In this thesis, the restorative effects of exposure to nature are examined through the lens of existing restoration theories. Limitations of existing theories, such as Attention Restoration Theory and Psycho-evolutionary Restoration Theory, are highlighted. To address the limitations of existing theories, an expanded theoretical framework is proposed: The expanded framework introduces a newly proposed neural mechanism and theory of restoration that build on existing theories by proposing a link to recently discovered reward systems in the ventral visual pathway. Results from six experiments provide consistent evidence to suggest that positive and negative responses to visual scenes are related to the low-level visuospatial properties of the scenes. Specifically, a discovery is made to suggest that the power of a limited visual spatial frequency range can consistently predict responses to natural, urban, and abstract scenes on measures of restoration (blink-rates, number of fixations, self-reported stress and pleasantness). This provides the first evidence to suggest that low-level visual properties of scenes may play an important role in affective and physiological responses to scenes. Furthermore, this newly discovered relationship provides a new way to objectively predict the relative restorative value of any given scene.

Made available in DSpace on 2015-05-14T13:16:34Z (GMT). No. of bitstreams: 1 arquivototal.PDF: 1526331 bytes, checksum: 38e40aec6b111371aebd1a5cba081a3c (MD5) Previous issue date: 2009-04-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Epilepsy is a brain dysfunction characterized by the repeated tendency of the brain to cause epileptic crisis and by the neurobiological, cognitive, psychological and social consequences of this condition. In these terms, the aim of this work is to determine the visual sensory threshold of children and adolescents who have and who do not have epilepsy, analyzing possible alterations in the form related to this dysfunction. The sensory threshold is defined as the smallest intensity of incentive a human being is capable of detecting. The contrast sensitivity function (CSF) is the inverse of the threshold curve of contrast (1/CSF). This way, the CSF is a tool that allows us to label the answer of SV to visual patterns in low, medium and high levels of contrast and evaluate possible sensorial alterations associated with the visual processing. The main idea is that the elevation or reduction of the CSF can happen deem to sensorial, cognitive and behavioral alterations. Twenty volunteers participated on this study, from both genders, between 7 and 17 years of age, 10 of whom nonepileptic and 10 epileptic (tonic-clonic crisis). All of them presented either normal or corrected visual accuracy and were distributed in groups that were equivalent in age. The resolutions were taken from the psychophysical forced-choice method, using the static sine wave gratings with spatial frequencies of 0.25, 2.0 and 8.0 cpd (cycles per degree of visual angle). During each experimental session, there were stimulus pares presented randomly (test stimulus and neutral), and the task of the participants was to choose always the test stimulus with one of the frequencies above. The criterion used was the one of three consecutive correct answers to low the contrast in one unity and just one mistake to increase the contrast in the same unity (20%). After each session, a sheet of results with the experimental situation was released and the six values of contrast were calculated by the reversions. The values of contrast obtained to each frequency were grouped in spreadsheets separated by condition (with or without epilepsy) and the big average was used as an estimative of the sensory threshold or of the sensibility to the contrast due to each spatial frequency tested. The analysis of variance (ANOVA) to repeated measures showed significant differences between the groups [F(1,238) = 11.80); p<0.01]. The analysis obtained with the help of the test posthoc Tukey HSD revealed a relevant dissimilarity only in the 0.25cpg (p<0.01)]. In other words, the results indicated an expressive alteration in the visual perception children and adolescents with epilepsy have. / A epilepsia é um distúrbio cerebral caracterizado pela predisposição persistente do cérebro para gerar crises epilépticas e pelas conseqüências neurobiológicas, cognitivas, psicológicas e sociais desta condição. Algumas pesquisas demonstram que distúrbios visuais são bastante freqüentes em pessoas com epilepsia. Nestes termos, o objetivo deste trabalho foi determinar o limiar sensório visual de crianças e adolescentes com e sem epilepsia, verificando possíveis alterações na percepção visual da forma relacionadas a este transtorno. O limiar sensório é definido como a menor intensidade de um estímulo que um ser humano é capaz de detectar. A função de sensibilidade ao contraste (FSC) é o inverso da curva de limiar de contraste (1/FSC). Assim, a FSC é uma ferramenta que permite caracterizar a resposta do SV para padrões visuais em níveis baixos, médios e altos de contraste e avaliar possíveis alterações sensoriais relacionadas ao processamento visual. A idéia principal é que a elevação ou redução da FSC pode está relacionada a alterações sensoriais, cognitivas e comportamentais. Participaram deste estudo, 20 voluntários de ambos os sexos com idades entre 7 e 17 anos, sendo 10 sem epilepsia e 10 com epilepsia (crises tônicoclônicas). Todos apresentavam acuidade visual normal ou corrigida e foram distribuídos pelos grupos atendendo ao critério de equivalência de idade. As medidas foram realizadas com o método psicofísico da escolha forçada, utilizando grade senoidal vertical estática com freqüências espaciais de 0,25; 2,0 e 8,0 cpg (ciclos por grau de ângulo visual). Durante cada sessão experimental, foram apresentados aleatoriamente pares de estímulos (estímulo de teste e neutro), e a tarefa dos participantes foi escolher sempre o estímulo de teste com uma das freqüências acima. O critério adotado foi o de três acertos consecutivos para diminuir o contraste em uma unidade, e apenas um erro para aumentar o contraste na mesma unidade (20%). Após cada sessão, o programa produzia uma folha de resultados com a situação experimental e os seis valores de contraste conseguidos pelas reversões. Os valores de contraste obtidos para cada freqüência foram agrupados em planilhas por condição (com e sem epilepsia) e a grande média foi utilizada como estimativa do limiar sensório ou da sensibilidade ao contraste em função de cada freqüência espacial testada. A análise de variância (ANOVA) para medidas repetidas mostrou diferenças significantes entre os dois grupos [F(1, 238) =11,80); p < 0,01]. Já a análise com o teste post-hoc Tukey HSD revelou diferença significante apenas na faixa de freqüências de 0,25 cpg (p < 0,01). Em termos gerais, os resultados demonstraram alteração significante na percepção visual da forma de crianças e adolescentes com epilepsia.

