Multimodal architectonic subdivision of the rostral part (area F5) of the macaque ventral premotor cortex

We used a cyto‐, myelo‐, and chemoarchitectonic (distribution of SMI‐32 and calbindin immunoreactivity) approach to assess whether the rostral histochemical area F5 of the ventral premotor cortex (PMv) comprises architectonically distinct areas, possibly corresponding to functionally different fields. Three areas were identified, occupying different parts of F5. One area, designated as “convexity” F5 (F5c), extends on the postarcuate convexity cortex adjacent to the inferior arcuate sulcus and is characterized, cytoarchitectonically, by a poorly laminated appearance, resulting from an overall cell population rather homogeneous in size and density. The other two areas, designated as “posterior” and “anterior” F5 (F5p and F5a, respectively), lie within the postarcuate bank at different anteroposterior levels. Major cytoarchitectonic features of F5p are a layer III relatively homogeneous in cell size and density, a cell‐dense layer Va, and the presence of relatively large pyramids in layer Vb. Major cytoarchitectonic features of F5a are the presence of relatively large pyramids in lowest layer III and a prominent, homogenous layer V. Furthermore, our results showed that F5c and F5p border caudally with a caudal PMv area corresponding to histochemical area F4, providing additional evidence for a general subdivision of the macaque PMv into a caudal and a rostral part, corresponding to F4 and to the F5 complex, respectively. The present data, together with other functional and connectional data, suggest that the three rostral PMv areas F5p, F5a, and F5c correspond to distinct cortical entities, possibly involved in different aspects of motor control and cognitive motor functions. J. Comp. Neurol. 512:183–217, 2009. © 2008 Wiley‐Liss, Inc.     

Cytochemical and pharmacological studies on polysensory neurons in the primate frontal cortex

Neurons of the squirrel monkey postarcuate cortex respond to a number of different sensory modalities. The pharmacological responses of these neurons to putative neurotransmitters, administered by microiontophoresis, was studied. Norepinephrine and serotonin had a powerful inhibitory action on the vast majority of cells at relatively low iontophoretic currents. The inhibitory action of norepinephrine was potentiated by low doses of desmethylimipramine; higher doses produced a direct slowing of discharge.Acetylcholine had mixed effects, exciting and inhibiting approximately equal numbers of neurons. The threshold current for acetylcholine responses was considerably higher than that for norepinephrine or serotonin.Treatment of freeze-dried slices of postarcuate cortex with paraformaldehyde vapor, after uptake of alpha-methyl norepinephrine or 6-hydroxytryptamine, showed an extensive plexus of fine fluorescent axons with characteristic varicosities, throughout the cortex. Many of the varicosities surrounded the soma of neurons.Light microscopic autoradiography of polysensory cortex, after subdural injection or incubation with tritiated norepinephrine or serotonin, revealed many grains along neuronal soma and major dendrites. With electron microscopy after this same treatment, autoradiographic grains were localized largely to fine unmyelinated axons and to small terminals making synaptic contact with the soma and large dendrites.After chronic treatment with 6-hydroxydopamine, fibers within the polysensory cortex which take up alpha-methyl norepinephrine or tritiated norepinephrine are greatly reduced in number, whereas fibers which take up 6-hydroxytryptamine or tritiated serotonin are still plentiful. These electrophysiological and cytochemical studies support the existence of norepinephrine and serotonin-containing inhibitory pathways to neurons of the postarcuate cortex of squirrel monkey.     

Thalamic projections to sensorimotor cortex in the macaque monkey: use of multiple retrograde fluorescent tracers.

