The cognitive and neural mechanisms involved in motor imagery of speech

Inner speech is a common phenomenon that influences motivation, problem-solving and self-awareness. Motor imagery of speech refers to the simulation of speech that gives rise to the experience of inner speech. Substantial evidence exists that several cortical areas are recruited in general motor imagery processes, including visual and speech motor imagery, but the evidence for primary motor cortex involvement is less clear. One influential model proposes that motor cortex is recruited during speech motor imagery, while another prominent model suggests motor cortex is bypassed. This thesis presents six experiments that explore the role of motor cortex in speech motor imagery. Experiments 1-3 build on established visual motor imagery tasks and expand these tasks to the speech motor imagery domain for the first time, using behavioural (experiments 1 and 2) and neuroimaging methods (experiment 3). Experiment 4 uses transcranial magnetic stimulation to explore motor cortex recruitment during a speech imagery condition, relative to a motor execution and baseline condition in hand and lip muscles. Experiments 5 and 6 use transcranial magnetic stimulation to explore speech motor imagery in tongue muscles relative to a hearing and a baseline condition. The results show that recruitment of motor cortex during speech motor imagery is modulated depending on task demands: simple speech stimuli do not recruit motor cortex, while complex speech stimuli are more likely to do so. The results have consequences specifically for models that always or never implicate motor cortex: it appears that complex stimuli require more active simulation than simple stimuli. In turn, the results suggest that complex inner speech experiences are linked to motor cortex recruitment. These findings have important ramifications for atypical populations whose inner speech experience may be impaired, such as those who experience auditory verbal hallucinations, or those with autism spectrum disorder

Detection of acetone in air using silver ion exchanged ZSM-5 and zinc oxide sensing films.

Zinc oxide (ZnO) based gas sensors with sliver ion exchanged ZSM-5 (Ag+ZSM-5) zeolite overlayer were created and tested for detection of acetone vapor in air. The ZnO and Ag+ZSM-5 films were deposisted on 400µm by 400µm platinum interdigitated electrodes on a silicon dioxide film on a silicon substrate. The microfabrication process of the interdigitated electrodes used for the sensors is presented. The synthesis and materials characterization of ZnO and Ag+ZSM-5 is discussed. Two types of sensors were developed, one with only a ZnO film and the other a ZnO film with Ag+ZSM-5 film on top. The acetone sensitivity was examined by exposing both sensors to dry air containing varying parts per million acetone at 350°C then measuring the resulting change in resistance across the electrodes. Both sensors showed sensitivity to acetone in air, however, the sensitivity in the ZnO and Ag+ZSM-5 films were greater than that of just the ZnO film. The utilization of the ZnO and Ag +ZSM-5 films as sensor has potential for detection of acetone in other gaseous mixtures, to include human breath

Trigger Conditions and Nasal Harmony in Terena

Proceedings of the Nineteenth Annual Meeting of the Berkeley Linguistics Society: General Session and Parasession on Semantic Typology and Semantic Universals (1993

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

The prion protein (PrP) binds Cu2+ in its N-terminal octarepeat domain. This unusual domain is comprised of four or more tandem repeats of the fundamental sequence PHGGGWGQ. Previous work from our laboratories demonstrates that at full copper occupancy, each HGGGW segment binds a single Cu2+. However, several recent studies suggest that low copper occupancy favors different coordination modes, possibly involving imidazoles from histidines in adjacent octapeptide segments. This is investigated here using a combination of X-band EPR, S-band EPR, and ESEEM, along with a library of modified peptides designed to favor different coordination interactions. At pH 7.4, three distinct coordination modes are identified. Each mode is fully characterized to reveal a series of copper-dependent octarepeat domain structures. Multiple His coordination is clearly identified at low copper stoichiometry. In addition, EPR detected copper−copper interactions at full occupancy suggest that the octarepeat domain partially collapses, perhaps stabilizing this specific binding mode and facilitating cooperative copper uptake. This work provides the first complete characterization of all dominant copper coordination modes at pH 7.4