How does Post-traumatic Amnesia differ from the Amnesic Syndrome and from Chronic Memory Impairment?

This study compared memory and attention functioning in three groups of patients: those in post-traumatic amnesia (PTA), those with the amnesic syndrome (AS) and those with chronic memory impairment (CMI) following severe head injury, but who were no longer in PTA. We also tested a control group, most of whom had sustained orthopaedic injuries. Subjects were assessed on tests of immediate and delayed memory, semantic and episodic memory, procedural learning, speed of comprehension, and attention. Patients in PTA differed from all other groups on semantic processing (errors), verbal fluency (animals) and simple reaction time. The best measures for discriminating PTA were accuracy of comprehension, verbal fluency, delayed logical memory, simple reaction time, and backward digit span.