Radioactive 2-deoxy-D-glucose incorporation into the prefrontal and premotor cortex of the monkey performing a forelimb movement

Radioactive 2-DG incorporation patterns in the mesial frontal cortex of task-performing monkeys

The pattern of radioactive 2-deoxy-D-glucose (2-DG) uptake in the rostral mesial cortex was investigated in seven hemispheres of four task-performing monkeys (a delayed-response task performed with a forelimb). A two-dimensional 2-DG map was constructed from frontal sections. Blob-like 2-DG incorporation sites (2-DG active sites) were observed in single frontal sections, e.g., in the anterior cingulate gyrus (CiG) and supplementary and primary motor cortices in the mesial surface, and around the superior precentral sulcus in the premotor area. Blob-like 2-DG incorporation sites were also observed in the medial part of the dorsal frontal cortex near the midline. However, most of these blob-like 2-DG active sites were revealed in fact not to be blobs. They formed rostrocaudally continuous streaks when they were constructed in a two-dimensional map. Streaks fused with one another in some areas, and gave off branches in other areas. These 2-DG uptake patterns were similar between the paired left and right hemispheres of three brains. It is highly probable that these 2-DG active streaks (or blobs) reflected neuronal activity related to somatomotor and/or eye movements, because the 2-DG-labeled areas included motor, premotor, supplementary motor, and possibly part of the supplementary eye fields. It is also probable that this 2-DG incorporation was related to cognitive or memory functions, because neuronal activity related to performance of a delayed-response was reported in the rostral mesial cortex and in the CiG.

The dorsomedial frontal cortex: eye and forelimb fields

This review yields three conclusions: first, the eye field as described using unit recording and electrical stimulation on behaving monkeys trained to fixate visual targets is much larger than the 4 mm2 area originally described. Second, the eye field and forelimb field share a similar neural space within the dorsomedial frontal cortex (DMFC); thus the electrophysiogical studies that have been conducted on visually guided and sensory-triggered forelimb movements must be re-evaluated, since none of these studies controlled eye movement and eye position independently. Third, a topographic map representing eye position in orbit has been discovered in the DMFC; it is proposed that this topographic map records the order of positions of the eyes and forelimbs during the acquisition of visually guided movement sequences.

Metabolic mapping of the forelimb motor system in the rat: local cerebral glucose utilization following execution of forelimb movements mainly involving proximal musculature

The present study was undertaken to establish a metabolic map of forelimb motor pathways under conditions of physiological activation. For that purpose, we used the [14C]2-deoxy-D-glucose (2-DG) method to identify forebrain and midbrain centers showing an increase in 2-DG uptake in animals trained to execute specific lever-pressing movements with the right forelimb. Following repetitive execution of these movements, principally involving proximal (shoulder, elbow, and wrist) muscles, increases in 2-DG uptake were found contralaterally in several neocortical or subcortical centers. The largest left-right differences in local cerebral glucose utilization (LCGU) were found in a central region of the sensorimotor cortex composed of the caudal part of area 3 of the frontal cortex (Fr3; p < 0.01), the intermediate part of area 1 of Fr (Fr1; p < 0.01), and the forelimb cortical area (p < 0.04). Fr3 was the brain center with the highest differences in left-right LCGU. This central region of the sensorimotor cortex seems to correspond closely to the caudal forelimb area of Neafsey et al. (1986). Intermediate left-right differences in LCGU were found (1) in the just-adjoining rostral-medial areas of the motor cortex involving the intermediate part of area 2 of Fr (Fr2; p < 0.01) and the rostral part of Fr1 (p < 0.04), and (2) in the rostral part of area 1 of the parietal cortex (Par1; p < 0.01) and the caudal part of area 2 of Par (Par2; p < 0.05), both corresponding to forelimb representation. Weak (not statistically significant) left-right differences in LCGU were found in the rostral parts of Fr2 and Fr3, in the caudal parts of Fr2 and Fr1, in the hindlimb cortical area, and in the caudal part of Par1 and the rostral part of Par2. In the remaining cortical areas (cingulate; agranular and granular retrosplenial; temporal; and occipital), there was practically no difference in left-right 2-DG uptake. In addition, increased 2-DG uptake was present contralaterally in several subcortical motor-related centers. In those centers in which a somatomotor map has been established (caudate putamen, ventral lateral and ventral posterolateral thalamic nuclei, and red nucleus), increased 2-DG uptake was found in regions corresponding to forelimb representation.(ABSTRACT TRUNCATED AT 250 WORDS)

