Disrupted integrity of the fornix is associated with impaired memory organization in schizophrenia.
BACKGROUND
The fornix is a major projection of the hippocampus to and from other brain regions. A previous diffusion tensor imaging (DTI) study has reported disrupted integrity of the fornix in patients with schizophrenia. However, functional significance of the DTI abnormalities of the fornix in schizophrenia has not been fully studied yet. We investigated an association between DTI abnormalities of the fornix and impairment of memory organization in schizophrenia.


METHODS
Thirty-one patients with schizophrenia and 65 age- and gender-matched healthy controls underwent DTI, and fractional anisotropy (FA) and mean diffusivity (MD) were measured in cross-sections of fornix tractography. In addition, all of the patients and 32 controls performed a verbal learning task specialized for evaluating memory organization, the verbal memory subscale of the Wechsler Memory Scale-Revised, the category- and letter fluency tests, and the Japanese version of National Adult Reading Test.


RESULTS
Statistically significant reduction of FA and increase of MD were found in the fornix of patients with schizophrenia compared with controls with no significant lateralization. A significant patients-specific correlation was found between increased MD in the left fornix and lower scores on utilization of semantic organization in the verbal learning task. In addition, increased MD in the right fornix showed a patients-specific association with poorer performance on the category fluency test, which indexes organization of long-term semantic memory. These patients-specific correlations, however, were not statistically lateralized to either hemisphere.


CONCLUSIONS
These results indicate that disrupted integrity of the fornix contributes to impaired memory organization in schizophrenia.
Takei
Kunio
K
Department of Neuropsychiatry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. takeik-tky@umin.ac
Yamasue
Hidenori
H
Abe
Osamu
O
Yamada
Haruyasu
H
Inoue
Hideyuki
H
Suga
Motomu
M
Sekita
Kayoko
K
Sasaki
Hiroki
H
Rogers
Mark
M
Aoki
Shigeki
S
Kasai
Kiyoto
K
D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping; D038524:Diffusion Magnetic Resonance Imaging; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D020712:Fornix, Brain / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012153:Retention, Psychology / Q000502:physiology; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology; D012565:Schizophrenic Psychology; D012660:Semantics; D014706:Verbal Learning / Q000502:physiology; D014888:Wechsler Scales