- Email: [email protected]
Processing negativity in schizotypal university students
654
Abstracts
BlOt PSYCHIATRY 1996;39:500-666
"'7.5 I. P ;:;0,008) revealed an incrcas~d positivity in the N400 rJnge in the control subjcds to sentence endings (Nouns: -3.5 j.L V; Adjcctive! gerunds: -0.7j.L V). but not in schizophrenics (Nouns: -3.7 j.L V; Adjcctivel gerunds: -3.1 !J.V). P600 amplitudc W3S likewise signilicllntty larger in controls than in schizophrenics (F. 83 =' 10.22. P "'0.002; CON; 6.2 j.L V; Sz 2,9 J.L V). This difference in event-relatcd brain potenlial morphology betwecn the two groups. with a lack of positivity to sentencc endings in schizophrenics, :iUggests that this task may be sensith'e to rt deficit which is ecntrulto psychotic thinkinz. namely. the inability of schizophrenics to inhibit selection of high probilbiJity homogruph meanings by automatic processes. This effect may underlie such positive symptoms of schizophrenia as loose associutions, tangentiality and demilment. This project was supported by the McDonnell·Pllw Program in Cognitive Neuroscience and the National Alliance for Rcsearch in Schizophrenia and Depression.
523. P300 SUBCOMPONENT ABNORMALITIES IN SIBLINGS DISCORDANT FOR SCHIZOPHRENIA B. Turetskyl, E.A. Colbath', T.D. Cnnnon 2 , & R.E.Our l Departments of IPsychiatry ancl ~Psychology, University of Pennsylvania. Philadelphia. PA 19104 Reduced P300 amplitude is ~l robust physiologic marker of infonmuion pro<:essing impainnellls in schilophrenia. However. it is not clear whether this is lln index of stnlC or tmit abnormalities. We have shown ·i~hU; ':"'w . . uu~J'v.j:(C ~h.uip r33o-.;;.n . ~ dccompor,cd into d:~tinct frontill. parielal and temporal subcomponents. Schizophrcnie patients exhibit impainnenls on frontal lind left temporal :;ubcomponents, lIllIt arc ind~pcnt!ent of acute clinicul stntus and correlllted with ench other. The purietal ~ubcom~onent. in contrnsl. is abnormal only in male patients {lOd IS nSliocHlted WIth stute: measures of illness tlurulion and medication. These results suggest that frontnl ami left temporal P300 subcomponenl measures may serve as selective trait markers of inforrnillion processing deficits in schizophr~nia. Pn:vious work in our laboratory has also demonstrateLl that both schizophrllnics and their nonschizophccnie siblings nrc impaired ncuropsychologically compared to normal controls. The cognitive pcrfonnance of nonschizophrenic siblings is intcnnelliutc between thnt of the schizophrenic siblings and the nonnal controls. suggesling that informlltion processing deficits aggregme in the family ~embcrs of.schizophrenics amI may indicate gcnetic l,'ulnernbility to the tllsordcr. :1.llS study further explore.~ Ihe question of genetic tnti! marker.i, by ellammll1g P300 subcomponent amplitudes in 11 probanlls with schizophrenin. 12 of their nonschizophrenic siblings. and 23 unreinted. demographically balanced. nonnal intlivitluals. Auditory P300 ERPs were recorded from all subjecls. Current source density tl'llnsfonnations were employed to provide topogrnphicillly localized :lnd reference-free measures of the activity of frontal (P3a), parietal (P3b) anllieft nnll right temporal (P3tL and P3tR) subcomponents, Patients had abnonnally low nmplitu?es of fr.ont~t, .teft temporal nnll parietul P300 subcomponents. Nonsclllzophren,c SIblings had melln nmplituues Ihnt were intcnnediate between patients and controls on P3a and P3tL. and they could not be sll)ti~tknlly diffcrcntiatlld from their ill siblings on tllese ,wo measures. However. they were identical to nonnal controls. nnd significantly greater Ih~n their schizophrenic siblings. on the parlelnl P3b subcompo. nent amphtulle. The~e results support the hypothesis that P3a anll P3tL arc selective Irait markers (If n fronto-tempernl neural network dysfunction In schizophrenia. They further suggest thilt these markeTS, in contr:lst to the pnrietal P3b. mllY refIe.;t genetic vulnernbiHty to the disort.lcr even in the absence of lIny observable symptomatology.
