THE RELATION OF AREA 13 ON ORBITAL SURFACE OF FRONTAL LOBES TO HYPERACTIVITY AND HYPERPHAGIA IN MONKEYS

Abstract

The posterior portion of the external orbital gyrus (posterior orbital gyrus), which Walker has recently differentiated as a new cytoarchitectural area (area 13) and which Bailey, Bremer and Sweet have demarcated physiologically from adjoining areas, was ablated in a series of monkeys. This procedure produced in a marked degree many of the symptoms described for prefrontal lobectomy by various workers under the term hyperactivity. Hyperactivity as a result of area 13 lesions, is manifested by long continued, methodical pacing or running of a regular, stereotyped character. Hyperactivity from area 13 lesions is quantitatively great, is consistently obtained and is always manifested in some degree within the 1st or 2d postoperative day; whereas similar hyperactivity from other prefrontal areas is said to be delayed in onset (as long as 2-3 wks.) and does not invariably occur. Ablation of neighboring regions by the same operative approach was without effect on activity. Other motor activites are not marked by hyperactivity but rather suffer reduction. Random, spontaneous activities and posturings are reduced in variety and quantity, as is emotional expressivity. There are also certain ill-defined behavior changes. All of these are most marked in the 1st postoperative wk. Hyperactivity is accompanied by a wt. loss and only a slight increase in food intake.