Mode of [14C] 2-deoxy-D-glucose uptake into retrosplenial cortex and other memory-related structures of the monkey during a delayed response

Physiological studies on the monkey retrosplenial (RS) cortex have been few, and its functional role remains to be investigated. In the present study, activity of the RS cortex was investigated using radioactive 2-DG while the monkey was performing a visual tracking task with a delay (a delayed-response task) for 45 minutes. A remarkable increase in 2-DG uptake was observed equally in the left as well as in the right RS cortex. The anterior nucleus of the thalamus also showed increased 2-DG uptake. In addition, other memory-related structures (prefrontal cortex, dorsomedial nucleus of the thalamus, amygdala and hippocampus) showed a similar increase in 2-DG uptake compared to control monkeys, though their respective absolute values were different from one another. Since the RS cortex receives afferents from the anterior nucleus of the thalamus, which is one of the main nuclei of the Papez circuit, it is assumed that the RS cortex is important in memory function. Therefore, the remarkable increase in 2-DG uptake in the present study could reflect some aspects of memory or learning processes required to perform the delayed response.

Connections of area 8 with area 6 in the brain of the macaque monkey

The corticocortical connections between the arcuate area (Walker's areas 8A and 45 or Brodmann's area 8) and the premotor and supplementary motor areas (Vogts' area 6) in the brain of the macaque monkey were studied microscopically with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), which was injected into Brodmann's area 8 primarily to elucidate the projections of area 8 into area 6. In addition, in the same material, the pattern of connections between the arcuate area and area 46 of the prefrontal cortex was studied. On the basis of the findings of the present study, an anatomical cortical hierarchy for areas 8, 6, and 46 is discussed. Anterogradely labeled axon terminals and retrogradely labeled cells appeared in the premotor area, in the supplementary motor area, and in area 46 on the side of injection; sites containing labeled axon terminals also contained labeled cells. In other words, the examined connections were reciprocal. In the labeled areas, labeled terminals and cells coexisted, and most formed radial columns. However, no labeling of cells and terminals was seen in the motor area (Brodmann's area 4). After injection of WGA-HRP into area 8A, labeled terminals and cells appeared predominantly in the superior premotor area (a region of the premotor area above the arcuate spur, Vogt and Vogt's upper areas 6a alpha and 6a beta), forming one, two, or three bands of label in the anteroposterior direction, whereas labeling occurred to a lesser extent in the inferior premotor area (a region of the premotor area below the arcuate spur, Vogt and Vogt's areas 4c, lower 6a alpha and 6b). In contrast, injection of WGA-HRP into area 45 resulted in the predominant labeling of the inferior premotor area with scant labeling in the superior premotor area. In the premotor area, labeled terminals were distributed over the entire cortical depth, although few were found in the lower half of layer III, and labeled cells were distributed mainly in layer III. In area 46 of the banks of the principal sulcus in the prefrontal cortex, labeled terminals were distributed in all cortical layers or over the entire cortical depth with a lower concentration in layer IV; labeled cells were found mostly in layers III and V, with a relatively high density in layer V.

