A versatile and modular tetrode-based device for single-unit recordings in rodentex vivoandin vivoacute preparations

The demand for affordable tools for recording extracellular activity and successfully isolating single units from different brain preparations has pushed researchers and companies to invest in developing and fabricating new recording devices. However, depending on the brain region of interest, experimental question or type of preparations, different devices are required thus adding substantial financial burden to laboratories. We have developed a simple and affordable tetrode-based device that allows interchangeable extracellular recordings of neural activity between in vivo and ex vivo preparations and can be easily implemented in all wet-bench laboratories. Spontaneous activity from several putative single neurons could be easily recorded and isolated by lowering the device into ex vivo cerebellum brain slices. The same device was also used in vivo , lowered into primary auditory cortex of adult anesthetized transgenic mice expressing channelrhodopsin in cortical neurons. Acoustic stimulation of the contralateral ear or direct laser optogenetic stimulation successfully evoked cortical activity at the recording site. Several isolated putative single neurons presented time-locked activity response to the different stimuli. In summary, we developed an affordable, versatile and modular device to facilitate tetrode extracellular recordings interchangeably between in vivo anaesthetized animals and ex vivo brain slice recordings. Highlights Developed a versatile and modular device to facilitate tetrode acute brain recordings interchangeably between in vivo and ex vivo preparations. Conducted ex vivo extracellular recordings in acute cerebellar slices. Conducted in vivo extracellular recordings in auditory cortex of anaesthetized mice. Recorded and isolated multiple single units in both acute slices and anaesthetized mice recordings using the same device. Device can be easily extended to accommodate optic fiber and cannula.