Development of Olfactory Communication and Cognition Lab, Centre des Sciences du Goût et de l'Alimentation, UBFC, CNRS, INRAe, Institut Agro, Université de Bourgogne, Dijon, France.
Biological Psychology and Neuropsychology, University of Hamburg, Hamburg, Germany.
Dev Sci. 2024 Nov;27(6):e13562. doi: 10.1111/desc.13562. Epub 2024 Aug 26.
To navigate their environment, infants rely on intersensory facilitation when unisensory perceptual demand is high, a principle known as inverse effectiveness. Given that this principle was mainly documented in the context of audiovisual stimulations, here we aim to determine whether it applies to olfactory-to-visual facilitation. We build on previous evidence that the mother's body odor facilitates face categorization in the 4-month-old brain, and investigate whether this effect depends on visual demand. Scalp electroencephalogram (EEG) was recorded in two groups of 4-month-old infants while they watched 6-Hz streams of visual stimuli with faces displayed every 6th stimulus to tag a face-selective response at 1 Hz. We used variable natural stimuli in one group (Nat Group), while stimuli were simplified in the other group (Simp Group) to reduce perceptual categorization demand. During visual stimulation, infants were alternatively exposed to their mother's versus a baseline odor. For both groups, we found an occipito-temporal face-selective response, but with a larger amplitude for the simplified stimuli, reflecting less demanding visual categorization. Importantly, the mother's body odor enhances the response to natural, but not to simplified, face stimuli, indicating that maternal odor improves face categorization when it is most demanding for the 4-month-old brain. Overall, this study demonstrates that the inverse effectiveness of intersensory facilitation applies to the sense of smell during early perceptual development. RESEARCH HIGHLIGHTS: Intersensory facilitation is a function of unisensory perceptual demand in infants (inverse effectiveness). This inverse relation between multisensory and unisensory perception has been mainly documented using audiovisual stimulations. Here we show that olfactory-to-visual facilitation depends on visual demand in 4-month-old infants. The inverse effectiveness of intersensory facilitation during early perceptual development applies to the sense of smell.
为了在单一感官知觉需求较高时探索环境，婴儿会依赖于感觉间促进作用，这一原理被称为逆向有效性。鉴于该原理主要是在视听刺激的背景下记录的，我们旨在确定其是否适用于嗅觉到视觉的促进作用。我们基于先前的证据，即母亲的体味有助于 4 个月大的婴儿对面部进行分类，并研究这种效应是否取决于视觉需求。在两组 4 个月大的婴儿中，我们记录了头皮脑电图（EEG），他们观看了每 6 个刺激显示一个面部的 6 Hz 视觉刺激流，以标记 1 Hz 的面部选择性反应。在一组中，我们使用了变量自然刺激（Nat 组），而在另一组中，我们简化了刺激（Simp 组）以减少知觉分类需求。在视觉刺激期间，婴儿交替暴露于其母亲的气味和基线气味中。对于这两组，我们都发现了一个枕颞部的面部选择性反应，但简化刺激的反应幅度更大，反映出视觉分类的要求较低。重要的是，母亲的体味增强了对自然而非简化的面部刺激的反应，表明当母亲的体味对 4 个月大的婴儿大脑最具要求时，它可以改善面部分类。总的来说，这项研究表明，感觉间促进作用的逆向有效性适用于早期感知发展过程中的嗅觉。研究亮点：在婴儿中，感觉间促进作用是单一感官知觉需求的函数（逆向有效性）。这种多感觉和单感觉知觉之间的逆关系主要是使用视听刺激来记录的。在这里，我们表明，嗅觉到视觉的促进作用取决于 4 个月大婴儿的视觉需求。在早期感知发展过程中，感觉间促进作用的逆向有效性适用于嗅觉。
