Patricia M. White

ERPs in schizophrenia: Effects of antipsychotic medication.

Thirty unmedicated schizophrenics were compared to 29 age-matched controls on auditory and visual event-related brain potential (ERP) paradigms. Twenty-one of these patients were tested again after 1 week on placebo and after 4 weeks on antipsychotic medication. Before treatment, N1, N2, and P3 components of the auditory ERP were smaller in the schizophrenics than in the controls. Although visual N2 was smaller in schizophrenics, visual P3 was not. In spite of significant clinical improvement with antipsychotic treatment, amplitudes of auditory and visual N1, N2, and P3 were not significantly changed. Higher blood levels of antipsychotic medication were related to reductions in auditory P3 latency, however. In addition, higher levels of cerebrospinal fluid (CSF) MHPG (methoxyhydroxyphenylglycol) were associated with larger auditory N1s and larger auditory and visual P3s, suggesting an influence of arousal on these components in schizophrenics. In spite of this influence, reduction of the auditory P3 in schizophrenia is an enduring trait of the disease, which is not affected by antipsychotic medication or clinical improvement.

Schizophrenics have fewer and smaller P300s: A single-trial analysis

Because P300 is typically measured from an average of single trials, variations among individual trials may account for P300 amplitude reduction so often seen in patients with schizophrenia. We tested three hypotheses regarding single-trial contribution to small average P300s in schizophrenics: normal P300s are elicited on some trials and no P300s on others, all trials have consistently small P300s, or P300 latency varies over trials. Nineteen schizophrenics and 35 controls were tested on a two-tone auditory oddball event-related potential (ERP) paradigm. ERPs recorded from the parietal electrode (Pz) were subjected to a P300-screening procedure in which a 2 Hz half-sine wave template was moved across the electroencephalogram (EEG) to find the point of best fit. If, for the point of best fit, the EEG:Template covariance was greater in the signal epoch (280-600 msec) than in the noise epoch (610-930 msec), and if the EEG:Template correlation was statistically significant, the trial passed the P300-screen and was deemed to have a P300. Three types of average ERPs were constructed: Traditional Average from all good (artifact-free, correct response) trials, P300-Screen Average from all good trials that also passed the P300-screen, and Latency Adjusted Average by aligning the P300-screen trials at the latency of maximum covariance. Traditional average ERPs were significantly smaller in schizophrenics than in controls. The results of the P300-screen confirmed all three hypotheses: schizophrenics had fewer trials passing the P300-screen, smaller P300s on each trial, and P300s that were more variable in latency across trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Attentional networks reveal executive function deficits in posttraumatic stress disorder.

Executive function was assessed with the Trail Making Test (Army Individual Test Battery; M. D. Lezak, 1983), the Comprehensive Trail Making Test (C. Reynolds, 2002), and a neurocognitive measure of executive control (Attentional Network Task [ANT]; J. I. Fan, B. D. McCandliss, T. Somer, A. Raz, & M. I. Posner, 2002) in 19 undergraduates with posttraumatic stress disorder (PTSD; Posttraumatic Stress Disorder Symptom Scale-Self-Report version; E. B. Foa, D. S. Riggs, C. V. Dancu, & B. O. Rothbaum, 1993), 15 high trauma participants without PTSD, and 18 low trauma control participants. Although groups did not differ on any trail making task or on the ANT measures of alerting or orienting, PTSD participants were significantly more impaired on the ANT executive network index than were high or low trauma control participants, even when level of depressive symptoms was covaried. Previous animal research identified a relationship between dopamine and the ANT measure of executive function. Elevated PTSD symptom severity and levels of hyperarousal, reexperiencing, and avoidance-numbing were associated significantly with executive function deficits indexed by the ANT. These results indicate a potentially subtle but specific deficit in executive function and a possible relationship between PTSD symptoms and irregularities in dopamine function.

The relationship between P300 amplitude and regional gray matter volumes depends upon the attentional system engaged.

