Occipital Cortical Regions Research Articles

The developmental plasticity of the dopamine systems in the rodent basal ganglia

rently emphasize activation with blood flow measures. However, there is lack of data on carefully screened unmedicated patients compared to socio-demographieally balanced healthy control subjects, with reliable q~'nitative measure of resting baseline metabolism. Thus, there is still debate on whether hypofrontality exists under this condition, or whether there are lateralized abnormalities. We measured glucose utilization using mF-fluoro-deoxyglucose (FIX;) and positron emission tornography (PET) in 42 unmedicated patients and 42 socio-demographitally balanced healthy controls. Subjects were screened for medical conditions affecting brain metabolism and controls were also screened for psychopathology in first-degree relatives. Measures were obtained during a standard resting baseline condition (eyes open, ears unoccluded). MRIs were also obtained. ROls for anatomically co-registered PET images ineluded caudate, insula, globus pallidus, lenticular rtu¢leus, thalamus, parahippoeampal gyms, uncus, hippocampus, amygdala, mammiilary bodies, ant.crier a ~ pose ~rjor ¢~ngulum (subcortical regions), midfrontal, dorsolateral prefrontal, inferior frontal, orbitofrontal, rect. ! gyms, superior temporal, midtemporal, inferotemporal, parietal, sensorimotor, occipitotemporal, and occipital (cortical regions), and anterior and posterior corpus callosum, cerebellum and midbrain. Results showed a remarkable similarity of topography when regions were averaged between the two hemisphere. Indeed, the means for patients and controls were entirely overlapping. However, a laterality index (L-R) showed higher left hemispheric metabolism in patients for the superior temporal (p<,05) and mid. temporal cortex (p<,001), and lower left than right activity in thalamus and midbrain (p<.01). Thus, patients with schizophrenia have normal to. pography of resting brain activity, with no suggestion of hypofrontality. The laterality fndings indicate relatively higher left hemispheric activation in cortical regions and a reverse effect for subeortical regions. This pattern will be related to clinical and neuropsychological data.

Effects of the richness of the environment on six different cortical areas of the cat cerebral cortex

The number and size of neurons and the cortical thickness were determined in areas 17, 18, 3B, 4γ, the posteromedial lateral suprasylvian area, and the primary auditive area of cats raised in an enriched and in an impoverished environment. A significant effect on the numerical density of neurons and on the size of the neuronal nuclei can be demonstrated in areas 17 and 18. We suggest that this preferential effect on occipital cortical regions is due to a different gradient of maturation among cortical regions.

Event-related potentials, spatial orienting, and reading disabilities.

Event-related potentials (ERPs) were used to investigate the effects of visual-spatial orienting on selective neural processing in boys with learning disabilities. Twenty-seven 8-12 year old boys were classified into four groups depending on whether or not they had a reading disability or attention deficit disorder. Event-related potentials were recorded over the left and right occipital, central, and frontal cortical regions. The behavioral task required the subjects 1) to rapidly switch their attention from the center to the periphery of the visual field (spatial component), and 2) to selectively respond to a target versus a nontarget flash when the target was presented in the relevant visual field (nonspatial component). The amplitude of two ERP components was enhanced in response to relevant as compared to irrelevant stimuli. The enhancement of an early negative occipital-central component, which peaked 180-200 ms following targets (N1), indicated that selective neural processing associated with spatial attention could be switched in 600 ms. This enhancement of N1 was greater in boys with than without a reading disability, which implies that reading disability is associated with enhanced spatial attention. The enhancement of a later positive component, which peaked 300-340 ms following targets (P3), suggested that nonspatial target selection was reduced in boys with a reading disability, particularly over the left occipital hemisphere. Target relevance and reading disability also influenced trial-to-trial variability in the ERP waveform. The effects of reading disability on event-related potentials did not vary as a function of attention deficit disorder, indicating that these two disorders are distinct.

Positron emission tomography study of human brain functional development.

