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Elisa Castaldi

Post-Doc in Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa

Contacts

  • Email: elisa.castaldi (AT) gmail.com
  • Telephone:  +39 050 3153172

Research laboratories

  • CNR Institute of Neuroscience, Pisa
  • Department of Psychology, University of Florence
  • Stella Maris Foundation, Pisa, Italy

Education

  • 2004-2007: Bachelor in Psycholocical Science, Final mark: 110/110 cum laude, Department of Psychology,  University Vita-Salute San Raffaele, Milan, Italy. Thesis Title: “Neural substrate of dyslexia”. Supervisor: Prof. Daniela Perani
  • 2007 – 2010 : Master degree in Cognitive Neuroscience, Final mark: 110/110 cum laude,University Vita-Salute San Raffaele, Milan, Italy. Thesis Title: “Selectivity to spatial phase of chromatic cortical mechanisms:  an fMRI study”. Supervisor: Prof. Maria Concetta Morrone.
  • 2011 – 2014: Doctoral School in Psychology and Neuroscience, University of Florence, Italy. Supervisor : David C Burr, M Concetta Morrone.
Current research and interests
  • Numerosity perception
  • Dyscalculia
  • Plasticity of the visual system
  • Retinal Prosthesis
  • fMRI

Publications

2016

Anobile, G., Castaldi, E., Turi, M., Tinelli, F. & Burr, D. C. (2016). Numerosity but not texture-density discrimination correlates with math ability in children, Dev Psychol, 8 (52), 1206-1216. PDF

Considerable recent work suggests that mathematical abilities in children correlate with the ability to estimate numerosity. Does math correlate only with numerosity estimation, or also with other similar tasks? We measured discrimination thresholds of school-age (6- to 12.5-years-old) children in 3 tasks: numerosity of patterns of relatively sparse, segregatable items (24 dots); numerosity of very dense textured patterns (250 dots); and discrimination of direction of motion. Thresholds in all tasks improved with age, but at different rates, implying the action of different mechanisms: In particular, in young children, thresholds were lower for sparse than textured patterns (the opposite of adults), suggesting earlier maturation of numerosity mechanisms. Importantly, numerosity thresholds for sparse stimuli correlated strongly with math skills, even after controlling for the influence of age, gender and nonverbal IQ. However, neither motion-direction discrimination nor numerosity discrimination of texture patterns showed a significant correlation with math abilities. These results provide further evidence that numerosity and texture-density are perceived by independent neural mechanisms, which develop at different rates; and importantly, only numerosity mechanisms are related to math. As developmental dyscalculia is characterized by a profound deficit in discriminating numerosity, it is fundamental to understand the mechanism behind the discrimination.

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.

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.

2013

Castaldi, E., Frijia, F., Montanaro, D., Tosetti, M. & Morrone, M. C. (2013). BOLD human responses to chromatic spatial features,Eur J Neurosci, 2 (38), 2290-2299. PDF

Animal physiological and human psychophysical studies suggest that an early step in visual processing involves the detection and identification of features such as lines and edges, by neural mechanisms with even- and odd-symmetric receptive fields. Functional imaging studies also demonstrate mechanisms with even- and odd-receptive fields in early visual areas, in response to luminance-modulated stimuli. In this study we measured fMRI BOLD responses to 2-D stimuli composed of only even or only odd symmetric features, and to an amplitude-matched random noise control, modulated in red-green equiluminant colour contrast. All these stimuli had identical power but different phase spectra, either highly congruent (even or odd symmetry stimuli) or random (noise). At equiluminance, V1 BOLD activity showed no preference between congruent- and random-phase stimuli, as well as no preference between even and odd symmetric stimuli. Areas higher in the visual hierarchy, both along the dorsal pathway (caudal part of the intraparietal sulcus, dorsal LO and V3A) and the ventral pathway (V4), responded preferentially to odd symmetry over even symmetry stimuli, and to congruent over random phase stimuli. Interestingly, V1 showed an equal increase in BOLD activity at each alternation between stimuli of different symmetry, suggesting the existence of specialised mechanisms for the detection of edges and lines such as even- and odd-chromatic receptive fields. Overall the results indicate a high selectivity of colour-selective neurons to spatial phase along both the dorsal and the ventral pathways in humans.

 


Conferences

  • Castaldi, E., Frijia, F., Tosetti, M., Montanaro, D., Morrone, M.C. Selectivity to spatial phase of chromatic cortical mechanisms: an fMRI study [Cavalese retreat CNR Institutes of Neuroscience 2011: Poster].
Theses
  • Castaldi, E., & Morrone, M.C. Selectivity to spatial phase of chromatic cortical mechanisms: an fMRI study. Honours Thesis, University Vita-Salute San Raffaele Milan (2009).
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