For invivo electrophysiology we have tried moving the left arm slightly forward and the right arm slightly backwards in relation to the animal, this works in that the arms dont clash and we hit our desired target however dorso-ventral movement is limited,what with wires and adapters getting in the way. The alternative is to insert the electrode at a different angle in relation to the surface of the brain? Would anyone have experienced this phenomenom of working with two arms on a frame for acute recordings? I think I should have payed more attention in trigonometry class!
Hi - yes we have for stratal plus brainstem plus collicular recordings - it's a nightmare ;) Yes you need the trig. and I will speak generically here rather than specific to hippocampus. It is easier to keep the arm orientated in the one of the planes and swing it at an angle going in on that same plane (we use ML as our axis of rotation and keep AP at normal, rather than e.g. giving it a degree of ML AND AP tilt, otherwise you have a more complicated calculation. So, first off do a mock up (or at the end of the last rat experiment before you euthanise) and see what angle the offending stereotaxic manipulator is best set to to make everything work. Use the rat atlas, identify your target nucleus and also the DV distance required to get from the top of the skull if you were to do straight down from the top (I call this aDV in attached). Then calculate the lateral distance from that point that you will need to have the electrode enter the brain at the angle on its way to the target nucleus. You calculate that by the attached. I hope this helps.!! Good luck, John Reynolds
Thanks John, thats really great, diagrams are always good. I should apologise to my maths teacher, who knew :)
John's question is great, but I could also recommend you look at the real brain/slices under the microscope to really assess your strategy, since the brain atlas is not that accurate. Based on what you see under the microscope, continue the adjustments until you have the right strategy.
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