Abstracts /International Journal of Psychophysiology 30 (1998) 95-271 215 half of the subjects; in the 2nd one, a pseudo-randomized sequence of stimuli of the 4 intensities was delivered. AEPs were recorded at midline electrodes (Fz, Cz, Pz) and at temporal leads (T3 and T4). Results showed that (1) PlNl and NlP2 amplitudes were sensitive to stimulus intensity in- creases, mainly when they were obtained at Fz and Cz; (2) Presentation of the different intensities in an ascendent or descendent way did not affect the amplitude/intensity func- tion; (3) The pseudo-randomized presentation of tone bursts produced higher amplitudes to intensity 4; (4) Intra-class correlations of the two sequences for each subject are con- siderably high. NR seems to be a fronto-central phenomenon which shows adequate reliability within the same recording session, as indexed by the correlations obtained between two forms of stimuli presentation. 563 THE EXPERIENCE OF POLYGRAPHIC EVALUA- TION OF READINESS FOR MILITARY SERVICE P.N. Ermakov and KG. Filatov Rostov-na-Donu State University, Faculty of Psychology In the light of the peculiarities of the modern stage of compul- sory conscription into the Russian Armed Forces it has be- come pertinent to study the psychological readiness of youths for military service, their psychophysiological and psychologi- cal idiosyncrasies at the time of being drafted into the army from the perspective of differential psychophysiology. A three-channel computer polygraph has been employed in the study to register the Electrodermal Activity, plethysmo- graphic and respiratory patterns of conscripts in the process of answering relevant questions on the state of health and inten- tion to serve in the armed forces. The prior registration of background indices not only ensured the stabilization, but also permitted to search for individual differences in their pattern. 105 conscripts took part in the study. The polygraphic research was conducted alongside the standard medical ex- amination at the military conscription office which has permit- ted in a number of cases to compare the LD mode with the medical indices for draft deferment. On the whole the re- search was regarded as a procedure, directed at establishing the idiosyncrasies of conscripts from the perspective of dif- ferential psychophysiology and the evaluation of psychological readiness for military service. In the course of the study some incongruities have been noticed between the statements, made by several conscripts during testing and their subsequent behavior. It was found that the marked GSR to relevant questions on health, psychological state of youths and their attitude toward military service (intention to serve in the armed forces) can indeed be used in a number of cases as indicators of deception. In the process of background indices registration fairly stable individual GSR differences related to the typological properties of the nervous system have been established. The results of the study have shown that the use of EDA is possible for the evaluation of the psychological readiness for military service. 564 A NEW FASTER MISMATCH NEGATIVITY PARADIGM FOR AUDITORY SENSORY MEMORY EVALUATION C. Grau, E. Yago, M.D. Polo, J. Ma. Serra and C. Escera Neurodynamics Laboratory, Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Spain A new MMN paradigm based on the auditory sensory memory trace theory for MMN is proposed for shortening MMN recording time. The strategy proposed for shortening MMN tests comprises collapsing the standard tones in a very short time, with the aim of developing the sensory memory trace as quickly as possible. Ten young subjects were studied with both the conventional and the new faster MMN paradigms. In addition, two memory probe intervals (MPIs), of 0.4 and 4.0 s, defined as the interval between the last stimulus of a train and the one starting the subsequent train (onset-to-onset), were evaluated with both the conventional and the faster paradigms. Both procedures provided identical MMNs in both MPI con- ditions. A suppression of the MMN was obtained with the new paradigm for a MPI of 5.0 seconds in a sample of older subjects, confirming that the new paradigm is a useful tool for exploring auditory sensory memory. Moreover, the new paradigm reduced MMN-eliciting time by nearly 2/3. Supported by EU contract BMH4-CT96-0819COBRAIN, and Spanish DGES-UE96-0038 and CICYT-PM950063. 565 APPROPRIATE CONTROL CONDITIONS FOR THE MISMATCH NEGATIVITY USING THE ODDBALL PARADIGM Jeffrey A. Marler and Craig A. Champlin Department of Communication Sciences and Disorders, The University of Texas at Austin, TX, USA The oddball paradigm is used to obtain an event-related potential (ERP) called the mismatch negativity (MMN). This paradigm differs from those typically used to acquire transient evoked potentials in that at least two stimuli are presented in pseudo-random order. The MMN is evoked when a low probability, acoustically different (deviant) stimulus is placed within a train of identical (standard), high probability auditory stimuli. The relative complexity of the oddball paradigm may affect the detection of valid responses, independent of the manipulated variable. The purpose of the present study was to determine which ‘control’ conditions should be considered when acquiring the MMN. Prior to obtaining the ERP data, a psychophysical test was used to determine thresholds for frequency discrimination (f + delta - f) in a group of normal adults. The ERPs were obtained using two experimental conditions and three control