1,721,053 research outputs found
Méthodologie en matière d’élaboration des plans d’occupation des sols
No full textRaffi M. Méthodologie en matière d’élaboration des plans d’occupation des sols. In: Droit et Ville, tome 1, 1976. Les plans d’occupation des sols. pp. 25-33
Optical recordings reveal a functional architecture for spatial attention in the posterior parietal cortex of the behaving macaque
No full textThe influence of spatial attention in the parietal cortex was evaluated using optical imaging of intrinsic signals at 605nm. The most dorsal aspects of area 7a and dorsal prelunate (DP) were imaged. Recordings were made in the right hemisphere of a macaque trained to fixate a 0.1° red dot and perform a cued detection task. Two 10° expanding optic flow stimuli were simultaneously presented 10° to the left and right (or above and below) the target. The monkey responded to a change in the structure of one of the two stimuli. A 2° white cue instructed the monkey as to which stimulus would change. A behavioral catch-trial control was also used for which the cue was incorrect. Behaviorally, there was a decrease in the reaction time of 25-50 msec when the monkey was correctly vs. incorrectly cued indicating a spatial attentional shift. The evoked optical response across the posterior parietal cortex depended on the locus of attention with the appearance of columns corresponding to the location of the attentional cue. We quantified these effects using a linear regression analysis. The columns were seen in all the experiments performed over 10 months and had the same dimension in both horizontal and vertical paradigm. These attentional columns were not seen in controls when just the cue was presented and the animal attended only to the central fixation point. For verification, multi-unit recordings were made using both the attentional task and the control task. The great majority of neurons showed no dependence at the onset of the stimuli upon the cue condition. A control paradigm in which the animal had to detect a central fixation point dimming showed that the cue alone had little or no effect on the firing rate. Thus the observed columns are not likely to result from the cue stimuli, but rather the spatial focus of the attention. The columns represent a novel functional architecture correlated with attention
Eye movements for performance. Saccades and microsaccades in elite table tennis players
No full textAim: Investigation of the combined occurrence and characteristics of saccades and microsaccades during free-viewing sport task, with the intention to explore gaze behaviour that would optimize information gathering for action outcome prediction.
Methods: Gaze behaviour of expert and novice table tennis players was recorder during a task in which subjects were instructed to predict the ball future direction after the opponent’s throw. Response accuracy, reaction time, fixations, microsaccades and saccades were recorded to estimate the relationship between gazing strategy and success in the task. Analysis of the sequence of saccades/fixations and microsaccade dynamics (during fixations) allowed to study allocation of overt or covert attention in successful predictions.
Results: Compared to novices, experts showed more correct responses (70% vs. 64%) with shorter reaction time (411.88±94.62 vs. 468.56±123.22 ms). Experts fixated more times and for longer periods, with more saccades and microsaccades, on hand-racket during forehand and on trunk during backhand drive technique. Furthermore, experts showed a narrower frequency distribution of microsaccade orientations when fixating on hand-racket and trunk areas, meaning that the attention was focused on those small locations.
Conclusions: Microsaccades and saccades can be related to the salience of interest areas during performance. Athletes who play ball games are repeatedly exposed to motion stimuli during their training, improving their perception of moving objects. The link between visuomotor performance and covert attention shifts could have a potential impact upon sports, as for example assessments of visual performance that can help to predict people who have elite potential. On these premises, one can suggest that vision training offers a mean to improve performance.
References:
1. Piras A, Raffi M, Lanzoni IM, Persiani M, & Squatrito S. (2015) Microsaccades and prediction of a motor act outcome in a dynamic sport situation. Invest Ophthalmol Vis Sci Title, 56(8), 4520–4530.
2. Piras A, Lanzoni IM, Raffi M, Persiani M, & Squatrito S. (2016). The within-task criterion to determine successful and unsuccessful table tennis players. Int J Sports Sci Coach, 11(4)
Rassegna bibliografica, "Ottocento: dal 1850 al 1900", a cura di Marangoni A., Merello I., Raffi M.E., Studi Francesi n. 199
No full textThe role of different warm-up protocols on cardiovascular and metabolic responses in dynamic apnoea
No full textRassegna Bibliografica, "Ottocento: dal 1850 al 1900", a cura di Marangoni A., Merello I., Raffi M.E., Studi Francesi 201
No full textUnderstanding the underlying mechanisms of Quiet Eye: the role of microsaccades and pupil-size during fixation.
No full textA Narrative Literature Review on the Role of Exercise Training in Managing Type 1 and Type 2 Diabetes Mellitus
Full text linkDiabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia associated with impaired carbohydrate, lipid, and protein metabolism, with concomitant absence of insulin secretion or reduced sensitivity to its metabolic effects. Patients with diabetes mellitus have a 30% more risk of developing heart failure and cardiovascular disease compared to healthy people. Heart and cardiovascular problems are the first cause of death worldwide and the main complications which lead to high healthcare costs. Such complications can be delayed or avoided by taking prescribed medications in conjunction with a healthy lifestyle (i.e., diet and physical activity). The American College of Sports Medicine and the American Diabetes Association recommend that diabetic people reduce total sedentary time by incorporating physical activity into their weekly routine. This narrative literature review aims to summarize and present the main guidelines, pre-exercise cardiovascular screening recommendations, and considerations for patients with diabetes and comorbidities who are planning to participate in physical activity programs
Analysis of microsaccades during extended practice of a visual discrimination task in the macaque monkey
Full text linkThe spatial location indicated by a visual cue can bias microsaccades directions towards or away from the cue. Aim of this work was to evaluate the microsaccades characteristics during the monkey's training, investigating the relationship between a shift of attention and practice. The monkey was trained to press a lever at a target onset, then an expanding optic flow stimulus appeared to the right of the target. After a variable time delay, a visual cue appeared within the optic flow stimulus and the monkey had to release the lever in a maximum reaction time (RT) of 700 ms. In the control task no visual cue appeared and the monkey had to attend a change in the target color. Data were recorded in 9 months. Results revealed that the RTs at the control task changed significantly across time. The microsaccades directions were significantly clustered toward the visual cue, suggesting that the animal developed an attentional bias toward the visual space where the cue appeared. The microsaccades amplitude differed significantly across time. The microsaccades peak velocity differed significantly both across time and within the time delays, indicating that the monkey made faster microsaccades when it expected the cue to appear. The microsaccades number was significantly higher in the control task with respect to discrimination. The lack of change in microsaccades rate, duration, number and direction across time indicates that the experience acquired during practicing the task did not influence microsaccades generation
Neuronal responses to optic flow in the monkey parietal area PEc
No full textArea PEc, a high order association area, is located in the dorsocaudal portion of the superior parietal cortex. PEc neurons encode visual motion signals, especially the direction of stimulus motion. The present study tested if PEc neurons also process visual correlates of self-motion. The extracellular activity of single neurons in response to optic flow stimuli was recorded in two monkeys (Macaca fascicularis) trained in a fixation task. The stimuli were produced by random dots simulating planar motion, radial expansion and radial contraction. A substantial number of PEc neurons were specifically activated by radial optic flow and were selective for the position of the focus of expansion with respect to the fovea. Eccentric positions of the focus of expansion were preferred. Almost all neurons showed opponent excitatory-inhibitory activity to expanding-contracting visual fields. Planar motion elicited very weak responses. Optic flow responsiveness is not entirely explained by classical bar sensitivity in PEc neurons, suggesting that optic flow and classical bar responses could serve different mechanisms in the integration of visuo-motor signals to prepare body movements
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