The determination of the local cerebral glucose utilization with the 2-deoxyglucose method

In the adult mammalian brain, the energy metabolism is almost entirely dependent on glucose. Furthermore, a close relationship between the energy metabolism and the functional activity could be shown. Thus, the functional activity of the brain or parts thereof can be quantified by measuring the cerebral metabolic rate for glucose. Studying in vivo the fate of a radioactive labeled analogue of glucose, the 2-deoxy-D-[1-14C]glucose, and using quantitative autoradiographic techniques, it is possible to estimate the cerebral glucose utilization of every discrete brain region. The advantage of the 2-deoxyglucose method is, that the local cerebral glucose utilization represents a "metabolic encephalography" (Sokoloff 1982).

Lowered cerebral glucose utilization in amyotrophic lateral sclerosis

Regional cerebral metabolic rates for glucose (rCMRGlc) were analyzed in 19 studies of 12 patients with amyotrophic lateral sclerosis (ALS) by positron emission tomography (PET) with [18F]2-fluoro-2-deoxy-D-glucose. In the 8 ALS patients with upper motor neuron signs, the mean cortical rCMRGlc was significantly lower than in 11 age-matched control subjects (p less than 0.01). The degree of hypometabolism correlated with the duration of the clinical signs and extended throughout the cortex and basal ganglia, but not to the cerebellum. Of the 4 such patients who had repeat PET scans, 3 demonstrated significant subsequent reduction in the rCMRGlc, corresponding to the worsening of the clinical picture. In contrast, 4 ALS patients with disease confined to lower motor neurons and 3 patients with lower motor neuron disease from old paralytic poliomyelitis had normal or near-normal rCMRGlc throughout the brain. Because histological evidence shows no generalized neuronal cell loss in the cortex of ALS patients, including in some cases the primary motor regions, the demonstration of severe generalized hypometabolism in structurally normal cortex indicates that some cortical neurons exist in a state of neuronal nonfunction, rather than cell death, and that anatomoclinical correlations may be more complex. The data also indicate that ALS with upper motor neuron involvement extends beyond the corticospinal tracts and differs in cortical function from the ALS confined to lower motor neurons or the other lower motor neuron disorders.

The functional anatomy of frontal lobe neglect in the monkey: behavioral and quantitative 2-deoxyglucose studies

A syndrome of hemisensory neglect follows damage to frontal association areas in monkeys and humans. To study the syndrome we removed frontal association cortex from the right hemisphere of macaque monkeys. After operation, behavioral testing showed conditional deficits in visual, somatosensory, and motor responses contralateral to the lesion. Brains of animals were studied with [14C]2-deoxyglucose autoradiography to evaluate functional neuroanatomical changes. Ipsilateral striatal and selected thalamic and midbrain nuclei exhibited depression of glucose utilization (10 to 60%). No consistent glucose utilization changes appeared in cortex or in primary motor or sensory pathways. Brains from unoperated control animals did not exhibit these changes, nor did brains from operated animals with behavioral recovery from neglect. We conclude that the symptoms of frontal lobe neglect in the monkey are the result of dysfunction within a widely distributed system of subcortical centers. The distribution of the dysfunction provides an explanation for some of the clinical features of neglect.

Radioactive deoxyglucose uptake into forelimb muscles in task performing monkeys

Incorporation of [14C]2-deoxy-d-glucose (2-DG) into forelimb muscles of task-performing monkeys was studied. Extensor muscles of used forelimbs showed a significant increase in 2-DG uptake; they were ext.dig.2nd and 3rd, ext.dig.com., ext.carp.rad. and ext.carp.uln. On the other hand, flexor muscles in the used forelimb did not show such a significant increase in 2-DG uptake. Muscles of non-used limbs, flexors or extensors, did not show a significant 2-DG uptake.

The neocortex of rats behaving in a driven rotating wheel shows a band characterized by preferential uptake of deoxyglucose

In comparison with control rats placed in a glass chamber, the neocortex of experimental rats performing in a motor-driven activity wheel shows a limited region of high metabolic activity, as revealed by the deoxyglucose radioautographic method. This region consists of a bilateral band located in the somesthetic area SI. An overlap of this labeling with the sensory and/or motor cortical representation of the head, and especially a correlation with head posture and movements, is discussed.