Erik N. Ringdahl

Whole-brain dynamic CT angiography and perfusion imaging

The availability of whole brain computed tomography (CT) perfusion has expanded the opportunities for analysing the haemodynamic parameters associated with varied neurological conditions. Examples demonstrating the clinical utility of whole-brain CT perfusion imaging in selected acute and chronic ischaemic arterial neurovascular conditions are presented. Whole-brain CT perfusion enables the detection and focused haemodynamic analyses of acute and chronic arterial conditions in the central nervous system without the limitation of partial anatomical coverage of the brain.

Structure of Attention in Children with Traumatic Brain Injury

Traumatic brain injury (TBI) is a common cause of disability among children in the United States, and attention deficits are frequently observed in both the acute and chronic phases of injury. The current study investigated models of attention in children with TBI and examined differential sensitivity of various components of these attention models to the severity of the brain injury. Participants included 151 children and adolescents (mean age 12.9 years, SD = 2.6) who had suffered TBI, and 50 normal controls (mean age 12.5 years old, SD = 2.2). All children were administered neuropsychological tests of attention as part of a comprehensive neuropsychological battery for brain injury (TBI group) or for the purposes of the current investigation (normal controls). Confirmatory factor analysis (CFA) of the attention tests indicated that a four-factor model of attention composed of Shift, Focus, Encode, and Sustain factors provided the best fit of the TBI group data. Factor scores were subsequently created and used to predict the severity of brain injury. All four factors were sensitive to TBI in that those with TBI performed significantly worse than the controls, but regression analysis indicated that only the Shift and Focus factors were significant predictors of TBI severity. These findings support the utility of a multicomponent model of attention to understand attention deficits resulting from TBI, and may be useful in determining those aspects of attention that are differentially impacted by TBI, in order to assist in assessment and rehabilitation planning.

Differential impairment of social cognition factors in bipolar disorder with and without psychotic features and schizophrenia

While it is well-established that patients with schizophrenia and bipolar disorder exhibit deficits in social cognition, few studies have separately examined bipolar disorder with and without psychotic features. The current study addressed this gap by comparing patients with bipolar disorder with (BD+) and without (BD-) psychotic features, patients with schizophrenia (SZ), and healthy controls (NC) across social cognitive measures. Principal factor analysis on five social cognition tasks extracted a two-factor structure comprised of social/emotional processing and theory of mind. Factor scores were compared among the four groups. Results identified differential patterns of impairment between the BD+ and BD- group on the social/emotional processing factor while all clinical groups performed poorer than controls on the theory of mind factor. This provides evidence that a history of psychosis should be taken into account while evaluating social cognition in patients with bipolar disorder and also raises hypotheses about the relationship between social cognition and psychosis.

Emotion perception abnormalities across sensory modalities in bipolar disorder with psychotic features and schizophrenia

Emotion perception deficits are a well-established feature of schizophrenia (SZ). Individuals with SZ have difficulty labeling emotional stimuli across auditory, visual, and audio-visual modalities and also misattribute threat towards neutral stimuli. The relationship between a history of psychosis and similar abnormalities in bipolar disorder (BD) is less clear. The current study set out to examine emotion perception across sensory modalities in a sample of 24 stabilized individuals meeting criteria for SZ, 24 remitted individuals meeting criteria for BD with psychotic features, 24 remitted individuals meeting criteria for BD without psychotic features, and 24 healthy controls. Results indicated that the bipolar with psychotic features group had intermediary performance between the SZ group and the other two groups for auditory, visual, and audio-visual items, with particularly poor performance in identifying angry stimuli. The SZ group misattributed neutral stimuli as negative when they were in visual format, but as positive when they were in auditory or audio-visual formats. The bipolar with psychotic features group had a trend towards misattributing more neutral visual stimuli as negative. These findings indicate that emotion perception deficits are present in BD with psychotic features and comparatively spared in BD without psychotic features, and that a similar bias of misattributing negative emotions to neutral visual stimuli may be present across diagnostic boundaries.

Beery-Buktenica Developmental Test of Visual-Motor Integration performance in children with traumatic brain injury and attention-deficit/hyperactivity disorder.

Evaluation of visuoconstructional abilities is a common part of clinical neuropsychological assessment, and the Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI; K. E. Beery & N. A. Beery, 2004) is often used for this purpose. However, few studies have examined its psychometric properties when used to assess children and adolescents with traumatic brain injury (TBI) or attention-deficit/hyperactivity disorder (ADHD), even though these are among the most common acquired and neurodevelopmental forms of brain dysfunction in children. This study examined the validity of VMI scores in 123 children with TBI and 65 with ADHD. The TBI and ADHD groups performed significantly worse than the standardization sample, obtaining VMI mean scores of 87.2 (SD = 13.7) and 93.5 (SD = 11.27). Previous research has noted decrements in visuoconstructional abilities in TBI but relative sparing in ADHD. To examine the criterion validity of VMI scores, the authors therefore compared these 2 groups. As anticipated, the TBI group performed significantly worse than the ADHD group, but receiver operator characteristic analysis indicated that VMI scores were poor at discriminating between groups. Nonetheless, convergent validity evidence supported interpretation of VMI scores as measuring perceptual organization in both groups. In particular, principal components analysis indicated that VMI total scores loaded with perceptual organization tests from the Wechsler Intelligence Scale for Children, 3rd ed. (WISC-III; D. Wechsler, 1997), and its highest correlation was with the WISC-III Perceptual Organization Index. Also, the VMI correlated significantly with the Grooved Pegboard test for the group with TBI. These findings suggest that VMI scores are sensitive to visuoconstructional and motor deficits in children with developmental and acquired brain dysfunction.

