Continuous-processing--related event-related potentials in children with attention deficit hyperactivity disorder

Visual information processing in children with attention deficit hyperactivity disorder (ADHD) was studied using event-related potentials recorded during two versions of the Continuous Performance Task (CPT). ADHD children made more errors, and had longer reaction times than normal children on both the single- and dual-target CPT. Event-related potential waveforms were normal in the ADHD children with reference to early processing stages, i.e., contingent negative variation, P1-N1 laterality, and processing negativities, suggesting that ADHD children did not differ in their level of preparedness or their ability to mobilize resources for target identification and categorization. With respect to later processing, P3 amplitude was reduced in the ADHD group, whereas P3 latency was longer than normal. ADHD children had a diminished late frontal negative component, suggestive of reduced involvement in postdecisional processing.

Display visual angle and attentional scanpaths on the span of apprehension task in schizophrenia

The effect of display visual angle on span of apprehension (SOA) task performance was investigated in patients with schizophrenia and nonpsychiatric individuals. Narrow and wide visual-angle presentations of 3- and 10-letter arrays were compared. Detection rates were significantly higher with narrow than wide visual angle for nonpsychiatric individuals; the performance of those with schizophrenia was stable across visual-angle conditions. Patients with schizophrenia were best discriminated from nonpsychiatric individuals in the narrow-angle, 10-letter condition. Scanpath analyses, which were based on the pattern of detection rates across different target quadrant locations, suggested that the patients with schizophrenia used a similar number and path of covert scan moves as did the controls. Hypotheses are discussed regarding which of the multiple cognitive processes tapped by the SOA task may be impaired in schizophrenia.

Pupillary responses index cognitive resource limitations

Cognitive task-evoked pupillary responses reliably index information-processing loads. However, previous studies have reported inconsistent findings regarding the nature of the pupillary response when processing demands approach or exceed available processing resources. This condition was examined in 22 normal undergraduates by using pupillometric recordings during a digit span recall task, with 5 (low load), 9 (moderate load), and 13 (excessive load) digits per string. Pupillary responses increased systematically with increased processing load (to-be-recalled digits) until the limit of available resources (memory capacity of 7 +/- 2 digits), when they reached asymptote and then declined with resource overload (> 9 digits). These findings suggest that pupillary responses increase systematically with increased processing demands that are below resource limits, change little during active processing at or near resource limits, and begin to decline when processing demands exceed available resources.

Span of apprehension deficits in older outpatients with schizophrenia

Performance on the span of apprehension task, a well-studied information processing task in schizophrenia research, was examined in 11 schizophrenia patients and 11 normal comparison participants, all over the age of 45 years. Subjects detected "T' and "F' targets in briefly-flashed arrays of 1, 6, and 12 letters on the span task. Consistent with previously reported findings in younger schizophrenia patients, the older patients detected significantly fewer targets in the larger (12-letter), but not smaller (1-, or 6-letter), arrays. The older schizophrenia patients also showed significantly slower reaction times in all array-size conditions. Neither age of onset nor duration of illness was significantly correlated with span task performance. The characteristic span of apprehension task deficit found in the older schizophrenia patients suggests that late-life schizophrenia shares a common cognitive impairment with childhood and young adulthood schizophrenia, and provides supportive evidence for a possible stable vulnerability trait deficit in schizophrenia that is independent of age of onset and duration of illness.

Display visual angle and attentional scanpaths on the span of apprehension task in schizophrenia

The effect of display visual angle on span of apprehension (SOA) task performance was investigated in patients with schizophrenia and nonpsychiatric individuals. Narrow and wide visual-angle presentations of 3- and 10-letter arrays were compared. Detection rates were significantly higher with narrow than wide visual angle for nonpsychiatric individuals; the performance of those with schizophrenia was stable across visual-angle conditions. Patients with schizophrenia were best discriminated from nonpsychiatric individuals in the narrow-angle, 10-letter condition. Scanpath analyses, which were based on the pattern of detection rates across different target quadrant locations, suggested that the patients with schizophrenia used a similar number and path of covert scan moves as did the controls. Hypotheses are discussed regarding which of the multiple cognitive processes tapped by the SOA task may be impaired in schizophrenia.

Children's color trails

Color Trails for Children was developed in response to the need for instruments which minimize cultural bias in neuropsychological testing. The test, similar in format to Trail Making, was designed to provide an evaluation of speeded visuomotor tracking while minimizing the influence of language. The present research involves two exploratory studies which examine the relationship between Color Trails for Children and Trail Making, factors that may affect performance times, and discriminant validity. Results indicate that the tests appear to measure the same neuropsychological domains, and administration of Trail Making did not significantly alter performance times on Color Trails. Increasing age and IQ were related to quicker completion time for both tests. Females were found to complete Color Trails 2 and Trail Making Part B more quickly than males in this sample. Comparison between children diagnosed with learning disabilities, attention deficits, or mild neurological conditions and a preliminary standardization sample supported the discriminant validity of Color Traits to distinguish between normal controls and children with altered neuropsychological functioning. Comparison between clinical conditions indicated that Color Trails 2 was particularly sensitive in discriminating among the groups. Although further research is needed, results suggest that Color Trails has the potential to be an effective research and clinical tool in child neuropsychological assessment.

