Anatomy of Fear.

In the study of pigeons after the ablation of various amounts of brain tissue, it appeared that when a sufficiently large amount of brain was removed, there was a corresponding amount of fear removed; the larger the portion of brain removed, the greater the portion of fear removed. This fact, that fear can be removed in stages by removing increasing portions of brain, seems to indicate that there is no definitely localized center for fear. It seems that the fear network spreads throughout the brain, and even after the removal of all of the cerebral hemispheres, there still remains in the residual brain, a functional portion of the fear network.

I give some findings from 4 pigeons of a series now under study. In all pigeons there appeared to be a gradual recovery of ability to show fear signs.

Of the 4, No. 1, had most brain left, and while showing, in nearly 12 months study, very much less fear than the normal pigeon, it showed considerably more than any of the other 3. On the 40th day, after being fed artificially, he flew from my knee onto the table, showing marked semblance of fear. On the 58th day, after being put down from the platform balance, he showed evidence of fear and flew 15 cm. up onto the other platform, as if trying to escape. On the 168th day to avoid being taken up, he ran and flew with such vigor and persistence that it required quite a chase to catch him. On the 251st day, when we tried to take him up, he ran under the table and out on the other side, flew up into the air, circled around, passed over the revolving book case and down on the other side (height of flight 2±M.; length 4±M.).