New Research published in Journal of Cognitive Neuroscience!
Taubert, J., Alais D., Burr, D. (2016). Different coding strategies for the perception of stable and changeable facial attributes, Sci. Rep., 6. PDF
Perceptual systems face competing requirements: improving signal-to-noise ratios of noisy images, by integration; and maximising sensitivity to change, by differentiation. Both processes occur in human vision, under different circumstances: they have been termed priming, or serial dependencies, leading to positive sequential effects; and adaptation or habituation, which leads to negative sequential effects. We reasoned that for stable attributes, such as the identity and gender of faces, the system should integrate: while for changeable attributes like facial expression, it should also engage contrast mechanisms to maximise sensitivity to change. Subjects viewed a sequence of images varying simultaneously in gender and expression, and scored each as male or female, and happy or sad. We found strong and consistent positive serial dependencies for gender, and negative dependency for expression, showing that both processes can operate at the same time, on the same stimuli, depending on the attribute being judged. The results point to highly sophisticated mechanisms for optimizing use of past information, either by integration or differentiation, depending on the permanence of that attribute.
New Research published in PLoS Biology!
Castaldi, E., Cicchini, G. M., Cinelli, L., Biagi, L., Rizzo, S. & Morrone, M. C. (2016). Visual BOLD Response in Late Blind Subjects with Argus II Retinal Prosthesis, PLoS Biol, 10 (14), e1002569. PDF
Retinal prosthesis technologies require that the visual system downstream of the retinal circuitry be capable of transmitting and elaborating visual signals. We studied the capability of plastic remodeling in late blind subjects implanted with the Argus II Retinal Prosthesis with psychophysics and functional MRI (fMRI). After surgery, six out of seven retinitis pigmentosa (RP) blind subjects were able to detect high-contrast stimuli using the prosthetic implant. However, direction discrimination to contrast modulated stimuli remained at chance level in all of them. No subject showed any improvement of contrast sensitivity in either eye when not using the Argus II. Before the implant, the Blood Oxygenation Level Dependent (BOLD) activity in V1 and the lateral geniculate nucleus (LGN) was very weak or absent. Surprisingly, after prolonged use of Argus II, BOLD responses to visual input were enhanced. This is, to our knowledge, the first study tracking the neural changes of visual areas in patients after retinal implant, revealing a capacity to respond to restored visual input even after years of deprivation.
New Research published in Neuroimage!
Castaldi, E., Aagten-Murphy, D., Tosetti, M., Burr, D. & Morrone, M. C. (2016). Effects of adaptation on numerosity decoding in the human brain, Neuroimage, (143), 364-377. PDF
Psychophysical studies have shown that numerosity is a sensory attribute susceptible to adaptation. Neuroimaging studies have reported that, at least for relatively low numbers, numerosity can be accurately discriminated in the intra-parietal sulcus. Here we developed a novel rapid adaptation paradigm where adapting and test stimuli are separated by pauses sufficient to dissociate their BOLD activity. We used multivariate pattern recognition to classify brain activity evoked by non-symbolic numbers over a wide range (20-80), both before and after psychophysical adaptation to the highest numerosity. Adaptation caused underestimation of all lower numerosities, and decreased slightly the average BOLD responses in V1 and IPS. Using support vector machine, we showed that the BOLD response of IPS, but not in V1, classified numerosity well, both when tested before and after adaptation. However, there was no transfer from training pre-adaptation responses to testing post-adaptation, and vice versa, indicating that adaptation changes the neuronal representation of the numerosity. Interestingly, decoding was more accurate after adaptation, and the amount of improvement correlated with the amount of perceptual underestimation of numerosity across subjects. These results suggest that numerosity adaptation acts directly on IPS, rather than indirectly via other low-level stimulus parameters analysis, and that adaptation improves the capacity to discriminate numerosity.
Professor Adriana Fiorentini: 1/11/1926 – 29/2/2016
Nicoletta Berardi, Concetta Morrone, Donatella Spinelli - Perception - in press
Adriana Fiorentini was for many decades a pillar of the CNR Institute for Neurophysiology (then Neuroscience). On the 29th February 2016 she passed away peacefully in her sleep, with a smile. A whole generation of vision scientists remembers her with love and respect. Her wisdom, intelligence, dedication to science, enthusiasm for research and love of knowledge set an example to us all. She was a role model of respect, generosity, patience, collaboration and true humility: discrete and reserved, always there for her students and colleagues. Born and schooled in Milan, she graduated in Physics in 1948 at the University of Florence, studying optics under Professor Giuliano Toraldo di Francia at the National Institute of Optics in Arcetri.
During her studies she noticed a strange contrast phenomenon, which she correctly interpreted as the visual illusion known as “Mach Bands”: this observation was fundamental in shifting her research interests towards visual perception. In her early post-graduate years at Arcetri (1948-1968), Adriana published many innovative studies on physiological optics and perception, which are cited to this day. To mention just two: the seminal demonstration of human receptive fields (or “perceptive fields”) defined by antagonistic center‐surround interactions; and her first (but not last) Nature paper (with Donald MacKay of Keele), demonstrating a neural (VEP) correlate of a perceptual phenomenon ...[PDF]
Lunghi, C., Morrone, M. C., Secci, J. & Caputo, R. (2016). Binocular Rivalry Measured 2 Hours After Occlusion Therapy Predicts the Recovery Rate of the Amblyopic Eye in Anisometropic Children, Invest Ophthalmol Vis Sci, 4 (57), 1537-1546. PDF
Adriana Fiorentini (1/11/1926 - 29/2/2016)
Adriana Fiorentini passed away peacefully in her sleep last Monday. Adriana was an inspirational pillar of the Pisa Vision Laboratory and leading international visual scientist for over half a century. She was well loved by all her colleagues and students who had the privilege to work with and learn from her. We will miss her.
- New Research published in Current Opinion in Behavioral Sciences
- New Research published in Scientific Reports
- A cycling lane for brain rewiring
- Short-term monocular deprivation alters early components of visual evoked potentials
- New Research published - September 2015
- The oblique effect is both allocentric and egocentric
- Strong Motion Deficits in Dyslexia Associated with DCDC2 Gene Alteration
- A low-cost and versatile system for projecting wide-field visual stimuli within fMRI scanners
Page 1 of 8