Original Article
Objective Assessment of Olfactory Function Using Functional Magnetic Resonance Imaging
Estudio objetivo del olfato mediante resonancia magnética funcional
Adolfo Toledanoa,b,
, Susana Borromeoc, Guillermo Lunac, Elena Molinad, Ana Beatriz Solanad, Pablo García-Poloa, Juan Antonio Hernándezc,d,e, Juan Álvarez-linerae
Corresponding author
a Consulta de Olfato, Hospital Universitario Fundación Alcorcón, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain
b Consulta de Olfato, Hospital Ruber Internacional, Madrid, Spain
c Departamento de Tecnología Electrónica, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain
d Laboratorio de Neuroimagen, Centro de Tecnología Biomédica, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain
e Fundación CIEN, Fundación Reina Sofía, Madrid, Spain
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Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain" "etiqueta" => "<span class="elsevierStyleSup">c</span>" "identificador" => "aff0015" ] 3 => array:3 [ "entidad" => "Laboratorio de Neuroimagen, Centro de Tecnología Biomédica, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain" "etiqueta" => "<span class="elsevierStyleSup">d</span>" "identificador" => "aff0020" ] 4 => array:3 [ "entidad" => "Fundación CIEN, Fundación Reina Sofía, Madrid, Spain" "etiqueta" => "<span class="elsevierStyleSup">e</span>" "identificador" => "aff0025" ] ] "correspondencia" => array:1 [ 0 => array:3 [ "identificador" => "cor0005" "etiqueta" => "⁎" "correspondencia" => "Corresponding author." ] ] ] ] "titulosAlternativos" => array:1 [ "es" => array:1 [ "titulo" => "Estudio objetivo del olfato mediante resonancia magnética funcional" ] ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:7 [ "identificador" => "fig0005" "etiqueta" => "Figure 1" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr1.jpeg" "Alto" => 2209 "Ancho" => 3185 "Tamanyo" => 374428 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0045" class="elsevierStyleSimplePara elsevierViewall">MRI-compatible olfactometer. The diagram shows how the image acquisition signal from the fMRI device activates the olfactometer software. In turn, the olfactometer software regulates the opening of the electrovalves to release the odours stored in the canisters. The odours travel through the tube up to the mask worn by the subject.</p>" ] ] ] "textoCompleto" => "<span class="elsevierStyleSections"><span id="sec0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Introduction</span><p id="par0005" class="elsevierStylePara elsevierViewall">It is estimated that in the United States there are 2.7 million people who suffer from olfactory disorders, i.e. about 1.4% of the total population. Approximately 200<span class="elsevierStyleHsp" style=""></span>000 Americans each year suffer a smell or taste problem.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1,2</span></a> In our practice, 1.7% of patients each month report a smell disorder as the main reason for consultation.<a class="elsevierStyleCrossRef" href="#bib0015"><span class="elsevierStyleSup">3</span></a></p><p id="par0010" class="elsevierStylePara elsevierViewall">The objective study of smell in humans is still an unresolved problem. The reasons for this are probably manifold. One possible factor is that man gives less importance to this sense than to others, such as sight and hearing. On the other hand, there are still various anatomical-physiological questions which remain unanswered, making it difficult to establish a correlation between an olfactory stimulus and an objective test, either electrophysiological or imaging.<a class="elsevierStyleCrossRef" href="#bib0020"><span class="elsevierStyleSup">4</span></a> Another problem is the difficulty of adequately controlling olfactory stimuli in terms of intensity and duration, in order to correlate a specific stimulus with the response elicited.<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a></p><p id="par0015" class="elsevierStylePara elsevierViewall">The first attempt to study smell objectively took place in the late 1960s of the past century, and employed the electrophysiological recording of odours.<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a> At present, the electrophysiological study of smell is done by electro-olfactograms<a class="elsevierStyleCrossRef" href="#bib0035"><span class="elsevierStyleSup">7</span></a> and olfactory evoked potentials.