The manufacturing of optical components, such as lenses or mirrors, consists of numeroussteps that are essential to the performance of the fnished optical system, such as the specifcation ofthe optical surface. For a longer period, the main focus has been in identifying and restricting thenegative effects of the low and high spatial frequency content of the surface. However, as technologyand optical equipment has become more advanced, the effects of the mid-spatial frequencies havebeen studied more, and continue to be a topic of research. As of now, there is still a need for methodsthat accurately predict and analyse the regime of mid-spatial frequencies, such that they can becontrolled during the specifcation phase, successfully limiting the need of post-processing steps.This work introduces a software tool, specifcally designed to approach this problem, which wasto be developed in Python as a contribution to the existing Optical Scripting Library at OHB. Byspecifying an optical component in terms of a Power Spectral Density function, together with thecontributions from different spatial frequency domains and the application of a ripple patterns, thissoftware tool can generate pseudo-random optical surfaces, which maintains the input specifcations.Furthermore, a Dynamic Link Library fle was developed, sharing the same functionality as thePython implementation, allowing for simulations using Zemax OpticStudio. Using the software tool,it was found that the relative error between input and output measurements were approximately0.78%, in terms of the Power Spectral Density Function. In addition, the result of analysing one of thetwo test cases indicate that the software tool is effective in predicting the infuence of mid-spatialfrequency errors, fulflling a previously measured predicition. The second test case proved that thesoftware tool can be used for mimicing surfaces of real measurements, holding the same specifcations.

No description available.

No description available.

