Troubleshooting
ISSUE	COUNTERMEASURES
Ictal discharges look ‘chunked’	Decrease the perfusion rate and/or lower the ACSF volume above the brain slice by adjusting the suction needle position.
No ictal activity	(1) Verify that CA3-driven fast interictal events do not propagate to the cortex. Use a small scalpel blade (e.g., n.10) or a needle to sever the Schaffer Collaterals if need be, but be careful not to cut the nylon threads of the slice hold-down anchor. A stereo- or upright microscope are best suited, whereas the inverted microscope makes this task very difficult.
(2) Check the slice viability: can strong electrical stimulation trigger ictal activity? Wait until about 2 h of 4AP application, then change brain slice if ictal activity does not occur.
The brain slice moves when placing the hold-down anchor	(1) Gently remove the slice anchor and reposition the brain slice.
(2) Check that the slice anchor is evenly  wet of 4AP-ACSF.
(3) Remove the 4AP-ACSF from the recording chamber to favor the brain slice adhesion to the MEA.
(4) Reposition the slice hold-down anchor.
The brain slice floats on the MEA chip after being transferred	(1) Gently aspirate excess ACSF with a Pasteur pipette.
			(2) The MEA chip might need to be re-coated.
Electrical stimulation does not elicit network responses	Increase stimulus intensity, change electrode pairs.
Electrical stimulation can elicit population responses in the proximal but not distal cortical areas	The issue is ikely due to poor connectivity or too low stimulus intensity. Electrical stimulation may be ineffective or effective in some cortical areas only. It is recommended to change brain slice.
Signal is noisy	(1) Check the reference electrode: noisy baseline can at times be caused by the incomplete fill of the inlet reservoir such that the reference electrodes does not completely deep into the ACSF.
(2) Check the overall grounding of equipment.
(3) Adjust the suction needle position so as to hear a constant, soft suction sound. Ground the suction needle.
(4) Clean the MEA external contacts with ethanol using a cotton swab.
(5) The MEA chip may be damaged: change MEA chip and check artifacts and the signal-to-noise ratio.