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PubMed1987

Electrophysiological and behavioral correlates of psychomotor responsivity in depression.

Psychomotor retardation is a frequently observed clinical feature of depressive states. This study attempted to assess the relationship between response slowness and central nervous system (CNS) activity by examining cortical evoked potentials (EPs) during psychomotor task performance. Patients consisted of 21 women who met Research Diagnostic Criteria (RDC) and exhibited a minimum Hamilton Rating Scale for Depression score of 18 at the end of a drug washout period, the scheduled time of testing. The same number of normal women with no history of psychiatric illness were employed as controls. Cortical EPs from Cz and integrated electromyogram (EMG) from the dominant forearm extensor were recorded and time-locked to warning and imperative stimuli of a standard, two-choice, fixed foreperiod reaction time (RT) task, which yielded behavioral measures of decision time (DT) and movement time (MT). Analysis focused on behavioral RTs, latency and amplitudes of EMG, sensory and slow cortical (CNV) EPs, and measures of input time (IPT), central processing time (CPT), and motor execution time (MET), derived from combinations of EP and EMG peak latencies. Patients exhibited slower DT and MT response times, delayed EMG latencies, and attenuated EP amplitudes. The derived CPT measure was also significantly longer in patients. These findings support the view that a central dysfunction is implicated in psychomotor retardation, and the results are discussed in relation to information processing theory.

Adult↗
PubMed1990

Event-related potential correlates of impaired attention in schizophrenic children.

Electrophysiological correlates of focused attention were studied in 13 schizophrenic and 19 age- and gender-matched children. Subjects performed a version of the Continuous Performance Task (CPT) in which a target was designated as any digit from 0 through 9 occurring on two successive stimulus presentations. Signal digits were surrounded by distractor digits which varied in position, value, and number. Event-related potentials (ERPs) elicited by each stimulus of a target pair were recorded from midline and homologous parietal, temporal, and occipital electrode placements. Schizophrenic children made significantly more errors of omission and commission than normal children. The amplitude and time course of the intertrial CNV was the same for both groups. There was a circumscribed amplitude asymmetry, left smaller than right, for the P1/N1 and P2 measures which was greater in normal than in schizophrenic children. The P3 component was significantly larger to the second stimulus of the target pair than to the first for both groups, and larger for the normal than the schizophrenic children to both stimuli.

Arousal↗
PubMed1995

Differential impairments of selective attention due to frequency and duration of cannabis use.

The evidence for long-term cognitive impairments associated with chronic use of cannabis has been inconclusive. We report the results of a brain event-related potential (ERP) study of selective attention in long-term cannabis users in the unintoxicated state. Two ERP measures known to reflect distinct components of attention were found to be affected differentially by duration and frequency of cannabis use. The ability to focus attention and filter out irrelevant information, measured by frontal processing negativity to irrelevant stimuli, was impaired progressively with the number of years of use but was unrelated to frequency of use. The speed of information processing, measured by the latency of parietal P300, was delayed significantly with increasing frequency of use but was unaffected by duration of use. The results suggest that a chronic buildup of cannabinoids produces both short- and long-term cognitive impairments.

Adolescent↗
PubMed1995

Improved event-related potential signs of selective attention after the administration of the cholecystokinin analog ceruletide in healthy persons.

