| The research presented herein uses several methods to expand our knowledge of the cognitive processes and brain regions involved in autobiographical memory. Chapter 1 presents a behavioral study, in which participants were asked to generate autobiographical memories and rate their phenomenological properties on a series of scales. Multiple regression analyses showed that the extent of reliving---considered a defining feature of autobiographical memory---was best predicted by ratings of visual imagery, auditory imagery, narrative coherence, and emotional intensity. Chapter 2 presents a critical review of neuropsychological impairments of visual imagery. This review resulted in the discovery of a new amnesic syndrome---one that results from posterior neocortical damage, not medial temporal damage. Chapter 3 presents a case study of MS, one of the patients reviewed in Chapter 2. Neuropsychological testing revealed that MS suffers from an impairment of visual memory as well as a severe autobiographical memory impairment; on the whole, his case provides further evidence for the roles of the posterior cortices in autobiographical memory. Chapter 4 extends the critical review in Chapter 2 to other brain regions and cognitive processes. The results showed that impairments of semantic memory and narrative reasoning were associated with autobiographical memory impairments, but not impairments of auditory imagery, spatial imagery, or imagery in other modalities. Chapter 5 presents a functional MRI study of autobiographical memory. Before undergoing scanning, participants generated autobiographical memories along with a few keywords for each memory. During scanning, participants were presented with their keywords; this task was interleaved with a semantic-retrieval task in which participants generated exemplars to category names. The results demonstrated that autobiographical retrieval required coactivation among the amygdala, the hippocampus, and the inferior frontal gyrus. On the whole, these studies shed further light on the processes involved in autobiographical memory, refine our understanding of the interactions among medial temporal and prefrontal regions during autobiographical memory retrieval, and expand the standard model of memory to include additional cognitive processes and brain regions. |
