Delayed response deficits induced by local injection of GABA antagonists (bicuculline and phaclofen) into area 46 in infant rhesus monkeys.

In freely moving infant rhesus monkeys, a small amount of GABAa or GABAb antagonist (bicuculline methiodide (BMI) or phaclofen (PHAC)) was injected into the left- or right-side of Walker's area 46 (BMI, left-side 18 sites, right-side 15 sites; PHAC, left-side six sites, right-side five sites). Deficits in the performance of a 5-s delayed response task were then studied. Regardless of which side of the brain was injected, the correct performance rate was reduced for the hand used most often. An increase in the number of error trials was seen both in the primary, most used and non-primary, less used hands. In addition, the number of perseverative errors, using the primary and non-primary hands, also increased. BMI and PHAC produced similar reductions in performance and increased perseveration. With BMI, no clear difference was observed in performance reduction between the left- and right-side injections, while a difference was observed in the increase in the number of perseverative errors. In monkeys that primarily used their right hands, the right-side BMI injections induced more perseverative errors to the left position with the right hand, and left-side injections induced perseverative errors to both the left and right positions with both the left and right hands. In monkeys that primarily used their left hands, right-side BMI injections induced more perseverative errors to the left position with both the left and right hands and left-side injections induced, as seen in the right hand users, perseverative errors to both the left and right positions with both the left and right hands. Such lateral differences were not observed with PHAC. These results suggest that both GABAa and GABAb inhibition of area 46 are involved in the correct performance of a 5-s delayed response task.