264 research outputs found
Defensive peripersonal space: the blink reflex evoked by hand stimulation is increased when the hand is near the face
No full textSambo CF, Liang M, Cruccu G, Iannetti GD. Defensive peripersonal space: the blink reflex evoked by hand stimulation is increased when the hand is near the face. J Neurophysiol 107: 880-889, 2012. First published November 16, 2011; doi:10.1152/jn.00731.2011.-Electrical stimulation of the median nerve at the wrist may elicit a blink reflex [hand blink reflex (HBR)] mediated by a neural circuit at brain stem level. As, in a Sherringtonian sense, the blink reflex is a defensive response, in a series of experiments we tested, in healthy volunteers, whether and how the HBR is modulated by the proximity of the stimulated hand to the face. Electromyographic activity was recorded from the orbicularis oculi, bilaterally. We observed that the HBR is enhanced when the stimulated hand is inside the peripersonal space of the face, compared with when it is outside, irrespective of whether the proximity of the hand to the face is manipulated by changing the position of the arm (experiment 1) or by rotating the head while keeping the arm position constant (experiment 3). Experiment 2 showed that such HBR enhancement has similar magnitude when the participants have their eyes closed. Experiments 4 and 5 showed, respectively, that the blink reflex elicited by the electrical stimulation of the supraorbital nerve, as well as the N20 wave of the somatosensory evoked potentials elicited by the median nerve stimulation, are entirely unaffected by hand position. Taken together, our results provide compelling evidence that the brain stem circuits mediating the HBR in humans undergo tonic and selective top-down modulation from higher order cortical areas responsible for encoding the location of somatosensory stimuli in external space coordinates. These findings support the existence of a "defensive" peripersonal space, representing a safety margin advantageous for survival
Attentional modulation of lateral interactions depends on eccentricity
No full textVisual attention has been found to facilitate texture segmentation in periphery by increasing spatial resolution (Yeshurun and Carrasco, 1998 Nature 396 72 - 75). Campana and Casco (2005 Perception 34 Supplement, this issue) show that attention not only increases spatial resolution but also reduces the effect of inhibitory short-range spatial interactions only in periphery. Casco et al (2005 Vision Research 45 2384 - 2396) found that attention produces a specific facilitation of texture segmentation when texture elements are oriented as the texture boundary (iso-oriented), probably resulting in enhancement of spatial interaction between texture elements. Is this modulation of facilitation by attention dependent on eccentricity? By using a RSVP paradigm, we manipulated, at 0 and 5 deg of eccentricity, the amount of attention allocated to orientation discrimination of a 3-Gabor-group, either horizontal or vertical, in which individual Gabors were either iso-oriented or ortho-oriented and differed by 45° in orientation from background Gabors. Our results show that when attentional resources are largely available, orientation discrimination of the iso-oriented group is facilitated both in fovea and in periphery. In contrast, the reduction of attention has different effects depending on eccentricity: a larger decrease in performance for iso-oriented than ortho-oriented groups in fovea, and a decrease in performance with ortho-oriented groups only, in periphery. Furthermore, whereas in periphery iso-oriented groups are far better discriminated than ortho-oriented ones, in fovea this difference is strongly reduced. These results indicate that in fovea attention is more engaged in grouping iso-oriented elements, whilst in the periphery only grouping of ortho-oriented elements needs attention. Overall, these results suggest that attention affects the strength of lateral interactions differently in fovea and periphery: reducing attention in the fovea reduces the strength of facilitatory lateral interactions between both iso-oriented and ortho-oriented Gabors, whereas in the periphery only the strength of facilitatory interactions between ortho-oriented Gabors is reduced
Anemone coronaria (L.) e Ranunculus asiaticus (L.)in floating system come possibile strategia per programmare la produzione
No full textAnemone e ranuncolo sono specie da fiore reciso tradizionalmente coltivate a terra. In questo lavoro viene verificata la possibilità di coltivare queste specie in floating system, al fine di anticipare la fioritura e migliorarne la produzione. In una prima prova, la coltivazione tradizionale in aiuola è stata confrontata con la coltivazione in floating system, impiegando quattro soluzioni nutritive diverse: una Hoagland a concentrazione standard, una Hoagland con concentrazione diluita a 2/3 e una a 1/3, e una Hoagland modificata nel rapporto N-K. Entrambe le specie possono essere coltivate in floating system anche se solamente ranuncolo ha dato risultati paragonabili, o superiori, a quelli ottenuti con tecniche tradizionali. La soluzione diluita ad 1/3 per anemone e a 2/3 per ranuncolo non hanno modificare la produzione rispetto alla concentrazione standard. In una seconda prova sono state confrontate quattro modalità di pre-germogliamento dei tuberi: nessun trattamento, 2 settimane a 15 °C, 2 settimane a 15 °C seguite da 2 a 5 °C e 4 settimane a 5 °C. Il pre-germogliamento ha anticipato la fioritura migliorando la produzione. Per entrambe le specie gli ultimi due trattamenti hanno fornito i migliori risultati
Effects of osmopriming treatments on seed germination of two types of radicchio (cichorium intybus var. silvestre)