524. ERPS AS A PROBE OF LANGU AGE PROCESSING DIFFICULTIES IN SCHIZOPHRENIA SPECTRUM DISORDERS M.A. Niznikiewicz, P.G. Nestor, B.F. O'Donnell, L. Seidman, C.C, Dickey, lE. Allard, R. Rhoades,
R.W. McCarley, & M.E. Shenton HilNurd Medical School. Brockton VAMC. & Massachusells Mentnl Hospital Ncuroimaging Lllooratory Abnonnal lise of language such as loose associations. tangcntinlity. and dernilmcnt have been observcd in schizophrenia and schizotypal personality disorder. Behilviornl research on language difficulties in schizophrenia spectrum disorders suggests abnonnal processes in lexical memory. ERPs provide a neuropliysiologicnl measure of lexical processing in schizophrenia disord~rs, We report a series of studies involving both schizophrenic and schizotypul subjects interprcting sentences (half of them made sens~ and half of them did not) and short. two sentence pumgraphs (in half of them. the second sentence WllS a gooLl continuation of the first one. and in half of them. it was not). Thc sentences were presented in the auditory and visual modalities. The paragraphs wer~ presented in the visual modality. In the wavefomlS recorded to the final word:; in sentences. the early components. NIOO and P200 did not differ between the schizophrenic and nonnal con Ito! groups. The N400. a component associtltcd with processcs in lexical memory. was more negmive (p < .03) ilntl iL'i peak latency (p < .001) was longer in the patient relative to the controt group in both modalities, Also. till' late positive component, P600. did not show significant group differences. The pattern of ERP abnonnalities in schizotypal subjects was similar to this fountl in schizophrcnic patients (p < .05). In the stully that involved schizOlYpU•• schizophrenic. and nomml control subjects, a highly similar pallem of results was obtained. These ERP similarities suggest similar processing uifficulties in the two clinical groups. The localization of the group differences to the N400 r~gio" suggests thallnngullgc problems in schizophrenia may be neurophysiologically related to lexical processer. indexed by the N400 rother Ih:1O to early, sensory processes, or hlle processcs inllexed by the P600. In lhe study using paragraphs, we explored the contribution of the working memory. Our preliminary re~ults intlicate that a larger memory load affects the N400 latency and amplitude in both patients and nonnal controls. The N400 llmplitud~ is more negmivc in patients suggesting that proces~cs in lexical m~mory milY be advcrsely innucnced by working memory demand~ perhaps ~f1ecling n difficulty in maintaining u verbill context for word process-
mg.
525, PROCESSING NEGATIVITY IN SCHIZOTYPAL UNIVERSITY STUDENTS
R.M. Roth, D. Milovan. & J. Baribeau Laborat~ry of.Human Neuropsychology and Neurophysiology, Concordia Umversity, Montrcnt, Quebec. H4B IR6
Disturbances in uttcntional selectivity have bcen frequently reported in schizophrcnicr. and populatioM at high-risk for schizophrenia due to 11
Abstracts
family history of the disorder. In the present invcstig3tion :l\tentionnl selectivity was evaluatcd in a putative high-risk sample of schizot)'pal university students. Subjecls consisted of High (n "" II) 3nd Low (n ;; II) schizotypals as determined by their cxtr~mc scores on the Schizotypal Personality Questionnaire (Rainc, 1991). Subjects completed a bin3urnl listening auditory sign31-deleclion task and both behavioral measures and event-related bl"'J.in pOlentials wcre recordcd. Two lechniques were used to score altentional selectivity effects on the ERP: peak picking of the early (Nde: 80-200 msec) and late (Ndl: 200 -500 msec) components of the negative difference (Nd) wavc (e.g. Woods 1990) and avernging epochs of data points over the temporal length of the Nd Wave (e.g. Michie et aI1991). Amplitude of thc processing negativity (PN) was measured from the Nd wavc over successive 100 msee epochs from 200 10 500 msec post-stimulus onset at Fz and Cz. ANOVA failed to re\'eal any group differences on either the behavioral measures (reaclion time. number of hits and false alarms). or amplitude diffcrences using either scoring technique. These findings contrast with previous observtltions of smaller amplitudc late PN in schizophrenics. Smaller P3b. and larger N2 and laIc slow negativity to task-relevant stimuli. previously observed in schizotypals (Roth, 1993), are thus unlikely to be due to an inability to maintain :mcntionul focus.
