Role of left superior temporal gyrus during name recall process: an event-related fMRI study.

When we cannot recall the name of a well-known person despite preserved access to his/her semantic knowledge, a phonological hint such as his/her initials sometimes helps us to recall the name. This type of recall failure appeared to occur by the transmission deficit from the lexical-semantic stage to the lexical-phonological stage in name recall processes, and the phonological cue appeared to activate this transmission, which leads to successful recall. We hypothesized that the brain regions responsible for the transmission would respond to the phonological cue that facilitates name recall, and would also respond to successful recall. A famous face image was presented with a phonological cue, and the subjects were required to recall and overtly pronounce the name during fMRI scanning. The behavioral results showed that the first syllable cue induced greater number of successful recall trials than both the non-verbal sound of the chime and the non-first syllable cue, suggesting that the first syllable facilitated name recall. The fMRI results demonstrated that two regions in the left superior temporal gyrus responded more strongly to the first syllable than both to the non-verbal sound of the chime and to the non-first syllable. In addition, these two regions were activated when the name recall was successful. These results suggest that two regions in the left superior temporal gyrus may play a crucial role in the transmission from the lexical-semantic to the lexical-phonological stage in the name recall processes.

Altered brain activation by a false recognition task in young abstinent patients with alcohol dependence.

BACKGROUND: Heavy alcohol intake induces both structural and functional changes in the central nervous system. Recent research developments converged on the idea that even in patients with alcohol dependence without apparent structural brain changes, some cognitive impairment exists, and associated functional change could be visualized by neuroimaging techniques. However, these data were from old (more than 50 years) patients using working memory and response inhibition tasks. Whether young abstinent patients show aberrant signs of brain activation is a matter of interest, specifically by the long-term memory retrieval task. METHODS: Subjects were 9 young patients with alcohol dependence with long-term abstinent (8 males and 1 female) and age- and education-matched 9 healthy controls (7 males and 2 females). We used a modified false recognition task in a functional MRI study. RESULTS: The young patients with alcohol dependence showed reduced activation in the right dorsolateral prefrontal cortex, anterior cingulate cortex (ACC), left pulvinar in the thalamus, and in the right ventral striatum, although behavioral performances and regional patterns of brain activation were similar between patients and controls. CONCLUSIONS: Long-term memory retrieval induced altered activations in prefrontal lobes, ACC, thalamus, and ventral striatum in young patients with alcohol dependence. These findings were correspondent to deficits of goal directed behavior, monitoring the erroneous responses, memory function, and drug-seeking behavior. Furthermore, these reduced activations can be considered as latent "lesions," suggesting subclinical pathology in alcoholic brains.

Laterality and aging of thalamic subregions measured by diffusion tensor imaging.

Thalamic nuclei are comprised of fibers connecting associated cortical regions, and abnormalities of the thalamus are correlated with abnormalities in cognition and behavior. Some previous studies showed the laterality of the whole thalamus and the regional differences among thalamic nuclei. This led us to assess regional characteristics in five major subregions of both sides of the thalamus using diffusion-tensor imaging. Statistically significant lateralities and regional differences were found among the thalamic subregions. Age has a significant correlation with diffusion-tensor imaging metrics where their projection areas are thought to be vulnerable to normal aging. Our results confirmed that the thalamic subregions behave independently, and their respective microstructures warrant further investigations.

Quantitative magnetic resonance spectroscopy of schizophrenia: relationship between decreased N-acetylaspartate and frontal lobe dysfunction.

Numerous studies using proton magnetic resonance spectroscopy (1H-MRS) have detected signal changes in schizophrenia. However, most studies investigated relative concentrations such as N-acetylaspartate/creatine plus phosphocreatine (NAA/Cre) and choline-containing compounds/creatine plus phosphocreatine (Cho/Cre), and individual metabolite concentrations have not been clarified. Using absolute quantification measurement of 1H-MRS, the aim of the present paper was to demonstrate the changes in metabolite concentrations in the frontal lobe of patients with chronic schizophrenia. The 1H-MRS was performed in the left frontal lobe in 14 patients with schizophrenia and in 13 healthy comparison subjects. Individual MRS peak concentration was quantified based on a frequency-domain fitting program: LCModel. The scores on the Positive and Negative Symptoms Scale and Wisconsin Card Sorting Test were used for clinical assessment. The NAA concentration was reduced in schizophrenic patients (average, 7.94 mmol/L, t=2.28, P<0.05) compared with healthy subjects (average=8.45 mmol/L) while choline, creatine or NAA/Cre ratio did not show any differences. The reduction in NAA concentration had a significant correlation with the severity of negative symptoms (r=-0.536, P<0.05) and poor performance in Wisconsin Card Sorting Test (r=-0.544, P<0.05). Using quantitative MRS, decreased NAA concentration was confirmed in the left frontal lobe of schizophrenic patients and was demonstrated to be correlated with negative symptoms and cognitive dysfunction in schizophrenia.