Event-related potentials (ERPs) and brain magnetic resonance images (MRIs) were acquired from 28 normal men, age 21-60 years. ERPs were recorded during 3 paradigms designed to elicit automatic or effortful attention, and a combination of both. MRI-derived measures of brain gray matter, white matter and cerebral spinal fluid (CSF) volumes were computed from frontal, parietal and temporal lobes. P300 amplitude correlated significantly with gray matter volumes but not with white matter or CSF volumes. Furthermore, the relationships between P300 amplitude and gray matter volumes reflected functional rather than direct topographical relationships: P300 recorded at Pz during automatically elicited attention correlated significantly with frontal but not parietal lobe gray matter volumes, P300 recorded during effortful attention correlated significantly with parietal but not frontal lobe gray matter volumes, and P300 recorded when both types of attention were invoked correlated significantly with both frontal and parietal gray matter volumes. Startle blinks, also elicited during automatic attention-engaging paradigms, were significantly correlated with frontal but not parietal lobe gray matter volumes. There was no evidence for a direct spatial relationship between P300 amplitude and the gray matter volumes underlying the recording electrode.

Ethnic variation in depressive symptoms in a community sample in Hawaii.

A modified CES-D was administered to a community sample of 176 European Americans (EA), 209 Native Hawaiians (NH), and 357 Japanese Americans (JA), yielding measures of depression, positive affect, depressed affect, somatic disturbance, and disturbed interpersonal relations. Positive affect was lower in JA relative to EA, consistent with findings among Native Japanese, a pattern attributed to cultural variation in emotion regulation. NH reported lower positive affect than EA, accompanied by elevated negative affect and somatic disturbance, suggesting generally higher levels of depressive symptoms. The three ethnic groups varied in mental health care usage with differing associations between depressive symptoms and experiences of stressful life events. Taken together, these results suggest ethnic variation in depressive symptoms may arise from differing cultural beliefs.

Experimental modification of P50 suppression

White and Yee (1997) found that normal suppression of the P50 component of the event-related potential was disrupted during a paired-click paradigm when nonpsychiatric subjects performed mental arithmetic (MA) problems aloud, concurrently with the presentation of auditory stimuli. In fact, the degree of disruption reflected in the P50 suppression ratio fell within the range that is typically observed in schizophrenia patients. The present study was conducted to clarify the processes that might underlie the apparent disruption of P50 suppression during performance of an oral MA task. Participants completed a series of tasks designed to examine the impact of competing cognitive activity, competing auditory stimulation, muscle activity, and acute psychological stress on P50 amplitude and P50 suppression. Results suggested that psychological stress and heightened facial muscle activity may exert modulatory effects on P50 suppression.

Attentional modulation of the P50 suppression deficit in recent-onset and chronic schizophrenia.

Schizophrenia is associated with deficits in P50 suppression to the second stimulus in a pair, a process often conceptualized as a preattentive index of sensory gating. This study assessed the malleability of the deficit by determining whether early attentional control can influence P50 gating across different phases of schizophrenia. Participants included 28 patients in the recent-onset (n = 16) or chronic (n = 12) phase of illness and 28 healthy comparison subjects. During the standard paradigm, chronic schizophrenia patients exhibited impaired P50 suppression relative to healthy subjects, whereas recent-onset schizophrenia patients were intermediate. Directing voluntary attention toward the initial stimulus yielded substantial improvements in the P50 ratio; recent-onset schizophrenia patients achieved ratio scores comparable to those of healthy participants, whereas chronic patients also improved and could no longer be distinguished clearly from the healthy comparison sample. Directing attention toward the second stimulus enhanced P50 amplitude to the second stimulus across groups, possibly because activation of the inhibitory mechanism was overridden or circumvented by task demands. Thus, P50 suppression may be primarily preattentive under standard conditions, but manipulation of early attention can exert a modulatory influence on P50, indicating that the suppression deficit is malleable in schizophrenia without pharmacological agents.

Left temporal deficit of P300 in patients with schizophrenia : effects of task

P300 is often, but not always, observed to be more reduced over left than right temporal lobes in patients with schizophrenia. The possibility that task differences contribute to the inconsistency in the literature was explored in this study. ERPs were collected from 17 right-handed men with schizophrenia (DSM-IIIR) and 11 right-handed healthy male community controls, performing three auditory oddball tasks - respond to a target tone by: (1) counting; (2) pressing a response button with the right index finger; or (3) pressing a response button with the left index finger. Although patients with schizophrenia had smaller and later P300 amplitudes than controls, they did not have smaller P300s over the left temporal scalp (T3) than over the right (T4). P300 recorded over the left (C3) and right (C4) motor cortices indicated sensitivity to responding hand, with greater negativity being associated with contralateral button pressing. Failure to find P300 asymmetry is not related to the presence or absence of a button pressing task, or the hand used for button pressing. Rather, P300 asymmetry may be related to structural neuroanatomical asymmetries.