Biomatematica, Bioestatistica e Bioinformatica (ESTSP)

Coding information in the hippocampus through phaseprecession means that the phase in the theta cycle in which a place cell fires provides information regarding the position of the rat in the place field. There are published models addressing the phase-precession effect but commonly they are grounded in stringent assumptions or ignore the fact that signals in the brain are subject to a high degree of variability and noise. Here we present a biophysical model for phase precession in hippocampal CA1 cells which takes into account the following experimental results: i) there is linear precession through the entire place field of at least 180°of advance for single trials; ii) the firing rate profile through the crossing of the entire place field is Gaussian shaped; iii) phase-precession is present in every trial and not only when the animal has been trained on the circuit; iv) precession occurs during 5 to 6 theta cycles during the crossing of the place field. Our model addresses the interaction between complex spike cells and theta cells in the CA1 field of the hippocampus. The model focuses in the functional block composed of a complex spike cell receiving input from a theta cell which is in turn modulated by the population theta rhythm. The dynamics of the two types of neurons are described by Integrate-and-Fire models with connections being represented as single exponential conductance synapses. Both cells are excited by inputs from the entorhinal cortex (EC) which are modeled using a nonhomogeneous Poisson process. The simulated input spike trains representing these inputs are both space modulated and theta rhythm modulated. Phase precession in our biologically plausible model is explained as a consequence of local theta acceleration affecting the complex spike responses. Although all theta cells form a weakly coupled network modulated by the theta rhythm, increased excitation to the pair complex spike cell / theta cell leads to a local acceleration of the average firing frequency of theta cells. The complex spike cell, modulated locally by the theta cell(s) with a rhythm which is slightly faster than the population theta, undergoes phase precession. Only complex spike cells, and associated theta cells, receiving more excitation (inside their respective place field) will exhibit phase precession. Our model implies that rate coding and phase coding in place cells are not produced from independent mechanisms. By its simplicity and reduced assumptions, it can be applied not only to the CA1 precession but also to other hippocampal subfields such as DG and CA3. In fact this model predicts precession in any network with the same architecture and subject to a clocking rhythm, independently of the involvement of the network in spatial tasks.

Electric wheelchairs are now more intelligent due to the use of algorithms that provide assisted driving. Typically, the user steers the electric wheelchairs with conventional analog joysticks. This implies the need for an appropriate methodology to map the position of the joystick handle in a Cartesian coordinate system to the wheelchair motor velocities. This mapping of joystick positions to individual wheel speed can be done in an infinite number of combinations. However it is this mapping that will determine the response behavior of the wheelchair to the user manual control. This paper describes the implementation of several joystick mappings in an intelligent wheelchair prototype. Experiments were performed in a realistic simulator using 25 users with distinct driving abilities. The users had 6 different joystick control mapping methods and for each user the usability and preference order was measured. The results achieved enable to conclude that a more direct mapping between the joystick's coordinates and the wheelchair behavior is preferred by the majority of the users.

Human behaviour knowledge is an important requirement for implementing realistic evacuation models. Although much work has been done in this field of research there are no universally accepted quantitative methods. In this paper we present a novel methodology for human behaviour elicitation that was coined SPEED (Simulation of Pedestrian and Elicitation of their Emergent Dynamics). An experimental setup to test the concept was envisaged and validated by a group of experts using the Delphi method. A test bed was designed using the Serious Games concept and 22 subjects were selected for a pilot test. Preliminary results are promising, showing that this methodology might be used for the elicitation of human behaviour of subjects when facing an emergency. Moreover, the data acquired is of great importance for the fire safety experts designing new buildings or planning strategies to improve emergency paths. Another possible outcome is to create an artificial population based on human behaviour to populate emergency evacuation simulators.

Serious Games are being increasingly used as a tool for various applications, contrary to the traditional entertainment purpose. One of their application domains is fire safety. Possible injuries from fires are a dangerous safety concern for children, for instance. Another important issue is the elicitation of behavioural knowledge to design and feed simulation models. The lack of human behaviour data is often referred to as a drawback to evacuation simulation designers. This paper addresses the aforementioned matters in respect to: i) acquiring valuable knowledge on children behaviour when facing the urgent need for evacuation; and ii) devising an educational tool. A group of 19 children from an elementary school played two different role plays using a Serious Game and the data of their behaviours was collected. Results were analysed and are here presented. Future work is two-fold: to expand and to refine data collection to other groups such as elderly; to use this data for crowd synthesis particularly for evacuation simulators.

Quality of life is a concept influenced by social, economic, psychological, spiritual or medical state factors. More specifically, the perceived quality of an individual's daily life is an assessment of their well-being or lack of it. In this context, information technologies may help on the management of services for healthcare of chronic patients such as estimating the patient quality of life and helping the medical staff to take appropriate measures to increase each patient quality of life. This paper describes a Quality of Life estimation system developed using information technologies and the application of data mining algorithms to access the information of clinical data of patients with cancer from Otorhinolaryngology and Head and Neck services of an oncology institution. The system was evaluated with a sample composed of 3013 patients. The results achieved show that there are variables that may be significant predictors for the Quality of Life of the patient: years of smoking (p value 0.049) and size of the tumor (p value<0.001). In order to assign the variables to the classification of the quality of life the best accuracy was obtained by applying the John Platt's sequential minimal optimization algorithm for training a support vector classifier. In conclusion data mining techniques allow having access to patients additional information helping the physicians to be able to know the quality of life and produce a well-informed clinical decision.

Intelligent wheelchairs can become an important solution to assist physically impaired individuals who find it difficult or impossible to drive regular powered wheelchairs. However, when designing the hardware architecture several projects compromise the user comfort and the wheelchair normal usability in order to solve robotic problems. In this paper we describe the main concepts regarding the design of the IntellWheels intelligent wheelchair. Our approach has a user-centered perspective, in which the needs and limitations of physically impaired users are given extensive attention at each stage of the design process. Finally, our design was evaluated through a public opinion assessment. A statistical analysis suggested that the design was effective to mitigate the visual and ergonomic impacts caused by the addition of sensorial and processing capabilities on the wheelchair.