title: An initial report of a new biological marker for bipolar disorder: P85 evoked brain potential.
abstract: OBJECTIVE
  Progress toward understanding the neurobiological and genetic underpinnings of bipolar disorder has been limited by the scarcity of potential biological markers that predict its occurrence. A measure of the integrity of brain inhibitory function, sensory gating, measured using the amplitude of the evoked potential at 50 ms to the first of two paired clicks divided by the response to the second, has been characterized as a biological marker for schizophrenia. Currently, no such biological marker exists for bipolar disorder. The goal of this research was to determine how gating of an auditory brain potential at 85 ms (P85), not previously examined in sensory gating studies, differentiated control and patient groups.
  
  
  METHODS
  P50 and P85 auditory evoked potentials were collected from individuals diagnosed with schizoaffective disorder (n = 45), paranoid schizophrenia (n = 66), and bipolar I disorder (n = 42) using DSM-IV criteria and the Structured Clinical Interview for DSM-IV; and from 56 healthy controls.
  
  
  RESULTS
  The P85 gating ratio was significantly larger in the bipolar disorder group compared to each of the other groups (F(3,204) = 5.47, p = 0.001, and post-hoc tests). The P50 gating ratio was significantly larger for the schizoaffective group than for the control group (F(3,204) = 2.81, p = 0.040), but did not differ from the ratio for the schizophrenia, paranoid type (p = 0.08) and bipolar groups.
  
  
  CONCLUSIONS
  The previously unstudied P85 gating ratio may provide a new marker specific to bipolar disorder. The findings will promote further studies to investigate the unique contribution of this measure as an endophenotype.
authors.affiliation: Department of Psychiatry and Human Behavior, University of California at Irvine, Irvine, California 92868, USA. jvpatter@uci.edu
authors.forename: Julie V
authors.initials: JV
authors.lastname: Patterson
authors.forename: Curt A
authors.initials: CA
authors.lastname: Sandman
authors.forename: Alex
authors.initials: A
authors.lastname: Ring
authors.forename: Yi
authors.initials: Y
authors.lastname: Jin
authors.forename: William E
authors.initials: WE
authors.lastname: Bunney
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D018692:Antimanic Agents / Q000494:pharmacology / Q000627:therapeutic use; D015415:Biomarkers; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D018020:Lithium Compounds / Q000494:pharmacology / Q000627:therapeutic use; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D011618:Psychotic Disorders / Q000175:diagnosis / Q000503:physiopathology; D012372:ROC Curve; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012563:Schizophrenia, Paranoid / Q000175:diagnosis / Q000503:physiopathology; D055139:Sensory Gating / Q000187:drug effects / Q000502:physiology*; D013223:Statistics as Topic; D014635:Valproic Acid / Q000494:pharmacology / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D018692:Antimanic Agents; D015415:Biomarkers; D018020:Lithium Compounds; D014635:Valproic Acid