Faculty Bibliography

Because of the frequent association of cerebellar structural defects with schizophrenia, the authors reanalyzed the metabolic brain images of patients with chronic schizophrenia to assess if they had abnormalities in cerebellar metabolism. They used carbon-11-2-deoxyglucose and positron emission tomography to study 18 medicated patients with chronic schizophrenia and 12 normal comparison subjects. Patients with schizophrenia showed significantly lower absolute and relative metabolism in the cerebellum than normal subjects

A dysfunction of pursuit eye tracking in psychiatric patients has been well documented, but its cause has not. Recent speculation implicates a pathological disinhibition of saccades in these patients. However, great variability in tracking performance was found among nine normal subjects, and tracking quality improved in each when asked to perform a simple analysis of the tracking target: saccade counts and amplitudes decreased, as did a root-mean-square (RMS) error measure of overall tracking performance. This improvement was as great at the end as at the beginning of the analysis condition, suggesting that the improvement is not due to increased attention to a novel task, but rather is the preferred mode of tracking automatically, while attending to target analysis. The anticipatory, purposive saccades produced in attending to the act of tracking thus can be studied as involuntary attention effects reflecting frontal lobe function, and used for diagnostic classification of attentional dysfunction.

When the eyes pursue a fixation point that sweeps across a moving background pattern, and the fixation point is suddenly made to stop, the ongoing motion of the back-ground pattern seems to accelerate to a higher velocity. Experiment I showed that this acceleration illusion is not caused by the sudden change in (i) the relative velocity between background and fixation point, (ii) the velocity of the retinal image of the background pattern, or (iii) the motion of the retinal image of the rims of the CRT screen on which the experiment was carried out. In experiment II the magnitude of the illusion was quantified. It is strongest when background and eyes move in the same direction. When they move in opposite directions it becomes less pronounced (and may disappear) with higher background velocities. The findings are explained in terms of a model proposed by the first author, in which the perception of object motion and velocity derives from the interaction between retinal slip velocity information and the brain's 'estimate' of eye velocity in space. They illustrate that the classic Aubert- Fleischl phenomenon (a stimulus seems to be moving slower when pursued with the eyes than when moving in front of stationary eyes) is a special case of a more general phenomenon: whenever we make a pursuit eye movement we underestimate the velocity of all stimuli in our visual field which happen to move in the same direction as our eyes, or which move slowly in the direction opposite to our eyes

The metabolic patterns of correlation among brain images obtained during resting conditions and during an eye tracking task were investigated in 12 controls and 18 chronic schizophrenics using positron emission tomography (PET) and deoxy[11C]glucose. Analyses of the interaction between brain regions revealed highly significant differences between groups under both test conditions. Schizophrenics showed lower correlations between anterior and posterior areas and between thalamus and cortical areas than the normals and less change between the baseline and the task than the normals. The schizophrenic subjects showed derangements in the pattern of interactions among brain areas, both under baseline and under activation as compared to the control group

Using PET VI and 11-CDG we replicated our earlier PET III and 18-FDG normal aging findings. Examination of young and old normal volunteers revealed the absence of any absolute regional age-related changes in glucose utilization. For the combined sample (N = 81) we did find evidence to suggest a relative hypofrontal change with increasing age. A strong relationship between age and ventricular size (CT) was also found. These findings suggest the preserved glucose metabolism of the resting aging brain in the presence of structural atrophic changes.

Using [11C]-deoxy-D-glucose and positron emission tomography (PET), the authors measured brain metabolism in 18 patients with chronic schizophrenia to assess which of the metabolic measures from two test conditions was more closely related to the patients' differing clinical characteristics. The two conditions were resting and activation, and an eye tracking task was used. Patients with more negative symptoms showed lower global metabolic rates and more severe hypofrontality than did the patients with fewer negative symptoms. Differences among the patients were distinguished by the task: sicker patients failed to show a metabolic activation response. These findings suggest that cerebral metabolic patterns reflect clinical characteristics of schizophrenic patients