Methods: We investigated the ERP to visual motion stimuli in agroup of 24 patients with the ICD 10 diagnosis of schizophrenia ofschizoaffective disorder and a matched group of healthy controls.The median age of patients was 26 years and the mean duration ofschizophrenia in the group was 7,1 years. The method for elicitingand recording event related potentials to motion visual stimulationwas described elsewhere (3). The area under curve (AUC)differences between responses to standard and deviant stimuliwere computed and their difference was used for the assessment.The global severity ratings of Schedule for the Deficit Syndrome(SDS) assessed by an experienced psychiatrist were used tocategorize patients into Deficit (N=13) and Non-deficit (N=11)subgroups. The MMN in midline and bilateral occipital leads werecompared between patients and their matched controls in Deficitand Non-deficit subgroups.Results: The significant MMN differences to controls in the midlineleads with the exception of Oz were present in the subgroup ofpatients with the severity rating greater than 1 in the severitycategorization of SDS. There were present no significant differencesfrom controls in the non-deficit subgroup, that did not score on theSDS severity rating. Significant differences in vMMN betweenseverity-defined deficit and non-deficit groups were confirmed infrontal (t=3,79; p=0.001) and central (t=2.19; p-0.0396) mid-line leads.Discussion: Visual mismatch negativity deficit in schizophrenia, inanalogy to auditory MMN deficit, is associated with poor socialfunctioning. Our data suggest that it may be linked to deficitsyndrome in schizophrenia. The visual MMN deficit in schizophre-nia may be interpreted as an index of a core cognitive dysfunctioncommon to different sensory inputs in a schizophrenia subgroup,which may be manifested by cognitive and negative symptoms andrequires different treatment approach. References: Umbricht D,Krljes S Mismatch negativity in Schizophrenia: a meta- analysisSchizophrenia Res 2005;76:320-8 Light GA, Braff DL Mismatchnegativity deficits are associated with poor functioning in schizo-phrenia patients, Archives Gen Psychiatry 2005;62:127-36 Urban A,Kremlaček J,Masopust J, Libiger J Visual mismatch negativity amongpatiens with schizophrenia, Schizophrenia Res 2008;102:320-8.

doi:10.1016/j.schres.2010.02.640

Poster 146MISMATCH NEGATIVITY TO DURATION DEVIANTS IN FIRSTEPISODE PSYCHOSIS AND IN THE PRODROME

Patricia T. Michie1,2,3, Rebbekah Atkinson1,2,3, Sally Hunt1,2,Raymond Inkpen1, Wendy Stojanov1, Sean Halpin4,Ulrich Schall1,2,3,41University of Newcastle Callaghan, NSW, Australia; 2Hunter MedicalResearch Institute Newcastle, NSW, Australia; 3Schizophrenia ResearchInstitute Sydney, NSW, Australia; 4Hunter New England Area HealthNewcastle, NSW, Australia

Background: Reduction in an early pre-attentive measure ofauditory change detection, mismatch negativity (MMN), is one ofthe most consistent findings in schizophrenia. In a recent study, ourgroup showed that a reduced MMN to changes in the duration andintensity of Background sounds is evident early in the course of theillness whereas reduced MMN to changes in the pitch of sounds isevident only in patients with longer illness duration. The aim of thisstudy was to determine whether duration MMN is also reduced infirst episode psychosis and those at ultra-high risk of developing apsychotic disorder, some of whom were in the prodromal phase.