526. MECHANISMS OF AUDITORY WORKING MEMORY DYSFUNCTION IN SCHIZOPHRENIA A.M. Shelley!, D.C. Javitt2 , & H.G. Vaughan, Jr.' I Albeit Einstein College of Mcdicine. Bronx. NY 10461: 2Nulhun Kline hlstitote for Psychiatric Research. Onmgeburg, NY 10962
Schizophrenics show severe abnormaHties of working memory system!!. but whether deficits reflect imp3ired in itial encoding, or prcm31ure decllY of llccurately encoded information. remains unknown. An event-relntell pOlcnti31 (ERP) index of auditory working memory is mismatch negativity (MMN). elicited in the 'oddball' purndigm, whenever a sequence of frequent repetitive standard stimuli is interruptcll by an infrequent. physically devicmt 'oddball' stimulus. Recent studics have dcmonstrolted that MMN amplitude is reduced significantly in schizophrenics (Shelley et al 1991. Javitt et al 1993), MMN is ideal for addressing whether workins memory impairments arc due to abnonnul encoding or premature lraee decay. PnrJmetric work in nonnal subjects liaS estnblished that MMN 3mplitude increnses both 3S the probability of deviants decreases and ns lSI decreases. By vurying the probability of the deviant. MMN :Jmplitude can pro\'ide an index of initial encOlling. and by varying the lSI between standards. MMN amplilude can provide an index of 3uditory memory trace dec:!y over time. This study ellnmines MMN differences betwecn chronic schizophrenic patients and normal controls when stimuli lJlocks arc varied systematically, with the probability of dcvi3nt stimuli 25%. 10%, 5% and 2. 5%. Dnd the lSI between standard stimuli 250ms, SOOrns. IODOms lind JOOOms. If lIudiiory working memory deficit!! in schizophrenia llre due to abnormal initial encoding, MMN umplitude differences between groups will be a function of deviant prob3bility and maxi mal as deviant probabi Iity decreases. If deficits are due to abnormal lrace decay. MMN amplitude differences will be n function of lSI lind maXimlllll!! 151 increases. Results urc discussed.
BIOI.. PSYCIUATRY 1996;39:500-666
655
527. ERP MEASURES OF VISUAL SPATIAL PROCESSING IN SCHIZOPHRENIA B.F. O'Donnell, H. Ohta, R.W. McCarley, H. Hokama, M.E. Karapelou, & S.E. Law Depanment of Psychiatry. Brocklon VAMC. Drockton MA 02401 & Harvard Medical School, Boston, MA Bchaviornl evidence suggests that patienls with schizophrenia have n deficit in the analysis of spatial position or nlovement, but the tcmporal stage of processing in which this (/el1cit appears is unknown. Visu31 event-related potentials (ERPs) recorded during a spatiallocaliu1\ion task were uscd to invesligate spatial processing in twelve male medicated schizophrenic patients and twelve age and gender matched controls. Four line segments were used as visual stimuli, presented on Ihe central right. cenlralleft. pcriphcml right and pcriphcmlleft of .. CRT screen (IS[:=: 1.2 s). EEG was recorded from 28 electrode sites referenced to the left earlobe. ERPs were recorded dllring a simple rcaction time ta.~k. when subjects responded to nil stimuli; and during discrimination t:lsks. when subjects respondcd to either central or pcriphcl"J.I infrequent (16%) target stimuli. The NI (150-210 ms). NZ (240-280 ms) and P3 (300-650 ms) components in the averaged ERPs were measured from peak vohnges at midline lind lateral electrode sites. N I amplitude to tnrget and nontarget stimuli was reduced in patients when a discrimination was required (p < .05). bUI did not diffcr from control subjccts lluring the simple reaction· time task. Patienls showed an allenuated Nlover the left compared to right later-II eleetroUe sites to right peripheral tarsct stimuli (diagnosis X visual field X hemisphere X electrode: p < ,005). N2 amplitude to the central (p < .001) but not pcripher'J.1 larget stimuli Wlt~ reduceu in schizophrenic putients. P3 amplitude did not differ between groups. Ancmional processes involved in spatiallocalizulion, indexed by the NI and N2 components, were affected by schizophrenia. The NI abnonnality was most scvere for target stimuli presented in the right visu31 field. suggesting more severe disturbance of left hemisphere visual processing.