Children with a schizophrenic disorder: neurobehavioral studies

This paper summarizes retrospective and cross-sectional neurobehavioral studies of schizophrenic children. Retrospective studies of schizophrenic children reveal that during early childhood, prior to the first onset of schizophrenic symptoms, most schizophrenic children showed delays in language acquisition and/or impairments and delays in visual-motor coordination. These impairments appear to be developmental delays rather than fixed neurobehavioral impairments, because cross-sectional studies conducted when the children are at least 10 years of age, after the first onset of psychosis, fail to detect the same deficits. The results of behavioral, cognitive/neuropsychological studies as well as the study of event-related potentials measured during performance of cognitive tasks suggests that schizophrenic children suffer from limitations in processing resources. It is argued that the developmental delays observed in schizophrenic children represent the greater time it takes them to automate certain skills. The delay in automation may reflect their limited information-processing capacity.

Persisting negative symptoms and information-processing deficits in schizophrenia: implications for subtyping

To test the hypothesis that schizophrenic patients with persisting negative symptoms have stable information-processing impairments compared with schizophrenic patients without persisting negative symptoms, 20 chronic schizophrenic outpatients were trichotomously subgrouped on the basis of the level of negative symptoms that they displayed across multiple rating periods over a 1-year period. Brief Psychiatric Rating Scale assessments of negative symptoms were used to assign subjects into either an operationally defined persisting negative symptom (PNS), transient negative symptom (TNS), or no negative symptom (NNS) subgroup. The level and pattern of these subgroups' performance on a visual information-processing task, the Span of Apprehension Test (SPAN), were compared. Although the three groups did not differ statistically in level of SPAN performance during a drug-free baseline, the PNS group had significantly poorer SPAN performance than the other two groups at the 1-year followup assessment. The SPAN performance of the TNS and NNS groups improved while the SPAN performance of the PNS group did not improve over the 1-year followup period.

Reduced attention-related negative potentials in schizophrenic adults

Event-related potentials were recorded from outpatient adult schizophrenics receiving maintenance doses of neuroleptics and from normal control subjects during performance of a reaction time task and a complex visual discrimination task, the Span of Apprehension. Difference potentials were computed to isolate endogenous activity associated with the processing demands of the Span task. Schizophrenics produce significantly less early endogenous negative activity than do normal subjects. This processing-related negativity reflects pattern matching activity to an attentional trace during the serial scan of the visual icon. We previously reported an identical reduction in processing-related negativity in childhood-onset schizophrenia, suggesting that this deficit is age independent. Both frontal contingent negative variation and an early frontal P3 were larger in the schizophrenics than in normal subjects, suggesting an inappropriate mobilization of nonspecific attentional resources. A later posterior P3 was significantly smaller in schizophrenics than in normal subjects.

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.

Information-processing deficits across childhood- and adult-onset schizophrenia

Event-related potentials were recorded for childhood- and adult-onset schizophrenia subjects performing the span of apprehension (Span) task, which is sensitive to vulnerability factors in schizophrenia. Subjects responded to the onset of the Span arrays in a reaction time condition and then responded differentially to the presence of one of two target letters in the Span condition. While neither the childhood- nor the adult-onset group exhibited abnormalities in preparatory contingent negative variation activity, both groups produced significantly less endogenous negative activity between 100 and 300 ms after Span stimulus onset than age-matched normals. This endogenous negative activity reflects attentional effort associated with serial search and stimulus identification. These results support the position that schizophrenia subjects are impaired in their ability to allocate adequate attentional resources for processing Span stimuli. Moreover, the similarity of this information-processing deficit in the two groups suggests that childhood- and adult-onset schizophrenia lie on a continuum in this regard.

Childhood-onset schizophrenia: editors' introduction

Descriptions of various psychotic symptoms in children began to appear in the psychiatric literature at about the same time as descriptions of psychotic symptoms in adults. For example, Kraepelin estimated that at least 3.5 percent of his cases of dementia praecox had onsets before age 10. The construct of "childhood schizophrenia" initially emerged from attempts to classify a broad range of psychotic children. By the late 1940s and 1950s, the diagnosis of "childhood schizophrenia" was given to many disturbed children who today would be considered to have infantile autism and other developmental disabilities. In the early 1970s infantile autism and its variants was differentiated from schizophrenia of childhood onset. These changes were incorporated in DSM-III, which returned to the practice before 1930 of diagnosing schizophrenia in children using the same criteria as for adults, with minor allowances for differences in the manifestations of these symptoms during childhood. The studies presented in this issue of Schizophrenia Bulletin use DSM-III, DSM-III-R, or ICD-9 criteria for schizophrenia.

