No description available.

No description available.

No description available.

No description available.

Contextual information influences the neuronal processing and perception of visual stimuli. The functional significance of this influence may be to increase the efficiency of visual processing by taking advantage of redundancies in natural scenes. Increased efficiency may come at a cost of introducing errors, especially when stimuli are incongruous with the context. For optimal performance the visual system may therefore balance efficiency with accuracy by dynamically controlling the influence of contextual information. Attention is an appropriate mechanism to set this balance since attention is high when errors are costly and therefore accuracy is preferable over efficiency, but attention is low when accuracy can be sacrificed for efficiency. States of attention are associated with increased acetylcholine (ACh) efflux into the cortex. The effect of ACh on cortical processing has been investigated in a number of in vitro studies. They show that ACh causes a selective inhibition of intracortical synapses while thalamocortical synapses are unaffected or even enhanced. Thus, ACh effectively switches cortical processing in favour of feedforward inputs. In the visual system this switching would be expected to reduce contextual influences, thought to be mediated by intracortical processing. These findings suggest the hypothesis that attention will reduce contextual influences by the action of ACh. To investigate this hypothesis I present work from four separate experiments. I found that attention caused a reduction in contextual influences at the level of human perception (Experiment 1) and at the level of neurons in primate V1 (Experiment 3). I also found the application of ACh to cells in VI of anaesthetised primates caused a reduction in non-classical receptive field modulation (Experiment 2), similar to the effect of attention. Finally I found that attentional modulation of neuronal responses in macaque V1 was partially blocked by the application of a cholinergic antagonist, scopolamine (Experiment 4). Taken together my findings demonstrate that attention causes a suppression of contextual influences at the level of perception and at the level of the primary visual cortex. These effects were at least partly mediated by cholinergic mechanisms.

Without the ability to learn about the world around us, and the relative location of objects within it, we would be unable to make our way from one location or goal to another. This ability to learn spatially and navigate is essential and therefore so is understanding how this is achieved. Traditionally there has been a split between the theory behind how we learn about temporal and spatial relationships. Since Tolman (1948) the generally accepted theory of human spatial learning is that a cognitive map, a mental representation, is developed as an environment is explored. This map is then automatically updated when new information is presented (O’Keefe & Nadel, 1987). Temporal learning however has been considered to be governed traditional associative principles (Thorndike, 1911; Pavlov, 1927), and later discrepancy learning (Rescorla & Wagner, 1972). A particular effect considered to be confined to temporal learning is that of cue-competition, where learning about one cue, or source of information, can compete with learning about another cue such as blocking (Kamin, 1969) or overshadowing (Pavlov, 1927). In a blocking design learning about the relationship between A and X can block later learning about a possible relationship between B and X. In overshadowing only one cue (A or B) is learnt about in relation to X when both are presented at the same time. The lack of competition effects in spatial learning was considered evidence for differing mechanisms for spatial and temporal learning, and whilst recent evidence has been found that suggests blocking can be found in human spatial learning (Alexander, Wilson & Wilson, 2009; Wilson & Alexander, 2008) most such examples utilise goal directed spatial search tasks. These are vulnerable to the criticisms of Mackintosh (2002) as they may not reflect 16 true spatial learning due to still having potential non-spatial solutions. Therefore it remains to be seen whether competition effects can be found when using unequivocal spatial measures. One area of investigation free of non-spatial explanations is that of spatial alignment effects. Spatial alignment effects refer to more efficient recall about an environment and the objects within it from an imagined perspective aligned with a particular source of information. One particular type is the First Perspective Alignment Effect (FPA) where recall from a perspective that is aligned with the very first perspective experienced is more efficient than others. Such effects are revealed through judgement of relative direction tasks which require the use and application of vectorial learning and measure orientation dependence. Spatial alignment effects and cue-competition were investigated in the following Virtual Environment (VE) experiments. Experiments 1, 2a, 2b and 2c investigated factors that could influence the presence of the FPA effect. Experiment 1 found that the FPA effect was present regardless of the level of detail in a VE, or type of VE (Indoor or Outdoor) experienced. Experiment 2a, 2b and 2c found that pre-exposure to a VE before training could attenuate the FPA effect, but only if the pre-exposure was relevant. Experiments 3 to 7 investigated whether evidence for competition effects could be found. Both Experiments 3 and 4, using an object array design and human movement respectively, were unable to provide the required alignment effects in isolation. Therefore no evidence for competition effects was forthcoming. Experiments 5 utilised an overshadowing design to see if competition could be found between the first-perspective and symbolic sources of information. No evidence of overshadowing was found but symbolic information was established as a potential source of spatial alignment. Experiments 6 and 7 used a blocking design to again look at competition between the first-perspective and the symbolic. Evidence was found for blocking; when the first-perspective was trained first it blocked subsequent learning about the symbolic. Experiments 6 and 7 therefore provide important evidence of competition effects in the spatial domain, free from alternative associative explanations. This is a key finding as it suggests a similar learning mechanism between temporal and spatial learning despite the differences in knowledge structure. The results are discussed further in relation to the salience hypothesis of Wilson, Wilson, Griffiths and Fox (2007), the quasi-modular explanation of spatial learning (Jeffery. 2010), the universalist account (Pearce, 2009) and associative learning mechanisms (Rescorla & Wagner, 1972; Mackintosh, 1975).