Les neurones des couches superficielles du collicule supérieur et du cortex visuel primaire du rat adulte sont sensibles à de basses fréquences spatiales de haut contraste défilant à des vitesses élevées. Entre les jours post-nataux 27-30 et l’âge adulte, les fréquences temporelles optimales des neurones du cortex visuel primaire augmentent, tandis que leurs seuils de contraste diminuent. Cependant, les fréquences spatiales optimales, les valeurs de résolution spatiale et les bandes passantes spatiales de ces neurones sont, dès l’ouverture des paupières, similaires à celles observées chez le rat adulte. Ces profils de réponse neuronale suggèrent que les projections rétino-colliculaires et rétino-géniculo-corticales sont essentiellement issues de neurones ganglionnaires rétinofuges magnocellulaires et koniocellulaires. Les neurones du cortex visuel primaire du rat ayant subi des convulsions hyperthermiques présentent, dès l’ouverture des paupières, de basses fréquences spatiales optimales, de larges bandes passantes directionnelles et temporelles ainsi que des seuils de contraste élevés par rapport aux neurones du rat normal. À l’âge adulte, de basses fréquences temporelles optimales et de larges bandes passantes spatiales sont également observées chez le rat ayant subi des convulsions hyperthermiques. L’altération des profils de réponse des neurones du cortex visuel primaire du rat ayant subi de convulsions hyperthermiques suggère un déséquilibre entre les mécanismes neuronaux excitateurs et inhibiteurs de cette aire corticale. Ces résultats suggèrent également qu’un épisode unique de convulsions fébriles infantiles suffit à altérer le développement des propriétés spatio-temporelles des champs récepteurs des neurones du cortex visuel primaire. / Neurons in superficial layers of the rat superior colliculus and primary visual cortex are sensitive to highly contrasted low spatial frequencies drifting at fast speeds. Between post-natal days 27-30 and adulthood, the optimal temporal frequencies of neurons in the primary visual cortex increase, whereas their contrast thresholds decrease. However, the optimal spatial frequencies, spatial resolution values and spatial bandwidths of these neurons are, soon after eyelid opening, similar to those observed in the adult rat. These neuronal response profiles suggest that the retino-collicular and retino-geniculo-cortical projections are mainly innervated by magnocellular and koniocellular retinal ganglion cells. Neurons in the primary visual cortex of rats having experienced hyperthermic seizures are, soon after eyelid opening, sensitive to low optimal spatial frequencies and show broad directional and temporal bandwidths, as well as elevated contrast thresholds when compared to neurons of normal rats. At adulthood, low optimal temporal frequencies and broad spatial bandwidths are also observed in rats having experienced hyperthermic seizures. The alteration of response profiles of neurons in the primary visual cortex of rats having experienced hyperthermic seizures suggests an unbalance between excitatory and inhibitory mechanisms in this cortical structure. These results also suggest that a single episode of febrile seizures could be sufficient to impede the development of the spatio-temporal receptive field properties of neurons in the primary visual cortex.

No description available.

Les neurones des couches superficielles du collicule supérieur et du cortex visuel primaire du rat adulte sont sensibles à de basses fréquences spatiales de haut contraste défilant à des vitesses élevées. Entre les jours post-nataux 27-30 et l’âge adulte, les fréquences temporelles optimales des neurones du cortex visuel primaire augmentent, tandis que leurs seuils de contraste diminuent. Cependant, les fréquences spatiales optimales, les valeurs de résolution spatiale et les bandes passantes spatiales de ces neurones sont, dès l’ouverture des paupières, similaires à celles observées chez le rat adulte. Ces profils de réponse neuronale suggèrent que les projections rétino-colliculaires et rétino-géniculo-corticales sont essentiellement issues de neurones ganglionnaires rétinofuges magnocellulaires et koniocellulaires. Les neurones du cortex visuel primaire du rat ayant subi des convulsions hyperthermiques présentent, dès l’ouverture des paupières, de basses fréquences spatiales optimales, de larges bandes passantes directionnelles et temporelles ainsi que des seuils de contraste élevés par rapport aux neurones du rat normal. À l’âge adulte, de basses fréquences temporelles optimales et de larges bandes passantes spatiales sont également observées chez le rat ayant subi des convulsions hyperthermiques. L’altération des profils de réponse des neurones du cortex visuel primaire du rat ayant subi de convulsions hyperthermiques suggère un déséquilibre entre les mécanismes neuronaux excitateurs et inhibiteurs de cette aire corticale. Ces résultats suggèrent également qu’un épisode unique de convulsions fébriles infantiles suffit à altérer le développement des propriétés spatio-temporelles des champs récepteurs des neurones du cortex visuel primaire. / Neurons in superficial layers of the rat superior colliculus and primary visual cortex are sensitive to highly contrasted low spatial frequencies drifting at fast speeds. Between post-natal days 27-30 and adulthood, the optimal temporal frequencies of neurons in the primary visual cortex increase, whereas their contrast thresholds decrease. However, the optimal spatial frequencies, spatial resolution values and spatial bandwidths of these neurons are, soon after eyelid opening, similar to those observed in the adult rat. These neuronal response profiles suggest that the retino-collicular and retino-geniculo-cortical projections are mainly innervated by magnocellular and koniocellular retinal ganglion cells. Neurons in the primary visual cortex of rats having experienced hyperthermic seizures are, soon after eyelid opening, sensitive to low optimal spatial frequencies and show broad directional and temporal bandwidths, as well as elevated contrast thresholds when compared to neurons of normal rats. At adulthood, low optimal temporal frequencies and broad spatial bandwidths are also observed in rats having experienced hyperthermic seizures. The alteration of response profiles of neurons in the primary visual cortex of rats having experienced hyperthermic seizures suggests an unbalance between excitatory and inhibitory mechanisms in this cortical structure. These results also suggest that a single episode of febrile seizures could be sufficient to impede the development of the spatio-temporal receptive field properties of neurons in the primary visual cortex.