528. VISUAL MEMORY DEFICITS IN SCHIZOPHRENIA: MEDICATION AND ERP CORRELATES E.F. Rabinowicz l •2 , R.A. Knight3 , G. Brudcr'·2, D.R. Owen4 , & J. Gonnan l •2 INew York State Psychiatric Institulc, New York, NY 10032; 2Columbia University, Ncw York. NY 10032: JBranueis University, Waltham, MA 62154, 4BrooklynCollege, Brooklyn, NY 11210 In a previous study the p:lIlem of pcrfonnMce on the Dot Enum~ration Perceptual Organization Task (DEPOT), n paradigm we developed to 3S!;eSS numerosity lind form lliscriminations of the sume perceptual stimuli. strongly susgested (/eficits in the Shorl Term Visual Memory (STVM) of patients with schizophrenia. The pre~ent study sought to determin~ the effects of medication status (j,e••on haloperidol, clozapine. or medication wilhdrawn) on DEPOT pcrfonnance. A new stlmple of subjects (N::::l7J:28 pOlients with schizophrenia. 9 with schizoaffective disorder and 36 nonpsychiatric controls) was lldmini!!tered DEPOT. A subsample (18 schizophrenic patients, 3 5chi7.0affcctive patients) were tested both on anll off haloperidol. Eight schizophrenic patienls were compared 011 haloperidol vs c1ozapine. At! critical findings on DEPOT corroboroted our original study. TIle lack of Q main medic3tion effect or
Abstracts
BlOt PSYCHIATRY 1996;39:500-666
"'7.5 I. P ;:;0,008) revealed an incrcas~d positivity in the N400 rJnge in the control subjcds to sentence endings (Nouns: -3.5 j.L V; Adjcctive! gerunds: -0.7j.L V). but not in schizophrenics (Nouns: -3.7 j.L V; Adjcctivel gerunds: -3.1 !J.V). P600 amplitudc W3S likewise signilicllntty larger in controls than in schizophrenics (F. 83 =' 10.22. P "'0.002; CON; 6.2 j.L V; Sz 2,9 J.L V). This difference in event-relatcd brain potenlial morphology betwecn the two groups. with a lack of positivity to sentencc endings in schizophrenics, :iUggests that this task may be sensith'e to rt deficit which is ecntrulto psychotic thinkinz. namely. the inability of schizophrenics to inhibit selection of high probilbiJity homogruph meanings by automatic processes. This effect may underlie such positive symptoms of schizophrenia as loose associutions, tangentiality and demilment. This project was supported by the McDonnell·Pllw Program in Cognitive Neuroscience and the National Alliance for Rcsearch in Schizophrenia and Depression.
