Perceptual Interpolation and Open-Ended Exploration of Auditory Icons and Earcons

Presented at the 17th International Conference on Auditory Display (ICAD2011), 20-23 June, 2011 in Budapest, Hungary.The design of cognitive artifacts for systematic exploration of sound spaces poses a significant challenge in auditory display re- search. This is especially the case if the artifact is to be based on the user’s individual perceptual capabilities rather than a pre- defined perceptual model or a purely numerical relationship be- tween the various sounds in the sound space. In this paper, we pro- pose a tensor algebraic tuning model that allows for the systematic tuning and interpolation of parametric auditory icons and earcons in a way that satisfies this challenge. The proposed approach views earcons as being composed of any number of auditory icons at a lower level, thus allowing for the systematic modification of both auditory icons and earcons via local and global interactions. Due to the granular representation used by the model, it becomes pos- sible to approximate the user’s perceptual sensitivity locally in the parametric space used to generate the auditory icons and earcons

Convulsant actions of 4-aminopyridine on the guinea-pig olfactory cortex slice

The effects of bath-applied 4-aminopyridine on neurones and extracellular potassium and calcium concentrations were recorded in slices of guinea-pig olfactory cortex. Neurones were orthodromically activated by stimulating the lateral olfactory tract. 4-Aminopyridine (3–10 μM) had the following effects: (1) an increase in the frequency and amplitude of spontaneous postsynaptic potentials: (2) a prolongation and oscillatory behaviour or orthodromically evoked postsynaptic potentials; (3) induction of spontaneous or stimulus-evoked seizure-type discharges which were accompanied by large rises in extracellular potassium and falls in calcium concentration; (4) a prolongation of the lateral olfactory tract population fibre spike. Prior to paroxysmal depolarization, membrane potential, input resistance and soma spike duration were unaffected. In the seconds before seizure discharges, a late hyperpolarizing potential (evoked by orthodromic stimulation) was reduced in amplitude or abolished. Diphenylhydantoin (50 μM) or magnesium ions (5 mM) prevented paroxysmal activity. Our results whow that 4-aminopyridine can produce seizure-type discharges in a brain slice preparation. The role of increased spontaneous potentials and possible loss of synaptic inhibition as causal factors for such discharges is discussed

Neurochemical Changes in the Mouse Hippocampus Underlying the Antidepressant Effect of Genetic Deletion of P2X7 Receptors.

Recent investigations have revealed that the genetic deletion of P2X7 receptors (P2rx7) results in an antidepressant phenotype in mice. However, the link between the deficiency of P2rx7 and changes in behavior has not yet been explored. In the present study, we studied the effect of genetic deletion of P2rx7 on neurochemical changes in the hippocampus that might underlie the antidepressant phenotype. P2X7 receptor deficient mice (P2rx7-/-) displayed decreased immobility in the tail suspension test (TST) and an attenuated anhedonia response in the sucrose preference test (SPT) following bacterial endotoxin (LPS) challenge. The attenuated anhedonia was reproduced through systemic treatments with P2rx7 antagonists. The activation of P2rx7 resulted in the concentration-dependent release of [3H]glutamate in P2rx7+/+ but not P2rx7-/- mice, and the NR2B subunit mRNA and protein was upregulated in the hippocampus of P2rx7-/- mice. The brain-derived neurotrophic factor (BDNF) expression was higher in saline but not LPS-treated P2rx7-/- mice; the P2rx7 antagonist Brilliant blue G elevated and the P2rx7 agonist benzoylbenzoyl ATP (BzATP) reduced BDNF level. This effect was dependent on the activation of NMDA and non-NMDA receptors but not on Group I metabotropic glutamate receptors (mGluR1,5). An increased 5-bromo-2-deoxyuridine (BrdU) incorporation was also observed in the dentate gyrus derived from P2rx7-/- mice. Basal level of 5-HT was increased, whereas the 5HIAA/5-HT ratio was lower in the hippocampus of P2rx7-/- mice, which accompanied the increased uptake of [3H]5-HT and an elevated number of [3H]citalopram binding sites. The LPS-induced elevation of 5-HT level was absent in P2rx7-/- mice. In conclusion there are several potential mechanisms for the antidepressant phenotype of P2rx7-/- mice, such as the absence of P2rx7-mediated glutamate release, elevated basal BDNF production, enhanced neurogenesis and increased 5-HT bioavailability in the hippocampus

Growth kinetics and modelling of S. cerevisiae (NCYC 431) during de-lignified waste banana fermentation and chemical characterization

S. cerevisiae (NCYC 431) growth kinetics was studied using mathematical models in order to ascertain the optimum operational parameters for banana waste fermentation. Chapman-Richards model was used to describe yeast growth kinetics under varying pH and temperatures and the results were compared to Bergter and Andrew models. Alkaline-delignification of the wastes was done to solubilize lignin prior fermentation. This is because lignin is a complex organic plant compound that has been reported not to be degraded easily by many microorganisms. From the results temperatures 22–28 °C and pH 4.5–5.6 were noted as optimum for yeast growth on delignified waste bananas (DWB). Chapman model results were close to Bergter and Andrew models with very low RMSE. Delignification was noted to aid yeast growth with higher microbial populations (log10 cfu/g) registered with DWB samples as compared to non-delignified waste bananas (NDWB). Also, chemical characterization of the DWB and NDWB indicated higher proteins and lipids in the former than the latter by 3 and 4% respectively. This suggested the possible use of the upgraded wastes as chicken feed supplements. Higher minerals in DWB of 8.6% also suggested the possible use of the waste as a nutrient-rich fertilizer