On a random walk with memory and its relation to Markovian processes

We study a one-dimensional random walk with memory in which the step lengths to the left and to the right evolve at each step in order to reduce the wandering of the walker. The feedback is quite efficient and lead to a non-diffusive walk. The time evolution of the displacement is given by an equivalent Markovian dynamical process. The probability density for the position of the walker is the same at any time as for a random walk with shrinking steps, although the two-time correlation functions are quite different.Comment: 10 pages, 4 figure

Acute stress affects peripersonal space representation in cortisol stress responders.

Peripersonal space is the representation of the space near the body. It is implemented by a dedicated multisensory-motor network, whose purpose is to predict and plan interactions with the environment, and which can vary depending on environmental circumstances. Here, we investigated the effect on the PPS representation of an experimentally induced stress response and compared it to a control, non-stressful, manipulation. We assessed PPS representation in healthy humans, before and after a stressful manipulation, by quantifying visuotactile interactions as a function of the distance from the body, while monitoring salivary cortisol concentration. While PPS representation was not significantly different between the control and experimental group, a relation between cortisol response and changes in PPS emerged within the experimental group. Participants who showed a cortisol stress response presented enhanced visuotactile integration for stimuli close to the body and reduced for far stimuli. Conversely, individuals with a less pronounced cortisol response showed a reduced difference in visuotactile integration between the near and the far space. In our interpretation, physiological stress resulted in a freezing-like response, where multisensory-motor resources are allocated only to the area immediately surrounding the body

Predictors of survival and technical success of bronchoscopic interventions in malignant airway obstruction

Background: Malignant airway obstruction (MAO) leads to quality of life impairment and increased mortality. Interventional bronchoscopy allows airway patency restoring, leading to a better survival. We investigated predictors of survival and successful bronchoscopic intervention among MAO patients. Methods: This observational prospective study enrolled 100 patients who were newly diagnosed with MAO. Survival was estimated with Kaplan-Meier method and curves compared by log-rank test. Multivariate analyses were performed using Cox proportional hazard models. Univariate and multivariate logistic regression were used for odds ratio calculation. Results: A proportion of 73% of the patients were male with a median age was 62.5 years (range, 21–88 years). Lung cancer was the most common primary malignancy (74%). The majority had single (61%), endoluminal (62%) lesions and were classified as grade III in Myer Cotton scale (57%). The most used techniques comprised mechanical debulking (n=81) and laser therapy (n=68). Twenty-two airway stents were placed. While eleven patients were considered untreatable, technical success was achieved in 78%. Haemorrhage was the most common acute complication (16%). No deaths occurred as a result of the procedure. Median global survival was 8 months. Adjusting for age and Eastern Cooperative Oncology Group Performance Status (ECOG), extrinsic compression or mixed airway obstructions [hazard ratio (HR) =2.075; P=0.012], successful bronchoscopic intervention (HR =0.468; P=0.025) and initiation of cancer treatment (HR =0.373; P=0.006) were independent predictors of survival. The absence of distal airway patency on thoracic CT was independently associated with failure of the intervention [odds ratio (OR) =0.013; P<0.001]. Conclusions: Interventional bronchoscopy has proven to be an efficient and safe strategy to manage MAO patients. The patients who benefit the most in terms of survival are those with purely endoluminal lesions, in whom technical success was achieved and those whose cancer-specific treatment was initiated. Distal airway patency on thoracic CT predicts the technical success of bronchoscopic intervention

Enhanced audio-tactile multisensory interaction in a peripersonal task after echolocation.

Peripersonal space (PPS) is created by a multisensory interaction between different sensory modalities and can be modified by experience. In this article, we investigated whether an auditory training, inside the peripersonal space area, can modify the PPS around the head in sighted participants. The auditory training was based on echolocation. We measured the participant's reaction times to a tactile stimulation on the neck, while task-irrelevant looming auditory stimuli were presented. Sounds more strongly affect tactile processing when located within a limited distance from the body. We measured spatially dependent audio-tactile interaction as a proxy of PPS representation before and after an echolocation training. We found a significant speeding effect on tactile RTs after echolocation, specifically when sounds where around the location where the echolocation task was performed. This effect could not be attributed to a task repetition effect nor to a shift of spatial attention, as no changes of PPS were found in two control groups of participants, who performed the PPS task after either a break or a temporal auditory task (with stimuli located at the same position of echolocation task). These findings show that echolocation affects multisensory processing inside PPS representation, likely to better represent the space where external stimuli, have to be localized