Room reflections and constancy in speech-like sounds: within-band effects

The experiment asks whether constancy in hearing precedes or follows grouping. Listeners heard speech-like sounds comprising 8 auditory-filter shaped noise-bands that had temporal envelopes corresponding to those arising in these filters when a speech message is played. The „context‟ words in the message were “next you‟ll get _to click on”, into which a “sir” or “stir” test word was inserted. These test words were from an 11-step continuum that was formed by amplitude modulation. Listeners identified the test words appropriately and quite consistently, even though they had the „robotic‟ quality typical of this type of 8-band speech. The speech-like effects of these sounds appears to be a consequence of auditory grouping. Constancy was assessed by comparing the influence of room reflections on the test word across conditions where the context had either the same level of reflections, or where it had a much lower level. Constancy effects were obtained with these 8-band sounds, but only in „matched‟ conditions, where the room reflections were in the same bands in both the context and the test word. This was not the case in a comparison „mismatched‟ condition, and here, no constancy effects were found. It would appear that this type of constancy in hearing precedes the across-channel grouping whose effects are so apparent in these sounds. This result is discussed in terms of the ubiquity of grouping across different levels of representation

Genetic interaction of Pax3 mutation and canonical Wnt signaling modulates neural tube defects and neural crest abnormalities

Mouse models provide opportunities to investigate genetic interactions that cause or modify the frequency of neural tube defects (NTDs). Mutation of the PAX3 transcription factor prevents neural tube closure, leading to cranial and spinal NTDs whose frequency is responsive to folate status. Canonical Wnt signalling is implicated both in regulation of Pax3 expression and as a target of PAX3. This study investigated potential interactions of Pax3 mutation and canonical Wnt signalling using conditional gain- and loss-of-function models of β-catenin. We found an additive effect of β-catenin gain of function and Pax3 loss of function on NTDs and neural crest defects. β-catenin gain of function in the Pax3 expression domain led to significantly increased frequency of cranial but not spinal NTDs in embryos that are heterozygous for Pax3 mutation, while both cranial and spinal neural tube closure were exacerbated in Pax3 homozygotes. Similarly, deficits of migrating neural crest cells were exacerbated by β-catenin gain of function, with almost complete ablation of spinal neural crest cells and derivatives in Pax3 homozygous mutants. Pax3 expression was not affected by β-catenin gain of function, while we confirmed that loss of function led to reduced Pax3 transcription. In contrast to gain of function, β-catenin knockout in the Pax3 expression domain lowered the frequency of cranial NTDs in Pax3 null embryos. However, loss of function of β-catenin and Pax3 resulted in spinal NTDs, suggesting differential regulation of cranial and spinal neural tube closure. In summary, β-catenin function modulates the frequency of PAX3-related NTDs in the mouse

Cellular and molecular mechanisms underlying Pax3-related neural tube defects

The neural tube is the developmental precursor of the central nervous system (CNS). Neural tube defects (NTDs) are among the commonest birth defects, affecting approximately 1 in 1000 pregnancies. They occur when the neural tube fails to close completely during neurulation, and result in an open region of the CNS. Spina bifida is an NTD affecting the spinal region, and it can lead to lifelong disability, including incontinence, motor difficulties, and paralysis below the level of the lesion. Exencephaly is an NTD affecting the cranial region, and is not compatible with life. Splotch mice carry a mutation in the Pax3 gene which leads to a functionally null Pax3 protein. Pax3 is important in the development of a number of tissues, and mutant embryos have defects in muscle development, and neural crest-derived tissues, such as the heart, peripheral nervous system and melanocytes. Additionally, embryos develop NTDs; they demonstrate spina bifida with complete penetrance and exencephaly with partial penetrance. The cellular mechanism behind the development of NTDs in Splotch embryos is not well understood. However excess apoptosis, premature neuronal differentiation, and reduced proliferation in the neural tube have all been proposed as potential causes. Furthermore, research has suggested a potential link between Pax3 and canonical Wnt signalling. The aim of this research was to study cellular defects in Splotch mice which are potentially causative of NTDs, and also to study the interaction between Pax3 and canonical Wnt signalling. It was found that excess apoptosis and premature neuronal differentiation are not causative of spina bifida in Splotch mice. However, reduced proliferation is present in the neural tube, and may be causative. Additionally, β-catenin loss- and gain-of-function mutations were used to study interaction between Pax3 and canonical Wnt signalling. β-catenin loss-of-function reduces Pax3 expression, and β-catenin gain-of-function worsens NTDs in Pax3 mutant embryos, whereas loss-of-function partially rescues exencephaly, but not spina bifida, in these embryos. β-catenin gain- and loss-of-function both also worsen neural crest defects in Pax3 mutant embryos. Therefore, Canonical Wnt signalling interacts with Pax3 during development, and affects the cranial and spinal regions of the neural tube differently. In summary, Pax3 mutation results in a number of defects in developing embryos, including NTDs and neural crest defects. Cellular processes have been studied in this research to identify abnormalities which could be causative of these defects, and a potential molecular link between Pax3 and the canonical Wnt signalling pathway has been identified, which could contribute to the observed phenotype

Cognitive improvement following repair of a basal encephalocele.

We report the case of a 55-year-old woman presenting with progressive memory impairment secondary to a transsphenoidal encephalocele involving her dominant medial temporal lobe. Her clinical deterioration was accompanied by radiological progression in the encephalocele's size and associated encephalomalacia. Through a temporal craniotomy, her encephalocele was resected and the defect closed. Baseline neuropsychological assessment indicated global cognitive impairment, but post-operatively, she reported improved memory and concentration. Standardized assessment reflected an improvement in perceptual skills and an associated improved recall of a complex figure. This is the first case report to date of a patient's memory improving following treatment of a basal encephalocele