A fundamental function of the visual system, and other sensory systems, due to resource limitations, is to optimally select task-relevant information from the barrage of information impinging the retina. In a series of experiments different aspects of attention to visual information for perception and recognition are addressed. Firstly, what information is selected? In Chapter 2, I begin with addressing the generic problem of knowing which information drives the perception of a stimulus. As a case study example, a first experiment using Bubbles (Gosselin and Schyns, 2001) determines the specific information underlying the perception of the stable percepts of an ambiguous image and shows that this information is grounded in different spatial filters processing each image interpretation. A further experiment employs frequency-specific adaptation to induce a perception of the image that is orthogonal to the adapting frequencies, validating this information drives the selective perception of the ambiguous image. Secondly, if we know the subset of information that is selected for the perception of an input, can the processing of information underlying a percept be selectively suppressed, thereby inducing an alternative percept? In the experiments of Chapter 3, I further apply this spatial frequency adaptation method to test the relevance of local image features for the perception of the 2 ambiguous image, and the recognition of gender in hybrid faces. While the results of the experiment on the perception of the ambiguous image suggest an effective method for testing the role of local stimulus information for perception, the results of the experiment on the recognition of gender in faces showed no effect of adaptation region on perception of gender. Thirdly, how does selective information use evolve with learning? And what are the mechanism(s) that enable this learning? In Chapter 4, I investigated the evolution of information use in the discrimination of unfamiliar faces using a perceptual learning paradigm. I used the method of noise masking to examine the facial regions observers used, over time, for successful discrimination, and to determine the mechanisms underlying performance improvements. The results showed that the efficiency of observers to use the information available increased with learning differentially across different regions of the face. Supplementary to examining attention to information in terms of the information content of the stimulus, another series of experiments investigated the effect of attention on the temporal dynamics of processing visual information, and the locus of this effect within the stream of information processing. Using spatial pre-cueing to manipulate attention and a speed-accuracy trade-off (SAT) method to examine the full time-course of visual processing, I analysed, in addition to the behavioural response and the parameters of the SATfunction, the lateralised readiness potential (LRP)and other components of the event-related brain potentials (ERPs) to determine the locus of any attentional modulations on the speed of processing. The results of three experiments showed that attention can speed up visual information processing, and that the locus of this effect is at later processing stages related to the categorisation of a stimulus.

No description available.

