Guido Marco Cicchini
Post-Doc in Cognitive Science, University of Florence
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Contacts
Research laboratories
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Current research and interests
- Temporal Perception
- Eye Movements
- Clinical Psychology
- Optimal Behaviour
2012
Anobile, G., Cicchini, G. M. & Burr, D. C. (2012). Linear mapping of numbers onto space requires attention,Cognition, 3 (122), 454-459. PDF
Mapping of number onto space is fundamental to mathematics and measurement. Previous research suggests that while typical adults with mathematical schooling map numbers veridically onto a linear scale, pre-school children and adults without formal mathematics training, as well as individuals with dyscalculia, show strong compressive, logarithmic-like non-linearities when mapping both symbolic and non-symbolic numbers onto the numberline. Here we show that the use of the linear scale is dependent on attentional resources. We asked typical adults to position clouds of dots on a numberline of various lengths. In agreement with previous research, they did so veridically under normal conditions, but when asked to perform a concurrent attentionally-demanding conjunction task, the mapping followed a compressive, non-linear function. We model the non-linearity both by the commonly assumed logarithmic transform, and also with a Bayesian model of central tendency. These results suggest that veridical representation numerosity requires attentional mechanisms.
Cicchini, G. M., Arrighi, R., Cecchetti, L., Giusti M. & Burr, D. C. (2012). Optimal Encoding of Interval Timing in Expert Percussionists, Journal of Neuroscience, in press. PDF
We measured temporal reproduction in human subjects with various levels of musical expertise: expert drummers, string musicians, and non-musicians. While duration reproduction of the non-percussionists showed a characteristic central tendency or regression to the mean, drummers responded veridically. Furthermore, when the stimuli were auditory tones rather than flashes, all subjects responded veridically. The behavior of all three groups in both modalities is well explained by a Bayesian model that seeks to minimize reproduction errors by incorporating a central tendency prior, a probability density function centered at the mean duration of the sample. We measured separately temporal precision thresholds with a bisection task; thresholds were twice as low in drummers as in the other two groups. These estimates of temporal precision, together with an adaptable Bayesian prior, predict well the reproduction results and the central tendency strategy under all conditions and for all subject groups. These results highlight the efficiency and flexibility of sensorimotor mechanisms estimating temporal duration.
Pooresmaeili, A., Cicchini, G. M., Morrone, M. C. & Burr, D. (2012). "Non-retinotopic processing" in Ternus motion displays modeled by spatiotemporal filters,J Vis, 1 (12), PDF
Recently, M. Boi, H. Ogmen, J. Krummenacher, T. U. Otto, & M. H. Herzog (2009) reported a fascinating visual effect, where the direction of apparent motion was disambiguated by cues along the path of apparent motion, the Ternus-Pikler group motion, even though no actual movement occurs in this stimulus. They referred to their study as a "litmus test" to distinguish "non-retinotopic" (motion-based) from "retinotopic" (retina-based) image processing. We adapted the test to one with simple grating stimuli that could be more readily modeled and replicated their psychophysical results quantitatively with this stimulus. We then modeled our experiments in 3D (x, y, t) Fourier space and demonstrated that the observed perceptual effects are readily accounted for by integration of information within a detector that is oriented in space and time, in a similar way to previous explanations of other motion illusions. This demonstration brings the study of Boi et al. into the more general context of perception of moving objects.
2011
Burr, D. C., Cicchini, G. M., Arrighi, R. & Morrone, M. C. (2011). Spatiotopic selectivity of adaptation-based compression of event duration, J Vis, 2 (11), 21; author reply 21a. PDF
A. Bruno, I. Ayhan, and A. Johnston (2010) have recently challenged our report of spatiotopic selectivity for adaptation of event time (D. Burr, A. Tozzi, & M. C. Morrone, 2007) and also our claim that retinotopic adaptation of event time depends on perceived speed. To assist the reader judge this issue, we present here a mass of data accumulated in our laboratories over the last few years, all confirming our original conclusions. We also point out that where Bruno et al. made experimental measurements (rather than relying on theoretical reasoning), they too find clearly significant spatiotopically tuned adaptation-based compression of event time but of lower magnitude to ours. We speculate on the reasons for the differences in magnitude.
2010
Morrone, M. C., Cicchini, M. & Burr, D. C. (2010). Spatial maps for time and motion,Exp Brain Res, 2 (206), 121-128. PDF
In this article, we review recent research studying the mechanisms for transforming coordinate systems to encode space, time and motion. A range of studies using functional imaging and psychophysical techniques reveals mechanisms in the human brain for encoding information in external rather than retinal coordinates. This reinforces the idea of a tight relationship between space and time, in the parietal cortex of primates.