The aim of this thesis was to investigate the input-specificity of sensory-induced plasticity in humans. This was achieved by varying the characteristics of sine gratings so that they selectively targeted distinct populations of neurons in the visual cortex. In Experiments 1-3, specificity was investigated with electroencephalography using horizontally- and vertically-oriented sine gratings (Experiment 1) or gratings of differing spatial frequency (Experiments 2 & 3). Increases in the N1b potential were observed only for sine gratings that were the same in orientation or spatial frequency as that used as the tetanus, suggesting that the potentiation is specific to the visual pathways stimulated during the induction of the tetanus. However, the increase in the amplitude of the N1b in Experiment 1 was not maintained when tested again at 50 minutes post-tetanus. This may have been due to depotentiation caused by the temporal frequency of stimulus presentation in the first post-tetanus block. To try to circumvent this potential confound, immediate and maintained (tested 30 minutes post-tetanus) spatial-frequency-specific potentiation were tested separately in Experiments 2 and 3, respectively. Experiment 3 demonstrated that the increased N1b was maintained for up to half an hour post-tetanus. In addition, the findings from Experiment 1, as well as the pattern of results from Experiments 2 and 3, indicate that the potentiation must be occurring in the visual cortex rather than further upstream at the lateral geniculate nucleus. In Experiment 4 functional magnetic resonance imaging was used to more accurately localise where these plastic changes were taking place using sine gratings of differing spatial frequency. A small, focal post-tetanic increase in the blood-oxygen-level-dependent (BOLD) response was observed for the tetanised grating in the right temporo-parieto-occipital junction. For the non-tetanised grating, decreases in BOLD were found in the primary visual cortex and bilaterally in the cuneus and pre-cuneus. These decreases may have been due to inhibitory interconnections between neurons tuned to different spatial frequencies. These data indicate that tetanic sensory stimulation selectively targets and potentiates specific populations of neurons in the visual cortex.

The aim of this thesis was to investigate the input-specificity of sensory-induced plasticity in humans. This was achieved by varying the characteristics of sine gratings so that they selectively targeted distinct populations of neurons in the visual cortex. In Experiments 1-3, specificity was investigated with electroencephalography using horizontally- and vertically-oriented sine gratings (Experiment 1) or gratings of differing spatial frequency (Experiments 2 & 3). Increases in the N1b potential were observed only for sine gratings that were the same in orientation or spatial frequency as that used as the tetanus, suggesting that the potentiation is specific to the visual pathways stimulated during the induction of the tetanus. However, the increase in the amplitude of the N1b in Experiment 1 was not maintained when tested again at 50 minutes post-tetanus. This may have been due to depotentiation caused by the temporal frequency of stimulus presentation in the first post-tetanus block. To try to circumvent this potential confound, immediate and maintained (tested 30 minutes post-tetanus) spatial-frequency-specific potentiation were tested separately in Experiments 2 and 3, respectively. Experiment 3 demonstrated that the increased N1b was maintained for up to half an hour post-tetanus. In addition, the findings from Experiment 1, as well as the pattern of results from Experiments 2 and 3, indicate that the potentiation must be occurring in the visual cortex rather than further upstream at the lateral geniculate nucleus. In Experiment 4 functional magnetic resonance imaging was used to more accurately localise where these plastic changes were taking place using sine gratings of differing spatial frequency. A small, focal post-tetanic increase in the blood-oxygen-level-dependent (BOLD) response was observed for the tetanised grating in the right temporo-parieto-occipital junction. For the non-tetanised grating, decreases in BOLD were found in the primary visual cortex and bilaterally in the cuneus and pre-cuneus. These decreases may have been due to inhibitory interconnections between neurons tuned to different spatial frequencies. These data indicate that tetanic sensory stimulation selectively targets and potentiates specific populations of neurons in the visual cortex.