Where to find information regarding the effect of ion concentration in the brain on behaviour?
The 'ion concentration in the brain' is a really general concept. A biochemist (I did Biochemistry in a, seemingly, previous lifetime) might approach this question by taking a brain, freeze drying it, then homogenize it and determine ion concentrations.

However, the effect of ion concentrations in the brain plays out its role in a much more confined space, namely across the cell's membranes. The differences in ion gradients across the neuron's membrane is what determines its responses. Further, different brain areas govern different responses. Gross changes in ion concentrations in the prefrontal cortex for instance will exert wildly different effects than the same procedure in the brain stem.

If you want to go this way, you should perhaps confine yourself to a specific area of the brain, and to a specific way of disregulating ion homeostasis. Or veer away from the idea entirely.

What you'd rather could use as a source of inspiration are zombie ants. These ants are 'zombified' by the fungus Ophiocordyceps unilateralis, which infects Camponotus leonardi ants that live in tropical rainforest trees. Once infected, the spore-possessed ant will climb down from its normal habitat and bite down on a leaf and then die.    

The fungus can only flourish at a certain temperature, humidity, location and distance from the ground. By hijacking ants they re-locate themselves to ideal spots. in fact, 95% of the ants found their way to the north side of a plant, about 25 centimeters above the ground, in an environment with 94 to 95 percent humidity and with temperatures between 20 and 30 degrees Celsius (Harmon, 2009).

Note, however, that the underlying pathophysiological underpinnings are entirely different from your original ion homeostasis idea.


Zombie ant. source: Wikipedia

Source
- Harmon, Sci Am, Fungus Makes Zombie Ants Do All the Work, July 2009