Calculate Erp Preliminary Research In Clinical Forensic Medical Expertise

【Background】One of the most important thinking activity in daily life is to calculate, and this involves many kinds of cognitive processing stages such as sensory, judgment, comparison and inference, it reflects a more thorough cognitive function .The ability closely associated with the person's IQ level is an important context for intelligence testing. Such as, WAIS-RC contains arithmetic, digit span test and digit symbol test. To the patients with head injuries, it is one of the most common findings in clinic and medico-legal expertise that computing capability drops, and this can seriously affect daily life, labor capacity and social communication of the patients. It is obvious that computing capability has important significance when assessing severity of the intellectual disability following trauma. Generally speaking, there are several means used to complete computing -capability -detection such as questioning, mental arithmetic and manual calculation. But these means depend on the subjects'level of cooperation. In forensic expertise, those wounded are affected by body condition and mental status. Or, because those afflicted want to recover damages, the result of the test does not often correspond to their actual capacity. So, the value of the test is restrained when applied in forensic medicine. Therefore it is of practical significance to establish an objective detection method for computing capability in order to meet medico-legal expertise's needs.Event-related potential (ERP) is a non-invasive method of measuring brain activity during cognitive processing. The transient electric potential shifts (so-called ERP components) are time-locked to the stimulus onset (e.g., the presentation of a word, a sound, or an image), it has high time resolution. In recent years, researchers try to use ERP technique to explore electrophysiological mechanism of number processing and mechanisms of calculating ability, and some specific ERP component which is related to number processing. In the present study we try to establish a calculating ability paradigm hope to offer a reliable and objective index for testing calculating ability in medico-legal expertise.【Objectives】Use a delayed verification paradigm (The arithmetic expression followed by an answer), we tried to working out arithmetic stimulates arrays for test, and then compare the characteristic and difference of the wounded and the normal people. Finally, explore the Correlation between WAIS-RC and the various components of ERP.【Methods】Utilizing 37 channel Neuroscan ERP instrument, 11 severe head injury patients and 46 normal volunteers were tested by aural oddball paradigm, the delayed verification paradigm and WAIS-RC. Then their intelligence quotient and amplitude and latency of the various components of ERP and the scalp distributive characteristics were obtained.【Results】1. Intelligence quotient etc. of TBI group (traumatic brain injury) were found to have remarkable changes(lower) as compared with the normal control group (P<0.01);2. P300 of TBI group mainly showed decrease in amplitude, prolongation of the latency and bad differential. There is a significant difference (P<0.05) compared with control group in latency of N2. There was a significant difference (P<0.01) in latencies and amplitudes of normal control group and TBI group;3. The test can obtain manifest ERP wave form on parietals, frons and occipital point (CZ, P3, P4 etc.). And the most stabile registration point is CZ;4. Data from the test showed that the mean amplitude and latency found no significant differences between male and female;5. The raw waveforms elicited by the arithmetic expression, correct answer and wrong answer are observed to be similar in control group. This wave form is formed by four components-- n1, p2, n2 and p3. P2 and n2 of correct answer showed bad differential, n2 and p3 of the arithmetic expression also showed bad differential. Waveform of wrong answer showed prolongation of the latency. There is a significant difference (P<0.01) compared with as of correct answer in latency of p2, n2, p3, and compared with as of the arithmetic expression in latency of n2, p3 (P<0.05). Latency of n2 and p3 of the arithmetic expression were longer than as of correct answer (P<0.05);6. The waveforms are similar to TBI group and control group. But it showed decrease in amplitude, prolongation of the latency and bad differential. The amplitude of p3 of correct answer and wrong answer have significant difference (P<0.01). The latency of n2, p3 of correct answer and p2 of wrong answer and p2, p3 of arithmetic expression have significant difference (P<0.01);7. IQ had significant negative correlation with the latency of p3 of wrong answer(r =-0.44, P< 0.01). It was stronger than correlation between IQ and the latency of auditory p3;8. Based on auditory p3 inference IQ model can only explain 5% of the total variation in IQ value. Based on wrong answer p3 inference IQ model can explain 17.2% of the total variation. And based on both two inference model can explain 18.8% of the total variation.【Conclusion】Arithmetic stimulates arrays can elicit the stable ERP waves, the amplitude and latency of p3 elicited by the arithmetic expression, correct answer and wrong answer were closely related to calculation ability. The most stabile registration point is CZ. The latency of p3 of wrong answer had significant negative correlation with IQ. It was stronger than the correlation between IQ and the latency of auditory p3. Using calculating ability paradigm could be better than auditory Oddball paradigm to use to evaluate damage degree of cognitive function.