Study Of Cognitive Functions And Neuroimaging Scanning In Late-onset Schizophrenia

Objective:1. To analyse clinical characteristics and explore the patterns of cognitive impairment of late-onset schizophrenia, then to address the association between cognitive function and clinical variables.2. To assess volumetric abnormalities of grey matter throughout the entire brain in individuals with late-onset schizophrenia, and to address the association between cognitive functions, clinical variables and grey matter of brain structure in patient groups.3. To assess white matter integrity throughout the entire brain in individuals with late-onset schizophrenia, and to address the association between cognitive function, clinical variables and white matter alterations in patient group.Methods:Using comprehensive neuropsychological tasks including Wisconsin card sorting test, verbal fluency test, digit span test, trial marking test, Stroop color word conflict test, instantly logical memory and Continuous Performance Test. We compared neuropsychological functions in patients with late-onset schizophrenia(n=45) and normal controls(n=41). 3D T1Weighted images were acquired by magnetic resonance imaging from19patients with late-onset schizophrenia and17healthy volunteers. Regional deviation in grey matter volume was assessed using optimized volumetric voxel-based morphometry.1.5T diffusion weighted images were acquired by magnetic resonance imaging from20patients with late-onset schizophrenia and17healthy volunteers. DTI was used to assess white matter integrity in patients and healthy controls. Differences in fractional anisotropy (FA) were measured using voxel-based morphometry.Results:1. All of patients with late-onset schizophrenia demonstrated a broad range of cognitive impairments. The patients manifest significant differences in memory, attention and performance function and visual motor tasks compared to healthy controls. In patients with late-onset schizophrenia, trial marking test part A performance was positively related to GAF (r=32, P=.041), but inversely to negative scale scores of PANSS (r=-0.46, P=013).2. Patients with late-onset schizophrenia showed decreased gray matter volume in right parietal postcentral gyrus BA1, right middle occipital gyrus BA18, bilateral superior frontal gyrus BA10/11, bilateral middle frontal gyrus BA8/6/10, bilateral superior frontal gyrus BA6/46, bilateral superior temporal gyrus BA38, left inferior temporal gyrus BA20and left middle temporal gyrus BA20. Within the patient group, volume of grey matter in bilateral frontal gyrus, bilateral temporal gyrus and right middle occipital gyrus was negatively related to duration of illness, whereas grey matter volume in right middle occipital gyrus and left temporal gyrus positively related to dosage of antipsychotics.Within the schizophrenia group, the performance of digit span test and instantly logical memory was positively related to volume of grey matter in bilateral frontal gyrus and left middle temporal gyrus. The score of Stoop test (color reading) was positively related to volume of grey matter in left superior frontal gyrus, whereas interference score was negatively related to that of right parietal postcentral gyrus and left middle temporal gyrus. Decreased volume of gray matter in left inferior frontal gyrus was correlated with poorer performance on the auditory error of CPT.3. Schizophrenic patients showed lower fractional anisotropy of white matter in left frontal precentral gyrus, left superior temporal gyrus, left medial frontal gyrus, left frontal sub-gyrus, right sub-lobar extra-nuclear, right temporal sub-gyrus, right temporal fusiform gyrus, right lingual gyrus, right occipital cuneus, and right cerebellar vermis, right cerebellum anterior lobe culmen.No significant correlation was found between duration of illness, antipsychotic medication dosages, PANSS scores and FA value of any of the clusters.An positive relationship of DTI fractional anisotropy (FA) values in left frontal gyrus, sub-lobar extra-nuclear, right temporal sub-gyrus and right sub-lobar extra-nuclear with attention performance was observed.Conclusion:1. Patients groups performed worse than normal control and showed a profile of cognitive impairment. Some cognitive indexes were associated with several clinical variables in patient groups.2. There was a significant decrease in gray matter volume in patients with late-onset schizophrenia in bilateral frontal gyrus, bilateral temporal gyrus, right parietal gyrus and right occipital gyruss. Among patients, longer duration of illness has also been associated with reduced volume of grey matter in brain regions which may be relieved by dosage of antipsychotic medication. Grey matter volume decrease in brain regions would be associated most strongly with poorer cognitive performance on memory and attention tests.3. The results are consistent with evidence that patients with late-onset schizophrenia exhibit abnormalities of neuron membrane disturbance. The white matter integrity is disconnection in left frontal lobe, bilateral temporal lobe, right occipital, right occipital and right cerebellum in patient groups. White matter impairment in left frontal lobe, right sub-lobar extra-nuclear and right temporal sub-gyrus was related to attention dysfunction in late-onset schizophrenic patients.