We used several fluorescent dyes (Fast Blue, Diamidino Yellow, Rhodamine Latex Microspheres, Evans Blue, and Fluoro-Gold) in each of eight macaques, to examine the patterns of thalamic input to the sensorimotor cortex of macaques 12 months or older. Inputs to different zones of motor, premotor, and postarcuate cortex, supplementary motor area, and areas 3b/1 and 2/5 in the postcentral cortex, were examined. Coincident labeling of thalamocortical neuron populations with different dyes (1) increased the precision with which their soma distributions could be related within thalamic space, and (2) enabled the detection by double labeling, of individual thalamic neurons that were common to the thalamic soma distributions projecting to separate, dye-injected cortical zones. Double-labeled thalamic neurons projecting to sensorimotor cortex were rarely seen in mature macaques, even when the injection sites were only 1-1.5 mm apart, implying that their terminal arborizations were quite restricted horizontally. By contrast, separate neuron populations in each thalamic nucleus with input to sensorimotor cortex projected to more than one cytoarchitecturally distinct cortical area. In ventral posterior lateral (oral) (VPLo), for example, separate populations of cells sent axons to precentral medial, and lateral area 4, medial premotor, and postarcuate cortex, as well as to supplementary motor area. Extensive convergence of thalamic input even to the smallest zones of dye uptake in the cortex (approximately 0.5 mm3) characterized the sensorimotor cortex. The complex forms of these projection territories were explored using 3-dimensional reconstructions from coronal maps. These projection territories, while highly ordered, were not contained by the cytoarchitectonic boundaries of individual thalamic nuclei. Their organization suggests that the integration of the diverse information from spinal cord, cerebellum, and basal ganglia that is needed in the execution of complex sensorimotor tasks begins in the thalamus.     

The involvement of monkey premotor cortex neurones in preparation of visually cued arm movements

Some neurones in macaque postarcuate premotor area modulate their firing frequency in relation to motor tasks which require visual information. We previously reported that a large proportion of these neurones modulate during execution of a detour reaching task in which the movement phase was separated in time from the phase in which the monkey received a visual cue for the movement required to retrieve a food reward. A large proportion of task-related neurones (75%) modulated during this 'visual' phase, in which no task-related movements were made. This modulation was related to the position of the food reward, which served as the visual cue. Most of these neurones were located in cortical area 6, close to the arcuate curvature and its spur, but also more caudally in area 4 and rostrally in area 8. In the present chronic recording experiments in monkeys, several variations of the original task were used in order to test whether the 'visual'-related neuronal modulation could be involved in preparation of the upcoming movement. This modulation is unlikely to be related to any eye or arm movements occurring during the visual phase or to changes in environmental illumination. Neither can it be related to the presence of the visual cue in a particular part of the visual field, since the pattern of neuronal modulation was similar when a cue with a fixed position was used. This modulation was, however, contingent upon the occurrence of food retrieval during the subsequent 'movement phase', since it was abolished or diminished during presentation of a 'food-reward' which the monkey did not retrieve. For several neurones, modulation pattern during the visual phase depended on whether the food reward was to be retrieved with a gross hand movement or with relatively independent finger movements. It is likely, therefore, that neurones in the postarcuate premotor cortex are involved in preparation for arm movements with the help of visual cues. The results are discussed in view of corticocortical pathways which might be involved in transmission of visual information from visual areas through parietal association areas and premotor cortex to the primary motor cortex.     

Long-latency corticocortical evoked responses in squirrel monkey frontal cortex

Early (5 to 15 msec) and late (120 to 180 msec) responses are evoked bilaterally in postarcuate cortex of unanesthetized squirrel monkeys by electrical stimulation of postcentral somatosensory cortex. Sectioning the precentral corpus callosum abolishes both early and late responses to contralateral stimulation and leaves unchanged the responses recorded at the same site to ipsilateral stimulation, suggesting that generation of the late response depends on generation of the early response in the same frontal lobe. Units in postarcuate cortex fire in relation to the early and late responses, but are silent in the period between them. Other investigators have suggested that late components of the direct cortical response and postinhibitory rebound of cortical neurons are dependent on input to cortex from the thalamus. Our data indicate, rather, that it is input to cortex from the mesencephalon, probably feeding through the thalamus, which is necessary. Late responses are selectively depressed or even abolished by bilateral lesions in and near the mesencephalic reticular formation (MRF) and by general anesthetic agents, but the convulsant stimulants, picrotoxin and pentylenetetrazol, can induce recovery of late responses after lesions or administration of anesthetic agents. The data are consistent with the interpretation that neurons in postarcuate cortex are excited to fire during the early surface response, undergo long-duration postsynaptic inhibition such as is generated in cortical neurons by activation of many cortical afferents, and then show postinhibitory rebound if input from the mesencephalic reticular formation has not been interrupted by lesions or anesthetic agents, or if the convulsants substitute for this input.     