Cholecystokinin (CCK) is co-localized with dopamine (DA) in neurons of the mesolimbic-frontocortical dopamine (DA) system, considered essential for the pathology of psychotic behavior and associated attention deficits. The present experiments in 13 healthy men aimed at examining the effects of the CCK analog ceruletide on attention as reflected by event-related brain potentials (ERPs). Subjects were tested according to a double-blind cross-over design on three occasions, following intravenous infusion of placebo, 0.5 microgram ceruletide, and 2.5 micrograms ceruletide. ERPs were recorded during the subject's performance on an auditory selective attention task including the concurrent presentation of frequent standard tones and infrequent deviant tones which the subject had to listen to, or to ignore. The processing negativity (PN) over frontocentral cortical areas, reflecting selective attention, was higher after ceruletide than placebo, this increase being most pronounced after the 2.5 micrograms dose (placebo -1.29 +/- 0.38 microV versus ceruletide -3.02 +/- 0.65 microV, p < .05). ERP signs of a general increase in cortical arousal after ceruletide did not reach significance. Likewise, mismatch negativity, an indicator of preattentive processing of stimulus deviance, was not significantly affected by the peptide. The results indicate that ceruletide affects human brain function primarily by improving selective attention.

Adult↗
PubMed1995

Auditory event-related brain potentials in autistic children and three different control groups.

ERPs to auditory stimuli, generated during an oddball task, were obtained in a group of autistic children and three control groups (normal, ADDH, and dyslectic children, respectively). The task included the presentation of standards, deviants, and novels and had a (between-group) passive vs. active (counting) condition. It was examined whether 1) it was possible to replicate several earlier findings, 2) autistics manifest an abnormal lateralization pattern of ERPs, 3) autistics have an abnormal mismatch negativity (MMN), and 4) differences between autistics and normals are really specific to the autistic group. The only finding that could be replicated was that autistics have a smaller A/Pcz/300. There was no evidence for abnormal lateralization or abnormal MMN; however, there was an unexpected effect of the task manipulation on the amplitude of the P3: in autistics, the occipital P3 to deviant stimuli was significantly larger in the active than in the passive condition, a finding, like the replication of the smaller A/Pcz/300, specific to the autistic group. It was suggested that the auditory occipital task effect is related to understimulation of the occipital lobe by visual stimuli in autistic children.

Adolescent↗
PubMed1994

Continuous-processing related ERPS in schizophrenic and normal children.

The continuous performance task (CPT) has proven to be sensitive to schizophrenic impairments. Multichannel event-related potential (ERP) data were recorded from schizophrenic and normal children during performance of easy and hard versions of the CPT. Schizophrenics produced fewer hits, more false alarms, and prolonged reaction times. Poor performance in schizophrenics was associated with four ERP abnormalities: (1) Schizophrenics did not exhibit the normal increase in amplitude of an early-onset, processing-related negativity from nontarget to target stimuli, suggesting a failure to appropriately allocate attentional resources to discriminative processing. (2) Although P3 amplitude to targets was not significantly smaller in schizophrenic children, the distribution of P3 amplitude between target and nontarget responses in the easy and hard versions of the CPT was abnormal, suggesting that schizophrenics differed in the strategic allocation of resources in later stages of CPT processing. (3) In all task conditions schizophrenics showed a parietal negative component with a latency of 400 msec seen in younger, but not older normal children, suggestive of maturational lag. (4) ERP data demonstrated absence of right-lateralized P1/N1 amplitude in schizophrenic children. Taken together these data indicate that at several stages of information processing, schizophrenics are deficient in the control and strategic allocation of processing resources.

Attention↗
PubMed1994

Lateralization of the Bereitschaftspotential to the left hemisphere in patients with major depression.

Fourteen patients with major depression and 18 healthy subjects performed a Bereitschaftspotential (BP) paradigm, which required them to clench the right fist at self-paced intervals. The BP was calculated as the integrated negative amplitude from BP onset to movement onset. The latter was defined by recording the electromyogram (EMG) from the right forearm. To evaluate lateralization, the integrated BPs at C3, C4, P3, and P4 were analyzed. In depressives, a significant asymmetry of the BP to the left was found, whereas in normals the BP was nearly symmetrically distributed around the midline. Three patients were retested when clinically improved. At that time the asymmetry to the left hemisphere had nearly vanished. This asymmetry to the left hemisphere is interpreted as a cortical deactivation of the right cerebral hemisphere and seems to be a state marker of depression.

Adolescent↗