Cognitive/neuropsychological studies of children with a schizophrenic disorder

This article summarizes a series of cognitive/neuropsychological studies of children with schizophrenia. One set of studies, which surveyed a broad range of neuropsychological functions, revealed no evidence that children with schizophrenia are consistently impaired in sensory, perceptual, or language functions. Rather, the studies showed that children with schizophrenia performed poorly on tasks requiring sensory, perceptual, and language processing that made extensive demands on information-processing capacity. A second series of studies, which examined visual information processing by manipulating the processing demands of span of apprehension tasks, yielded similar findings. The key characteristic of tasks that elicit impaired performance in children with schizophrenia is that the task makes extensive demands on processing resources. This suggests that these children have limited information-processing capacity. Three hypotheses are proposed concerning the cognitive processes that are impaired in children with schizophrenia: (1) the cognitive processes that seem to be impaired in these children are part of a more general, hierarchically organized attention system; (2) the component processes of the system are subserved by different brain structures; and (3) the structures are part of a network that includes the frontal lobe and thalamus in interaction with the reticular activating system.

Effects of attention training on information processing in schizophrenia

This study evaluated the impact of a cognitive retraining intervention designed to enhance the attention skills of schizophrenia patients. The dependent variables included measures of perceptual sensitivity and sustained vigilance derived from a visual continuous performance test, as well as visual span of apprehension and world-list recall. Sixteen subjects received approximately 15 hours of repeated practice with computer-mediated vigilance tasks. Seventeen subjects were assigned to a no-treatment control group. All subjects were rated on measures of negative and positive symptoms before treatment. Despite improved performance on the training tasks, no significant changes on the outcome measures were observed following treatment. Thus, it is suggested that cognitive rehabilitation interventions with schizophrenia patients stress the teaching of behavioral strategies that bypass deficits, rather than remediating deficiencies in basic abilities, such as attention.

Event-related potentials in high-functioning adult autistics: linguistic and nonlinguistic visual information processing tasks

Event-related potentials (ERPs) were recorded from high-functioning adult autistics and age- and IQ-matched normal controls during performance of two non-linguistic information processing tasks, the Continuous Performance Task (CPT) and Span of Apprehension (SPAN), and an Idiom Recognition Task (IRT) involving idiomatic, literal and nonsense phrases. The autistics exhibited behavioral deficits only when attempting to identify idiomatic phrases. The ERP correlate of that deficit was greatly reduced N400 to idioms. In addition, autistics produced larger N1 amplitudes in all tasks, and larger P3s in the IRT and CPT.

Preliminary associations between motor procedural learning, basal ganglia T2 relaxation times, and tardive dyskinesia in schizophrenia

The hypothesis that the caudate nucleus is involved in the pathophysiology of tardive dyskinesia (TD) in schizophrenia was investigated by examining motor procedural learning on the pursuit rotor task and basal ganglia T2 relaxation times (T2) determined using magnetic resonance imaging (MRI). Increased severity of TD was associated with shortened caudate T2 and decreased motor learning. Motor-learning scores of schizophrenic patients with and without TD did not differ significantly from those of normal control subjects, but motor learning in the schizophrenic patients correlated with caudate T2. The results suggest that a corticocaudate system subserves motor procedural learning and provide converging evidence from neuropsychological and MRI measures suggesting caudate involvement in TD.

Span of apprehension in schizophrenic patients as a function of distractor masking and laterality

Twenty schizophrenic patients, 10 depressed control patients, and 20 normal control subjects were compared in a forced-choice, target-detection method for assessing the span of apprehension. The detection task required the subject to report which of 2 target letters was presented among 7 other (distractor) letters. Performance accuracy was examined as a function of target location and whether the distractor letters were masked after their presentation. The backward masking of the distractors improved target-detection accuracy of both control groups but reduced accuracy of the schizophrenic group. In addition, schizophrenics performed particularly poorly on targets located in the left half or lower half of the display. These results suggest that response to the masking of distractors may be a new index of attentional shortcoming in schizophrenia. Various theoretical explanations for the target location findings are also discussed.