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a> An electro-olfactogram involves the collection of electrical activity in the nasal olfactory epithelium through the application of intranasal electrodes. Olfactory evoked potentials consist in the collection of electrical activity (olfactory bulb and/or frontal cortex) using external electrodes. Both techniques employ expensive apparatus and take a long time. They are eminently used in research and therefore are not performed normally in daily practice.</p><p id="par0020" class="elsevierStylePara elsevierViewall">Moreover, functional magnetic resonance imaging (fMRI) studies can detect brain activity when subjects perform psychocognitive, sensory or motor tasks. fMRI imaging enables the noninvasive study of brain activity while subjects perform a particular task, by detecting small signal changes dependent on blood oxygen level (BOLD signal). These changes are the result of a neural response induced by repeated cycles of stimulation conditions (i.e. experimental conditions) and resting conditions (i.e. control conditions). In recent years, functional neuroimaging has become a very promising technique as a tool for the analysis of the olfactory system.<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a> One problem with these devices is the need to coordinate the stimulus, whatever this may be, with the collection of images. Furthermore, fMRI is not compatible with the use of metal devices inside the same room.</p><p id="par0025" class="elsevierStylePara elsevierViewall">The aim of this work is to show the results among normal subjects of an olfactometer capable of generating olfactory tasks in the context of an fMRI study of brain activity.</p></span><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Material and Methods</span><p id="par0030" class="elsevierStylePara elsevierViewall">The olfactometer developed at the Department of Electronic Technology of Universidad Rey Juan Carlos has been designed specifically for olfactory stimulation. It automatically generates olfactory stimuli which are suitable for fMRI experiments, as it synchronises the olfactory task with the acquisition of magnetic resonance imaging (MRI) through the trigger signal of the scanner. It produces a selective and controlled stimulation of the olfactory system. Among the parameters that can be controlled are the selection and sequencing of odours, the frequency and duration of stimuli and the intensity of the stimulus.</p><p id="par0035" class="elsevierStylePara elsevierViewall"><a class="elsevierStyleCrossRef" href="#fig0005">Fig. 1</a> shows a schematic of the device. It consists of several dispensers (up to 8) which receive an air flow regulated by a flowmeter. The choice of odour is done by actuating specific electrovalves. After the air pump are two filters, one for particles and another with activated carbon, for the removal of other odours which could be introduced accidentally. A computer with a sequence control board enables the opening and closing of the electrovalves, as well as synchronisation of the stimuli with image acquisition.</p><elsevierMultimedia ident="fig0005"></elsevierMultimedia><p id="par0040" class="elsevierStylePara elsevierViewall">A specific software program has also been developed in order to design olfactory tasks, so they can be executed automatically and remotely during image acquisition. The MRI data were obtained with a 3<span class="elsevierStyleHsp" style=""></span>T General Electric MRI scanner located at Centro Alzheimer Fundación Reina Sofía (<a class="elsevierStyleCrossRef" href="#fig0010">Fig. 2</a>). The fMRI sequence used was a gradient-echo functional sequence with echo-planar k-space acquisition. The GE-EPI (gradient-echo echo-planar imaging) sequence acquisition parameters were as follows: RT (repetition time)=3<span class="elsevierStyleHsp" style=""></span>s, ET (echo time)=minimum full, FA (flip angle)=90°, matrix of 96×128 samples, FOV (field of view)=22<span class="elsevierStyleHsp" style=""></span>cm, section thickness of 2.4<span class="elsevierStyleHsp" style=""></span>mm, space of 0<span class="elsevierStyleHsp" style=""></span>mm between sections and full volume of 34 sections.</p><elsevierMultimedia ident="fig0010"></elsevierMultimedia><p id="par0045" class="elsevierStylePara elsevierViewall">Two types of paradigms were designed for functional imaging: block design and event-related activation design. Only the results obtained with the event-related activation design are shown, since it was the most effective way to visualise brain activation associated with an olfactory stimulus and to eliminate the effects of habituation of the primary olfactory cortex (POC).