Corticofugal connections between the cerebral cortex and brainstem vestibular nuclei in the macaque monkey

The distribution of cortical efferent connections to brainstem vestibular nuclei was quantitatively analysed by means of retrograde tracer substances injected into different electrophysiologically identified parts of the brainstem vestibular nuclear complex of five Java monkeys (Macaca fascicularis). Three polysensory vestibular areas were found to have a substantial projection to the vestibular nuclei: area 2v located at the tip of the intraparietal sulcus, the parietoinsular vestibular cortex (PIVC) covering the most occipital part of the granular insula (Ig) and the retroinsular area (Ri or reipt), and the dorsolateral part of the somatosensory area 3a (“area 3aV” neck/trunk region). From physiological recording experiments, these three cortical fields were known to contain many neurons responding to stimulation of semicircular canals as well as to optokinetic (area 2v, PIVC) and somatosensory stimuli (PIVC, area 3a). These three regions form the inner cortical vestibular circuit. Besides these polysensory vestibular cortical fields, three other circumscribed cortical regions of the macaque brain were also found to project directly to the brainstem vestibular nuclei: a circumscribed part of the postarcuate premotor cortex (area 6pa), part of the agranular and the adjacent dysgranular cortex located around the cingulate sulcus (area 6c/23c), and a predominantly visual (optokinetic) association field located at the fundus of the lateral sulcus (area T3). These areas are known to have connections with the structures of the inner cortical vestibular circuit. Only a few efferent connections to the brainstem vestibular nuclei were found for the different parts of cytoarchitectonic area 7. Significant differences were found between the efferent innervation patterns of the axons originating in the six cortical areas mentioned and ending in the various compartments of the vestibular nuclear complex. Vestibular nuclei with a dominant output to the gaze motor system of the brainstem receive efferent connections preferably from the parietoinsular vestibular cortex. Vestibular structures with their primary output to skeletomotor centers, however, receive stronger efferent connections from areas 6pa and 3a. The ventrolateral nucleus, which sends efferent axons to both the oculomotor and skeletomotor systems of the brainstem and the spinal cord, also receives its main cortical efferents from the somatomotor area 6 and from area 3aV. Through these connections the cortical somatomotor system may directly influence vestibuloocular and vestibulocollic reflexes. It is speculated that the corticofugal connections to the vestibular brainstem nuclei are predominantly inhibitory, suppressing vestibular reflexes during cortically controlled goal-directed movements. © 1994 Wiley-Liss, Inc.     

Cortico-cortical projections of the motorcortical larynx area in the rhesus monkey

The efferent cortico-cortical projections of the motorcortical larynx area were studied in three rhesus monkeys (Macaca mulatta), using biotin dextranamine as anterograde tracer. Identification of the larynx area was made with the help of electrical brain stimulation and indirect laryngoscopy. Heavy projections were found into the surrounding ventral and dorsal premotor cortex (areas 6V and D), primary motor cortex (area 4), the homolog of Broca's area (mainly area 44), fronto- and parieto-opercular cortex (including secondary somatosensory cortex), agranular, dysgranular and granular insula, rostral-most primary somatosensory cortex (area 3a), supplementary motor area (area 6M), anterior cingulate gyrus (area 24c) and dorsal postarcuate cortex (area 8A). Medium projections could be traced to the ventrolateral prefrontal and lateral orbital cortex (areas 47L and O), the primary somatosensory areas 3b and 2, the agranular and dysgranular insula, and the posteroinferior parietal cortex (area 7; PFG, PG). Minor projections ended in the lateral and dorsolateral prefrontal cortex (areas 46V and 8B), primary somatosensory area 1 and cortex within the intraparietal sulcus (PEa) and posterior sulcus temporalis superior (TPO). Due to its close spatial relationship to the insula on the one hand and the premotor cortex on the other, the larynx area shows projections which, in some respects, are not typical for classical primary motor cortex.     

