Movement organization and delayed alternation behavior of monkeys following selective ablation of frontal cortex

The delayed alternation problem was tested in monkeys either according to the routine procedure (SS test), or when additional cues were added which were operating in the moment of executing the response. These additional cues involved different sensations in effort of the perfomed movement – sliding heavy object vs. sliding light object (sS test), as well as different sensations in pattern of movement and joints - sliding vs. lifting of an object (SL test). In normal the training of SL task was the easiest one, whereas the sS task was in some animals much more difficult than the SS task, and in others equivalent to this task. Removals in dorsolateral prefrontal cortex were made: total, only principalis sulcus, and only the rest of the area. Total and principalis lesions produced a severe impairment of all three tasks, while the third lesion produced only a slight deficit. The character of the impairment in the first two groups largely depended on the order in which the animals learned the three tasks in the pre-operative training.