A calendar savant with episodic memory impairments

Abstract

Patients with memory disorders have severely restricted learning and memory. For instance, patients with anterograde amnesia can learn motor procedures and retain some restricted ability to learn new words and factual information. However, such learning is inflexible and frequently inaccessible to conscious awareness. Here we present a case of patient AC596, a 25-year-old male with severe episodic memory impairments, presumably due to anoxia during a preterm birth. In contrast to his poor episodic memory, he exhibits savant-like memory for calendar information that can be flexibly accessed by day, month, and year cues. He also has the ability to recollect the exact date of a wide range of personal experiences over the past 20 years. The patient appears to supplement his generally poor episodic memory by using memorized calendar information as a retrieval cue for autobiographical events. These findings indicate that islands of preserved memory functioning, such as a highly developed semantic memory system, can exist in individuals with severely impaired episodic memory systems. In this particular case, our patient's memory for dates far outstripped that of normal individuals and served as a keen retrieval cue, allowing him to access information that was otherwise unavailable.

Figure 1

Figure 1a. Patient AC596’s performance on Experiment 2, Calendar Task 1: day from date, binned by decade. The dotted line represents chance performance. The gray bar represents AC596’s lifespan overlapping with the epochs of peak performance. Figure 1b. Patient AC596’s performance on Experiment 3, Calendar Task 2 & 3: year and month from date. His performance on both tasks is significantly greater then chance, which are, 14.3% for months, and 8% for years.

Figure 2

Patient AC596 and D. Drowos’ recollection of attendance at past Philadelphia professional sporting events. AC596 was able to recall details of 8 past National Football League and Major League Baseball games dating back to 2003, while compared to D. Drowos who was able to recall only 2 specific dates that occurred within a 3 month time period prior to testing.

Figure 3

Patient AC596 and 12 matched controls performance on the Celebrity Face Task. The bars show the average performance of control participants, while the white circles indicate the patient’s performance. Patient AC596’s recall of famous names was significantly lower then controls for all three subtests. His recall of birthplace and birthmother information was also impaired, but he performed numerically better then controls when asked to recall birthdates.