August 2021
Volume 62, Issue 11
Open Access
ARVO Imaging in the Eye Conference Abstract  |   August 2021
Label-free in vivo Photoacoustic Imaging of Mouse Cortical Responses to Visual Stimulation
Author Affiliations & Notes
  • KAI-WEI CHANG
    Biomedical Engineering, University of Michigan College of Engineering, Ann Arbor, Michigan, United States
  • Yunhao Zhu
    Nanjing University, Nanjing, Jiangsu, China
  • Xueding Wang
    Biomedical Engineering, University of Michigan College of Engineering, Ann Arbor, Michigan, United States
    Radiology, University of Michigan Michigan Medicine, Ann Arbor, Michigan, United States
  • Kwoon Wong
    Ophthalmology and Visual Sciences, University of Michigan Michigan Medicine, Ann Arbor, Michigan, United States
    Molecular, Cellular & Developmental Biology, University of Michigan College of Literature Science and the Arts, Ann Arbor, Michigan, United States
  • Guan Xu
    Ophthalmology and Visual Sciences, University of Michigan Michigan Medicine, Ann Arbor, Michigan, United States
    Biomedical Engineering, University of Michigan College of Engineering, Ann Arbor, Michigan, United States
  • Footnotes
    Commercial Relationships   KAI-WEI CHANG, None; Yunhao Zhu, None; Xueding Wang, None; Kwoon Wong, None; Guan Xu, None
  • Footnotes
    Support  NIH grants 1R01DK12568701 and 5R37CA22282903
Investigative Ophthalmology & Visual Science August 2021, Vol.62, 49. doi:
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    • Get Citation

      KAI-WEI CHANG, Yunhao Zhu, Xueding Wang, Kwoon Wong, Guan Xu; Label-free in vivo Photoacoustic Imaging of Mouse Cortical Responses to Visual Stimulation. Invest. Ophthalmol. Vis. Sci. 2021;62(11):49.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The lack of a noninvasive or minimally invasive imaging technique has long been a challenge to the investigation of brain activities in mice. Functional magnetic resonance imaging and the more recently developed diffuse optical imaging both suffer from limited spatial resolution. Photoacoustic (PA) imaging combines the sensitivity of optical excitation to hemodynamics changes, and the spatial resolution of ultrasound detection. In this study, we evaluated the feasibility of using a label-free, real-time PA tomography (PAT) system to measure visually evoked hemodynamic changes in the mouse visual cortex.

Methods : A 1064 nm pulse laser with a repetition rate of 10 Hz was used as the PAT light source; this wavelength was chosen to avoid stimulating the mice’s retinal photoreceptors. The output beam was expanded to cover the whole horizontal surface of the brain. The acoustic signals were detected by a ring-shaped ultrasound transducer array with a 5 cm diameter and a 10 MHz central frequency.
The performance of the imaging system was examined by measuring visual responses within the primary visual cortex (V1) in 4 rd1 retinal degenerate mice and 4 wild-type (C57BL/6) mice. After overnight dark adaptation, the animals were anesthetized by i.p. injection of acepromazine at 5mg/kg in conjunction with 1% isoflurane. The scalps of the animals were removed to minimize optical and acoustic attenuation. Both eyes of each mouse were exposed to white light flickering at 1 Hz for 20 s. The correlation coefficient of the temporal traces at each pair of pixels equidistant from the midline of the brain was calculated.

Results : The imaging system has resolved the vasculatures in the mouse brain and responses to retinal photostimulation in the V1 region (Fig. 1). Fig. 2A shows representative temporal traces at the pixels with maximum values in the correlation maps. Fig. 2B shows significantly higher signal peak intensity and shorter response latency in the wild-type mice than in the rd1 mice.

Conclusions : The PAT system in this study has sufficient sensitivity and resolution to resolve the hemodynamics within V1 in mice under retinal photostimulation. Therefore, PAT is a potential tool for investigating visually evoked neural activities in the mouse brain.

This is a 2021 Imaging in the Eye Conference abstract.

 

 

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