Health - Olds & Milner (1954)
Procedure
Results
Conclusions
Aims
To see if electrical self stimulation of the brain acts as a reward, punishment, or neither (neutral stimulus)
To see if stimulation has a reinforcing impact on behaviour
To find if there are structures in the brain that reinforce stimulation's impact on behaviour
The septal area of the brain (and the other 2 to a lesser extent) is part of a system of structures associated with rewarding effects when stimulated. Other areas either produced punishing effects or were neutral
The methodology used in this study can be used in the future to clarify mechanisms of reward
Lab experiment.
DV - The number of lever presses when stimulation was switched on (acquisition) and off (extinction)
IV - The location in the brain where the electrical self-stimulation took place
The brains of 15 rats were electrically stimulated by an implanted electrode. The study started 3 days after the implanting as to give the rats time to adjust.
They were tested in a Skinner Box, and were only stimulated when they pressed the lever. They were tested in 2 ways
Acquisition testing (3 hours a day) - the rats self stimulated by pressing the lever
Extinction testing (30 mins a day) - When the rats pressed the lever, they weren't stimulated
Provides acquisiton score - Proportion of time spent pressing the lever when being stimulated
Provides extinction score - Proportion of time spent pressing the lever without being stimulated.
This is the baseline score.
If the acquisiton score is higher than the extinction score, the stimulation must be rewarding as the rats aren't going to stimulate themselves if it hurts
After testing, the rats were killed and their brains examined so that their electrode implants could be fully located and the researchers draw conclusions.
Rewarding stimulation was found in 7 out of the 15 rats tested, focused on 3 main branches
Mammillothalamic tract
Cingulate cortex
Septal area
Evaluation