Biological motion drives perception and action

Marcus Missal Presenting a few dots moving coherently on a screen can yield to the perception of human motion. This perception is based on a specific network that is segregated from the traditional motion perception network and that includes the superior temporal sulcus (STS). In this study, we investigate whether this biological motion perception network could influence the smooth pursuit response evoked by a point-light walker. We found that smooth eye velocity during pursuit initiation was larger in response to the point-light walker than in response to one of its scrambled versions, to an inverted walker or to a single dot stimulus. In addition, we assessed the proximity to the point-light walker (i.e. the amount of information about the direction contained in the scrambled stimulus and extracted from local motion cue of biological motion) of each of our scrambled stimuli in a motion direction discrimination task with manual responses and found that the smooth pursuit response evoked by those stimuli moving across the screen was modulated by their proximity to the walker. Therefore, we conclude that biological motion facilitates smooth pursuit eye movements, hence influences both perception and action

Beware ‘persuasive communication devices’ when writing and reading scientific articles

Authors rely on a range of devices and techniques to attract and maintain the interest of readers, and to convince them of the merits of the author’s point of view. However, when writing a scientific article, authors must use these ‘persuasive communication devices’ carefully. In particular, they must be explicit about the limitations of their work, avoid obfuscation, and resist the temptation to oversell their results. Here we discuss a list of persuasive communication devices and we encourage authors, as well as reviewers and editors, to think carefully about their use

Justify your alpha

In response to recommendations to redefine statistical significance to p ≤ .005, we propose that researchers should transparently report and justify all choices they make when designing a study, including the alpha level

Tracking the invisible requires prediction and internal models

In order to grasp an object in their visual field, humans orient their visual axis to targets of interest. While scanning their environment, humans perform multiple saccades (rapid eye movements that correct for a position error between eye and target) to align their visual axis with objects of interest. Humans are also able to track objects that move in their environment by means of smooth pursuit eye movements (slow eye movements that correct for any velocity error between eye and target, i.e. for any retinal slip). The appearance of a moving stimulus in the environment elicits smooth pursuit eye movements with a latency of around 100ms. Accordingly, the smooth pursuit system accounts for a change in the trajectory of a moving target with a similar delay. Due to this delay, the oculomotor system needs to develop strategies to avoid the build up of position error during tracking of a moving target. To do so, the oculomotor system uses prediction to try and anticipate the future target trajectory. However, this strategy is limited to conditions where target trajectory is predictable. Otherwise, primates have to combine pursuit and saccades in visual tracking of unpredictable moving targets to avoid large position error. This thesis focuses on both the prediction mechanisms and the interactions between saccades and pursuit. In order to investigate prediction mechanisms, we asked human subjects to pursue a moving target when it was transiently occluded. During occlusions, subjects continued to pursue the invisible target. This thesis demonstrates that this predictive pursuit response is based on a dynamic internal representation of target motion, i.e. a representation that evolves with time. This internal representation could be either built up by repetition of the same target motion or extrapolated on the basis of the pre-occlusion target motion. In addition, it is shown that during occlusions, saccades are adjusted in order to account for the large variability of the smooth pursuit response. As a consequence, it shows that the smooth pursuit command is used by internal models in order to predict future smooth pursuit response. These results demonstrate that both prediction and internal models are necessary to track the invisible and the visible.(FSA 3) -- UCL, 200