TABLE 3.

Troubleshooting table.

Step	Problem	Possible reason	Solution
22	Incomplete anesthesia: persistent response to toe pinch	High tolerance or clearance	Administer additional 10% volume ketamine/xylazine (or corresponding isoflurane increment)
31	Poor cannula positioning observed during histological validation Excess bleeding after craniotomy	Stereotactic coordinates based on brain atlas are not accurate for the experimental animal age or strain Vessel trauma	Tune the co-ordinates for age and species Place cotton swab over craniotomy site. When hemostasis is achieved, irrigate craniotomy site with sterile saline
33	Excess bleeding after cannula placement	Vessel trauma	Place cotton swab over craniotomy site. When hemostasis is achieved, irrigate the site with sterile saline
37	No solution can be injected	Needles may clog after advancement through intact tissue	Replace the needle
46	No electrical signal is recorded Electrical noise observed during recording Optical stimulation does not modulate physiology	Sensitive electrode tip has been damaged by contact Ground loop present in the setup Opsin-expressing cells may be distant from recording electrode	After confirming integrity of electrical connections, replace electrode Check all converging grounds to the table and the table ground to the amplifier. Confirm that the ground wire is in contact with the tissue and provide ~30–50 μl saline to the ground wire to ensure electrical connectivity Calculate relevant scattering parameters (accounting for light wavelength, intensity and source geometry) in the context of local neuroanatomy. Optrode may need to be redesigned accordingly or optrode positioning may need to be revised by complete retraction and replacement
56	Fiber breakage during behavior	Rotational behavior results in fiber torsion	Employ fiberoptic commutator to relieve torsion; some light loss may result