Optical imaging spectroscopy in the unanaesthetised rat

Area of Science:

• Neuroscience
• Physiology

Background:

• Investigating brain activity often requires anesthesia, which can alter physiological responses.
• Understanding the hemodynamic response in awake animals is crucial for studying natural brain function.

Purpose of the Study:

• To develop and validate a method for imaging cortical hemodynamic responses in awake, behaving rats.
• To compare hemodynamic responses in awake versus anesthetized states.

Main Methods:

• Developed a chronic cranial window preparation in rats for optical imaging and spectroscopy.
• Stimulated whiskers and measured hemodynamic responses using optical imaging spectroscopy (OIS).
• Compared data from awake rats with data from rats under urethane anesthesia.

Main Results:

• Successfully imaged local cortical hemodynamic responses to whisker stimulation in awake rats.
• Hemodynamic responses were qualitatively similar but approximately 5 times larger in awake rats compared to anesthetized rats.
• The preparation allowed for data collection over multiple days.

Conclusions:

• The described method enables non-invasive imaging of brain activity in awake rodents.
• Anesthesia significantly attenuates the cortical hemodynamic response to somatosensory stimulation.
• This technique facilitates the study of neurological processes in awake, behaving animals.