Understanding the impact of pleasant odours on the emotional processing networks in the brain

了解宜人的气味对大脑情绪处理网络的影响

• 批准号: 2779474
• 金额: --
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2779474
• 关键词: Understanding; impact; pleasant; odours; emotional

Olfaction is one of the two chemical senses able to detect small volatile compounds found in the air. It is important for many behaviours such as food localisation, identifications of threats and danger, and possible mates. Anatomically, it is the only sense presenting a trajectory that bypasses the thalamus, region known for its main role in emotional modulation. Because of this peculiarity, many researchers have investigated the interaction between olfaction and the emotional network, using a wide range of methodologies. It has been found that the brain processes odorants based on their hedonic valence. Most EEG studies have shown the evidence of this interaction in the late positive potential (LPP) components as odour-valence modulation of face/body expression recognition. Moreover, fMRI results suggested that the piriform cortex is mainly associated to subjective odour intensity, while the posterior orbitofrontal cortex is mainly associated to the subjective hedonic tone of the odorant. However, most of the research has only investigated this interaction using odours with very different hedonic tones. Hence, our aim is to focus specifically on how pleasant odours, therefore with similar hedonic tone, influence the emotional processing neural networks, by using neuroimaging techniques. Moreover, we are investigating this influence on emotional judgements towards external stimuli (pictures of faces, objects, and scenario) and on self-reported internal moods. This research has many applications, especially in the industrial and engineering setting and in the medical field (e.g., aromatherapy). In the first year, a scoping review was conducted to understand the volume of previous findings regarding this interaction and identify the gaps in the literature. The eligible criteria required only human-based studies, involving neuroimaging techniques, aiming to investigate specifically the interaction between odours and emotions. Based on its findings, the PhD general aim and question were formulated. After, a behavioural within-subjects study was conducted as pilot, to select the best stimuli. The odours were Vanilla, Rose, Lavender, Lemon and clean air (as control); they were delivered to the participant's nostrils using an olfactometer. As visual stimuli, pictures showing happy and neutral faces, emotional and neutral objects, and emotional and neutral landscapes were selected. For each picture, participants were required to rate the pleasantness while smelling each odour. Moreover, they were required to rate their emotional states (nostalgic, happy, disgusted, thirsty, sensual, relaxed, and hungry) during each odour. The quantitative analysis is conducted using ANOVAs and linear modelling. This study's findings will lead to the proper set of stimuli for the next study, which will be an EEG research, aiming to find the neural correlates of the interaction between odours and emotions. It will be based on ERP or time-frequency analysis. Following this, during the third year, the current goal is to conduct an fMRI study to further investigate this interaction and map the brain regions involved.Since the hypotheses are merely exploratory, proper expectations are not made yet. However, based on the most consistent findings, vanilla might be the odour with the strongest influence on improving emotional judgements and internal moods. This could due to the strict similarity with the breastfeeding odour, which resemble the vanilla one.

嗅觉是能够检测空气中微小挥发性化合物的两种化学感官之一。它对于许多行为都很重要，例如食物本地化、威胁和危险识别以及可能的配偶。从解剖学上讲，它是唯一呈现绕过丘脑轨迹的感觉，该区域以其在情绪调节中的主要作用而闻名。由于这种特殊性，许多研究人员使用多种方法研究了嗅觉和情感网络之间的相互作用。研究发现，大脑根据气味的享乐价来处理气味。大多数脑电图研究已经证明了晚期正电位（LPP）成分中这种相互作用作为面部/身体表达识别的气味价调节。此外，功能磁共振成像结果表明，梨状皮层主要与主观气味强度相关，而后眶额皮层主要与气味物质的主观享乐基调相关。然而，大多数研究仅使用具有截然不同的享乐基调的气味来研究这种相互作用。因此，我们的目标是通过使用神经影像技术，特别关注令人愉悦的气味（因此具有相似的享乐基调）如何影响情绪处理神经网络。此外，我们正在研究这种对外部刺激（面部、物体和场景的图片）的情绪判断以及自我报告的内部情绪的影响。这项研究有很多应用，特别是在工业和工程环境以及医学领域（例如芳香疗法）。第一年，进行了范围界定审查，以了解先前有关这种相互作用的研究结果的数量，并找出文献中的差距。合格的标准只需要基于人类的研究，涉及神经成像技术，旨在专门研究气味和情绪之间的相互作用。根据其发现，制定了博士学位的总体目标和问题。之后，进行了一项试点行为研究，以选择最佳刺激。气味为香草、玫瑰、薰衣草、柠檬和清洁空气（作为对照）；使用嗅觉计将它们传送到参与者的鼻孔。作为视觉刺激，选择了显示快乐和中性面孔、情感和中性物体以及情感和中性风景的图片。对于每张图片，参与者都需要在闻每种气味时对愉悦程度进行评分。此外，他们还需要对每种气味的情绪状态（怀旧、快乐、恶心、口渴、性感、放松和饥饿）进行评分。使用方差分析和线性建模进行定量分析。这项研究的发现将为下一项研究提供适当的刺激，下一项研究将是脑电图研究，旨在找到气味和情绪之间相互作用的神经关联。它将基于 ERP 或时频分析。此后的第三年，当前的目标是进行功能磁共振成像研究，以进一步研究这种相互作用并绘制所涉及的大脑区域图。由于假设仅仅是探索性的，因此尚未做出适当的预期。然而，根据最一致的研究结果，香草可能是对改善情绪判断和内部情绪影响最大的气味。这可能是由于与母乳喂养的气味非常相似，类似于香草味。