An MRI study of adolescent patients with either schizophrenia or bipolar disorder as compared to healthy control subjects.

BACKGROUND: There are few imaging studies in adolescent patients with either schizophrenia or bipolar disorder. Such studies are of interest because adolescents may have a more severe illness and neurodevelopmental events may have a greater role in their pathophysiology. METHODS: We compared 20 patients with schizophrenia and 15 patients with bipolar disorder (10 to 18 years) to 16 normal adolescents on magnetic resonance imaging (MRI) measures of intracranial volume and ventricular and sulcal enlargement. Two planned comparison contrasts were employed, one comparing the two patient groups to each other (contrast 1), and one comparing both patient groups combined to control subjects (contrast 2). RESULTS: None of the contrast 1 comparisons (schizophrenia vs bipolar) were statistically significant. Contrast 2 comparisons (control subjects vs patients) were statistically significant for intracranial volume (reduced in patients) as well as frontal and temporal sulcal size (increased in patients). CONCLUSIONS: The patient groups were not statistically significantly different from each other on any measure. The combined patient groups were different from control subjects on intracranial volume and frontal and temporal sulcal size. Also, there was evidence for ventricular enlargement, after removal of a control subject with an extreme value. These findings indicate that the same abnormalities noted in adult populations are present in adolescents.

Motion perception and aging.

The authors used a correlated motion paradigm to investigate the effects of aging and gender on motion sensitivity. In 2 experiments with a total of 50 elderly and 50 young subjects, motion thresholds were significantly higher for elderly women. The correlated motion signal, which was embedded in random motion, may have been coherent to subjects in much the same way a form is in Witkin's Embedded Figures Test (EFT). In Experiment 2, EFT scores were obtained. A significant positive relationship between motion thresholds and EFT performance was found within each age group. Although gender-related perceptual style differences may contribute to motion perception effects, the authors argue that a common neural factor contributes to performance on both the EFT and the correlated motion task.

A magnetic resonance imaging study of thalamic area in adolescent patients with either schizophrenia or bipolar disorder as compared to healthy controls.

The purpose of this study was to compare thalamic size in adolescent patients with either schizophrenia or bipolar disorder and healthy controls. T2-weighted axial magnetic resonance images were used to manually define the area of the thalamus for 20 schizophrenia patients, 15 bipolar patients and 16 normal control subjects, all of whom were adolescents. Two orthogonal planned contrasts were tested: Contrast 1, patients with schizophrenia vs. patients with bipolar disorder; and Contrast 2, both patient groups taken as a single group compared to controls. Contrast 1 was not statistically significant for right or left thalamic area. Contrast 2 was statistically significant and indicated reductions in thalamic area in the patients as compared to controls. The same pattern of results emerged after adjustment for total brain volume. Our results indicate that thalamic abnormalities reported in adult schizophrenic and bipolar patients are also observed in adolescent patients. Our findings also add to the evidence implicating the thalamus in the pathophysiology of schizophrenia and bipolar disorder.

Brain activation during silent word generation evaluated with functional MRI.

This is a study of word generation during functional MRI (fMRI). Eleven normal healthy subjects were instructed to generate words covertly, (i.e., silently) that began with particular letters. Images were acquired on a conventional 1.5T scanner at three contiguous axial planes encompassing language-related areas of the temporal and frontal lobe. The data were analyzed at the level of a Talairach box, after individually fitting the proportional Talairach grid system to each slice. The main variable of interest was the number of activated pixels within a Talairach box. Boxes with a significant increase in the proportion of activated pixels were located in three regions of the left neocortex: (1) Brodmann areas 44 and 45 in the dorsolateral frontal cortex (Broca's area), (2) areas 21 and 37 in the temporal cortex, (3) and the striate/extrastriate cortex (areas 17 & 18). The results are discussed in terms of a cognitive model of word generation and are compared, in detail, with the results of prior relevant imaging studies.

The relationship between smooth pursuit performance, motion perception and sustained visual attention in patients with schizophrenia and normal controls.

BACKGROUND: In this study, we tested the hypothesis that low smooth pursuit gain in schizophrenia is related to an abnormality in motion perception. METHODS: The subjects were 19 schizophrenics treated with clozapine and 19 controls. In addition to smooth pursuit and motion perception paradigms, sustained attention was also assessed using a continuous performance task (CPT). RESULTS: In the patient group, there was a statistically significant negative correlation between smooth pursuit gain and motion perception threshold (r = -0.60, P < 0.01). This relationship was not secondary to attention deficits as assessed by the CPT. CONCLUSIONS: Our results are consistent with the notion that the smooth pursuit gain deficit is related to a deficit in motion perception rather than in attention. Brain area V5 (also referred to as "MT' in macaque), located in the parieto-occipital region, is known to be critically important both for motion perception and gain. Thus, our results point to an abnormality in this area in schizophrenia.