<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a></p><p id="par0050" class="elsevierStylePara elsevierViewall">The paradigm used responded to an event-related design, in which the duration of activation and resting blocks was 15<span class="elsevierStyleHsp" style=""></span>s. The duration of the olfactory stimulus (butanol, mint or coffee) was 2<span class="elsevierStyleHsp" style=""></span>s for the entire series, which consisted of 9 cycles (<a class="elsevierStyleCrossRef" href="#fig0015">Fig. 3</a>). Breathing was recorded by “respiratory gating”, for later use in data processing. The protocol did not include “sniffing” and, therefore, subjects did not know when the olfactory stimulus would be presented.</p><elsevierMultimedia ident="fig0015"></elsevierMultimedia><p id="par0055" class="elsevierStylePara elsevierViewall">The following transformations were applied to the fMRI images prior to data analysis: 3D motion correction, temporal high-pass filtering set to the stimulation paradigm, temporary correction and spatial smoothing.</p><p id="par0060" class="elsevierStylePara elsevierViewall">So as to avoid inter-subject and intra-subject variability, analysis was conducted by regions of interest (ROI), through a segmentation of subcortical/cortical structures.</p><p id="par0065" class="elsevierStylePara elsevierViewall">Functional images were constructed by convolving a sequence of square pulses of 2-s duration. These pulses were synchronised with the application of olfactory stimuli with the canonical haemodynamic response function (HRF) (<a class="elsevierStyleCrossRef" href="#fig0020">Fig. 4</a>). The registration of breathing was used as a regressor in the analysis.</p><elsevierMultimedia ident="fig0020"></elsevierMultimedia><p id="par0070" class="elsevierStylePara elsevierViewall">The analysis of study results was performed using the software tool SPM8 (statistical parametric mapping) developed by University College London for neuroimaging data analysis.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a></p></span><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Results</span><p id="par0075" class="elsevierStylePara elsevierViewall">Cortical reactivity was obtained in different brain areas involved in olfactory tasks (<a class="elsevierStyleCrossRef" href="#fig0025">Fig. 5</a>). The entorhinal cortex and amygdala, which are related to emotions, showed a higher reactivity than other areas.</p><elsevierMultimedia ident="fig0025"></elsevierMultimedia><p id="par0080" class="elsevierStylePara elsevierViewall">With a significance level between 4.5% and 2% of BOLD contrast:<ul class="elsevierStyleList" id="lis0005"><li class="elsevierStyleListItem" id="lsti0005"><span class="elsevierStyleLabel">1</span><p id="par0085" class="elsevierStylePara elsevierViewall">Entorhinal cortex: 4.5% BOLD contrast.</p></li><li class="elsevierStyleListItem" id="lsti0010"><span class="elsevierStyleLabel">2</span><p id="par0090" class="elsevierStylePara elsevierViewall">Amygdala: 3% BOLD contrast.</p></li><li class="elsevierStyleListItem" id="lsti0015"><span class="elsevierStyleLabel">3</span><p id="par0095" class="elsevierStylePara elsevierViewall">Insula: 2.5% BOLD contrast.</p></li><li class="elsevierStyleListItem" id="lsti0020"><span class="elsevierStyleLabel">4</span><p id="par0100" class="elsevierStylePara elsevierViewall">Putamen: 2.5% BOLD contrast.</p></li><li class="elsevierStyleListItem" id="lsti0025"><span class="elsevierStyleLabel">5</span><p id="par0105" class="elsevierStylePara elsevierViewall">Visual cortex: 2% BOLD contrast.</p></li></ul></p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Discussion</span><p id="par0110" class="elsevierStylePara elsevierViewall">Functional MRI enables us to locate the cortical areas which are activated by different stimuli: visual,<a class="elsevierStyleCrossRef" href="#bib0060"><span class="elsevierStyleSup">12</span></a> sound<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a> and somatosensory.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a> In this work we qualitatively and quantitatively demonstrate the activation of different cortical areas in the brains of subjects by normal olfactory stimuli: entorhinal cortex, amygdala, insula, putamen, and visual cortex.