From over 100 children studied with 2-deoxy-2[18F]fluoro-D-glucose and positron emission tomography we selected 29 children (aged 5 days to 15.1 years) who had suffered transient neurological events not significantly affecting normal neurodevelopment. These 29 children were reasonably representative of normal children and provided an otherwise unobtainable population in which to study developmental changes in local cerebral metabolic rates for glucose (lCMRGlc). In infants less than 5 weeks old lCMRGlc was highest in sensorimotor cortex, thalamus, brainstem, and cerebellar vermis. By 3 months, lCMRGlc had increased in parietal, temporal, and occipital cortices; basal ganglia; and cerebellar cortex. Frontal and dorsolateral occipital cortical regions displayed a maturational rise in lCMRGlc by approximately 6 to 8 months. Absolute values of lCMRGlc for various grey matter regions were low at birth (13 to 25 mumol/min/100 gm), and rapidly rose to reach adult values (19 to 33 mumol/min/100 gm) by 2 years. lCMRGlc continued to rise until, by 3 to 4 years, it reached values of 49 to 65 mumol/min/100 gm in most regions. These high rates were maintained until approximately 9 years, when they began to decline, and reached adult rates again by the latter part of the second decade. The highest increases of lCMRGlc over adult values occurred in cerebral cortical structures; lesser increases were seen in subcortical structures and in the cerebellum. This time course of lCMRGlc changes matches that describing the process of initial overproduction and subsequent elimination of excessive neurons, synapses, and dendritic spines known to occur in the developing brain. The determination of changing metabolic patterns accompanying normal brain development is a necessary prelude to the study of abnormal brain development with positron emission tomography.

Visual event-related potentials to colored patterns and color names: Attention to features and dimension

Four right-handed males and 4 right-handed females were instructed to match pairs of stimuli (colored flashes with either colored patterns or color names) presented sequentially to the central retina. Subjects were to respond to the second stimulus of a pair when it matched the first stimulus in terms of (1) sensory color or (2) word meaning. ERPs recorded from the second stimulus of a pair over occipital and frontal cortical regions indicate the following: (1) Interdimension effects reflect an early and more global discrimination process between colored patterns and word patterns per se. The source of this effect appears to be localized in occipital cortical regions. (2) Intradimension effects were evident later in time and reflect a more refined discrimination process between particular features within a dimension rather than between dimensions. The intradimension color effect began earlier in time than the word effect (229 msec versus 318 msec in the occipital data) and appears to be localized in posterior temporal regions. The onset of the word effect appears to have two neural generators: an early effect localized in frontal regions (274 msec) and a later effect localized in occipital regions (318 msec). The hierarchical model of language processing seems to hold true predominantly in posterior cortical regions. Effects associated with linguistic processing were evident in frontal regions before effects were noted in the occipital regions. This result suggests that either: (1) word information is processed simultaneously and independently in the different regions, or (2) anterior regions feedback onto posterior regions and, therefore, influence the processing in this region.

The pattern of cortical projections from the intermediate parts of the magnocellular nucleus basalis in the rat demonstrated by tracing with Phaseolus vulgaris-leucoagglutinin

The pattern and distribution of the cortical projections from intermediate parts of the cholinergic basal magnocellular nucleus were studied by anterogradely transported Phaseolus vulgaris-leucoagglutinin. This immunocytochemical tracing technique reveals the detailed morphology and distibution of efferents from this intermediate area in the nucleus basalis to the various areas and layers of cortex and amygdala. Major projections with a relatively high density of terminal boutons were found in layers I, II and VI of the frontal cortex, in layers V and VI of parietal and temporal areas, in the entire perirhinal and entorhinal cortices, and in the basolateral nucleus of the amygdaloid body. From the nucleus basalis area studied, few if any projections could be demonstrated to cingulate and occipital cortical regions.

The oldest primate endocast.

AbstractThe endocranial cast of Tetonius homunculus, a 55 million year old tarsioid primate, is primitive in having relatively large olfactory bulbs and small frontal lobes, but remarkably advanced for an Early Eocene mammal in its voluminous occipital and temporal lobes. Expansion of occipital and temporal cortical regions of the brain suggests improvement in visual and auditory function, which may have been an important factor in the Early Eocene radiation of the primates.