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Despite having equal duration, stimuli in physical motion are perceived to last longer than static ones. Here, we investigate whether illusory motion stimuli produce a time-dilation effect similar to physical motion. Participants performed a duration discrimination task that compared the perceived duration of static stimuli with and without illusory motion to a reference stimulus. In the first experiment, we observed a 4% increase in the number of “longer” responses for the illusory motion images than static stimuli with equal duration. The time-dilation effect, quantified as a shift in the Point of Subjective Equality (PSE), was approximately 55 ms for a 2-second stimulus. Although small, the effect was replicated in a second experiment in which the total number of standard-duration repetitions was reduced from 73 to 19. In the third experiment, we found a positive linear trend between the strength of the illusory motion and the magnitude of the time-dilation effect. These results demonstrate that, similar to physical motion stimuli, illusory motion stimuli are perceived to last longer than static stimuli. Furthermore, the strength of the illusion influences the extent of the lengthening of perceived duration.

Background. In deep-seated brain tumors, adequate preoperative planning is mandatory to assess the best surgical corridor to obtain maximal safe resection. Functional diffusor tensor imaging (DTI) tractography based on navigated transcranial magnetic stimulation (nTMS) motor mapping has proven to be a valid preoperative examination method in adults. The aim of this paper is to present the application of nTMS and functional DTI tractography in a series of pediatric diencephalic tumors. Material and methods. Three patients affected by thalamic (one) and thalamopeduncular tumor (two) were successfully examined with nTMS motor mapping and DTI tractography between October 2020 and October 2021 (F:M 3:0, mean age 12 years ± 0.8). Cortical representation of leg, hand and mouth were determined in the affected hemisphere and the positive stimulation spots were set as seeds point for tractography. Results. Mapping of the motor cortex and tracts reconstruction for leg and hand were successful in all patients, while facial function was properly mapped in one patient only. In all cases, the procedure was well tolerated and no adverse events were recorded. Spatial relationships between tumor and functional tissue guided the surgical planning. Extent of the resection varied from 96.1% to 100% with a postoperative new motor deficit in one patient. Conclusions. nTMS and DTI fiber tracking is a feasible, effective and well-tolerated method to identify motor pathway in deep-seated lesion in pediatric population.