and origin of the subjective symptoms

Repeatable group differences in the collective behaviour of stickleback shoals across ecological contexts.

This is the final version of the article. Available from Royal Society via the DOI in this record.Establishing how collective behaviour emerges is central to our understanding of animal societies. Previous research has highlighted how universal interaction rules shape collective behaviour, and that individual differences can drive group functioning. Groups themselves may also differ considerably in their collective behaviour, but little is known about the consistency of such group variation, especially across different ecological contexts that may alter individuals' behavioural responses. Here, we test if randomly composed groups of sticklebacks differ consistently from one another in both their structure and movement dynamics across an open environment, an environment with food, and an environment with food and shelter. Based on high-resolution tracking data of the free-swimming shoals, we found large context-associated changes in the average behaviour of the groups. But despite these changes and limited social familiarity among group members, substantial and predictable behavioural differences between the groups persisted both within and across the different contexts (group-level repeatability): some groups moved consistently faster, more cohesively, showed stronger alignment and/or clearer leadership than other groups. These results suggest that among-group heterogeneity could be a widespread feature in animal societies. Future work that considers group-level variation in collective behaviour may help understand the selective pressures that shape how animal collectives form and function.This research was supported by the Biotechnology and Biological Sciences Research Council (a BBSRC Graduate Research Studentship to J.W.J.), the Association for the Study of Animal Behaviour (ASAB Research Grants to J.W.J. and N.J.B.), the Royal Society (Dorothy Hodgkin Fellowship to N.J.B.) and the Deutsche Forschungsgemeinschaft (Eigene Stelle grant to K.L.L.)

A desktop expert system for the differential diagnosis of dementia:an evaluation study

Evince-I is a desktop expert system for the differential diagnosis of dementia, implemented on a personal computer. It is intended to assess the effectiveness of this new technology in modeling a psychiatrist who uses international guidelines for diagnosing dementia. EVINCE-I was tested in diagnosing 19 patients with varying stages of dementia and 10 patients showing other disorders except dementia. EVINCE-I and the human expert were in perfect agreement on the diagnosis of dementia and correlated highly on the diagnosis of dementia of the Alzheimer type and multiple infarct dementia. EVINCE-I thus offers important possibilities as a tool in investigating the data and procedures used by the human expert

Differential diagnosis of dementia:a comparison between the expert system EVINCE and clinicians

The diagnostic performance of the expert system EVINCE was compared with that of 85 clinicians in diagnosing 10 patients suspected of suffering from dementia. A multidisciplinary expert committee provided a standard diagnosis as reference for comparison. The results showed that the syndrome and etiologic diagnoses made by EVINCE were in very close agreement with those of the expert committee and that the diagnostic performance of EVINCE was better than that of the average clinician. The present findings indicate that expert systems, especially those within the realm of complex multidimensional medical problems, could be a valuable aid in medical practice