Methods: Of 63 young adults (mean age 19+//03.4 years, 20 male)who volunteered for the study, 42 were outpatients of a mentalhealth service focussed on identifying and treating young people atrisk of developing psychosis. Of these, 12 met criteria for a firstepisode psychosis (FEP: mean age 21+//03.1 years, 6 male), andthe remaining 30 met criteria for being at ultra-high risk ofdeveloping psychosis (UHR: mean age 17+//03.4 years, 9 male).Six of the UHR group made a confirmed transition to schizophrenia(UHR-T) in the follow-up period and 20 did not (UHR-NT) with theoutcomes for 4 unknown. 21 healthy participants without apersonal history of mental illness or a first or second-degreebiological relative with a history of a psychotic disorder made upthe control group (CON: mean age 20+//02.4 years, 6 male). ERPswere recorded from Fz, Cz and the mastoids with a nose referencein to standards and deviants delivered in two separate tonesequences (ISI=600 ms), one where standards (92.5%) were50 ms and deviants 100 ms and another where the stimulusduration of standards and deviants was reversed. MMN (deviantminus standard ERP) was derived for short and long durationsounds from these 2 sequences.Results: MMN amplitude to long duration sounds was significantlyreduced in both the FEP group and the UHR group relative to CON.In addition, the peak latency of MMN was increased in the FEPgroup relative to controls. Similar results were evident for the shortduration sounds but the group differences were not as robust anddid not survive correction for group differences in mean amplitudeof standard ERPs measured over the same interval as MMN. Therewas also evidence that the P3a following MMN was reduced in theFEP and UHR groups. Although the numbers were too small in theUHR-T group for statistical comparisons, visual inspection of thedistribution of MMN across groups revealed that all of those wholater developed schizophrenia (UHR-T group) produced MMNs thatwere smaller than the median MMN amplitude of CON and werevery similar to FEP, whereas UHR-NT exhibited greater overlap withCON.Discussion: The results indicate that MMN to duration deviants isnot only reduced and delayed in first episode psychosis but is alsoreduced in those young people identified as at risk of developing apsychotic disorder and furthermore provide preliminary evidencethat reduced duration maybe a marker of the prodromal phase.

doi:10.1016/j.schres.2010.02.641

Poster 147ERP ABNORMALITIES DURING SEMANTIC PROCESSING INADOLESCENTS AT-RISK FOR PSYCHOSIS

Jennifer Murphy1, Caroline Rawdon2, Deirdre Twomey1, RichardRoche2, Mary Cannon1

1Royal College of Surgeons in Ireland Dublin, n/a, Ireland; 2NationalUniversity of Ireland, Maynooth Kildare, n/a, Ireland

Background: Self-reported psychotic-like experiences in adoles-cence are associated with a 5 to 16 fold increased risk of clinicalpsychotic disorder in adulthood. A growing body of researchsuggests similar impairments and risk factor profiles for adolescentswith psychotic symptoms and patients with schizophrenia. Adoles-cence is an important age group for studying the developmentaltrajectory to psychosis since it is during this period when firstpsychotic symptoms are most likely to appear. Language processingdeficits are among the most common clinical features of schizo-phrenia. The N400 ERP component is the most reliably identifiedindex of semantic processing with the amplitude and latency of thiscomponent being reduced in patients and also in first degree

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relatives of patients with schizophrenia and in individuals geneti-cally at-risk for schizophrenia (Guerra et al., 2009).Methods: Participants aged 11-13 years were recruited from schoolsin the North Kildare region using the 7-item Adolescent Psychotic-like Symptom Screener (APSS) (Kelleher et al., 2009) and inter-viewed using the Schedule for Affective Disorders and Schizophreniafor School-aged Children. Following the interview, 33 adolescentsunderwent EEG testing. Of these,15 were considered to be at-risk forpsychosis based on a score of two or more on the screeningquestionnaire. A comparison group of 18 adolescents who scoredone or less on the screening questionnaire comprised the comparisongroup. While recording 64-channel EEG, the participants completedthe semantic language task based on the original Kutas and HillyardN400 paradigm (Kutas and Hillyard, 1988). Participants werepresented with 66 sentences in which the last word was eithercongruous or incongruous with the preceding context. E.g. "Everyyear they held their annual dog". The task was to indicate whetherthe sentences made sense or not. Thirty-eight sentences weresemantically congruous and 28 were semantically incongruous.Results: There were no significant group differences in accuracy andreaction time on the task overall. On comparing accuracy forcongruous and incongruous sentences, there was a main effect forsentence type (p=0.0001). A multivariate ANOVA revealed sig-nificant group differences (p<0.05) in overall amplitude at FP2, andat TP10. Significant group differences (p<0.005) were also found foramplitude at TP10 on the incongruent incorrect condition,(p=.005), with the at-risk yielding larger amplitude than controls.On comparing congruent and incongruent correct responses, therewere significant group differences (p<0.05) at FP2, and significantgroup differences in the incongruent incorrect condition, with largeramplitude for controls. The laterality index revealed right lateraliza-tion for the at-risk group and left lateralization for the control group.Discussion: The results of the current study revealed significantdifferences in language processing in adolescents at-risk forpsychosis. The main effect of sentence type suggested that accuracywas reduced and reaction time was prolonged for incongruoussentences for both groups. On the task overall, the at-risk and controlgroups differed significantly in amplitude at fronto-parietal area FP2and at temporo-parietal area TP10, with controls yielding higheramplitude at FP2 and the at-risk group showing higher amplitude atTP10 during the incongruent incorrect condition. The laterality indexand the higher amplitude at TP10 for the at-risk group support thewell established literature of reduced left hemispheric lateralizationin individuals at-risk for schizophrenia on the P300 component(Bramon et al., 2008, Van der Stelt and Belger, 2005).

