Some features of the dorsolateral frontal and inferotemporal syndromes in monkeys

Our frontal- and temporal-lobe experiments to date support the following conclusions. Anterior temporal or inferotemporal lesions affect object learning set retention, and older work dealing with this task has indicated that temporal ablations, at the very least, retard initial acquisition of the set. Inferotemporal monkeys may lose object sets and yet have no deficits in either the learning or short-term retention of single visual habits. Their well-known impairments in visual pattern learning are products of background-cue learning which become most marked in test situations which bias their responses to these cues. Their pattern-learning deficit is an accentuation of a normal characteristic of the monkey, and implies no profound qualitative alteration of the way that they perceive stimuli. Our work that has dealt with frontal preparations indicates that Jacobsen's effect can be produced either by proactive interference or by difficulties in attending. The latter are probably compensable if lesions are produced in very early infancy, but data from experiments with cats has suggested that perseverative interferences are not. Perseverative tendencies can be suppressed with practice in discrimination learning situations, but the tendencies can then be fully reinstated by relatively minor distractions. Frontal-lobe lesions have almost no effects upon object learning set formation, nor do they have important effects upon a monkey's short-term retention of a habit.