Span of apprehension in schizophrenic patients as a function of distractor masking and laterality

Twenty schizophrenic patients, 10 depressed control patients, and 20 normal control subjects were compared in a forced-choice, target-detection method for assessing the span of apprehension. The detection task required the subject to report which of 2 target letters was presented among 7 other (distractor) letters. Performance accuracy was examined as a function of target location and whether the distractor letters were masked after their presentation. The backward masking of the distractors improved target-detection accuracy of both control groups but reduced accuracy of the schizophrenic group. In addition, schizophrenics performed particularly poorly on targets located in the left half or lower half of the display. These results suggest that response to the masking of distractors may be a new index of attentional shortcoming in schizophrenia. Various theoretical explanations for the target location findings are also discussed.

Reduced attention-related negative potentials in schizophrenic children

ERPs were recorded from normal and schizophrenic children during performance of a reaction time task (RT) followed by a complex visual discrimination, the span of apprehension task (Span), sensitive to vulnerability factors in schizophrenia. Subjects responded rapidly to the onset of the visual arrays in the RT condition and differentially to the presence of 1 of 2 target letters in the Span condition. The EEG was recorded at 19 scalp sites and ERPs included activity 1 sec before through 1 sec after Span array onset. Difference potentials (Span-RT) were computed to remove unvarying exogenous activity, thus isolating endogenous activity associated with the processing demands of the Span task. When RT and Span task ERPs are compared, schizophrenic children produced a significantly smaller than normal increment in endogenous negative activity. This endogenous negativity differed in its topography and time course from the exogenous components (P1, N1 and P2), and most likely reflects attentional effort associated with serial search, pattern recognition and stimulus identification. We believe that the current results support the position that schizophrenics are impaired in their ability to allocate adequate attentional resources for the processing of the Span stimuli. It is important to note that this deficit is apparent quite early in discriminative processing.

Interrater reliability of the Structured Clinical Interview for DSM-III-R, Axis II: schizophrenia spectrum and affective spectrum disorders

Three interviewers (second raters) blindly rated 15 audiotapes each of the Structured Clinical Interview for DSM-III-R, Axis II (SCID-II) administered to the first degree relatives of probands with either DSM-III-R schizophrenia, schizoaffective disorder, or bipolar disorder, for a total of 45 second ratings. Interrater reliability was determined using the intraclass correlation coefficient and ranged from 0.60 to 0.84. The previous studies of the reliability of structured interviews for diagnosing personality disorders are summarized and compared to the present findings. We conclude that the SCID-II can be reliably used to diagnose schizophrenia-spectrum and affective spectrum disorders in the first degree family members of probands with schizophrenic or bipolar affective disorders.

Behavior problems and adaptive functioning in children with mild and severe closed head injury

Assessed behavior problems and adaptive functioning in children with mild or severe closed head injuries, on average more than 2 years postaccident. To ensure that any problems detected in the present study were not merely preexisting problems, potential subjects were excluded if there was a history of preexisting CNS damage, significant developmental delay, or behavior problems. Children with severe head injuries had an excessive rate of behavior problems and impaired adaptive functioning. Children with mild head injuries also had an excessive rate of behavior problems (comparable to that of children with severe head injuries) but did not have impaired adaptive functioning. Results are discussed in terms of six alternative ways brain injury and behavior problems can be related functionally.

Genetic factors for the span of apprehension test: a study of normal twins

The Partial Report Span of Apprehension test has been found to detect cognitive deficits in some first degree relatives of schizophrenic patients. To assess the relative contribution of genetic vs. environmental factors on this measure, 19 monozygotic and 14 dizygotic female twin pairs, selected from a normal population, were tested on the Span of Apprehension test and an IQ test. Both Span of Apprehension test performance and IQ score had high heritabilities: 0.65 and 0.71, respectively. The mode of transmission for performance on the Span of Apprehension test appears to operate in a nonadditive manner. A multivariate behavioral-genetic model applied to the Span of Apprehension and IQ measures indicated that slightly less than half of the genetic effects important for the Span of Apprehension test are found in common with the genetic factors important for IQ. The phenotypic correlation between the Span of Apprehension and IQ measures can be attributed entirely to genetic factors. The influence of unique genetic components in the performance of the Span of Apprehension test in the general population heightens the promise of this measure as a genetic marker for schizophrenia.

Controlled information processing resources and the development of automatic detection responses in schizophrenia

The relation between resource limitations and the type of processing (automatic vs. controlled) on a multiple-frame search task (MFST) was examined in 15 schizophrenic and 15 normal control subjects. After 320 trials of consistently mapped practice, the patients' detection accuracy was normalized, and the effect of processing load (letter array size) on their detection accuracy was eliminated, which suggests automatization. Changes in load effects with practice could not be used as an index of automatization in control subjects, because of their unexpected lack of load effects at the beginning of practice. In a dual-task (MFST during auditory shadowing) condition after MFST practice, patients' MFST accuracy deteriorated nonsignificantly, and patients' shadowing declined significantly. The findings suggest schizophrenics have reduced available processing resources, but research is needed to determine whether this is due to abnormal automatization.