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The ability to navigate with limited vision is a skill that is often employed in our daily lives. Navigating without vision to a remembered target has previously been studied. However, not much is known about the attention required to perform blind navigation. We examined the effect of aging and presence of obstacles on the attentional demands of blind navigation. We evaluated reaction time, navigation errors and average walking speed in an 8 meter walking path, with or without obstacles, in the absence of vision. Results showed that older participants had increased reaction time and increased linear distance travelled as opposed to young participants, that obstacles increased reaction time and decreased average walking speed in all participants, and that emitting the reaction time stimulus early in the trial increased the linear distance travelled. Interpretation of the results suggests that aging and presence of obstacles augments the attentional demands of blind navigation.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

The ability to navigate with limited vision is a skill that is often employed in our daily lives. Navigating without vision to a remembered target has previously been studied. However, not much is known about the attention required to perform blind navigation. We examined the effect of aging and presence of obstacles on the attentional demands of blind navigation. We evaluated reaction time, navigation errors and average walking speed in an 8 meter walking path, with or without obstacles, in the absence of vision. Results showed that older participants had increased reaction time and increased linear distance travelled as opposed to young participants, that obstacles increased reaction time and decreased average walking speed in all participants, and that emitting the reaction time stimulus early in the trial increased the linear distance travelled. Interpretation of the results suggests that aging and presence of obstacles augments the attentional demands of blind navigation.

Morphological, electrophysiological and biochemical changes have been shown to occur in the retina, lateral geniculate nucleus, and visual cortex of light deprived animals. We attempted to determine whether the dark-rearing of rats from birth to 15, 30 and 60 days of age alters the ability of noradrenaline (NA) 30 μM, potassium chloride (KCI) 50 μM, adenosine 30 μM and combinations of NA and KCI with adenosine to stimulate the _in vitro formation of cyclic AMP (cAMP) in visual cortical slices and, as an internal control, in frontal cortical slices. At 15 and 30 days of age there was an 11% and 2170 reduction, respectively, compared to normally reared controls, in the stimulation of cAMP formation in a 5 minute incubation with NA in both frontal and visual cortical slices. After 60 days of dark-rearing, however, this was reversed in that the NA stimulation of cAMP formation was 23% and 357» higher than controls in frontal and visual cortical slices. In frontal cortical slices of rats dark-reared for 15 and 30 days there was a significant reduction in the stimulation of cAMP formation in a 20 minute incubation with NA. No differences were observed between 30 day old experimental and control animals in studies of the accumulation of cAMP in frontal and visual cortical slices incubated for various times with KCI. The stimulation of cAMP formation induced by KCI and adenosine in a 5 minute incubation was 5770 and 397o higher, respectively, in frontal cortical slices of 60 day old experimental animals than controls while the response in visual cortical slices was unaffected. The differences found between 60 day old experimental and control animals were abolished in both visual and frontal cortical slices when adenosine was used in combination with NA or KCI. Studies of the accumulation of cAMP in slices incubated for various times with NA revealed that the effect observed in the visual cortex after 30 days of light deprivation was due to a decrease in the maximum level of cAMP reached within a 20 minute incubation period, whereas in the frontal cortex the maximum level attained within a 20 minute incubation period was unaffected. These results are discussed in terms of our present knowledge concerning supersensitivity and plasticity in the central nervous system and the role of cAMP in nerve. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

The purpose of this study was to determine if physical restraint is a major factor in the elicitation of the hallucination phenomena associated with perceptual (or sensory) deprivation studies. Experimental subjects were exposed to three one-hour sessions of perceptual deprivation one week apart, with physical restraint being used during the second session. A group of control subjects was used to determine t he effects of three unrestrained sessions of perceptual deprivation. No significant differences were found between sessions for the experimental group in terms of number of reports or the cumulative duration of the reports. There was also no difference found between the two groups for any session. The data and experiences of the individual subjects are discussed at length with particular attention to the effects of the restraint procedure on indications of stress or anxiety levels (expressed in terms of time estimation and subjective reports). Recommendations for the use of more objective measures of anxiety such as biofeedback and electroencephalographic equipment are made as well as better defining procedures for the measurement of the hallucination phenomena. It is further suggested that the group design is not suited to the study of hallucinations due to the great degree of variability. A new procedure for the unobtrusive measure of the duration of the hallucinations is used successfully in this study and may prove to be a useful tool for future studies in this area.

