PubMed HealthSearch

Biomedical subjects

C Person

Publications and source records attributed to C Person.

6 recordsLinked to original sources

Bee foraging in uncertain environments using predictive hebbian learning.

Recent work has identified a neuron with widespread projections to odour processing regions of the honeybee brain whose activity represents the reward value of gustatory stimuli. We have constructed a model of bee foraging in uncertain environments based on this type of neuron and a predictive form of hebbian synaptic plasticity. The model uses visual input from a simulated three-dimensional world and accounts for a wide range of experiments on bee learning during foraging, including risk aversion. The predictive model shows how neuromodulatory influences can be used to bias actions and control synaptic plasticity in a way that goes beyond standard correlational mechanisms. Although several behavioural models of conditioning in bees have been proposed, this model is based on the neural substrate and was tested in a simulation of bee flight.

Animals

[Absence of nocturnal decrease in blood pressure in 24-hour blood pressure monitoring: an indication of secondary hypertension].

Non invasive 24 hours ambulatory blood pressure monitoring was performed in 81 patients with secondary hypertension (renoparenchymatous nephropathy n = 15, diabetic nephropathy n = 10, Conn's disease n = 4, renal artery stenosis n = 15, pheochromocytoma n = 2, hemodialysis patients n = 15 and patients after kidney transplantation n = 20). The results were compared to 201 patients with essential hypertension. The results showed that 98.5% of patients with essential hypertension have a nightly decline in blood pressure of at least 15 mmHg (systolic + diastolic), whereas 69% of patients with secondary hypertension showed either an attenuated circadian rhythm or no circadian rhythm. Patients with pheochromocytoma who had a night time increase in blood pressure demonstrated the greatest difference to the essential hypertension collective followed by patients with diabetic nephropathy, Conn's disease and the group of patients after kidney transplantation. After successful treatment of the condition leading to hypertension circadian periodicity returned in some patients. In summary these results suggest that the absence of a night time decline in blood pressure during 24-hour-ambulatory monitoring is an indication of secondary hypertension.

Adrenal Gland Neoplasms