Frontal eye field efferents in the macaque monkey: I. Subcortical pathways and topography of striatal and thalamic terminal fields

Anterograde tracers (tritiated leucine, proline, fucose; WGA-HRP) were injected into sites within the frontal eye fields (FEF) of nine macaque monkeys. Low thresholds (less than or equal to 50 microA) for electrically evoking saccadic eye movements were used to locate injection sites in four monkeys. Cases were grouped according to the amplitude of saccades evoked or predicted at the injection site. Dorsomedial prearcuate injection sites where large saccades were elicited were classified as lFEF cases, whereas ventrolateral prearcuate sites where small saccades were evoked were designated sFEF cases. One control case was injected in the medial postarcuate area 6. We found five descending fiber bundles from FEF; fibers to the striatum, which enter the caudate nucleus at or just rostral to the genu of the internal capsule; fibers to the claustrum, which travel in the external capsule; and transthalamic, subthalamic, and pedunculopontine fibers. Our results indicate that transthalamic and subthalamic pathways supply all terminal sites in the thalamus, subthalamus, and tegmentum of the midbrain and pons, whereas pedunculopontine fibers appear to terminate in the pontine and reticularis tegmenti pontis nucleus exclusively. Frontal eye field terminal fields in the striatum were topographically organized: lFEF projections terminated dorsal and rostral to sFEF projections. Thus, lFEF terminal fields were located centrally in the head and body of the caudate nucleus and a small dorsomedial portion of the putamen, whereas sFEF terminal fields were located in ventrolateral parts of the caudate body and ventromedial parts of the putamen. In the claustrum, lFEF projections terminated dorsal and rostral to sFEF projections. Projections from FEF terminated in ventral and caudal parts of the subthalamic nucleus without a clear topography. By comparison, terminal fields from medial postarcuate area 6 were located more caudally and laterally in the striatum and claustrum than projections from FEF, and more centrally in the subthalamic nucleus. In the thalamus, FEF terminal patches in some thalamic nuclei were also topographically organized. Projections from lFEF terminated in dorsal area X, dorsolateral medial dorsal nucleus, pars parvicellularis (MDpc), and the caudal pole of MDpc, whereas projections from sFEF terminated in ventral area X, medial dorsal nucleus, pars multiformis, and caudal medial dorsal nucleus pars densocellularis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ipsilateral cortical projections to areas 3a, 3b,and 4 in the macaque monkey

In the macaque monkey area 3a of the cerebral cortex separates area 4, a primary motor cortical field, from somatosensory area 3b, which has a subcortical input mainly from cutaneous mechanoreceptive neurons. That each of these cortical areas has a unique thalamic input was illustrated in the preceding paper. In the present experiments the cortical afferent projections to these 3 areas of the sensorimotor cortex monkey were visualized and compared, using 4 differentiable fluorescent dyes as axonal retrogradely transported labels. The cortical projection patterns to areas 3a, 3b, and 4 were similar in that they each consisted of (a) a “halo” of input from the immediately surrounding cortex, and (b) discrete projections from one or more remote cortical areas. However, the pattern of remote inputs from precentral, mesial, and posterior parietal cortex was different for each of the 3 cortical target areas. The cortical input configuration was least complex for area 3b, its remote input projecting mainly from insular cortex. The pattern of discrete cortical inputs to the motor area 4, however, was more complex, with projections from the cingulate motor area (24c/d), the supplementary motor area, postarcuate cortex, insular cortex, and postcentral areas 2/5. Area 3a, in addition to the proximal projections from the immediately surrounding cortex, also received input from the supplementary motor area, cingulate motor cortex, insular cortex, and areas 2/5. Thus, this pattern of cortical input to area 3a resembled more closely that of the adjacent motor rather than that of the somatosensory area 3b. Contrasting with this, however, the thalamic input to area 3a was largely from somatosensory VPLc (abbreviations from Olszewski [1952] The Thalamus of the Macaca mulatta. Basel: Karger) and not from VPLo (with input from cerebellum, and projecting to precentral motor areas). © 1993 Wiley-Liss, Inc.     

Interactions of sensory and nonspecific thalamic inputs to cortical polysensory units in the squirrel monkey

Possible influences of nonspecific thalamocortical projections on sensory responsiveness of single units of polysensory cortex were investigated. Sensory responses in the postarcuate polysensory area (PPA) of the squirrel monkey were paired with antecedent low-frequency (10/sec) trains of stimuli applied to intralaminar nonspecific thalamic nuclei, to elicit recruiting responses indicative of activation of the nonspecific system. Recruiting responses were more prominent in the PPA than primary cortex and, in PPA units, their elicitation typically suppressed the sensory responses with which they were paired, without similarly affecting unpaired inputs to PPA. The reduction in responsiveness persisted for several minutes after the period of pairing in about one-half of the PPA units examined. Primary sensory cortical units were not similarly affected. The data suggest that nonspecific thalamic nuclei project more strongly to polysensory than to primary sensory cortex and that these projections may have the capacity to modulate selectively the responsiveness of polysensory units to peripheral inputs. Possible implications of such plasticity concerning learning are discussed.     