523. P300 SUBCOMPONENT ABNORMALITIES IN SIBLINGS DISCORDANT FOR SCHIZOPHRENIA B. Turetskyl, E.A. Colbath', T.D. Cnnnon 2 , & R.E.Our l Departments of IPsychiatry ancl ~Psychology, University of Pennsylvania. Philadelphia. PA 19104 Reduced P300 amplitude is ~l robust physiologic marker of infonmuion pro<:essing impainnellls in schilophrenia. However. it is not clear whether this is lln index of stnlC or tmit abnormalities. We have shown ·i~hU; ':"'w . . uu~J'v.j:(C ~h.uip r33o-.;;.n . ~ dccompor,cd into d:~tinct frontill. parielal and temporal subcomponents. Schizophrcnie patients exhibit impainnenls on frontal lind left temporal :;ubcomponents, lIllIt arc ind~pcnt!ent of acute clinicul stntus and correlllted with ench other. The purietal ~ubcom~onent. in contrnsl. is abnormal only in male patients {lOd IS nSliocHlted WIth stute: measures of illness tlurulion and medication. These results suggest that frontnl ami left temporal P300 subcomponenl measures may serve as selective trait markers of inforrnillion processing deficits in schizophr~nia. Pn:vious work in our laboratory has also demonstrateLl that both schizophrllnics and their nonschizophccnie siblings nrc impaired ncuropsychologically compared to normal controls. The cognitive pcrfonnance of nonschizophrenic siblings is intcnnelliutc between thnt of the schizophrenic siblings and the nonnal controls. suggesling that informlltion processing deficits aggregme in the family ~embcrs of.schizophrenics amI may indicate gcnetic l,'ulnernbility to the tllsordcr. :1.llS study further explore.~ Ihe question of genetic tnti! marker.i, by ellammll1g P300 subcomponent amplitudes in 11 probanlls with schizophrenin. 12 of their nonschizophrenic siblings. and 23 unreinted. demographically balanced. nonnal intlivitluals. Auditory P300 ERPs were recorded from all subjecls. Current source density tl'llnsfonnations were employed to provide topogrnphicillly localized :lnd reference-free measures of the activity of frontal (P3a), parietal (P3b) anllieft nnll right temporal (P3tL and P3tR) subcomponents, Patients had abnonnally low nmplitu?es of fr.ont~t, .teft temporal nnll parietul P300 subcomponents. Nonsclllzophren,c SIblings had melln nmplituues Ihnt were intcnnediate between patients and controls on P3a and P3tL. and they could not be sll)ti~tknlly diffcrcntiatlld from their ill siblings on tllese ,wo measures. However. they were identical to nonnal controls. nnd significantly greater Ih~n their schizophrenic siblings. on the parlelnl P3b subcompo. nent amphtulle. The~e results support the hypothesis that P3a anll P3tL arc selective Irait markers (If n fronto-tempernl neural network dysfunction In schizophrenia. They further suggest thilt these markeTS, in contr:lst to the pnrietal P3b. mllY refIe.;t genetic vulnernbiHty to the disort.lcr even in the absence of lIny observable symptomatology.
524. ERPS AS A PROBE OF LANGU AGE PROCESSING DIFFICULTIES IN SCHIZOPHRENIA SPECTRUM DISORDERS M.A. Niznikiewicz, P.G. Nestor, B.F. O'Donnell, L. Seidman, C.C, Dickey, lE. Allard, R. Rhoades,
R.W. McCarley, & M.E. Shenton HilNurd Medical School. Brockton VAMC. & Massachusells Mentnl Hospital Ncuroimaging Lllooratory Abnonnal lise of language such as loose associations. tangcntinlity. and dernilmcnt have been observcd in schizophrenia and schizotypal personality disorder. Behilviornl research on language difficulties in schizophrenia spectrum disorders suggests abnonnal processes in lexical memory. ERPs provide a neuropliysiologicnl measure of lexical processing in schizophrenia disord~rs, We report a series of studies involving both schizophrenic and schizotypul subjects interprcting sentences (half of them made sens~ and half of them did not) and short. two sentence pumgraphs (in half of them. the second sentence WllS a gooLl continuation of the first one. and in half of them. it was not). Thc sentences were presented in the auditory and visual modalities. The paragraphs wer~ presented in the visual modality. In the wavefomlS recorded to the final word:; in sentences. the early components. NIOO and P200 did not differ between the schizophrenic and nonnal con Ito! groups. The N400. a component associtltcd with processcs in lexical memory. was more negmive (p < .03) ilntl iL'i peak latency (p < .001) was longer in the patient relative to the controt group in both modalities, Also. till' late positive component, P600. did not show significant group differences. The pattern of ERP abnonnalities in schizotypal subjects was similar to this fountl in schizophrcnic patients (p < .05). In the stully that involved schizOlYpU•• schizophrenic. and nomml control subjects, a highly similar pallem of results was obtained. These ERP similarities suggest similar processing uifficulties in the two clinical groups. The localization of the group differences to the N400 r~gio" suggests thallnngullgc problems in schizophrenia may be neurophysiologically related to lexical processer. indexed by the N400 rother Ih:1O to early, sensory processes, or hlle processcs inllexed by the P600. In lhe study using paragraphs, we explored the contribution of the working memory. Our preliminary re~ults intlicate that a larger memory load affects the N400 latency and amplitude in both patients and nonnal controls. The N400 llmplitud~ is more negmivc in patients suggesting that proces~cs in lexical m~mory milY be advcrsely innucnced by working memory demand~ perhaps ~f1ecling n difficulty in maintaining u verbill context for word process-
mg.