2009
Cicchini, G. M. & Morrone, M. C. (2009). Shifts in spatial attention affect the perceived duration of events,J Vis, 1 (9), 9 1-13. PDF
We investigated the relationship between attention and perceived duration of visual events with a double-task paradigm. The primary task was to discriminate the size change of a 2 degree circle presented 10 degrees left, right, above, or below fixation; the secondary task was to judge the temporal separation (from 133 ms to 633 ms) of two equiluminant horizontal bars (10 deg x 2 deg) briefly flashed 12 degrees above or below fixation. The stimulus onset asynchrony (SOA) between primary and secondary task ranged from -1300 ms to +1000 ms. Temporal intervals in proximity of the onset of the primary task stimuli were perceived strongly compressed by up to 40%. The effect was proportional to the size of the interval with a maximum effect at 100 ms SOA. Control experiments show that neither primary-task difficulty, nor the type of primary task discrimination (form or motion, or equiluminant or luminance contrast) nor spatial congruence between primary and secondary task alter the effect. Interestingly, the compression occurred only when the intervals are marked by bars presented in separated spatial locations: when the interval is marked by two bars flashed in the same spatial position no temporal distortion was found. These data indicate that attention can alter perceived duration when the brain has to compare the passage of time at two different spatial positions, corroborating earlier findings that mechanisms of time perception may monitor separately the various spatial locations possibly at high level of analysis.
Burr, D., Silva, O., Cicchini, G. M., Banks, M. S. & Morrone, M. C. (2009). Temporal mechanisms of multimodal binding,Proc Biol Sci, 1663 (276), 1761-1769. PDF
The simultaneity of signals from different senses-such as vision and audition-is a useful cue for determining whether those signals arose from one environmental source or from more than one. To understand better the sensory mechanisms for assessing simultaneity, we measured the discrimination thresholds for time intervals marked by auditory, visual or auditory-visual stimuli, as a function of the base interval. For all conditions, both unimodal and cross-modal, the thresholds followed a characteristic 'dipper function' in which the lowest thresholds occurred when discriminating against a non-zero interval. The base interval yielding the lowest threshold was roughly equal to the threshold for discriminating asynchronous from synchronous presentations. Those lowest thresholds occurred at approximately 5, 15 and 75 ms for auditory, visual and auditory-visual stimuli, respectively. Thus, the mechanisms mediating performance with cross-modal stimuli are considerably slower than the mechanisms mediating performance within a particular sense. We developed a simple model with temporal filters of different time constants and showed that the model produces discrimination functions similar to the ones we observed in humans. Both for processing within a single sense, and for processing across senses, temporal perception is affected by the properties of temporal filters, the outputs of which are used to estimate time offsets, correlations between signals, and more.
Binda, P., Cicchini, G. M., Burr, D. C. & Morrone, M. C. (2009). Spatiotemporal distortions of visual perception at the time of saccades,J Neurosci, 42 (29), 13147-13157. PDF
Both space and time are grossly distorted during saccades. Here we show that the two distortions are strongly linked, and that both could be a consequence of the transient remapping mechanisms that affect visual neurons perisaccadically. We measured perisaccadic spatial and temporal distortions simultaneously by asking subjects to report both the perceived spatial location of a perisaccadic vertical bar (relative to a remembered ruler), and its perceived timing (relative to two sounds straddling the bar). During fixation and well before or after saccades, bars were localized veridically in space and in time. In different epochs of the perisaccadic interval, temporal perception was subject to different biases. At about the time of the saccadic onset, bars were temporally mislocalized 50-100 ms later than their actual presentation and spatially mislocalized toward the saccadic target. Importantly, the magnitude of the temporal distortions co-varied with the spatial localization bias and the two phenomena had similar dynamics. Within a brief period about 50 ms before saccadic onset, stimuli were perceived with shorter latencies than at other delays relative to saccadic onset, suggesting that the perceived passage of time transiently inverted its direction. Based on this result we could predict the inversion of perceived temporal order for two briefly flashed visual stimuli. We developed a model that simulates the perisaccadic transient change of neuronal receptive fields predicting well the reported temporal distortions. The key aspects of the model are the dynamics of the "remapped" activity and the use of decoder operators that are optimal during fixation, but are not updated perisaccadically.
2008
Cicchini, G. M., Valsecchi, M. & De'Sperati, C. (2008). Head movements modulate visual responsiveness in the absence of gaze shifts,Neuroreport, 8 (19), 831-834. PDF
Visuospatial attention is strongly associated with saccades. Given that gaze shifts are often accomplished by combined eye-head movements, attention may also be coupled to head movements. We showed that simply turning the head without shifting the gaze is sufficient to cause a transient unbalance in responding to a visual stimulus. Manual responses to a stimulus flashed shortly before the onset of a horizontal head movement were faster in congruent trials, when the head moved towards the stimulus, than in incongruent trials, when the head moved away from the stimulus. These effects are similar to those observed for saccades. We take this as evidence for a tight link between visuospatial attention and head movements, even when the gaze does not shift.
