ABSTRACT
In 1957 Scoville and Milner reported that bilateral medial temporal-lobe resection in man, sufficient to remove or damage the anterior hippocampus and hippocampal gyrus (Fig. 10.1 A), causes a persistent impairment of recent memory. Furthermore this impairment depends on the extent of hippocampal removal, with no effects occurring if only unilateral removal is performed. The bilateral resections left early memories, technical skill, personality and general intelligence unimpaired (Fig. 10.1B). Scoville and Milner concluded that ‘the anterior hippocampus and hippocampal gyrus, either separately or together, are critically concerned in the retention of current experience.’ This conclusion was subsequently quantified by Prisko (1963). She sampled five different sets of stimuli, each set constituting a separate task, with three of the tasks visual and two auditory; the stimuli used were clicks, tones, shades of red, light flashes and nonsense patterns. Normal subjects averaged only one error in twelve trials even with an intratrial interval of 60 sec whereas a subject with bilateral medial temporal-lobe resection has only one error if one stimulus immediately follows the other, but if the stimuli were separated by 60 sec the score approached the chance level of six errors in 12 trials (Fig. 10.1C).
