Endepols Heike, Feng Albert S, Gerhardt H Carl, Schul Johannes, Walkowiak Wolfgang
Zoological Institute, University of Cologne, Weyertal 119, 50923, Cologne, Germany.
Behav Brain Res. 2003 Oct 17;145(1-2):63-77. doi: 10.1016/s0166-4328(03)00098-6.
Diencephalic and midbrain auditory nuclei are involved in the processing of auditory communication signals in anurans [Comparative Hearing: Fish and Amphibians, Springer-Verlag, New York, 1999, p. 218], but their exact roles in acoustically guided behavior, such as female phonotaxis, are unclear. To address this question, behavioral experiments were combined with lesions of dorsal thalamic nuclei and the midbrain torus semicircularis. Females were tested in two-alternative-forced-choice phonotactic experiments before and after a defined brain area was lesioned. During phonotactic tests, females had to choose between a "standard" synthetic call and one of three different variants, each of which had a single acoustic property (pulse rate, pulse rise-time, sound spectrum) that differed from the standard synthetic call. Results showed that dorsomedial thalamus lesions produced little or no effect on phonotaxis. In contrast, superficial and deep thalamus lesions, as well as lesions of the torus semicircularis, significantly decreased the number of phonotactic responses and increased the response time. Superficial thalamus lesions also abolished or reversed preferences for the standard call in the rise-time and sound spectrum tests. This effect is likely to have been caused by an imbalance in the stimulation of the thalamus by the low- and high-frequency pathways because these preferences were not affected in animals with more extensive lesions that included the superficial thalamus. Our data suggest that the torus semicircularis, but not the dorsal thalamus is crucial for phonotaxis in gravid, reproductively active females. Although dorsal thalamic nuclei seem to play a role in spectral sensitivity, they may additionally have motivational or attentional functions that contribute to achieving a state of phonotactic readiness.
间脑和中脑听觉核参与无尾两栖类动物听觉通讯信号的处理[《比较听觉：鱼类和两栖动物》，施普林格出版社，纽约，1999年，第218页]，但它们在诸如雌性趋声行为等声学引导行为中的确切作用尚不清楚。为了解决这个问题，行为实验与背侧丘脑核和中脑半规管隆起的损伤相结合。在特定脑区损伤前后，对雌性进行双选强制趋声行为实验测试。在趋声测试中，雌性必须在一个“标准”合成叫声和三个不同变体之一之间做出选择，每个变体都有一个与标准合成叫声不同的声学特性（脉冲率、脉冲上升时间、声谱）。结果表明，背内侧丘脑损伤对趋声行为几乎没有影响或没有影响。相比之下，丘脑浅层和深层损伤以及半规管隆起损伤显著减少了趋声反应的数量并增加了反应时间。丘脑浅层损伤还在上升时间和声谱测试中消除或逆转了对标准叫声的偏好。这种效应可能是由低频和高频通路对丘脑刺激的不平衡引起的，因为在包括丘脑浅层在内的更广泛损伤的动物中，这些偏好并未受到影响。我们的数据表明，半规管隆起而非背侧丘脑对妊娠、生殖活跃的雌性趋声行为至关重要。虽然背侧丘脑核似乎在频谱敏感性中起作用，但它们可能还具有促进达到趋声准备状态的动机或注意力功能。
