Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
Autori: T. VELHO, O. IANCU, P. D. ROBERTS, C. V. MELLO
Editorial: Society for Neuroscience Abstracts/Annual Meeting Publications, 2007.
When songbirds hear song and other complex sounds, the expression of activity-dependent genes is markedly induced in discrete areas of the auditory pathway, including the dorsal part of the midbrain’s lateral nucleus (MLd) and the caudomedial nidopallium (NCM). Importantly, the strength of this transcriptional response depends on stimulus type, with conspecific song inducing higher overall expression of zenk, Arc and c-Fos mRNAs compared to other sounds. However, it is not clear whether different stimuli lead to the recruitment of different numbers of sound-responsive neurons or to different levels of activation and ensuing mRNA expression per neuron. To further investigate the transcriptional response to auditory stimulation and the sensory representation of complex sounds in songbirds, we used fluorescent in situ hybridization to map zenk-expressing neurons in the MLd and NCM in parasagittal sections of adult female zebra finches stimulated with conspecific (CON) and heterospecific (HET) songs, white-noise (WN) and pure tones (TON) and sacrificed at the peak of the zenk mRNA response (n=3 birds/group). Our analysis shows that the number and position of zenk-positive neurons in NCM are stimulus-dependent. Birds stimulated with CON had a higher number of zenk-expressing neurons compared to all other stimuli. Furthermore, the expression patterns for different classes of stimuli differed markedly in the spatial distribution of responsive cells. Principal component analysis (PCA) revealed that the density and spatial distribution of responsive neurons are sufficient to discriminate among the NCM maps resulting from the different stimulus categories. In contrast, the number of activated neurons in MLd did not differ among birds stimulated with CON, HET or WN, whereas TON-stimulated birds showed no significant induction above unstimulated control levels. In addition, PCA showed that the MLd maps for CON, HET and WN are indistinguishable based on density and spatial distribution of responsive neurons. Overall, these results indicate that the auditory pallium has a greater capacity to discriminate among complex sounds than the midbrain, based on the populations of song-responsive neurons recruited, consistent with a hierarchical processing within the songbird auditory system.
Cuvinte cheie: Neuroethology: Vocal/Social Communication