Transient Visual Evoked Potential (TVEP) has been used as one of the valuable diagnostic tool in the clinical environment. Various types of analysis have been performed on TVEP recordings for identifying diagnostically significant information. Conventional methods of detection of visual anomalies, based on TVEPs require long periods of testing and averaging. Hence, the problem of patient fatigue affects the accuracy of the results. A spectral component based method is proposed to identify the effect of rate of stimulation on the spectral components and change in P100 latency value for normal subject TVEP. The spectral components are identified using Welch's averaged periodogram and latencies are identified using the averaging method. Using the method proposed here one could identify the latency with lesser period of testing irrespective of the rate of stimulation. Introduction TVEP is an important diagnostic test for specific ophthalmological and neurological disorders (Misra et al 1999, AbdelMageed 2002, Lauritzen et al 2004, Momose et al 2004, Suttle and Turner 2004). The clinical use of TVEP is mainly based on the peak amplitude and latency of P100 (Nogawa et al 1991, Xu et al 1992). In general, the stimulation rate used for the recording is 1Hz. But it requires minimum of 50-60 trials for calculating P100 value. Usually, it takes minimum of 30 minutes for completing the entire procedure and the fatigue condition affects the procedure. Higher rate of stimulation is preferred to reduce the procedure time and also to reduce fatigue levels in patients. But at higher rate of stimulation, identification of P100 peaks becomes very difficult and there is also an increase in the latency compared to that of the latency obtained using the 1Hz stimulation rate. All the previous studies confirmed that the as the rate of stimulation increases there will be a change in the latency (Misra et al 1999, Heravian et al 1999) and none of the studies have shown the correlation between the rate of stimulation and the change in TVEP P100 latency.In this paper, a spectral component based method has been proposed to identify the effect of rate of stimulation on the spectral components and change in P100 latency value for normal subjects TVEP. Materials And Method SubjectsExperiments were carried with subjects in the Neurology Department of a leading Medical Institute from 2003 to 2004. Experiments were carried out with 300 normal subjects (19 – 62 years old, 125 females and 175 males). Patients have been chosen in such a way that all subjects have the latency value exactly 100 msec.TVEP RecordingTVEP was performed in a specially equipped electro diagnostic procedure room (darkened, sound attenuated room). Initially, the patient was made to sit comfortably approximately one meter away from the pattern-shift screen. Subjects were placed in front of a black and white checkerboard pattern displayed on a video monitor. The checks alternate black/white to white/black at a rate of approximately twice per second. Every time the pattern alternates, the patient's visual system generates an electrical response that was detected and was recorded by surface electrodes, which were placed on the scalp overlaying the occipital and parietal regions with reference electrodes in the ear. The patient was asked to focus his gaze onto the center of the screen. Each eye was tested separately (monocular testing). Only the rate of stimulation is changed. Other parameters remained constant (brightness, contrast, stimulation pattern size etc.,). The response of each stimulation rate was done for 30 cycles and stored and similarly responses repeated for remaining rate of stimulation also (2Hz, 3Hz, 4Hz, 5Hz and 6Hz stimulation).Data AnalysisFor each patient P100 latency value were identified manually by moving the cursor over the averaged waveform. The analogue signal is digitized at a sampling rate of 1024 samples/sec. Using Welch's averaged periodogram method the spectral c
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