Understanding the Pathophysiology of Alzheimer's Disease and Mild Cognitive Impairment: A Mini Review on fMRI and ERP Studies

The prevalence of Alzheimer's disease (AD) is predicted to increase rapidly in the coming decade, highlighting the importance of early detection and intervention in patients with AD and mild cognitive impairment (MCI). Recently, remarkable advances have been made in the application of neuroimaging techniques in investigations of AD and MCI. Among the various neuroimaging techniques, functional magnetic resonance imaging (fMRI) has many potential advantages, noninvasively detecting alterations in brain function that may be present very early in the course of AD and MCI. In this paper, we first review task-related and resting-state fMRI studies on AD and MCI. We then present our recent fMRI studies with additional event-related potential (ERP) experiments during a motion perception task in MCI. Our results indicate that fMRI, especially when combined with ERP recording, can be useful for detecting spatiotemporal functional changes in AD and MCI patients

Increased amygdala reactivity following early life stress : a potential resilience enhancer role

Background: Amygdala hyper-reactivity is sometimes assumed to be a vulnerability factor that predates depression; however, in healthy people, who experience early life stress but do not become depressed, it may represent a resilience mechanism. We aimed to test these hypothesis examining whether increased amygdala activity in association with a history of early life stress (ELS) was negatively or positively associated with depressive symptoms and impact of negative life event stress in never-depressed adults. Methods: Twenty-four healthy participants completed an individually tailored negative mood induction task during functional magnetic resonance imaging (fMRI) assessment along with evaluation of ELS. Results: Mood change and amygdala reactivity were increased in never-depressed participants who reported ELS compared to participants who reported no ELS. Yet, increased amygdala reactivity lowered effects of ELS on depressive symptoms and negative life events stress. Amygdala reactivity also had positive functional connectivity with the bilateral DLPFC, motor cortex and striatum in people with ELS during sad memory recall. Conclusions: Increased amygdala activity in those with ELS was associated with decreased symptoms and increased neural features, consistent with emotion regulation, suggesting that preservation of robust amygdala reactions may reflect a stress buffering or resilience enhancing factor against depression and negative stressful events

Visual Event-related Potentials in Progressive Supranuclear Palsy

The purpose of this study is to assess the cognitive function in early stages of progressive supranuclear palsy (PSP). Visual event-related potentials (visual ERPs) were examined in five non-demented patients with PSP and seven control subjects. ERPs were recorded using Figure (non-verbal) and Kanji (verbal) oddball paradigms. The latencies and amplitudes of N100 and P300 components were not significantly different between the PSP and control groups. However, the score of Hasegawa's dementia scale-revised (HDSR) was correlated with P300 amplitudes in the Figure task only in the PSP group. Since the P300 amplitude is related to attentional resources, changes in visual ERP induced by non-verbal stimuli might be associated with the attentional impairment even in early stages of PSP. In the Kanji task but not in the Figure task, the reaction time was prolonged in the PSP group, and positively correlated with the P300 latency in both groups. Visual verbal stimuli might be a good tool to evaluate the information processing in the early stages of PSP.　　 Recording of visual ERP using both non-verbal and verbal stimuli could be helpful to assess a mild cognitive dysfunction in PSP.This work was supported by grants-in-aid from the Ministry of Education, Science and Culture and from the Ministry of Health and Welfare of Japan

Effects of Nicotine Chewing Gum on UPDRS Score and P300 in Early-onset Parkinsonism

It has been reported that nicotine shows some beneficial effects on Parkinson's disease. The purpose of the present study is to assess the therapeutic effects of nicotine chewing gum in patients with early-onset parkinsonism (EOP). The subjects were 8 patients with early-onset parkinsonism (male/ female = 4/ 4, mean age; 51.3 years). Four out of 8 patients had a history of smoking (smokers). To estimate the effects of nicotine gum, the scores on the Unified Parkinson's Disease Rating Scale (UPDRS) and auditory event-related potentials (ERPs) were studied before and after taking nicotine gum in the EOP patients. In smokers, UPDRS scores improved by more than 10 % and the P300 latency of auditory ERPs was shortened by more than 30 msec. In contrast, nicotine had no remarkable effects on UPDRS scores or auditory ERPs in non-smokers. We suggest that nicotine chewing gum may be a possible choice for the treatment of patients with EOP, especially when they are smokers

Amelioration of Persistent, Non-Ketotic Hyperglycemia-Induced Hemichorea by Repetitive Transcranial Magnetic Stimulation

Diabetic hemichorea-hemiballism with non-ketotic hyperglycemia is usually a benign syndrome. Here, we report a 78-year-old woman with persistent hemichorea (HC) for longer than 1 year with a recurrence after rapid correction of hyperglycemia. Following the disappearance of the characteristic T1 hyperintensity at 3 months after onset, an MRI demonstrated T2* hypointensity and atrophic changes in the contralateral striatum, suggesting irreversible neuronal loss and some vascular proliferation. The electrophysiological examination using transcranial magnetic stimulation revealed significantly shorter cortical silent periods (CSPs) on the contralateral primary motor cortex (M1), possibly in relation to cortical hyperexcitability. We have applied 10 daily sessions of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the contralateral M1 to reduce the hyperexcitability. The HC was suppressed during and for several minutes after rTMS with prolongation of CSPs. After rehabilitation therapy, the patient was able to walk independently with a walker. We suggest that the combination of low-frequency rTMS and rehabilitation therapy may be a possible choice in medically refractory involuntary movements