In this work, a device for generating automated olfactory stimuli in functional magnetic resonance imaging (fMRI) studies is described. The novel issues of our design are: synchronization between the acquisition and the olfactory task, automated control of experimental parameters (odorants sequences, frequency, time and concentration of stimuli). Finally, we present the preliminary results obtained on a General Electric 3 Tesla MRI scanner belong to The Alzheimer Project of the Fundación Reina Sofía.
Objective: To show the results of a device that generates automated olfactory stimuli suitable for functional magnetic resonance imaging (fMRI) experiments. Material and methods: Ten normal volunteers, 5 women and 5 men, were studied. The system allows the programming of several sequences, providing the capability to synchronise the onset of odour presentation with acquisition by a trigger signal of the MRI scanner. The olfactometer is a device that allows selection of the odour, the event paradigm, the time of stimuli and the odour concentration. The paradigm used during fMRI scanning consisted of 15-s blocks. The odorant event took 2 s with butanol, mint and coffee. Results: We observed olfactory activity in the olfactory bulb, entorhinal cortex (4%), amygdala (2.5%) and temporo-parietal cortex, especially in the areas related to emotional integration. Conclusions: The device has demonstrated its effectiveness in stimulating olfactory areas and its capacity to adapt to fMRI equipment.
Estudio objetivo del olfato mediante resonancia magnetica funcional
ResumenObjetivo: Mostrar los resultados del olfatometro capaz de generar tareas olfativas en un equipo de resonancia magnetica funcional (fMRI).
Olfatometro; RetroalimentacionMaterial y metodos: Estudiamos 10 sujetos normales: 5 varones y 5 mujeres. El olfatometro esta disenado para que el estimulo que produce se sincronice con el equipo de fMRI mediante la serial desencadenante que suministra el propio equipo. El olfatometro es capaz de: seleccionar el olor, secuenciar los distintos olores, programar la frecuencia y duracion de los olores y controlar la intensidad del olor. El paradigma utilizado responde a un diseno de activacion asociada a eventos, en el que la duracion del bloque de activacion y de reposo es de 15 s. La duracion del estimulo olfativo (butanol, menta o cafe) es de 2 segundos, durante toda la serie que consta de 9 ciclos. Resultados: Se ha observado reactividad (contraste BOLD) en las diferentes areas cerebrales involucradas en las tareas olfativas: bulbo olfatorio, cortex entorrinal (4%), amigdala (2,5%) y cortex temporoparietal. Las areas relacionadas con integracion de las emociones tienen una reactividad mayor. Conclusiones: El dispositivo propuesto nos permite controlar de forma automatica y sincronizada los olores necesarios para estudiar la actividad de las areas olfatorias cerebrales mediante fMRI.
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