1,720,963 research outputs found
The role of task-irrelevant information in perceptual learning
No full textIn human perception, visual perceptual learning is a well-known effect, showing that the adult neural system can achieve long-term enhanced performance on a visual task as a result of visual experience (Fahle & Poggio, 2002). The mechanisms underlying visual perceptual learning were debated for decades. Task-relevance, attention and awareness were thought necessary for perceptual learning (Shiu & Pashler, 1992; Ahissar & Hochstein, 1993; Schoups, Vogel, Qian, and Orban, 2001), but this view has been challenged by the discovery of task-irrelevant perceptual learning (TIPL), which occurs for task-irrelevant, unattended and even sub-threshold stimuli (Watanabe, Nanez & Sasaki, 2001). TIPL is a slow phenomenon, because thousands of training trials are necessary in order to observe perceptual learning for task-irrelevant stimuli. However, a fast form of TIPL (fast-TIPL) has been recently studied in the context of perceptual memories, accounting evidence of a learning mechanism similar to TIPL, in which task-irrelevant stimuli are better learned when presented at behaviourally relevant points in time (Lin, Pype, Murray & Boynton, 2010).
In the present dissertation, the role of task-irrelevant stimuli in visual perceptual learning is examined. The first line of experiments aimed to deepen the understanding about the mechanisms underlying visual perceptual learning by investigating whether perceptual learning can be produced by the mere exposure to a task-irrelevant, sub-threshold feature, even when, during training, participants attend and perform a task on another feature of a homologous stimulus to that used during test stages. Additionally, the task-specificity of TIPL was examined. The results provided further evidence about TIPL by corroborating the hypothesis that TIPL can occur even when the training stimuli are homologous to those in pre- and post-test. A further interesting finding was that the visual perceptual learning yielded by the task-irrelevant and sub-threshold feature is task-specific, because it occurs only in the task for which participants received a specific training, and is not transferred to another task performed on the same stimulus. Second, it has been investigated whether and how the modulation of the primary task difficulty level affects TIPL, by using a fast-TIPL paradigm which allows to study the phenomenon of TIPL within a single experimental session. In a dual-task condition, the amount of attention towards task-irrelevant stimuli which is needed for fast-TIPL to be observed was investigated by modulating the attentional and cognitive load of the primary task. The results showed a massive dual-task interference between the processing of primary task stimuli and the processing and encoding of task-irrelevant stimuli: the increase in the attentional and cognitive load required by the primary task determined a complete depletion of attentional resources such as no other resources remained available to process the task-irrelevant stimuli
Early-light embryonic stimulation suggests a second route, via gene activation, to cerebral lateralization in vertebrates
Full text linkGenetic factors determine the asymmetrical position of vertebrate embryos allowing asymmetric environmental stimulation to shape cerebral lateralization. In birds, late-light stimulation, just before hatching, on the right optic nerve triggers anatomical and functional cerebral asymmetries. However, some brain asymmetries develop in absence of embryonic light stimulation. Furthermore, early-light action affects lateralization in the transparent zebrafish embryos before their visual system is functional. Here we investigated whether another pathway intervenes in establishing brain specialization. We exposed chicks’ embryos to light before their visual system was formed. We observed that such early stimulation modulates cerebral lateralization in a comparable vein of late-light stimulation on active retinal cells. Our results show that, in a higher vertebrate brain, a second route, likely affecting the genetic expression of photosensitive regions, acts before the development of a functional visual system. More than one sensitive period seems thus available to light stimulation to trigger brain lateralization
Location transfer of perceptual learning: Passive stimulation and double training
No full textSpecificity has always been considered one of the hallmarks of perceptual learning, suggesting that per- formance improvement would reflect changes at early stages of visual analyses (e.g., V1). More recently, however, this view has been challenged by studies documenting complete transfer of learning among dif- ferent spatial locations or stimulus orientations when a double-training procedure is adopted. Here, we further investigate the conditions under which transfer of visual perceptual learning takes place, confirm- ing that the passive stimulation at the transfer location seems to be insufficient to overcome learning specificity. By contrast, learning transfer is complete when performing a secondary task at the transfer location. Interestingly, (i) transfer emerges when the primary and secondary tasks are intermingled on a trial-by-trial basis, and (ii) the effects of learning generalization appear to be reciprocal, namely the pri- mary task also serves to enable transfer of the secondary task. However, if the secondary task is not per- formed for a sufficient number of trials, then transfer is not enabled. Overall, the results lend support to the recent view that task-relevant perceptual learning may involve high-level stages of visual analyses
