Togoli Irene, Arrighi Roberto
International School for Advanced Studies (SISSA), Trieste, Italy.
Department of Neuroscience, Psychology, Pharmacology and Child Health, University of Florence, Florence, Italy.
Front Hum Neurosci. 2021 Aug 11;15:713565. doi: 10.3389/fnhum.2021.713565. eCollection 2021.
Humans and other species share a perceptual mechanism dedicated to the representation of approximate quantities that allows to rapidly and reliably estimate the numerosity of a set of objects: an Approximate Number System (ANS). Numerosity perception shows a characteristic shared by all primary visual features: it is susceptible to adaptation. As a consequence of prolonged exposure to a large/small quantity ("adaptor"), the apparent numerosity of a subsequent ("test") stimulus is distorted yielding a robust under- or over-estimation, respectively. Even if numerosity adaptation has been reported across several sensory modalities (vision, audition, and touch), suggesting the idea of a central and a-modal numerosity processing system, evidence for cross-modal effects are limited to vision and audition, two modalities that are known to preferentially encode sensory stimuli in an external coordinate system. Here we test whether numerosity adaptation for visual and auditory stimuli also distorts the perceived numerosity of tactile stimuli (and vice-versa) despite touch being a modality primarily coded in an internal (body-centered) reference frame. We measured numerosity discrimination of stimuli presented sequentially after adaptation to series of either few (around 2 Hz; low adaptation) or numerous (around 8 Hz; high adaptation) impulses for all possible combinations of visual, auditory, or tactile adapting and test stimuli. In all cases, adapting to few impulses yielded a significant overestimation of the test numerosity with the opposite occurring as a consequence of adaptation to numerous stimuli. The overall magnitude of adaptation was robust (around 30%) and rather similar for all sensory modality combinations. Overall, these findings support the idea of a truly generalized and a-modal mechanism for numerosity representation aimed to process numerical information independently from the sensory modality of the incoming signals.
人类和其他物种共享一种专门用于表示近似数量的感知机制，该机制能够快速且可靠地估计一组物体的数量：即近似数字系统（ANS）。数量感知展现出所有主要视觉特征所共有的一个特性：它易于适应。由于长时间接触大量/少量的数量（“适应刺激”），随后（“测试”）刺激的表观数量会被扭曲，分别产生强烈的低估或高估。即便数量适应已在多种感觉模态（视觉、听觉和触觉）中被报道，这暗示了存在一个中枢性且跨模态的数量处理系统，但跨模态效应的证据仅限于视觉和听觉，这两种模态已知会优先在外部坐标系中对感觉刺激进行编码。在此，我们测试对于视觉和听觉刺激的数量适应是否也会扭曲触觉刺激的感知数量（反之亦然），尽管触觉是主要以内部（以身体为中心）参考系进行编码的一种模态。我们测量了在适应一系列少量（约2赫兹；低适应）或大量（约8赫兹；高适应）脉冲后依次呈现的刺激的数量辨别能力，这些适应刺激和测试刺激涵盖了视觉、听觉或触觉的所有可能组合。在所有情况下，适应少量脉冲会导致对测试数量的显著高估，而适应大量刺激则会产生相反的结果。适应的总体幅度很大（约30%），并且对于所有感觉模态组合而言相当相似。总体而言，这些发现支持了存在一种真正通用且跨模态的数量表征机制的观点，该机制旨在独立于传入信号的感觉模态来处理数字信息。
