Capacity of visual short-term memory after unilateral frontal or anterior temporal-lobe resection.

The effect of unilateral temporal- or frontal-lobe lesions on the capacity of short-term memory for a single pattern was explored; this measure has been designated pattern span. Pattern span was assessed under different delays and with and without distraction. Both the passage of time and presence of distraction decreased pattern span for all subject groups. Right anterior temporal lobectomy did not result in an impairment in pattern span in any condition, whereas right frontal-lobe excisions were associated with impaired span in all conditions. It is suggested that this deficit represents a decreased ability to encode the more complex patterns under a time constraint.