Perimetric study of field defects in monkeys after cortical and retinal ablations

Monocular visual field defects were studied in two monkeys. In one, the macular retina was destroyed by photocoagulation, producing a central scotoma and consistent 5° eccentric fixation. In a second animal the effects of removal of macular projection area in striate cortex and subsequent photocoagulation of the macula were compared. The cortical operation produced a partial field defect, i.e. a region of diminished sensitivity but not a scotoma, which became with practice much smalle than the region of retina whose primary projection area had been ablated. A 10° eccentric fixation was observed. Following the second, retinal, operation a macular scotoma was demonstrated whose size and position corresponded closely with the area of retinal destruction as determined by photography of the fundus and later histological examination of the retina.     

Left orbital frontal activation in pathological anxiety

Twelve patients with anxiety disorder were studied with respect to regional cerebral blood flow (rCBF) using a 32-detector system with the 133 Xe inhalation technique. Measurements were taken during a rest condition and during anxiety induction. Anxiety relevant to the patient's psychological disorder was induced with a projective test, the meta-contrast technique (MCT). Increased blood flow in the orbital frontal region of the left hemisphere was observed in each of the 11 subjects who showed evidence of experiencing anxiety during the procedure. In a second study four additional anxiety patients were studied with a high-resolution (254-detector)Xe rCBF system. In addition to the anxiety and resting conditions, a neutral verbalization condition was added to control for the verbal aspects of the anxiety induction procedure. The results again showed the experience of anxiety to be accompanied by increased blood flow in the left orbital frontal region, with the patients showing this flow increase to be greater in the posterior, paralimbic, areas of the region. These results are consistent with previous suggestions of left hemisphere involvement in anxiety. They also suggest that imaging methods may allow research into what appears to be exaggerated corticolimbic activity in this disorder.     

Plasticity and functions of the orbital frontal cortex

We compare the effects of psychoactive drugs such as morphine and amphetamine on the synaptic organization of neurons in the orbital frontal (OFC) and medial frontal (mPFC) regions in the rat. Both regions are altered chronically by exposure to intermittent doses of either drug but the effects are area-dependent. For example, whereas morphine produces increased spine density in OFC but decreased spine density in mPFC. The differential response of the OFC and mPFC to drugs is paralleled by an areal-dependent effect of gonadal hormones on these regions as well: males have greater dendritic arborization in the mPFC whereas females have a greater arborization in the OFC. We also compared the effects of neonatal injury to the OFC and mPFC on cognitive, motor, and social behaviors as well as on the anatomical organization of the remaining brain. Again, there were differential effects of the treatments to the OFC and mPFC. Neonatal OFC lesions allowed virtually complete functional recovery of cognitive and motor behaviors, which was correlated with mild abnormalities in cerebral development compared to the more severe deficits and morphological sequelae following mPFC lesions at the same ages. One exception was the effect of OFC on social behavior, which was severe regardless of whether the injury was in infancy or adulthood. It is proposed that both drug-induced and developmental abnormalities in the integrity of OFC neurons may lead to deficits in social behavior or other behavioral pathologies, possibly including depression.     

Orientation and lever responding in auditory discriminations in squirrel monkeys.

Head orientation during auditory discriminations was studies in squirrel monkeys using a two-lever trial-by-trial procedure. Animals were studied using auditory discriminations based on the position of the sound and on the spectral content differences between a pure tone and a noise. After the percentage of correct responses reached asymptote, head orientation was measured using videotape recordings. Orientation occurred on virtually every trial and was under the control of the position of the sound under all conditions. Lever responding was controlled by the same parameters of the sound under some conditions, and by different parameters in others. Orientation and lever responding were correlated (a level response could be predicted from the direction of orientation) when both responses were under the control of the same parameters of the sound. The two responses were uncorrelated when they were controlled by different parameters of the sound. Orientation and lever responding were not functionally related.