The Investigation of Simultaneous EEG and Eye Tracking Characteristics During Fixation Task in Mild Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disorder that occurs many years before the first clinical symptoms. Finding more exact, significant, and valuable criteria or indices for the diagnosis of the mild form of Alzheimer's disease is very important for clinical and research purposes. Electroencephalography (EEG) and eye tracking biomarkers would provide noninvasive tools for the early detection of AD. Due to the advantages of EEG and eye tracking, in this study, we employed them simultaneously to conduct research on the mild AD. For this purpose, 19 patients with mild AD were compared with 19 gender- and age-matched normal subjects who did not have any history of cognitive or neurological disorders. EEG and eye-tracking data were concurrently collected in both groups in a fixation task. Our results revealed that the total fixation duration was significantly shorter for the AD patients, but their fixation frequency was more than that of the controls. In addition, increased theta power and decreased alpha power were observed in the AD group. Interestingly, there was a statistically significant correlation between fixation frequency and alpha power in the parietal area in the control group. However, this connection was not statistically significant in the AD group. The findings also indicated an elevated coherence in the AD patients in the parieto-occipital area. It is assumed that the AD patients might use the neural compensational processes for the fixation state. This study provides evidence for the simultaneously EEG and eye-tracking changes in the areas, which are involved in the control of the fixational eye movements.

Effects of infantile repeated hyperglycemia on neuronal density of hippocampus and pentylentetrazol induced convulsions in male wistar rats.

OBJECTIVE(S): High blood glucose induces molecular, cellular, morphological and behavioral changes in the brain. Metabolic disturbances, contribute to the hippocampus injury and development of partial focal seizures. The aim of this study was to investigate the effects of infantile repeated hyperglycemia on neuronal density of hippocampal CA3 region in newborn Wistar male rats and its effect on chemoconvulsant pentylentetrazol (PTZ) induced generalized seizures in adults. MATERIALS AND METHODS: Ten days old male Wistar rats were randomly divided into 2 groups (n=20 for each): hyperglycemic and control. Hyperglycemia was induced by intraperitoneal injections of 2 g/kg dextrose solution, twice a day, for 2 weeks. Control animals received saline solution in the same manner. Blood glucose was regularly measured. After that, the brains of rats from each group (n=10) were removed for histological analysis of the CA3 region of hippocampus by stereological method. Other animals (n=10) were kept to grow older. Afterwards, seizure was induced in hyperglycemic and control adult rats, by an intraperitoneal injection of 45 mg/kg PTZ solution and then latency of convulsions onset and severity of seizures for each group were recorded. RESULTS: RESULTS showed that hippocampal neuronal density decreased significantly and susceptibility to PTZ induced convulsions increased in experimental animals. CONCLUSION: The result determined that repeated increments in daily blood sugar levels in infantile period may damage neuronal structures of hippocampus and also make adults more susceptible to PTZ induced convulsions in adulthood period.