Effect of Transcranial Alternating Current Stimulation(tACS) for Early Alzheimer's Disease

Alzheimers Disease Assessment Scale Cognitive section(ADAS-Cog)

The changes in Alzheimers Disease Assessment Scale Cognitive section (ADAS-Cog) will constitute the major research outcome measure used to assess response to transcranial alternating current stimulation (tACS).The ADAS-Cog scale is a scale used for clinical assessment of dementia patients with some memory efficiency tests, which can be used as an objective assessment of memory. The scale is considered a tool capable of providing a specific assessment of the severity of cognitive and non-cognitive behavioral impairments in people with Alzheimer's disease or dementia. The advantage of the ADAS-Cog compared to other scales used in the same clinical area is that its score quantifies clinical and impressionistic aspects of the patient assessed by the examiner, as well as objectively defined cognitive characteristics. The higher the ADAS-Cog score, the worse the cognitive function. The minimum value is 0 and the maximum is 86.

electroencephalography

EEG recordings were obtained from each subject based on 64 electrode locations of the International 10-20 system (sampling frequency 1000Hz).The recorded EEG data were filtered with a second order band-pass Butterworth filter with cutoff frequencies of 0.5 and 60 Hz. For each testing condition, data with muscular, ocular and other types of artifacts were manually discarded and 60 seconds of stationary EEG signal were selected. Only these segments were accepted for further analysis. The analysis in the frequency domain was performed using Welch's periodogram method. Recordings were segmented into tracts of 10 seconds each, windowed with a Hanning window, with 50% overlap. The relative powers of the spectral components in the typical spectral bands delta (δ: 0.5-4 Hz), theta (θ: 4-8 Hz), alpha1 (α1: 8-10.5 Hz), alpha2 (α2: 10.5-13 Hz), beta1 (β1: 13-20 Hz), beta2 (β2: 20-30 Hz) and gamma (γ: 30-60 Hz) were computed by dividing the absolute power in each band by the total power.

Associative Memory

The associative memory test uses facial cue word recall. The subjects memorized 20 photos of faces displayed on a screen in gray scale for 4 seconds each. When each card was presented, a common word appeared alongside the face. The subjects had to remember associations between faces and words by association. After a delay of about a minute after the study ended, the subjects were shown 12 of the same faces in different random orders, instructing them to recall the words that appeared with each face during the study. Recorded the correct number of words each face recalled. The faces were taken from a database of 24 amateur models. Each test format included only male or female faces.

MMSE(Mini Mental State Examination)

The full name of MMSE is mini-mental state examination, and the scale consists of 30 subject, include the following seven aspects: time orientation, place orientation,immediate memory,attention and calculation,delay memory,language, visual space.One point is awarded for each question correctly answered during MMSE evaluation. If subject give the wrong answer or don't know answe he/she awarded 0 score, scope of scale score of 0 to 30 points. The higher the score, the better.

LMT (Logic Memory Test)

The changes in LMT will constitute the secondary research outcome