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Item does not contain fulltext The spatial limits of sensory acquisition (its sensory horizon) is a fundamental property of any sensorimotor system. In the present study, we sought to determine whether there is a sensory horizon for the human haptic modality. At first blush, it seems obvious that the haptic system is bounded by the space where the body can interact with the environment (e.g., the arm span). However, the human somatosensory system is exquisitely tuned to sensing with tools-blind-cane navigation being a classic example of this. The horizon of haptic perception therefore extends beyond body space, but to what extent is unknown. We first used neuromechanical modelling to determine the theoretical horizon, which we pinpointed as six meters. We then used a psychophysical localization paradigm to behaviorally confirm that humans can haptically localize objects using a six-meter rod. This finding underscores the incredibly flexibility of the brain's sensorimotor representations, as they can be adapted to sense with an object many times longer than the user's own body. 6 p.

Contains fulltext : 221839.pdf (Publisher’s version ) (Open Access) Objective: To assess the role of visual measures and retinal volume to predict the risk of Parkinson disease (PD) dementia. Methods: In this cohort study, we collected visual, cognitive, and motor data in people with PD. Participants underwent ophthalmic examination, retinal imaging using optical coherence tomography, and visual assessment including acuity and contrast sensitivity and high-level visuoperception measures of skew tolerance and biological motion. We assessed the risk of PD dementia using a recently described algorithm that combines age at onset, sex, depression, motor scores, and baseline cognition. Results: One hundred forty-six people were included in the study (112 with PD and 34 age-matched controls). The mean disease duration was 4.1 (±2·5) years. None of these participants had dementia. Higher risk of dementia was associated with poorer performance in visual measures (acuity: p = 0.29, p = 0.0024; contrast sensitivity: ρ = -0.37, p < 0.0001; skew tolerance: ρ = -0.25, p = 0.0073; and biological motion: p = -0.26, p = 0.0054). In addition, higher risk of PD dementia was associated with thinner retinal structure in layers containing dopaminergic cells, measured as ganglion cell layer (GCL) and inner plexiform layer (IPL) thinning (p = -0.29, p = 0.0021; p = -0.33, p = 0.00044). These relationships were not seen for the retinal nerve fiber layer that does not contain dopaminergic cells and were not seen in unaffected controls. Conclusion: Visual measures and retinal structure in dopaminergic layers were related to risk of PD dementia. Our findings suggest that visual measures and retinal GCL and IPL volumes may be useful to predict the risk of dementia in PD. 11 p.

Contains fulltext : 246730.pdf (Publisher’s version ) (Open Access) Physical proximity is important in social interactions. Here, we assessed whether simulated physical proximity modulates the perceived intensity of facial emotional expressions and their associated physiological signatures during observation or imitation of these expressions. Forty-four healthy volunteers rated intensities of dynamic angry or happy facial expressions, presented at two simulated locations, proximal (0.5 m) and distant (3 m) from the participants. We tested whether simulated physical proximity affected the spontaneous (in the observation task) and voluntary (in the imitation task) physiological responses (activity of the corrugator supercilii face muscle and pupil diameter) as well as subsequent ratings of emotional intensity. Angry expressions provoked relative activation of the corrugator supercilii muscle and pupil dilation, whereas happy expressions induced a decrease in corrugator supercilii muscle activity. In proximal condition, these responses were enhanced during both observation and imitation of the facial expressions, and were accompanied by an increase in subsequent affective ratings. In addition, individual variations in condition related EMG activation during imitation of angry expressions predicted increase in subsequent emotional ratings. In sum, our results reveal novel insights about the impact of physical proximity in the perception of emotional expressions, with early proximity-induced enhancements of physiological responses followed by an increased intensity rating of facial emotional expressions. 14 p.

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Item does not contain fulltext Tool use is a defining feature of the human species. Tool-in-hand, humans can manipulate their environment in novel ways as well as process the sensory information arising during mechanical contact. This fact has led cognitive neuroscience researchers over the last few decades to explore how tool-based body augmentation impacts the behavior and neural processing of their users. In this chapter, we explore the findings of this research and draw some tentative conclusions about its implications for the sensorimotor system. We first survey research, conducted over the past decade, that has found that using a tool modulates body representations underlying action and somatosensory perception. This research includes both behavioral and neural approaches. We then focus on the sensory and functional underpinnings driving the tool-induced plasticity to body representations. Finally, we describe a novel means to evaluate the incorporation of tools into the sensorimotor system: The ability of humans to sense the locations of external objects with a tool. We will discuss how this research has already gained powerful insight into the relationship between tools and the body, as well as challenging our conception of the boundaries of the somatosensory system.