doi:10.1016/j.schres.2010.02.642

Poster 148CLONIDINE NORMALIZES SENSORIMOTOR GATING DEFICITS INCHRONIC PATIENTS WITH SCHIZOPHRENIA

Bob Oranje, Birte Y. GlenthojCenter for Neuropsychiatric Schizophrenia Research, Faculty of HealthSciences, Copenhagen University, University Psychiatric CenterGlostrup, Glostrup, Denmark

Background: Evidence is accumulating that cognitive deficits formcore features in schizophrenia. Several studies have shownimprovements of prefrontal cognitive function by α2-agonists inschizophrenia. In the present study it was investigated whetherclonidine (an α2-adrenoceptor agonist) could normalize sensor-imotor gating deficits in schizophrenia.

Methods: Twenty male chronic patients with schizophrenia whowere stable on their antipsychotic medication and twenty healthymale volunteers were assessed in an auditory prepulse inhibition ofthe startle reflex (PPI) paradigm on 5 occasions separated by aminimum of one week: once after oral administration of placeboand once after 25, 50 75 and 150 μg of clonidine.Results: Patients showed deficient PPI compared to the healthycontrols in the placebo condition. Dosages of 25, 50 and 75 μg ofclonidine significantly increased PPI in the patients compared toplacebo, to such a level that it was no longer significantly differentfrom the healthy controls.Discussion: Since even low dosages of clonidine added to thecurrent antipsychotic treatment of the patients were found tonormalize their PPI deficits, it suggests that α2-agonists are potentagents to normalize sensorimotor gating deficits in schizophrenia.Since sensorimotor gating deficits are thought to underlie psychoticsymptoms, these results have a potentially high clinical relevance.

doi:10.1016/j.schres.2010.02.643

Poster 149COMPARISON OF CLINICAL ROUTINE EEG AND QUANTITATIVEEEG IN FIRST EPISODE OF PSYCHOSIS AND AT-RISK MENTALSTATE INDIVIDUALS

Marlon O. Pflueger1, Ute Gschwandtner1, Ronan Zimmermann1,2,Manuela Gaggiotti2, Vitaliy Semenin2, Anita Riecher-Rössler1, PeterFuhr21Psychiatric Outpatient Clinic, University Hospital Basel, Basel,Switzerland; 2Department of Neurology, University Hospital Basel,Basel, Switzerland

Background: Intermittent focal or general pathological slow waveactivity detected in routine clinical EEG assessment is moreprevalent in patients with a first episode of psychosis (FE) andAt-Risk Mental State (ARMS) than in normal controls and helps, inconjunction with psychopathological symptoms, to correctly pre-dict a first psychotic episode in ARMS individuals. We hypothesizethat ARMS individuals and FE showing intermittent focal or generalslow wave pathology are characterized by an elevated global fieldpower density in the delta and theta range, and that this findingpredicts psychosis in ARMS individuals in a similar way as doesroutine clinical EEG assessment.Methods: EEG of 27 FE and 32 ARMS subjects were recorded underresting state conditions with eyes closed. Two blinded neurologistsanalyzed the EEGs visually for presence of focal or general slowingand epileptiform discharges. Additionally, Fast Fourier Transformwas performed utilizing Brain Vision Analyzer©. The powerspectrum was subdivided into 7 bands and was plotted accordingto the presence and absence of intermittent slow wave activity. Anoptimal range was defined in order to quantify what in clinical EEGassessment is coined as pathological slow wave activity. Logisticregression analysis was performed to predict incidence of psychosis.Results: Individuals with intermittent slow wave pathology werecharacterized by a range of increased theta activity (4 - 7 Hz) (t=-2.9;df=20.1; p=.008). This range has been derived as optimal in terms ofa maximal power difference between those with and withoutintermittent slowwave pathology and aminimal number of bins used.However, there was no power difference in this range with regard to alater onset of psychosis nor was any predictive power related to it.Discussion: Focal or general slow wave pathology in ARMSindividuals and FE is reflected by a range of increased power densityrelated to the theta band, but the increase detected in global fieldanalysis is modest due to its resticted manifestation in time and/or

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