Evaluation Of Intelligence Quotient Using Multi-Paradigm ERP And Its Application In Forensic Identification

【Background】After recovery from the acute phase of severe traumatic brain injury(sTBI),patients usually have extensive cognitive impairments,including attention deficit,hypomnesia,aphasia and anarithmia,and so on.Intelligence disorder is commonlyimpaired in a TBI patient,and it may persist for several years.In forensic practice,accurateassessment of a patient's intellectual ability is essential in the determination of handicapdegree.Wechsler Adult Intelligence Scale (WAIS) is the most frequently administeredneuropsychological test,but this test entails verbal or behavioral responses from the patient.Unfortunately,following neurological trauma,patients tend to suffer from speech and/ormotor disabilities,which render the assessment of cognitive functioning with standardneuropsychological tests difficult or impossible.Especially,forensic assessment of braininjury is likely invalid if the subject involved is not 100% honest,or refuses to cooperate.Marked discrepancy could be found between the test performance or claimed disability andthe objective findings.Event-related potentials (ERP) is of value in the neuropsychologicalevaluation by providing a neurophysiologic index of patients' on-line cognitive functioning,and it is less affected by motivational factors than behavioral measurement.Somecomponents of ERP were reported to be able to reflect the information processing speeds,attention capacity,and the updating of working memory,and were significantly correlatedwith the intelligence as assessed by standardized neuropsychological tests.Some forensicresearchers have recognized the value to evaluate the severity of intelligence disorder in theevaluation of neuropsychological functions by ERP.【Objectives】According to the contents of WAIS-RC and the theory of ERP,five ERPstimulus paradigms were developed,including visual and auditory Oddball,picture-recognition,pictures naming and digital calculation.These studies was to investigate thefeatures of ERP elicited by these paradigms in healthy persons and patients with sTBI,and evaluate the correlations between intelligence quotient and the components of ERP,anddevelop some regression models for estimating intellectual status by using some ERPindexes of these paradigms in forensic expertise.【Methods】EEG were recorded on-line in 29 patients with intelligence impairmentinduced by sTBI (sTBI group) and 46 healthy volunteers (the controls) by Neuroscan's ERP,while they were asked to performance on the 5 paradigms (compare target and non-targetpictures and judge whether it was target stimulus),including visual and auditory Oddballtask,picture-recognition,pictures naming and digital calculation,and the character of ERPcomponents were analyzed off-line for these paradigms effects.Intelligence quotient (IQ)was measured using the Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC).【Results】(1) The sTBI patients' scores of all sub-tests and mean intelligence quotientin WAIS-RC were significantly lower than those of the controls (P＜0.01).(2) Thecomponents of visual P₃₀₀ elicited by Oddball paradigm included P2,N2 and P3,andauditory P₃₀₀ included N1,P2,N2 and P3.P3 from auditory stimuli was shorter in latencythan that from the visual stimuli.When compared to the control group,the mean latencyand amplitude of P₃₀₀ in sTBI patients were significantly longer and smaller (P＜0.01).Thelatency of visual and auditory P3 was significantly negatively correlated with FIQ incontrols and sTBI patients (r≈-0.30～-0.42,P＜0.05).(3) In the control group,P₁₇₀ andP₅₀₀ were two positive-going waves in the 170-ms and 500-ms post-stimulus range fortarget and non-target stimuli of picture recognition paradigm.There had no difference onthe latency of P₁₇₀ and P₅₀₀ between target and non-target stimuli,but P₅₀₀ amplitude oftarget stimulus was significantly higher than that of non-target stimulus (P＜0.01).Compared to controls,the mean amplitude and latency of P₁₇₀ and P₅₀₀ of sTBI patients wassignificantly lower and prolonged (P＜0.01).In control group and sTBI group,the latencyof P₅₀₀ was significant negatively correlated with IQ (r=-0.62～-0.68,P＜0.01).(4) Thecomponents of ERP elicited by pictures naming paradigm included N1_pn,P2_pn,N2_pn andP3_pn,and the P3_pn latency of target stimulus was significantly prolonged than that ofnon-target stimulus (P＜0.01).The mean amplitude and latency of P3_pn of sTBI patientswere significantly lower and prolonged than those of controls (P＜0.01).The latency of P3_pn of target stimulus was negatively correlated with IQ (r=-0.68～-0.76,P＜0.01).(5)The components of ERP elicited by digital calculation paradigm included N1_c,P2_c,N2_c andP3_c.The P3_c amplitude of correct answer stimulus was highest,while the P3_c latency oferror answer stimulus was longest (P＜0.01).The mean amplitude and latency of P3_c ofsTBI patients were significantly lower and prolonged than those of controls (P＜0.01).Thelatency of P3_c of error answer was negatively correlated with VIQ and FIQ (r=-0.45～-0.60,P＜0.01).(6) The independent variables of regression equation for evaluating IQincluded the latency of AP₃₀₀,VP₃₀₀,P₅₀₀,P_3c and P_3pn.There had five models in controlgroup and eight models in sTBI group,and these regression equations had no significantcolinearity.When combined AP₃₀₀Lat,P₅₀₀Lat,P_3cLat and P_3pnLat in controls,the modelcould predict FIQ accounted for 58% of the variance,and when combined P₅₀₀Lat,P_3cLat,P_3pnLat and VP₃₀₀Lat in sTBI group,the model could predict FIQ accounted for 73% of thevariance.There was no significant difference between the FIQ evaluated by multi-paradigmERP and WAIS-RC.【Conclusion】The patients of sTBI had significant intelligence impairment.Thelatency and amplitude of components of ERP elicited by the paradigms of visual andauditory Oddball task,picture-recognition,pictures naming and digital calculation weresensitive to the cognitive deficits,and the latency of AP₃₀₀,VP₃₀₀,P₅₀₀,P_3c and P_3pn weresignificantly correlated with IQ.Multi-paradigm ERP may be an objective method forassessing the severity of intelligence impairment by in forensic practice.