Right temporofrontal cortex as critical locus for the ecphory of old episodic memories.

A 54 year old patient of average intelligence with a severe and enduring loss of old autobiographical memories after herpes simplex type 1 infection is described. She was tested with a comprehensive neuropsychological battery two years after the infection. Special emphasis was laid on examining different aspects of retrograde memory. The neurological examination involved MRI and SPECT. Brain damage was found mainly in the right temporofrontal region, but minor left sided damage to this region seems possible. The patient was in the normal or slightly subnormal range for all tested anterograde memory functions, but manifested severe retrograde memory deficits with respect to episodic old memories and more moderate deficits in tests of general knowledge (semantic old memories). It is concluded that the ecphory of old autobiographical memories relies heavily on an activation of the right lateral temporofrontal junction area, but that probably only some complementary left hemispheric damage to these regions will lead to major and persistent retrograde amnesia. Alternatively, the disconnection between major prefrontal and posterior cortical regions may provide a basis for retrograde amnesia.