</p><p id="par0115" class="elsevierStylePara elsevierViewall">The cortical areas activated are those that have been implicated in the integration of olfactory stimuli, including some regions of the limbic system. The POC area is the most commonly activated: entorhinal cortex and amygdala. We must remember that the POC is not a single area, but rather 5 structurally different regions, located in the ventral and medial surfaces of each brain hemisphere: the anterior olfactory nucleus, amygdala, olfactory tubercle, piriform and periamygdaloid cortex and, finally, the rostral entorhinal cortex.<a class="elsevierStyleCrossRef" href="#bib0075"><span class="elsevierStyleSup">15</span></a> The amygdala is a heterogeneous structure with numerous nuclei which is located in the anterior temporal lobe. One of these nuclei is the corticomedial nuclear group, which appears to be connected with parts of the hypothalamus involved in regulating food intake, as well as in regulating some reproductive behaviours in animals.<a class="elsevierStyleCrossRefs" href="#bib0075"><span class="elsevierStyleSup">15,16</span></a> Furthermore, the entorhinal cortex is located in the parahippocampal gyrus. It is believed that this area is important in allowing certain scents to evoke past memories. This cortex projects towards the hippocampal formation, which has been found to be essential in converting short-term memories into long-term memories.<a class="elsevierStyleCrossRefs" href="#bib0075"><span class="elsevierStyleSup">15,16</span></a></p><p id="par0120" class="elsevierStylePara elsevierViewall">As for the quantitative study of cortical activation, the results were surprising. If we consider that the gold standard is obtained by measuring the BOLD contrast in motor activation studies (moving a finger or hand and measuring activation of motor cortical areas) with values around 5%, we can conclude that a BOLD contrast of 4.5% in the entorhinal cortex and 3% in the amygdala represent considerable activation values for a sensory stimulus.<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a> Therefore, we believe that either the odorous stimulus activates olfactory cortical areas very intensely by itself, or else the stimulation device is so pure and precise that it enables a high-intensity activation image to be collected.One of the main problems in the objective study of smell is the impossibility of controlling some parameters of olfactory stimuli, such as the type of odour, its duration, intensity and frequency. The advantage of the olfactometer is that it enables researchers to vary the stimuli (type of odour, intensity, duration, creating predetermined olfactory tasks, etc.) from outside the MRI room without having to distract the patient, and therefore, without creating brain activation distortions or artefacts. In addition, our olfactometer was synchronised with the acquisition of the fMRI device through its trigger signal, thus enabling a perfect synchronisation between stimulus emission and image acquisition. This allowed us to design various olfactory tasks for the study of complex cortical functions: memory, emotions, appetite, sexuality, etc. Devices which stimulate the sense of smell are not new and many are available in the market.<a class="elsevierStyleCrossRefs" href="#bib0085"><span class="elsevierStyleSup">17–19</span></a> The problem is that they are very expensive and difficult to manufacture. At present, we can find some similar devices.<a class="elsevierStyleCrossRefs" href="#bib0050"><span class="elsevierStyleSup">10,20–22</span></a></p><p id="par0125" class="elsevierStylePara elsevierViewall">Olfactometers available in the market have a common design in that they are constructed with metal components, making them bulky and very heavy, thus preventing them from being kept inside the scanner room. This was not a limitation for our olfactometer, since our device is portable and enables the stimuli to be managed from outside the MRI room. Only the tubes which deploy the stimulus and the mask for the subject need to be kept in the room.</p><p id="par0130" class="elsevierStylePara elsevierViewall">Having an olfactometer available in our consultation will enable us to assess, in an objective manner, the olfactory ability of subjects, either through fMRI or olfactory evoked potentials. It will also allow us to establish correlations between subjective smell tests and objective responses, as well as an objective study of olfactory condition. Murphy et al.