Στο πρώτο μέρος της έρευνάς μας, επιχειρείται η τεκμηρίωση της επιλογής του θέματος, έτσι ώστε να διατυπωθεί και να δικαιολογηθεί ο σκοπός και ο στόχος της έρευνας. Τις τελευταίες δεκαετίες, ερευνητές τόσο από τον χώρο της ψυχολογίας όσο και από τον χώρο της εκπαίδευσης, τονίζουν την σπουδαιότητα του υλικού χώρου στην ανάπτυξη και εκμάθηση εννοιών. Επιχειρούν να ερευνήσουν και να εισάγουν έννοιες που συνδέονται τόσο με τον χώρο όσο και με μορφές αναπαράστασής του. Ερευνούν τις ικανότητες των παιδιών στην κατανόηση και χρησιμοποίησή των αναπαραστάσεων αυτών. Αρχικά γίνεται μια αποσαφήνιση των εννοιών του χώρου, της έννοιας της αναπαράστασης και των μορφών αναπαράστασης του χώρου. Στη συνέχεια γίνεται μια μικρή ιστορική αναδρομή και αναφορά ερευνών σχετικών με μορφές αναπαράστασης του χώρου που διαπραγματεύονται κυρίως χάρτες, μοντέλα, αεροφωτογραφίες και φωτογραφίες. Η φωτογραφία είναι μια μορφή αναπαράστασης του χώρου, ίσως η πιο απλή, λόγω της φανερής ομοιότητας με τον χώρο και χρησιμοποιείται κυρίως ως βασικό βοηθητικό υλικό για την διεξαγωγή ερευνών αλλά και δραστηριοτήτων στο νηπιαγωγείο. Στη έρευνα αυτή εξετάζεται η ικανότητα των παιδιών προσχολικής εκπαίδευσης να την αντιλαμβάνονται ως μορφή αναπαράστασης του χώρου και να τη χρησιμοποιούν ως χάρτη για να βρουν τη θέση τους αλλά και τη θέση άλλων αντικειμένων στο χώρο καθώς και να υποδεικνύουν σε φωτογραφία τη θέση αντικείμενων του πραγματικού χώρου. Στη συνέχεια αναφερόμαστε και τονίζουμε στοιχεία του αναλυτικού προγράμματος σπουδών του νηπιαγωγείου όπου συνδέονται με έννοιες του χώρου, με μορφές αναπαράστασης του και με τη φωτογραφία. Στο δεύτερο μέρος παρουσιάζουμε το μεθοδολογικό πλαίσιο της εργασίας μας, το αντικείμενο της έρευνας που απορρέει από την θεωρητική προβληματική και γίνεται παρουσίαση των ερευνητικών ερωτημάτων και του δείγματος. Η διερεύνηση πραγματοποιήθηκε με ατομικές συνεντεύξεις με 18 νήπια και προνήπια ηλικίας περίπου 5,5 ετών. Τέλος στο τρίτο μέρος της εργασίας παρουσιάζονται τα αποτελέσματα, η ανάλυση τους καθώς και τα συμπεράσματα. Από τα αποτελέσματα της έρευνας φαίνεται ότι η ικανότητα των παιδιών να αντιλαμβάνονται και να χρησιμοποιούν τη φωτογραφία ως μορφή αναπαράστασης του χώρου, για να βρουν τη θέση τους, τη θέση του φωτογράφου, τη θέση αντικειμένων στο χώρο καθώς και να υποδεικνύουν τη θέση αντικειμένων του πραγματικού χώρου στις φωτογραφίες, δεν είναι ακόμα πλήρως αναπτυγμένη καθώς το μεγαλύτερο μέρος των παιδιών δυσκολεύεται και δεν μπορεί να πραγματοποιήσει με επιτυχία όλες τις δραστηριότητες. / In the first part of our investigation, we attempt to document the choice of topic, to formulate and justify the purpose and objective of the research. In recent decades, researchers from both the fields of psychology and education, stress the importance of space at the development and learning of concepts. They attempt to investigate and introduce concepts related to both space itself and forms of its representation. They investigate the children’s ability to understand and use these representations. Originally we clarify the concepts of space, the concept of representation and forms of representation of space. This is followed by historical background and reference researches related to forms of representation of space, regarding mainly maps, models, aerial photographs and images. Photograph is the simplest form of representation of space, because of the apparent similarity to the space and is mainly used as a basic reference material for conducting research and activities in kindergarten. This survey tests the ability of preschool education children to perceive photographs as a form of representation of space and use it as a map to indicate their own position, the position of the photographer and the position of other objects in real space. Then we talk and stress components of the kindergarten curriculum associated with notions of space, forms of representation and photographs. The second part presents the methodological framework of our work, the research stemming from the theoretical problematic and the research’s questions and sample. The investigation carried out by individual interviews with 18 toddlers and preschoolers aged approximately 5.5 years. Finally the third part of the work presents the results, their analysis and conclusions. From the survey results it appears that children's ability to understand and use photographs as a form of representation of space, to find their place, the location of the photographer, location of objects in space and indicate the position of real space objects in images are not yet fully developed as the majority of the children finds difficulties in carrying out all of the activities successfully.