Brain Activation Display Functional Asymmetry in Response to Action, Background and Tonal Frequency During a Pitch Memory Processing: An fMRI Study / Jurnal Sains Kesihatan Malaysia

@#In this study, the asymmetry of the main effects of action, background and tonal frequency during a pitch memory processingwere investigated by means of brain activation. Eighteen participants (mean age 27.6 years) were presented with low andhigh frequency tones in quiet and in noise. They listen, discriminate and recognize the target tone against the final tonein a series of four distracting tones. The main effects were studied using the analysis of variance (ANOVA) with action (towring (rubber bulb) vs. not to wring), background (in quiet vs. in noise) and frequency (low vs. high) as the factors (andlevels respectively). The main effect of action is in the right pre-central gyrus (PCG), in conformation with its contralateralbehavior. The main effect of background indicated the bilateral primary auditory cortices (PAC) and is right lateralized,attributable to white noise. The main effect of frequency is also observed in PAC but bilaterally equal and attributable tolow frequency tones. Despite the argument that the temporo-spectral lateralization dichotomy is not especially rigid asrevealed by the main effect of frequency, right lateralization of PAC for the respective main effect of background clearlydemonstrates its functional asymmetry suggesting different perceptual functionality of the right and left PAC.

The Age-related Changes of the Expression of Caspase-3 and the apoptosis States of Neurons in Primary Auditory Cortex(AI) of C57BL/6J Mice / 听力学及言语疾病杂志

Objective This study is to study the age related changes of the expression of caspase-3 and the apoptosis states of neurons in primary auditory cortex of 15 young C57BL/6J mice(2 months, 15～20 g) and 15 old C57BL/6J mice(10 months, 50～60 g) and to determine probable physical effects underlying these changes. This paper also discusses the relationship of caspase-3 and apotosis states in primary auditory cortex, the possible role of caspase-3 in primary auditory cortex and the pathogenesis of presbycusis. Methods The immunohistochemical methods were applied to explore the differences of the expression of caspase-3 and the apoptosis states determined by TUNEI. method in the primary auditory cortex between young and old C57BL/6J mice. Results The expression of caspase-3 and apoptosis in Al of old C57BL/6J mice was significantly higher than that in the counterpart of young C57BL/6J mice. Conclusion The results presented a direct morphological evidence for the strengthening of caspase-3 in the primary auditory cortex in old C57BL/6J mice. This method has an important role in the formation and development of presbycusis. The expression of caspase-3 participated in the regulatory procedure of apoptosis and may be a possible factor of the etiologies of presbycusis.

The Changes of Peripheric Auditory Activity Induced the Expression of Synaptic NMDA Receptors in Auditory cortex in Vivo / 听力学及言语疾病杂志

Objective To study the changes of N-methyl-D-aspartate receptors(NMDARs) expression at local sy-(napses) in auditory cortices after ototoxic deafened and following electrical intracochear stimulation(EIS).Methods We prepared highly purified synaptosomes from primary auditory cortex by two discontinuous gradient centrifugations, and compared the differences of NMDA receptors expression in ototoxic deafened group control group, normal control group and different experimental groups (EIS from 0.5h to 2h ) by Western blotting.Results We found that EIS for as little as half and one hour the adult and developmental rats of auditory deprivation can induce a significant increase in NMDAR subunit2A (NR2A) protein. But the changes of NMDAR subunit1(NR1) and NMDAR subunit2B(NR2B) are not significant.Conclusion There is a rapid activity-dependent expression of synaptic NR2A receptors in primary auditory cortex in vivo.

AGE-RELATED CHANGES OF GABAergic NEURONS AND ASTROCYTES IN CAT PRIMARY AUDITORY CORTEX / 解剖学报

Objective A morphometric study was carried out on GABAergic neurons and astrocytes in primary auditory cortex of 4 young cats (1-3 years old, 20-2.5 kg) and 4 old cats (10-13-year-old, 3-3.5 kg), in order to explore the age-related changes and the probably physical effects underlying these changes. Methods The same regions of the primary auditory cortex (AI) were comparatively studied. Nissl staining and immunohistochemical methods were applied to explore the differences of GABAergic neurons and astrocytes(specifically labeled by GFAP as a mark as antibody) in the primary auditory cortex(Al) between young and old cats. Serial cross-sections from two age groups were stained with Nissl for layer structure observation and demonstration of neurons; Adjacent sections were stained with anti_GABA immunohistochemistry for localizing and characterizing GABAergic and with anti-GFAP for astrocytes in AI. Results The diameter, density and number of GABAergic neurons in Al of old cats declined significantly compared with the counterpart in young cats, especially in layers Ⅱ,Ⅲ of AI; but the change in GFAP-IR cells was reversed: old cats showed clearly larger number and stronger staining of GFAP-IR cells than that in young cats. The GFAP-IR cell bodies and dendrites swelled obviously in old cats, especially in layer Ⅰ of AI and in white matter. Conclusion The result presented a direct morphological evidence for weakness of GABAergic intracortical inhibition, which is considered to be a possible mechanism for age-related acoustic function decline. The enhanced function of astrocytes may play an important role in decreasing the GABA content in AI of the old individuals.