Afferent and efferent projections of the inferior area 6 in the macaque monkey

The rostral part of the agranular frontal cortex (area 6) can be subdivided on the basis of its cytoarchitecture, enzymatic properties, and connections into two large sectors: a superior region, lying medial to the spur of the arcuate sulcus, and an inferior region, lying lateral to it. In this study we traced the afferent and efferent connections of the inferior region of area 6 by injecting small amounts of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and fluorescent tracers (fast blue and diamidino yellow) into restricted parts of inferior area 6 and in physiologically determined fields of area 4. There is an ordered topographic pattern of connections between inferior area 6 and area 4. The region near the spur of the arcuate sulcus (hand field) projects to the area 4 hand field while the lateral part of inferior area 6 (mouth field) is connected with the corresponding field in area 4. The organization of the connections between the two fields is, however, different. The hand fields in area 6 and 4 have direct reciprocal projections, whereas the mouth field in the postarcuate cortex relays information to area 4 via a zone intermediate between the arcuate and the central sulcus. This zone corresponds to the cytochrome oxidase area F4 (Matelli, Luppino, and Rizzolatti: Behav. Brain Res. 18: 125-137, '85). The inferior area 6 also has topographically organized connections with the supplementary motor area. The inferior area 6 receives and sends fibers to a series of discrete cortical areas located in the lower cortical moiety (Sanides: The Structure and Function of the Nervous Tissue, Vol. 5. New York: Academic Press, pp 329-453, '72). These areas that form a broad ring around the central sulcus are the ventral bank of the principal sulcus and the adjacent area 46, the precentral operculum (PrOC), area SII (Jones and Burton: J. Comp. Neurol. 168:197-248, '76), the parietal operculum, and the rostral part of the inferior parietal lobule including the lower bank of the intraparietal sulcus. Finally, the inferior area 6 has sparse but consistent connections with insular and cingulate cortices. The functional significance of this complex pattern of connections is discussed.     

Corticocortical efferent systems in the monkey: a quantitative spatial analysis of the tangential distribution of cells of origin

The laminar and tangential distributions of association neurons projecting from areas 4 and 6 of the frontal lobe to area 5 of the superior parietal lobule were studied in macaque monkeys by using horseradish peroxidase histochemistry. In both areas 4 and 6 association neurons were medium-large pyramidal cells of layers II and III, and pyramidal and fusiform cells of layers V-VI. Tangentially, they were distributed unevenly over the cortical surface occupying only certain parts of areas 4 and 6, including the dorsomedial part of area 6, the proximal arm region of Woolsey's M1 map, parts of the postarcuate cortex, and the supplementary motor area. Within these projection zones, the number of projection cells waxed and waned in a periodic fashion. Quantitative methods, including spectral analysis techniques, were used to characterize precisely spatial periodicities along the rostrocaudal dimension. The same quantitative analyses were used to determine the nature of the tangential distribution of corticocallosal cells of area 5 projecting to contralateral area 5. Both association and callosal spectra contained a strong component in the range of low spatial frequencies, corresponding to periods greater than 2 mm. Moreover, a consistent peak was observed in both spectra at spatial frequencies corresponding to periods ranging from 0.85 to 1.28 mm. This peak is in accord with the hypothesis of a modular organization of the cells of origin of these projection systems.     

Buccal hemineglect

OBJECTIVES: To determine whether the peripersonal and intrapersonal buccal space can be affected by a hemispheric stroke and to evaluate the clinical signs resulting from buccal neglect. METHODS: A prospective study comparing 2 groups of patients with hemiplegia, 1 with a right hemispheric lesion and the other with a left hemispheric lesion. Patients were selected consecutively on the basis of specific criteria at least 1 month after stroke. RESULTS: Buccal hemineglect was usually concomitant with other hemineglect phenomena resulting from lesions of the right hemisphere (10 of 12 in right lesions and 1 of 12 in left lesions). Clinical signs associated with this condition consisted of impaired swallowing (retention, defective insalivation, presence of food debris in the left hemibuccal space, loss of saliva from the left side of the mouth, and choking); loss of the ability to perceive salty, sweet, or acid tastes; and impaired buccal representation. These problems were usually incorrectly diagnosed initially. Outcome was usually favorable, but functional disorders persisted in some patients for more than 18 months. The underlying attention and representation mechanisms are discussed with reference to experimental lesions of the postarcuate (area 6) cortex in rhesus monkeys. The area around the mouth may be considered to be, as in monkeys, a peripersonal space, ie, probably of little functional importance. The lesion may involve area 6 or its projections to the thalamus or posterior parietal cortex. CONCLUSIONS: Buccal hemineglect, which is likely to cause social embarrassment, should be considered whenever the oral phase of swallowing is impaired in a context of neglect syndromes. Prophylactic measures and rehabilitation can reduce the impact and complications of the condition (food bolus).     

