Brain Stimulation

1. Mind, Brain and Behavior PSYC 2600
Lecture: Brain Stimulation

2. Brain stimulation can be made (1) chemically, but introducing drugs that affect neural chemistry
(typically at the level of the synapse), or by applying (2) electrical stimulation (very small currents)
that produce action potentials of nearby neurons (as few as about 35 neurons at a time).
Chemical stimulation can be applied to the entire brain (systemic administration) or to highly
localized areas of the brain (microinjection) which requires a surgical procedure.
Electrical stimulation is always applied to a small, localized area of the brain (microstimulation).
Widespread electrical stimulation would result in a seizure, and is only used as a medical treatment
of severe depression.

3. Systemic Chemical Stimulation
Systemic administration (entire brain) is typically performed with:
1. Intravenous (or intramuscular, or intraperitoneal)
2. Inhalant (lungs efficiently transport drugs to blood)
3. Oral (pills)
In all cases, the drug needs to cross blood-brain barrier in order to affect the brain.

4. DrugTesting of Systemic Administration
clinical drug testing basic research psychoactive drugs
Pre-administration psychological testing
Drug administration
pharmacokinetics
Testing during drug effects
Compare test results pre- and during
within-subjects repeated measures

5. Localized Chemical Stimulation
Chemical stimulation of a localized brain area requires:
1. Injection guide equipment, often mounted on the head
2. A narrow tube (cannula) that is surgically inserted into the brain
3. A microinjector, which releases a very small amount of the drug through the cannula

6. Electrical Stimulation of the Brain
Microelectrical stimulation can be applied to localized areas of the
brain. Electrical stimulation takes advantage of the normal
physiology of neurons.
Normally, neurons are in a state of a resting potential
If neurotransmitters bring the membrane potential
to -55 mV, an action potential occurs.
Microelectrical stimulation bypasses the normal
neurotransmitter effects, and forces the neural
membrane potential to above -55 mV, causing
an action potential

7. Localizing Areas of the Brain
In order to target a specific brain area, a map of brain areas is use (StereotaxicAtlas). Positioning of
the electrode tip or the cannula tip is then directed by means of a Stereotaxic Device.

8. Experimental Application of Brain Stimulation
Micro-stimulation may be applied to behaving animals in order to explore the role of localized brain
areas. For example, rats may be trained bar press (left figure) or navigate in a radial maze (right
image) in order to acquire food reward.

9. Deep Brain Electrical Stimulation
Electrical stimulation may also be used as a clinical therapy for Parkinson’s disease.