525, PROCESSING NEGATIVITY IN SCHIZOTYPAL UNIVERSITY STUDENTS
R.M. Roth, D. Milovan. & J. Baribeau Laborat~ry of.Human Neuropsychology and Neurophysiology, Concordia Umversity, Montrcnt, Quebec. H4B IR6
Disturbances in uttcntional selectivity have bcen frequently reported in schizophrcnicr. and populatioM at high-risk for schizophrenia due to 11
Abstracts
family history of the disorder. In the present invcstig3tion :l\tentionnl selectivity was evaluatcd in a putative high-risk sample of schizot)'pal university students. Subjecls consisted of High (n "" II) 3nd Low (n ;; II) schizotypals as determined by their cxtr~mc scores on the Schizotypal Personality Questionnaire (Rainc, 1991). Subjects completed a bin3urnl listening auditory sign31-deleclion task and both behavioral measures and event-related bl"'J.in pOlentials wcre recordcd. Two lechniques were used to score altentional selectivity effects on the ERP: peak picking of the early (Nde: 80-200 msec) and late (Ndl: 200 -500 msec) components of the negative difference (Nd) wavc (e.g. Woods 1990) and avernging epochs of data points over the temporal length of the Nd Wave (e.g. Michie et aI1991). Amplitude of thc processing negativity (PN) was measured from the Nd wavc over successive 100 msee epochs from 200 10 500 msec post-stimulus onset at Fz and Cz. ANOVA failed to re\'eal any group differences on either the behavioral measures (reaclion time. number of hits and false alarms). or amplitude diffcrences using either scoring technique. These findings contrast with previous observtltions of smaller amplitudc late PN in schizophrenics. Smaller P3b. and larger N2 and laIc slow negativity to task-relevant stimuli. previously observed in schizotypals (Roth, 1993), are thus unlikely to be due to an inability to maintain :mcntionul focus.
526. MECHANISMS OF AUDITORY WORKING MEMORY DYSFUNCTION IN SCHIZOPHRENIA A.M. Shelley!, D.C. Javitt2 , & H.G. Vaughan, Jr.' I Albeit Einstein College of Mcdicine. Bronx. NY 10461: 2Nulhun Kline hlstitote for Psychiatric Research. Onmgeburg, NY 10962
Schizophrenics show severe abnormaHties of working memory system!!. but whether deficits reflect imp3ired in itial encoding, or prcm31ure decllY of llccurately encoded information. remains unknown. An event-relntell pOlcnti31 (ERP) index of auditory working memory is mismatch negativity (MMN). elicited in the 'oddball' purndigm, whenever a sequence of frequent repetitive standard stimuli is interruptcll by an infrequent. physically devicmt 'oddball' stimulus. Recent studics have dcmonstrolted that MMN amplitude is reduced significantly in schizophrenics (Shelley et al 1991. Javitt et al 1993), MMN is ideal for addressing whether workins memory impairments arc due to abnonnul encoding or premature lraee decay. PnrJmetric work in nonnal subjects liaS estnblished that MMN 3mplitude increnses both 3S the probability of deviants decreases and ns lSI decreases. By vurying the probability of the deviant. MMN :Jmplitude can pro\'ide an index of initial encOlling. and by varying the lSI between standards. MMN amplilude can provide an index of 3uditory memory trace dec:!y over time. This study ellnmines MMN differences betwecn chronic schizophrenic patients and normal controls when stimuli lJlocks arc varied systematically, with the probability of dcvi3nt stimuli 25%. 10%, 5% and 2. 5%. Dnd the lSI between standard stimuli 250ms, SOOrns. IODOms lind JOOOms. If lIudiiory working memory deficit!! in schizophrenia llre due to abnormal initial encoding, MMN umplitude differences between groups will be a function of deviant prob3bility and maxi mal as deviant probabi Iity decreases. If deficits are due to abnormal lrace decay. MMN amplitude differences will be n function of lSI lind maXimlllll!! 151 increases. Results urc discussed.
