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Michele Fornaciai

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Michele Fornaciai

PhD Student in Neuroscience, University of Florence


Contacts

  • Email: fornaciai (AT) hotmail.it

Research laboratories

  • Department of Neuroscience, Psychology, Pharmacology and Child Health, University of Florence
  • CNR Institute of Neuroscience, Pisa
  • Departmente of Psychological and Brain Sciences, University of Massachusetts Amherst

Education

  • 2007 - 2010 Bachelor in General and Experimental Psychology, University of Florence
  • 2010 - 2012 Master degree in Psychology (Experimental Psychology), University of Florence
  • 2012 - 2016 PhD course in Neuroscience

Current research and interests

  • Time perception
  • Numerosity perception
  • Motion perception

Publications

2017

Fornaciai, M. & Park, J. (2017). Distinct Neural Signatures for Very Small and Very Large Numerosities, Frontiers in Human Neuroscience, (11), PDF

Behavioral studies of numerical cognition have shown that perceptual threshold for numerosity discrimination depends on the range of numerical values to be estimated. Discrimination threshold is constant when comparing very small numerosities via the mechanism called subitizing, while it increases as a function of numerosity for numbers beyond that range governed by subitizing. However, when numerosity gets so large that the individual elements start to form a cluttered ensemble, discrimination threshold increases as a function of the square root of numerosity. These behavioral patterns suggest that our sense of number is not based on a unitary mechanism and is rather based on multiple numerosity processing mechanisms depending on the absolute numerosity to be estimated. In this study, we demonstrate neurophysiological evidence for such multiple mechanisms. Participants electroencephalogram (EEG) was recorded while they viewed arrays containing either very small (14) or very large (100400) number of dots with systematic variations in non-numerical cues. A linear model that tested the effects of numerical and non-numerical cues on the visual-evoked potentials (VEPs) revealed strong neural sensitivity to numerosity around 160180 ms over right occipito-parietal sites irrespective of the numerical range presented. In contrast, earlier neural responses (similar to 100 ms) showed markedly distinct patterns across the different numerical ranges tested. These results indicate that differences in behavioral response patterns in numerosity estimation across various numerical ranges may arise from the differences in the first stages of visual analysis. Collectively, the findings provide a firmer ground for the idea that there exists a brain system specifically dedicated for numerosity processing, yet they also suggest that multiple early visual cortical mechanisms converge to that numerosity processing stage later in the visual stream.


2016

Fornaciai, M., Arrighi, R. & Burr, D. C. (2016). Adaptation-Induced Compression of Event Time Occurs Only for Translational Motion, Scientific Reports, (6), 23341. PDF

Adaptation to fast motion reduces the perceived duration of stimuli displayed at the same location as the adapting stimuli. Here we show that the adaptation-induced compression of time is specific for translational motion. Adaptation to complex motion, either circular or radial, did not affect perceived duration of subsequently viewed stimuli. Adaptation with multiple patches of translating motion caused compression of duration only when the motion of all patches was in the same direction. These results show that adaptation-induced compression of event-time occurs only for uni-directional translational motion, ruling out the possibility that the neural mechanisms of the adaptation occur at early levels of visual processing.

Fornaciai, M., Cicchini, G. M. & Burr, D. C. (2016). Adaptation to number operates on perceived rather than physical numerosity, Cognition, (151), 63-67.PDF

Humans share with many animals a number sense, the ability to estimate rapidly the approximate number of items in a scene. Recent work has shown that like many other perceptual attributes, numerosity is susceptible to adaptation. It is not clear, however, whether adaptation works directly on mechanisms selective to numerosity, or via related mechanisms, such as those tuned to texture density. To disentangle this issue we measured adaptation of numerosity of 10 pairs of connected dots, as connecting dots makes them appear to be less numerous than unconnected dots. Adaptation to a 20-dot pattern (same number of dots as the test) caused robust reduction in apparent numerosity of the connected-dot pattern, but not of the unconnected dot-pattern. This suggests that adaptation to numerosity, at least for relatively sparse dot-pattern, occurs at neural levels encoding perceived numerosity, rather than at lower levels responding to the number of elements in the scene.


2015

Fornaciai, M. & Binda, P. (2015). Effect of saccade automaticity on perisaccadic space compression, Front Syst Neurosci, (9), 127. PDF

Briefly presented stimuli occurring just before or during a saccadic eye movement are mislocalized, leading to a compression of visual space toward the target of the saccade. In most cases this has been measured in subjects over-trained to perform a stereotyped and unnatural task where saccades are repeatedly driven to the same location, marked by a highly salient abrupt onset. Here, we asked to what extent the pattern of perisaccadic mislocalization depends on this specific context. We addressed this question by studying perisaccadic localization in a set of participants with no prior experience in eye-movement research, measuring localization performance as they practiced the saccade task. Localization was marginally affected by practice over the course of the experiment and it was indistinguishable from the performance of expert observers. The mislocalization also remained similar when the expert observers were tested in a condition leading to less stereotypical saccadic behavior-with no abrupt onset marking the saccade target location. These results indicate that perisaccadic compression is a robust behavior, insensitive to the specific paradigm used to drive saccades and to the level of practice with the saccade task.



Theses

  • Fornaciai M. “Percezione visiva del movimento e meccanismi temporali”. (Visual perception of motion and temporal mechanisms). University of Florence, Faculty of Psychology (2012).

Conferences

  • Fornaciai, Arrighi, Burr, “Fast Translational Motion, but not Radial, Circular or Biological Motion, Causes Spatially Selective Adaptation of Event Duration”, talk at ICTTP 2014 (International conference on timing and time perception), Corfù 31/03-03/04/2014

 

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