Inter-letter spacing, inter-word spacing, and font with dyslexia friendly features: testing text readability in people with and without dyslexia
Full text linkOver the last years, several studies have suggested a possible link between dyslexia and deficits in low-level visual processing (e.g., excessive crowding). At the same time, specially designed “Dyslexia Friendly”fonts appeared on the market. This class of fonts presents two main features: the particular graphic characteristics of the letterform designed to avoid confusion between similarly shaped letters, and wider inter-letter and inter-word spacing to limit crowding. The literature testing the efficacy of “Dyslexia Friendly” fonts in improving reading accuracy and increasing reading speed is controversial. We evaluated the impact of letterform (with vs. without dyslexia-friendly graphic features), inter-letter spacing (standard vs. increased) and inter-word spacing (standard vs. increased) on reading accuracy and speed. Two groups of 64 children each, with and without dyslexia, read aloud 8 equivalent texts. The data collected failed to show any effect from the letterform. As regards spacing, the data showed that reading speed is impaired by an increase in inter-letter spacing not combined with an adequate increase in inter-word spacing
Visual perceptual learning of task-irrelevant feature of the stimulus: preliminary results
Full text linkDuring pre- and post-tests participants performed a 3-dot Vernier task and a 3-dot bisection task. During training participants performed a luminance
discrimination task on the same 3-dot stimulus. The task-irrelevant feature of the stimulus manipulated during training was the position of the middle dot. Our results suggest that perceptual learning can occur as a result of mere exposure to a subthreshold and task-irrelevant feature of the stimulus. The present findings add new evidence in support of task-irrelevant PL, which seems to occur not only when two different stimuli are used during test and training, but also when the same stimulus is used in both stages
Perception of biological motion. No sensitivity differences between patients with Parkinson's disease and healthy observers
No full textThe use of biological motion (BM) stimuli (point-light walkers PLW) may be a novel alternative to improve the clinical impact of Action Observation treatments in Parkinson's Disease, by directing the patient's attentional focus on gait kinematics. However, the recognition of biological motion in Parkinson's patients has thus far been controversial. To evaluate the clinical feasibility of using BM stimuli in Action Observation treatments, we aimed at investigating whether Parkinson's patients in the ON-state condition can identify and use gender-specific cues conveyed by the body structure and by the kinematics of gait of a PLW. 30 Parkinson's patients and 30 healthy elderly observers were tested in a gender identification task with PLW. Parkinson's patients were able to correctly identify the gender of PLW; no differences were found between the two groups of observers. While for both groups, the gender identification task was easier when it required a judgment on a healthy PLW. Lastly, we found that females were more sensitive than males in our identification task. Our study shows that Parkinson's patients in the ON-state condition are able to extract subtle structural and kinematic characteristics from biological motion stimuli, which is favorable to the use of BM in Action Observation treatments
Is lack of attention necessary for task-irrelevant perceptual learning?
No full textPerceptual learning can occur for a feature irrelevant to the training task, when it is sub-threshold and outside of the focus of attention (task-irrelevant perceptual learning, TIPL); however, TIPL does not occur when the task-irrelevant feature is supra-threshold. Here, we asked the question whether TIPL occurs when the task-irrelevant feature is sub-threshold but within the focus of spatial attention. We tested participants in three different discrimination tasks performed on a 3-dot stimulus: a horizontal Vernier task and a vertical bisection task (during pre- and post-training sessions), and a luminance task (during training). In Experiment 1 we found that attending to luminance differences within the same stimulus that contains a sub-threshold horizontal offset (an irrelevant feature during training) does not preclude TIPL, as revealed by an improvement in the Vernier task, but not in the bisection task. This conclusion was confirmed in Experiment 2, in which the 3-dot stimulus used during training did not include a horizontal offset
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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