BIOI.. PSYCIUATRY 1996;39:500-666
655
527. ERP MEASURES OF VISUAL SPATIAL PROCESSING IN SCHIZOPHRENIA B.F. O'Donnell, H. Ohta, R.W. McCarley, H. Hokama, M.E. Karapelou, & S.E. Law Depanment of Psychiatry. Brocklon VAMC. Drockton MA 02401 & Harvard Medical School, Boston, MA Bchaviornl evidence suggests that patienls with schizophrenia have n deficit in the analysis of spatial position or nlovement, but the tcmporal stage of processing in which this (/el1cit appears is unknown. Visu31 event-related potentials (ERPs) recorded during a spatiallocaliu1\ion task were uscd to invesligate spatial processing in twelve male medicated schizophrenic patients and twelve age and gender matched controls. Four line segments were used as visual stimuli, presented on Ihe central right. cenlralleft. pcriphcml right and pcriphcmlleft of .. CRT screen (IS[:=: 1.2 s). EEG was recorded from 28 electrode sites referenced to the left earlobe. ERPs were recorded dllring a simple rcaction time ta.~k. when subjects responded to nil stimuli; and during discrimination t:lsks. when subjects respondcd to either central or pcriphcl"J.I infrequent (16%) target stimuli. The NI (150-210 ms). NZ (240-280 ms) and P3 (300-650 ms) components in the averaged ERPs were measured from peak vohnges at midline lind lateral electrode sites. N I amplitude to tnrget and nontarget stimuli was reduced in patients when a discrimination was required (p < .05). bUI did not diffcr from control subjccts lluring the simple reaction· time task. Patienls showed an allenuated Nlover the left compared to right later-II eleetroUe sites to right peripheral tarsct stimuli (diagnosis X visual field X hemisphere X electrode: p < ,005). N2 amplitude to the central (p < .001) but not pcripher'J.1 larget stimuli Wlt~ reduceu in schizophrenic putients. P3 amplitude did not differ between groups. Ancmional processes involved in spatiallocalizulion, indexed by the NI and N2 components, were affected by schizophrenia. The NI abnonnality was most scvere for target stimuli presented in the right visu31 field. suggesting more severe disturbance of left hemisphere visual processing.
528. VISUAL MEMORY DEFICITS IN SCHIZOPHRENIA: MEDICATION AND ERP CORRELATES E.F. Rabinowicz l •2 , R.A. Knight3 , G. Brudcr'·2, D.R. Owen4 , & J. Gonnan l •2 INew York State Psychiatric Institulc, New York, NY 10032; 2Columbia University, Ncw York. NY 10032: JBranueis University, Waltham, MA 62154, 4BrooklynCollege, Brooklyn, NY 11210 In a previous study the p:lIlem of pcrfonnMce on the Dot Enum~ration Perceptual Organization Task (DEPOT), n paradigm we developed to 3S!;eSS numerosity lind form lliscriminations of the sume perceptual stimuli. strongly susgested (/eficits in the Shorl Term Visual Memory (STVM) of patients with schizophrenia. The pre~ent study sought to determin~ the effects of medication status (j,e••on haloperidol, clozapine. or medication wilhdrawn) on DEPOT pcrfonnance. A new stlmple of subjects (N::::l7J:28 pOlients with schizophrenia. 9 with schizoaffective disorder and 36 nonpsychiatric controls) was lldmini!!tered DEPOT. A subsample (18 schizophrenic patients, 3 5chi7.0affcctive patients) were tested both on anll off haloperidol. Eight schizophrenic patienls were compared 011 haloperidol vs c1ozapine. At! critical findings on DEPOT corroboroted our original study. TIle lack of Q main medic3tion effect or