Increased Functional Connectivity of the Intraparietal Sulcus Underlies the Attenuation of Numerosity Estimations for Self-Generated Words.

Previous studies have shown that self-generated stimuli in auditory, visual, and somatosensory domains are attenuated, producing decreased behavioral and neural responses compared with the same stimuli that are externally generated. Yet, whether such attenuation also occurs for higher-level cognitive functions beyond sensorimotor processing remains unknown. In this study, we assessed whether cognitive functions such as numerosity estimations are subject to attenuation in 56 healthy participants (32 women). We designed a task allowing the controlled comparison of numerosity estimations for self-generated (active condition) and externally generated (passive condition) words. Our behavioral results showed a larger underestimation of self-generated compared with externally generated words, suggesting that numerosity estimations for self-generated words are attenuated. Moreover, the linear relationship between the reported and actual number of words was stronger for self-generated words, although the ability to track errors about numerosity estimations was similar across conditions. Neuroimaging results revealed that numerosity underestimation involved increased functional connectivity between the right intraparietal sulcus and an extended network (bilateral supplementary motor area, left inferior parietal lobule, and left superior temporal gyrus) when estimating the number of self-generated versus externally generated words. We interpret our results in light of two models of attenuation and discuss their perceptual versus cognitive origins.SIGNIFICANCE STATEMENT We perceive sensory events as less intense when they are self-generated compared with when they are externally generated. This phenomenon, called attenuation, enables us to distinguish sensory events from self and external origins. Here, we designed a novel fMRI paradigm to assess whether cognitive processes such as numerosity estimations are also subject to attenuation. When asking participants to estimate the number of words they had generated or passively heard, we found bigger underestimation in the former case, providing behavioral evidence of attenuation. Attenuation was associated with increased functional connectivity of the intraparietal sulcus, a region involved in numerosity processing. Together, our results indicate that the attenuation of self-generated stimuli is not limited to sensory consequences but is also impact cognitive processes such as numerosity estimations.

Audio-Tactile and Peripersonal Space Processing Around the Trunk in Human Parietal and Temporal Cortex: An Intracranial EEG Study.

Interactions with the environment happen within one's peripersonal space (PPS)-the space surrounding the body. Studies in monkeys and humans have highlighted a multisensory distributed cortical network representing the PPS. However, knowledge about the temporal dynamics of PPS processing around the trunk is lacking. Here, we recorded intracranial electroencephalography (iEEG) in humans while administering tactile stimulation (T), approaching auditory stimuli (A), and the 2 combined (AT). To map PPS, tactile stimulation was delivered when the sound was far, intermediate, or close to the body. The 19% of the electrodes showed AT multisensory integration. Among those, 30% showed a PPS effect, a modulation of the response as a function of the distance between the sound and body. AT multisensory integration and PPS effects had similar spatiotemporal characteristics, with an early response (~50 ms) in the insular cortex, and later responses (~200 ms) in precentral and postcentral gyri. Superior temporal cortex showed a different response pattern with AT multisensory integration at ~100 ms without a PPS effect. These results, represent the first iEEG delineation of PPS processing in humans and show that PPS and multisensory integration happen at similar neural sites and time periods, suggesting that PPS representation is based on a spatial modulation of multisensory integration.