Auditory stream segregation impairments in schizophrenia

We used behavior and event-related potentials (ERPs) to examine auditory stream segregation in people with schizophrenia and control participants. During each trial, a context pattern was presented, consisting of low (A) and high (B) tones and silence (-) in a repeating ABA- pattern, with a frequency separation (Δf) of 3, 6, or 12 semitones. Next, a test ABA-pattern was presented that always had a 6-semitone Δf. Larger Δf during the context resulted in more perception of two streams and larger N1 and P2 ERPs, but less perception of two streams during the test pattern. These effects of Δf were smaller in schizophrenia. Individuals with schizophrenia also showed a reduced effect of prior perceptual judgments. Overall, the findings demonstrate that people with schizophrenia have abnormalities in segregating sounds. These abnormalities result from difficulties utilizing frequency cues in addition to reduced temporal context effects.

Negative symptoms in bipolar disorder and schizophrenia: A psychometric evaluation of the brief negative symptom scale across diagnostic categories

Past studies have demonstrated that the Brief Negative Symptom Scale (BNSS) has excellent psychometric properties in patients with schizophrenia. In the current study, we extended this literature by examining psychometric properties of the BNSS in outpatients diagnosed with bipolar disorder (n=46), outpatients with schizophrenia (n=50), and healthy controls (n=27). Participants completed neuropsychological testing and a clinical interview designed to assess negative, positive, disorganized, mood, and general psychiatric symptoms. Results indicated differences among the 3 groups in the severity of all BNSS items, with SZ and BD scoring higher than CN; however, SZ and BD only differed on blunted affect and alogia items, not anhedonia, avolition, or asociality. BD patients with a history of psychosis did not differ from those without a history of psychosis on negative symptom severity. The BNSS had excellent internal consistency in SZ, BD, and CN groups. Good convergent and discriminant validity was apparent in SZ and BD groups, as indicated by relationships between the BNSS and other clinical rating scales. These findings support the validity of the BNSS in broadly defined serious mental illness populations.

Comprehensive Trail Making Test Performance in Children and Adolescents With Traumatic Brain Injury

The sensitivity of the Trail Making Test to brain damage has been well-established over many years, making it one of the most commonly used tests in clinical neuropsychological evaluations. The current study examined the validity of scores from a newer version of the Trail Making Test, the Comprehensive Trail Making Test (CTMT), in children and adolescents with traumatic brain injury (TBI). Participants included 242 children and adolescents, 121 with sustained TBI and 121 normal control participants, who were matched to the individuals with TBI on age and sex. Receiver operating characteristic analysis indicated that the CTMT composite index provided the best overall classification, with a correct classification rate of 79%. Differences between the TBI and control groups remained stable across age. These findings indicate that the CTMT is sensitive to TBI and overall demonstrates classification rates that are comparable with some other versions of the Trail Making Test. Whether the CTMT will exhibit similar classification accuracy in adults with TBI and for other neurological disorders awaits further investigation.

Auditory processing deficits in bipolar disorder with and without a history of psychotic features

Auditory perception deficits have been identified in schizophrenia (SZ) and linked to dysfunction in the auditory cortex. Given that psychotic symptoms, including auditory hallucinations, are also seen in bipolar disorder (BD), it may be that individuals with BD who also exhibit psychotic symptoms demonstrate a similar impairment in auditory perception.

Preliminary evidence for reduced auditory lateral suppression in schizophrenia

BACKGROUND Well-documented auditory processing deficits such as impaired frequency discrimination and reduced suppression of auditory brain responses in schizophrenia (SZ) may contribute to abnormal auditory functioning in everyday life. Lateral suppression of non-stimulated neurons by stimulated neurons has not been extensively assessed in SZ and likely plays an important role in precise encoding of sounds. Therefore, this study evaluated whether lateral suppression of activity in auditory cortex is impaired in SZ. METHODS SZ participants and control participants watched a silent movie with subtitles while listening to trials composed of a 0.5s control stimulus (CS), a 3s filtered masking noise (FN), and a 0.5s test stimulus (TS). The CS and TS were identical on each trial and had energy corresponding to the high energy (recurrent suppression) or low energy (lateral suppression) portions of the FN. Event-related potentials were recorded and suppression was measured as the amplitude change between CS and TS. RESULTS Peak amplitudes of the auditory P2 component (160-260ms) showed reduced lateral but not recurrent suppression in SZ participants. CONCLUSIONS Reduced lateral suppression in SZ participants may lead to overlap of neuronal populations representing different auditory stimuli. Such imprecise neural representations may contribute to the difficulties SZ participants have in discriminating complex stimuli in everyday life.