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Quantitative Analysis of Thalamic Regions in Response to Blue Light in the Leopard Frog (Rana pipiens)

Institution: Wilson High School, Reading, PA, United States, 19609; Alvernia University, Reading, PA, United States, 19607

Published onJan 31, 2021
Quantitative Analysis of Thalamic Regions in Response to Blue Light in the Leopard Frog (Rana pipiens)

Blue light has powerful effects on human health. During the day, blue light exposure elevates mood, alertness and cognition. Excessive exposure at night is linked to sleep disorders, depression, cancer, and heart disease. The neural mechanisms responsible for mediating these effects are unclear. Frogs have a unique response to blue light – they are attracted to it more so than any other colored light. Elucidation of the neural mechanisms responsible for guiding the frog’s recognition of blue light may help describe the influence of blue light on vertebrate nervous systems in general. In frogs, a distinctive response to blue light is seen in a retinorecipient area of the anterior thalamus known as the NCZ (neuropil of Bellonci/Corpus Geniculatum Zone). The NCZ is reciprocally connected to an area of the posterior medial dorsal thalamus (PMDT). In order to assess the PMDT’s physiological relationship with NCZ and its role in mediating responses to blue light, a Fourier transform is used to analyze extracellularly recorded multicellular receptive fields in the NCZ and PMDT. Results indicate: (i) the NCZ is characterized by a main tonic oscillatory response to blue light; (ii) blue light elicits tonic oscillatory electrical responses in the PMDT quite similar to the responses to blue light in the NCZ. This analysis suggests a reciprocal connection between NCZ and PMDT. PMDT has no other connections besides the NCZ, therefore, the visual activity recorded in PMDT is derived from activity originating in the NCZ. Primary visual activity in the NCZ may be modulated by cells in the PMDT, creating a feedback loop that guides the frog’s responses to blue light. The discovery of a novel, blue light-driven thalamic circuit in the frog suggests similar circuits may be present in other vertebrates, and may be a potential target for therapies.

Keywords: Electrophysiology, Fourier transform, Thalamus, Blue light, Rana pipiens, Vision

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