We studied the functional anatomy of affect-laden autobiographical memory in normal volunteers. Using H 2 15 O positron emission tomography (PET), we measured changes in relative regional cerebral blood flow (rCBF). Four rCBF measurements were obtained during three conditions: REST, i.e., subjects lay at rest (for control); IMPERSONAL, i.e., subjects listened to sentences containing episodic information taken from an autobiography of a person they did not know, but which had been presented to them before PET scanning (nonautobiographical episodic memory ecphory); and PERSONAL, i.e., subjects listened to sentences containing information taken from their own past (autobiographical episodic memory ecphory).Comparing IMPERSONAL with REST (nonautobiographical episodic memory ecphory) resulted in relative rCBF increases symmetrically in both temporal lobes including the temporal poles and medial and superior temporal gyri. The same loci, however, with a stronger lateralization to the right hemisphere were activated in the comparison PERSONAL to REST (autobiographical episodic memory ecphory). In addition, the right temporomesial, right dorsal prefrontal, right posterior cingulate areas, and the left cerebellum were activated. A comparison of PERSONAL and IMPERSONAL (autobiographical vs nonautobiographical episodic memory ecphory) demonstrated a preponderantly right hemispheric activation including primarily right temporomesial and temporolateral cortex, right posterior cingulate areas, right insula, and right prefrontal areas. The right temporomesial activation included hippocampus, parahippocampus, and amygdala.These results suggest that a right hemispheric network of temporal, together with posterior, cingulate, and prefrontal, areas is engaged in the ecphory of affect-laden autobiographical information.

What distinguishes the recall of real-life experiences from that of self-created, fictitious emotionally laden information? Both kinds of information belong to the episodic memory system. Autobiographic memories constitute that part of the episodic memory system that is composed of significant life episodes, primarily of the distant past. Functional imaging was used to study the neural networks engaged in retrieving autobiographic and fictitious information of closely similar content. The principally activated brain regions overlapped considerably and constituted temporal and inferior prefrontal regions plus the cerebellum. Selective activations of the right amygdala and the right ventral prefrontal cortex (at the level of the uncinate fascicle interconnnecting prefrontal and temporopolar areas) were found when subtracting fictitious from autobiographic retrieval. Furthermore, distinct foci in the left temporal lobe were engaged. These data demonstrate that autobiographic memory retrieval uses (at least in non-brain damaged individuals) a network of right hemispheric ventral prefrontal and temporopolar regions and left hemispheric lateral temporal regions. It is concluded that it is the experiential character, its special emotional infiltration and its arousal which distinguishes memory of real-life from that of fictitious episodes. Consequently, our results point to the engagement of a bi-hemispheric network in which the right temporo-prefrontal hemisphere is likely to be responsible for the affective/arousal side of information retrieval and the left-hemispheric temporal gyrus for its engram-like representation. Portions of the neural activation found during retrieval might, however, reflect re-encoding processes as well.

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