Neural theory for the perception of causal actions

The efficient prediction of the behavior of others requires the recognition of their actions and an understanding of their action goals. In humans, this process is fast and extremely robust, as demonstrated by classical experiments showing that human observers reliably judge causal relationships and attribute interactive social behavior to strongly simplified stimuli consisting of simple moving geometrical shapes. While psychophysical experiments have identified critical visual features that determine the perception of causality and agency from such stimuli, the underlying detailed neural mechanisms remain largely unclear, and it is an open question why humans developed this advanced visual capability at all. We created pairs of naturalistic and abstract stimuli of hand actions that were exactly matched in terms of their motion parameters. We show that varying critical stimulus parameters for both stimulus types leads to very similar modulations of the perception of causality. However, the additional form information about the hand shape and its relationship with the object supports more fine-grained distinctions for the naturalistic stimuli. Moreover, we show that a physiologically plausible model for the recognition of goal-directed hand actions reproduces the observed dependencies of causality perception on critical stimulus parameters. These results support the hypothesis that selectivity for abstract action stimuli might emerge from the same neural mechanisms that underlie the visual processing of natural goal-directed action stimuli. Furthermore, the model proposes specific detailed neural circuits underlying this visual function, which can be evaluated in future experiments.     

Sociodemographic and Clinical Differences Between Suicide Ideators and Attempters: A Study of Mood Disordered Patients 50 Years and Older

Our study sought to characterize mood disordered suicide ideators and attempters 50 years and older admitted to a psychiatric ward either for a recent suicide attempt or for ongoing suicidal ideation. We enrolled 50 patients with suicide ideation consecutively admitted to an inpatient department and 50 patients admitted for a suicide attempt made in the last 48 hours. Suicide attempters more frequently had low social support and an age of onset of mood disorder of 46 years and older, and less frequently had a history of suicidal behaviors in the family members and pharmacological treatment, despite the fact that the groups did not differ with regard to antidepressants prescribed. The groups were not distinguishable based on several variables assumed to be risk factors for suicide behavior, such as proximal life events and stressors or alcohol use disorders. In both samples, comorbidity with organic diseases, the presence of stressful life events in the past 12 months, and a diagnosis of major depression were frequently reported. In conclusion, the presence of low social support and the absence of a pharmacotherapy may increase suicidal behaviors in patients at risk.     

Suicide Attempts in Major Depressed Patients with Personality Disorder

Suicide attempters who met criteria for borderline personality disorder (BPD) comorbid with major depressive disorder (MDD) were compared to both suicide attempters suffering from MDD alone and to attempters with comorbid MDD and other personality disorders (PD). Participants were 239 (158 patients with comorbid PD and 81 patients with MDD without comorbidity) inpatients consecutively admitted after a suicide attempt made in the last 24 hours. Suicide attempters with comorbid MDD and BPD had more frequent previous suicide attempts and were more likely to have a history of aggressive behaviors and alcohol and drug use disorders compared with patients suffering from MDD without Axis II comorbidity.