Electrical and Chemical Stimulation of Brain Tissue in Vivo

Although central manipulations with electrical and chemical stimulation techniques are invaluable for investigating mechanisms of brain function, the use of this approach is often criticized for the “nonphysiological” nature of such interventions. This criticism mainly applies to the use of artificial stimuli in relation to possible “non-specific” effects. Examples of such problems are particularly salient with chemical stimulation techniques and include factors such as osmotic and pH influences, selectivity of drug action and so on. At another level it is important to recognize the fact that local brain stimuli may activate or inhibit only a segment of the mechanisms involved in the phenomenon that is studied—brain circuits do not act in isolation. These considerations may usefully be held in mind when interpreting the influences of local brain manipulations.