No full textTo improve germination of two types of radicchio ('Rosso di Chioggia', RCh, and 'Bianco di Chioggia', WCh) various pre-sowing treatments were evaluated. A non-soaked control was compared with seeds primed for 2, 4, 6, 8 hours in plain water (hydropriming) or in solutions containing the following concentration of polyethylene glycol (PEG 6000) and potassium nitrate (KNO3): a) PEG at -0.5, -0.9 and -1.7 MPa; b) KNO3 at -0.12, -0.24 and -0.52 MPa. After soaking, seeds were rinsed and placed in petri-dishes at 20 or 27°C germination temperature. Pre-sowing treatments affected the germination percentage more than the mean time of germination, and the effects were more evident in RCh and when 20°C germination temperature was applied. Generally, the higher germination percentage was obtained with longer hydropriming (6-8 hrs) and with short treatment (2 hrs) with osmotic compounds. KNO3 proved to be less effective than PEG which gave, on average, the best results at -0.5 and -0.9 MPa water potential
The effect of seed quality (seed colour variation) on storability, germination temperature and field performance of radicchio
No full textThe possible role played by seed colour (uniformly light-L, slightly black variegated-LB, widely black variegated-BL, uniformly black-B, purple-P) in the seed quality of 'Rosso di Treviso precoce' and 'Rosso di Chioggia' radicchio was investigated. The effect of seed-storage length (two, seven months) was also studied in 'Rosso di Treviso precoce'. For better evaluation of seed quality, germination tests were carried out at 12, 20 and 28°C. The influence of seed characteristics on crop yield was then investigated in the field. Germinability and seed vigour were linked to colour. Reduced germination was observed with L seeds. Moreover, when germinated, L seeds gave rise to plants with reduced ability to form heads, thus reducing the marketable yield. As colour became increasingly darker, seeds germinated faster and more uniformly, and germinability was higher. The differences apparently resulted from incomplete seed development, as shown by the close relationship between germinability and seed weight, and by the smaller embryos of lighter seeds. Sensitivity to temperature changed with seed colour and radicchio type. The L seeds of both types germinated poorly whatever the temperature. The other lots germinated best at 28°C, excluding the LB and P seeds of 'Rosso di Chioggia' which gave better results at 20°C. The negative effect of 12°C was more evident in P seeds of 'Rosso di Chioggia'. Only germinability at 12°C decreased during storage but, whatever the temperature, germination rate decreased with time
The effect of seed quality (seed colour variation) on storability, germination temperature and field performance of radicchio
No full textThe possible role played by seed colour (uniformly light-L, slightly black variegated-LB, widely black variegated-BL, uniformly black-B, purple-P) in the seed quality of 'Rosso di Treviso precoce' and 'Rosso di Chioggia' radicchio was investigated. The effect of seed-storage length (two, seven months) was also studied in 'Rosso di Treviso precoce'. For better evaluation of seed quality, germination tests were carried out at 12, 20 and 28°C. The influence of seed characteristics on crop yield was then investigated in the field. Germinability and seed vigour were linked to colour. Reduced germination was observed with L seeds. Moreover, when germinated, L seeds gave rise to plants with reduced ability to form heads, thus reducing the marketable yield. As colour became increasingly darker, seeds germinated faster and more uniformly, and germinability was higher. The differences apparently resulted from incomplete seed development, as shown by the close relationship between germinability and seed weight, and by the smaller embryos of lighter seeds. Sensitivity to temperature changed with seed colour and radicchio type. The L seeds of both types germinated poorly whatever the temperature. The other lots germinated best at 28°C, excluding the LB and P seeds of 'Rosso di Chioggia' which gave better results at 20°C. The negative effect of 12°C was more evident in P seeds of 'Rosso di Chioggia'. Only germinability at 12°C decreased during storage but, whatever the temperature, germination rate decreased with time
Diversity Analysis of Sweet Potato Genetic Resources Using Morphological and Qualitative Traits and Molecular Markers
No full textThe European Union (EU) market for sweet potatoes has increased by 100% over the last five years, and sweet potato cultivation in southern European countries is a new opportunity for the EU to exploit and introduce new genotypes. In view of this demand, the origins of the principal Italian sweet potato clones, compared with a core collection of genotypes from Central and Southern America, were investigated for the first time. This was accomplished by combining a genetic analysis, exploiting 14 hypervariable microsatellite markers, with morphological and chemical measurements based on 16 parameters. From the molecular analyses, Italian accessions were determined to be genetically very similar to the South American germplasm, but they were sub-clustered into two groups. This finding was subsequently confirmed by the morphological and chemical measurements. Moreover, the analysis of the genetic structure of the population suggested that one of the two groups of Italian genotypes may have descended from one of the South American accessions, as predicted on the basis of the shared morphological characteristics and molecular fingerprints. Overall, the combination of two different characterization methods, genetic markers and agronomic traits, was effective in differentiating or clustering the sweet potato genotypes, in agreement with their geographical origin or phenotypic descriptors. This information could be exploited by both breeders and farmers to detect and protect commercial varieties, and hence for traceability purposes
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