<a class="elsevierStyleCrossRef" href="#bib0115"><span class="elsevierStyleSup">23</span></a> correlated the butanol threshold in the CCCRC olfactory test with evoked potential values obtained using an olfactometer. Lorig et al.<a class="elsevierStyleCrossRef" href="#bib0120"><span class="elsevierStyleSup">24</span></a> have worked on the correlation between olfactory thresholds in psychophysical tests and their correlation with evoked potentials. Kobal et al.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a> have used an olfactometer to study anosmic patients through olfactory evoked potentials.</p><p id="par0135" class="elsevierStylePara elsevierViewall">We believe that our olfactometer has room for improvement. The olfactory study lasts no more than 45<span class="elsevierStyleHsp" style=""></span>min. This time does not differ much from the time it takes to conduct a structural MRI study. However, having patients wear a mask makes them feel more uncomfortable and, possibly, more cramped. On the other hand, the stimulus must travel through a tube into the nose. It is possible that some degradation occurs along the route before the stimulus arrives at the nose. An electronic nose which can measure the exact concentration of the stimulus upon its arrival at both nostrils could be attached to the mask, in order to know the exact concentration which reaches the subject.</p><p id="par0140" class="elsevierStylePara elsevierViewall">Numerous studies still remain to be conducted before normal values for brain activation areas, both quantitative and qualitative, can be established depending on the tasks designed and basic variables such as age and gender. In the future, objective studies of olfaction will open up a very interesting field of study for the early diagnosis of some neuropsychiatric diseases: Parkinson's disease,<a class="elsevierStyleCrossRefs" href="#bib0125"><span class="elsevierStyleSup">25,26</span></a> Alzheimer's disease,<a class="elsevierStyleCrossRefs" href="#bib0135"><span class="elsevierStyleSup">27,28</span></a> eating disorders, sexual disorders, etc.</p></span><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Financing</span><p id="par0145" class="elsevierStylePara elsevierViewall">This work was financed by the <span class="elsevierStyleGrantSponsor">OLFACTOSENSE Consortium</span>, by the <span class="elsevierStyleGrantSponsor">Education Council of the Community of Madrid</span>, the <span class="elsevierStyleGrantSponsor">MMA Foundation</span> and the <span class="elsevierStyleGrantSponsor">MAPFRE Foundation</span>.</p></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Conflict of Interests</span><p id="par0150" class="elsevierStylePara elsevierViewall">The authors have no conflicts of interest to declare.</p></span></span>" "textoCompletoSecciones" => array:1 [ "secciones" => array:12 [ 0 => array:2 [ "identificador" => "xres95013" "titulo" => array:5 [ 0 => "Abstract" 1 => "Objective" 2 => "Material and methods" 3 => "Results" 4 => "Conclusions" ] ] 1 => array:2 [ "identificador" => "xpalclavsec82164" "titulo" => "Keywords" ] 2 => array:2 [ "identificador" => "xres95012" "titulo" => array:5 [ 0 => "Resumen" 1 => "Objetivo" 2 => "Material y métodos" 3 => "Resultados" 4 => "Conclusiones" ] ] 3 => array:2 [ "identificador" => "xpalclavsec82165" "titulo" => "Palabras clave" ] 4 => array:2 [ "identificador" => "sec0005" "titulo" => "Introduction" ] 5 => array:2 [ "identificador" => "sec0010" "titulo" => "Material and Methods" ] 6 => array:2 [ "identificador" => "sec0015" "titulo" => "Results" ] 7 => array:2 [ "identificador" => "sec0020" "titulo" => "Discussion" ] 8 => array:2 [ "identificador" => "sec0025" "titulo" => "Financing" ] 9 => array:2 [ "identificador" => "sec0030" "titulo" => "Conflict of Interests" ] 10 => array:2 [ "identificador" => "xack35155" "titulo" => "Acknowledgement" ] 11 => array:1 [ "titulo" => "References" ] ] ] "pdfFichero" => "main.pdf" "tienePdf" => true "fechaRecibido" => "2010-01-11" "fechaAceptado" => "2012-01-16" "PalabrasClave" => array:2 [ "en" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Keywords" "identificador" => "xpalclavsec82164" "palabras" => array:3 [ 0 => "Functional magnetic resonance imaging" 1 => "Olfactometer" 2 => "Feedback" ] ] ] "es" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Palabras clave" "identificador" => "xpalclavsec82165" "palabras" => array:3 [ 0 => "Resonancia magnética funcional" 1 => "Olfatómetro" 2 => "Retroalimentación" ] ] ] ] "tieneResumen" => true "resumen" => array:2 [ "en" => array:2 [ "titulo" => "Abstract" "resumen" => "<span class="elsevierStyleSectionTitle">Objective</span><p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">To show the results of a device that generates automated olfactory stimuli suitable for functional magnetic resonance imaging (fMRI) experiments.