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.

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.

Manual inspection is a prevailing practice for quality assessment of poultry meat, but it is labor-intensive, tedious, and subjective. This thesis aims to assess the efficacy of an emerging structured illumination reflectance imaging (SIRI) technique with machine learning approaches for assessing WS and microbial spoilage in broiler breast meat. Broiler breast meat samples were imaged by an in house-assembled SIRI platform under sinusoidal illumination. In first experiment, handcrafted texture features were extracted from direct component (DC, corresponding to conventional uniform illumination) and amplitude component (AC, unique to the use of sinusoidal illumination) images retrieved from raw SIRI pattern images build linear discriminant analysis (LDA) models for classifying normal and defective samples. A further validation experiment was performed using deep learning as a feature extractor followed by LDA. The third experiment was on microbial spoilage assessment of broiler meat, deep learning models were used to extract features from DC and AC images builds on classifiers. Overall, this research has demonstrated consistent improvements of AC over DC images in assessing WS and spoilage of broiler meat and that SIRI is a promising tool for poultry meat quality detection.

No description available.

No description available.

Les neurones du cortex visuel primaire (aire 17) du chat adulte répondent de manière sélective à différentes propriétés d’une image comme l’orientation, le contraste ou la fréquence spatiale. Cette sélectivité se manifeste par une réponse sous forme de potentiels d’action dans les neurones visuels lors de la présentation d’une barre lumineuse de forme allongée dans les champs récepteurs de ces neurones. La fréquence spatiale (FS) se mesure en cycles par degré (cyc./deg.) et se définit par la quantité de barres lumineuses claires et sombres présentées à une distance précise des yeux. Par ailleurs, jusqu’à récemment, l’organisation corticale chez l’adulte était considérée immuable suite à la période critique post-natale. Or, lors de l'imposition d'un stimulus non préféré, nous avons observé un phénomène d'entrainement sous forme d'un déplacement de la courbe de sélectivité à la suite de l'imposition d'une FS non-préférée différente de la fréquence spatiale optimale du neurone. Une deuxième adaptation à la même FS non-préférée induit une réponse neuronale différente par rapport à la première imposition. Ce phénomène de "gain cortical" avait déjà été observé dans le cortex visuel primaire pour ce qui est de la sélectivité à l'orientation des barres lumineuses, mais non pour la fréquence spatiale. Une telle plasticité à court terme pourrait être le corrélat neuronal d'une modulation de la pondération relative du poids des afférences synaptiques. / Primary visual cortex neurons in adult cat are selective to different image properties as orientation, contrast and spatial frequency. This selectivity is characterized by action potentials as electrical activity from the visual neurons. This response occurs during the presentation of a luminous bar in the receptive fields of the neurons. Spatial frequency is the amount of luminous bars in a grating presented from a precise distance from the eyes and is measured in cycles per degree. Furthermore, it was establish until recently that cortical organisation in the adult remains inflexible following the critical period after birth. However, our results have revealed that spatial frequency selectivity is able to change after an imposition of a non-preferred spatial frequency, also called adapter. Following cortical activity recordings, there is a shift of the spatial frequency tuning curves in the direction of the adapter. A second adaptation at the same non-preferred spatial frequency produced a different neural response from the first adaptation. This “short-term plasticity” was already observed in the primary visual cortex for orientation selective neurons but not yet for spatial frequency. The results presented in this study suggest that such plasticity is possible and that visual neurons regulate their electrical responses through modulation of the weights of their synaptic afferences.

Les neurones du cortex visuel primaire (aire 17) du chat adulte répondent de manière sélective à différentes propriétés d’une image comme l’orientation, le contraste ou la fréquence spatiale. Cette sélectivité se manifeste par une réponse sous forme de potentiels d’action dans les neurones visuels lors de la présentation d’une barre lumineuse de forme allongée dans les champs récepteurs de ces neurones. La fréquence spatiale (FS) se mesure en cycles par degré (cyc./deg.) et se définit par la quantité de barres lumineuses claires et sombres présentées à une distance précise des yeux. Par ailleurs, jusqu’à récemment, l’organisation corticale chez l’adulte était considérée immuable suite à la période critique post-natale. Or, lors de l'imposition d'un stimulus non préféré, nous avons observé un phénomène d'entrainement sous forme d'un déplacement de la courbe de sélectivité à la suite de l'imposition d'une FS non-préférée différente de la fréquence spatiale optimale du neurone. Une deuxième adaptation à la même FS non-préférée induit une réponse neuronale différente par rapport à la première imposition. Ce phénomène de "gain cortical" avait déjà été observé dans le cortex visuel primaire pour ce qui est de la sélectivité à l'orientation des barres lumineuses, mais non pour la fréquence spatiale. Une telle plasticité à court terme pourrait être le corrélat neuronal d'une modulation de la pondération relative du poids des afférences synaptiques. / Primary visual cortex neurons in adult cat are selective to different image properties as orientation, contrast and spatial frequency. This selectivity is characterized by action potentials as electrical activity from the visual neurons. This response occurs during the presentation of a luminous bar in the receptive fields of the neurons. Spatial frequency is the amount of luminous bars in a grating presented from a precise distance from the eyes and is measured in cycles per degree. Furthermore, it was establish until recently that cortical organisation in the adult remains inflexible following the critical period after birth. However, our results have revealed that spatial frequency selectivity is able to change after an imposition of a non-preferred spatial frequency, also called adapter. Following cortical activity recordings, there is a shift of the spatial frequency tuning curves in the direction of the adapter. A second adaptation at the same non-preferred spatial frequency produced a different neural response from the first adaptation. This “short-term plasticity” was already observed in the primary visual cortex for orientation selective neurons but not yet for spatial frequency. The results presented in this study suggest that such plasticity is possible and that visual neurons regulate their electrical responses through modulation of the weights of their synaptic afferences.

Ultraprecision single point diamond turning is required to produce parts with sub-nanometer surface roughness and sub-micrometer surface profiles tolerances. These parts have applications in the optics industry, where tight form accuracy is required while achieving high surface finish quality. Generally, parts can be polished to achieve the desired finish, but then the form accuracy can easily be lost in the process rendering the part unusable. Currently, most mid to low spatial frequency surface finish errors are inspected offline. This is done by physically removing the workpiece from the machining fixture and mounting the part in a laser interferometer. This action introduces errors in itself through minute differences in the support conditions of the over constrained part on a machine as compared to the mounting conditions used for part measurement. Once removed, the fixture induced stresses and the part’s internal residual stresses relax and change the shape of the generally thin parts machined in these applications. Thereby, the offline inspection provides an erroneous description of the performance of the machine. This research explores the use of a single, high resolution, capacitance sensor to quickly and qualitatively measure the low to mid spatial frequencies on the workpiece surface, while it is mounted in a fixture on a standard ultraprecision single point diamond turning machine after a standard facing operation. Following initial testing, a strong qualitative correlation exists between the surface profiling on a standard offline system and this online measuring system. Despite environmental effects and the effects of the machine on the measurement system, the capacitive system with some modifications and awareness of its measurement method is a viable option for measuring mid to low spatial frequencies on a workpiece surface mounted on an ultraprecision machine with a resolution of 1nm with an error band of ±5nm with a 20kHz bandwidth. / Thesis / Master of Applied Science (MASc)