Recent research has indicated a causal link between oxytocin and spirituality. The present experiment sought to examine the effects of intranasal oxytocin (IN-OT) and absorption on mysticism and spirituality in a sensory deprivation setting. The results failed to find any main effects of IN-OT on mysticism, or on spirituality. Interaction effects were discovered however, where IN-OT interacted with absorption both on mysticism and spirituality. More specifically IN-OT undermined the association between absorption and outcomes that were observed in the placebo control condition. The results contradict the findings from the only previous experiment conducted on IN-OT and spirituality. The interaction effects align with previous research on IN-OT, suggesting an increase in suggestibility among low absorption scorers. These results motivate further research on the relation between oxytocin, absorption and spirituality, keeping the idea of suggestibility in mind.

In the amphibious fish Polypterus senegalus, focussing on lateral line, vision and electrosensation, we investigated sensory abilities, their interactions, and changes in their effects on locomotor behaviour between aquatic and terrestrial environments. First, we blocked lateral line, vision, or both, and examined effects on locomotion in both environments. Both senses affected both types of locomotion. When fish could see but not feel, variation in several kinematic variables increased, suggesting that sensory integration may affect locomotor control. Next, we assessed response to optokinetic stimuli of varying size and speed. Temporal and spatial visual acuity were both low, as expected in a nocturnal ambush predator. Visual ability in air was much reduced. Finally, we attempted to record electrogenesis in Polypterus, but did not observe the electric discharges reported in a previous study. Future studies might examine changes in sensory function, interaction and importance in behaviour in Polypterus raised in a terrestrial environment.

Synaptic connectivity is highly plastic in early development and undergoes extensive remodeling in response to changes in neuronal activity and sensory experience. Microglia, the resident central nervous system macrophages, participate in shaping mature neuronal circuits by dynamically surveying the brain parenchyma and pruning away less active synaptic connections. However, it is unknown how changes in neuronal activity regulates microglial pruning within circuits and whether this activity-dependent pruning is necessary to achieve plasticity. Using the rodent somatosensory circuit, I identified that microglia engulf and eliminate synapses in the cortex following early postnatal (P4) unilateral removal of mouse whiskers. I found this early life microglial synaptic remodeling requires specific chemokine signaling between neurons and microglia. Mice that lack expression of either the neuronal chemokine CX3CL1 (fractalkine), or its microglial receptor CX3CR1, have significantly reduced microglial synapse engulfment and fail to eliminate synapses following whisker removal. To gain more insight into how this signaling is regulated, I performed both single-cell RNA sequencing of the primary somatosensory cortex as well as microglia-specific Translating Ribosome Affinity Purification (TRAP) sequencing. I identified that the majority of central nervous system (CNS) cell populations in the somatosensory cortex, including microglia, undergo transcriptional changes following whisker removal. Further, the transcriptional changes in microglia after whisker cauterization require expression of the receptor CX3CR1. Importantly, I also found that Adam10, a gene encoding the metalloprotease known to post-translationally cleave CX3CL1 into a soluble chemokine, is upregulated in the deprived cortex after whisker ablation. Pharmacological inhibition of ADAM10 inhibits microglia-mediated removal of synapses in the deprived cortex. These data support a mechanism by which cleavage of membrane-bound CX3CL1 by ADAM10 is necessary for neuronal signaling to microglia via CX3CR1 to induce transcriptional changes within microglia upstream of synaptic engulfment and elimination following sensory deprivation.

Boucharq and Corson (1976) found that subjects required to lower heart rate to avoid the loss of money used the strategy of attending to meaningless stimulation twice as often as subjects required to lower heart rates to obtain money, and that subjects decreasing heart rate to avoid the loss of money performed significantly better than subjects required to lower heart rate to obtain money. Seven male and seven female undergraduates participated in a study designed to test the hypothesis that visual focusing on meaningless stimulation and biofeedback would produce larger heart rate decreases than biofeedback alone. Each subject attended three baseline sessions followed by six treatment sessions in which subjects experienced either biofeedback and the meaningless stimulus, or biofeedback alone. The principal dependent measure was heart rate, although frontalis EMG, and EEG Alpha/Theta production were recorded for correlation with heart rate. The results showed that the biofeedback and meaningless stimulus group showed significantly higher heart rates on four of the six treatment sessions when compared to the biofeedback alone group, although neither group evidenced a learning curve. Correlations between heart rate and EMG, and heart rate and EEG frequencies were nonsignificant for all sessions. The findings of this study do not support Bouchard and Corson's (1976) hypothesis that subjects who learned to reduce heart rate did so by focusing attention on meaningless stimulation.