</p> <span class="elsevierStyleSectionTitle">Material and methods</span><p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">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<span class="elsevierStyleHsp" style=""></span>s with butanol, mint and coffee.</p> <span class="elsevierStyleSectionTitle">Results</span><p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">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.</p> <span class="elsevierStyleSectionTitle">Conclusions</span><p id="spar0020" class="elsevierStyleSimplePara elsevierViewall">The device has demonstrated its effectiveness in stimulating olfactory areas and its capacity to adapt to fMRI equipment.</p>" ] "es" => array:2 [ "titulo" => "Resumen" "resumen" => "<span class="elsevierStyleSectionTitle">Objetivo</span><p id="spar0025" class="elsevierStyleSimplePara elsevierViewall">Mostrar los resultados del olfatómetro capaz de generar tareas olfativas en un equipo de resonancia magnética funcional (fMRI).</p> <span class="elsevierStyleSectionTitle">Material y métodos</span><p id="spar0030" class="elsevierStyleSimplePara elsevierViewall">Estudiamos 10 sujetos normales: 5 varones y 5 mujeres. El olfatómetro está diseñado para que el estímulo que produce se sincronice con el equipo de fMRI mediante la señal desencadenante que suministra el propio equipo. El olfatómetro es capaz de: seleccionar el olor, secuenciar los distintos olores, programar la frecuencia y duración de los olores y controlar la intensidad del olor. El paradigma utilizado responde a un diseño de activación asociada a eventos, en el que la duración del bloque de activación y de reposo es de 15<span class="elsevierStyleHsp" style=""></span>s. La duración del estímulo olfativo (butanol, menta o café) es de 2 segundos, durante toda la serie que consta de 9 ciclos.</p> <span class="elsevierStyleSectionTitle">Resultados</span><p id="spar0035" class="elsevierStyleSimplePara elsevierViewall">Se ha observado reactividad (contraste BOLD) en las diferentes áreas cerebrales involucradas en las tareas olfativas: bulbo olfatorio, córtex entorrinal (4%), amigdala (2,5%) y córtex temporoparietal. Las áreas relacionadas con integración de las emociones tienen una reactividad mayor.</p> <span class="elsevierStyleSectionTitle">Conclusiones</span><p id="spar0040" class="elsevierStyleSimplePara elsevierViewall">El dispositivo propuesto nos permite controlar de forma automática y sincronizada los olores necesarios para estudiar la actividad de las áreas olfatorias cerebrales mediante fMRI.</p>" ] ] "NotaPie" => array:1 [ 0 => array:2 [ "etiqueta" => "☆" "nota" => "<p class="elsevierStyleNotepara">Please cite this article as: Toledano A, et al. Estudio objetivo del olfato mediante resonancia magnética funcional. Acta Otorrinolaringol Esp. 2012;63:280–5.</p>" ] ] "multimedia" => array:5 [ 0 => array:7 [ "identificador" => "fig0005" "etiqueta" => "Figure 1" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr1.jpeg" "Alto" => 2209 "Ancho" => 3185 "Tamanyo" => 374428 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0045" class="elsevierStyleSimplePara elsevierViewall">MRI-compatible olfactometer. The diagram shows how the image acquisition signal from the fMRI device activates the olfactometer software. In turn, the olfactometer software regulates the opening of the electrovalves to release the odours stored in the canisters. The odours travel through the tube up to the mask worn by the subject.</p>" ] ] 1 => array:7 [ "identificador" => "fig0010" "etiqueta" => "Figure 2" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr2.jpeg" "Alto" => 712 "Ancho" => 955 "Tamanyo" => 73821 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0050" class="elsevierStyleSimplePara elsevierViewall">Volunteer subject wearing the dispenser mask. As shown by the image, the mask may create a space conflict and cramped feeling for the subject.</p>" ] ] 2 => array:7 [ "identificador" => "fig0015" "etiqueta" => "Figure 3" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr3.jpeg" "Alto" => 756 "Ancho" => 2485 "Tamanyo" => 141753 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0055" class="elsevierStyleSimplePara elsevierViewall">The event-related paradigm used, in which the duration of the activation and resting blocks is 15<span class="elsevierStyleHsp" style=""></span>s. The duration of the olfactory stimulus (butanol, mint or coffee) is 2<span class="elsevierStyleHsp" style=""></span>s for the entire series, consisting of 9<span class="elsevierStyleHsp" style=""></span>cycles.</p>" ] ] 3 => array:7 [ "identificador" => "fig0020" "etiqueta" => "Figure 4" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr4.jpeg" "Alto" => 960 "Ancho" => 956 "Tamanyo" => 209772 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0060" class="elsevierStyleSimplePara elsevierViewall">Haemodynamic response in olfactory functional areas. The image shows how there is an increase in oxygen consumption in the brain area studied when the stimulus is released (green arrow), unlike in the resting phase (red arrow). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)</p>" ] ] 4 => array:7 [ "identificador" => "fig0025" "etiqueta" => "Figure 5" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr5.jpeg" "Alto" => 1462 "Ancho" => 999 "Tamanyo" => 297240 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0065" class="elsevierStyleSimplePara elsevierViewall">Three-dimensional reconstruction of fibre and cortical activation results in olfactory pathways. The image shows how the olfactory areas of the olfactory bulb, entorhinal cortex, hippocampus and amygdala are activated. In addition, the tractography technique allows us to assess the status of the nerve fibres through which the stimulus travels (yellow arrows). 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| Year/Month | Html | Total | |
|---|---|---|---|
| 2023 March | 1 | 0 | 1 |
| 2021 March | 0 | 1 | 1 |
| 2021 January | 0 | 2 | 2 |
| 2020 November | 0 | 1 | 1 |
| 2020 August | 0 | 2 | 2 |
| 2020 July | 0 | 1 | 1 |
| 2020 May | 0 | 1 | 1 |
| 2020 April | 0 | 1 | 1 |
| 2020 March | 12 | 5 | 17 |
| 2020 February | 17 | 4 | 21 |
| 2020 January | 18 | 11 | 29 |
| 2019 December | 23 | 6 | 29 |
| 2019 November | 26 | 16 | 42 |
| 2019 October | 13 | 6 | 19 |
| 2019 September | 32 | 6 | 38 |
| 2019 August | 15 | 1 | 16 |
| 2019 July | 14 | 18 | 32 |
| 2019 June | 35 | 15 | 50 |
| 2019 May | 81 | 20 | 101 |
| 2019 April | 60 | 16 | 76 |
| 2019 March | 13 | 6 | 19 |
| 2019 February | 10 | 6 | 16 |
| 2019 January | 15 | 6 | 21 |
| 2018 December | 8 | 5 | 13 |
| 2018 November | 18 | 4 | 22 |
| 2018 October | 28 | 6 | 34 |
| 2018 April | 20 | 2 | 22 |
| 2018 March | 14 | 3 | 17 |
| 2018 February | 3 | 0 | 3 |
| 2018 January | 23 | 1 | 24 |
| 2017 December | 11 | 1 | 12 |
| 2017 November | 15 | 1 | 16 |
| 2017 October | 9 | 1 | 10 |
| 2017 September | 15 | 4 | 19 |
| 2017 August | 30 | 1 | 31 |
| 2017 July | 22 | 3 | 25 |
| 2017 June | 29 | 7 | 36 |
| 2017 May | 42 | 5 | 47 |
| 2017 April | 28 | 1 | 29 |
| 2017 March | 23 | 29 | 52 |
| 2017 February | 20 | 7 | 27 |
| 2017 January | 21 | 0 | 21 |
| 2016 December | 24 | 6 | 30 |
| 2016 November | 43 | 4 | 47 |
| 2016 October | 39 | 6 | 45 |
| 2016 September | 28 | 4 | 32 |
| 2016 August | 24 | 5 | 29 |
| 2016 July | 18 | 2 | 20 |
| 2016 June | 40 | 8 | 48 |
| 2016 May | 44 | 16 | 60 |
| 2016 April | 44 | 10 | 54 |
| 2016 March | 46 | 17 | 63 |
| 2016 February | 49 | 18 | 67 |
| 2016 January | 50 | 15 | 65 |
| 2015 December | 37 | 20 | 57 |
| 2015 November | 22 | 14 | 36 |
| 2015 October | 33 | 18 | 51 |
| 2015 September | 30 | 9 | 39 |
| 2015 August | 40 | 4 | 44 |
| 2015 July | 44 | 7 | 51 |
| 2015 June | 16 | 2 | 18 |
| 2015 May | 23 | 5 | 28 |
| 2015 April | 35 | 5 | 40 |
| 2015 March | 35 | 8 | 43 |
| 2015 February | 42 | 6 | 48 |
| 2015 January | 51 | 6 | 57 |
| 2014 December | 45 | 7 | 52 |
| 2014 November | 39 | 4 | 43 |
| 2014 October | 46 | 11 | 57 |
| 2014 September | 37 | 6 | 43 |
| 2014 August | 41 | 14 | 55 |
| 2014 July | 34 | 4 | 38 |
| 2014 June | 8 | 5 | 13 |
| 2014 May | 8 | 2 | 10 |
| 2014 April | 11 | 3 | 14 |
| 2014 March | 17 | 5 | 22 |
| 2014 February | 9 | 3 | 12 |
| 2014 January | 5 | 3 | 8 |
| 2013 December | 13 | 6 | 19 |
| 2013 November | 14 | 5 | 19 |
| 2013 October | 34 | 8 | 42 |
| 2013 September | 13 | 6 | 19 |
| 2013 August | 7 | 2 | 9 |
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