Attention-related unit activity in the frontal association cortex during a go/no-go visual discrimination task

Unit activity related to a go/no-go visual discrimination task was studied in four rhesus monkeys. We recorded 272 task-related cells from frontal cortex in a region extending from the midprincipal sulcus to the central sulcus, and medially to the cingulate sulcus. Units located in anterior regions (dorsolateral prefrontal and anterior cingulate cortex) were typically related to both go and no-go trials (designated type II units) and showed similar ("symmetrical") activity in both kinds of trials; some of them also showed prestimulus ("anticipatory") activity. Such units were present but less common in posterior regions (postarcuate and precentral and posterior cingulate cortex). Units in these posterior regions were active predominantly in go trials (designated type I units). Also found posteriorly were "asymmetrical" type II cells whose activity was greater in go trials and occurred later in the trial, around the behavioral response. The anterior symmetrical and anticipatory type II units in the frontal association cortex were similar to such units described earlier in the brain stem reticular formation and may have similar functions in supporting focused and preparatory attention. On the other hand, asymmetrical type II units in the posterior frontal regions may have a role in the initiation of visually guided motor behavior.     

The locus of the posterior subdivision of the inferotemporal visual learning area in the monkey

In an attempt to define the posterior subdivision of the inferotemporal visual learning area more precisely than before, pattern discrimination retention, serial object discrimination learning and concurrent object discrimination learning were tested in 16 monkeys with lesions in one of four different cytoarchitectural areas; TEO, OA, OB and OC, and in five unoperated monkeys. Marked impairment was found only in pattern discrimination retention and only in the monkeys with lesions of area TEO. It was concluded that the posterior limit of the inferotemporal visual learning area is at the ascending limb of the inferior occipital sulcus, and that the posterior subdivision thus comprises the single anatomical area TEO and does not extend into areas OA and OB.     

Different types of norepinephrinergic receptors are involved in preoptic area mediated independent modulation of sleep-wakefulness and body temperature

The preoptic area is known to regulate sleep-wakefulness and body temperature. It was suggested earlier that though sleep-wakefulness and body temperature may affect each other, the preoptic area mediated influence on those two physiological phenomena is likely to be independent of alteration in each other. Since intrapreoptic area norepinephrine could modulate both those functions, study of that system was undertaken. It was hypothesized that since the preoptic area has different types of norepinephrinergic receptors (viz. alpha 1, alpha 2 and beta), independent modulation of those two functions was probably due to activation or inactivation of separate receptors. Hence, the effects of different agonist and antagonist of those receptors individually as well as in combination into the preoptic area were studied on those two functions in freely moving rats. The results suggest that norepinephrine induced preoptic area mediated influence on the body temperature is primarily regulated by the alpha 1 receptors while the sleep and wakefulness are regulated by alpha 2 and beta receptors, respectively. The finding should help in explaining several poorly understood observations reported earlier and it suggests that similar phenomena may possibly exist in other system involving other neurotransmitters as well.     

Neuronal cell migration for the developmental formation of the mammalian striatum

The mammalian striatum is the largest receptive component of the basal ganglia circuit. It is involved in the control of various aspects of motor, cognitive, and emotional functions. In the telencephalon, the striatum has a unique histological property totally different from the cortical area and its ontogenesis remains largely unknown. In this review, we introduce recent advances in the understanding of neuronal cell migration, one of the most critical processes in the early phase of histogenesis that occurs in the embryonic striatum. It appears that there are three major modes of neuronal cell migration in the developmental formation of the striatum. They are (radial) outward, tangential, and inward migration, supplying the striatum with projection neurons, interneurons, and early-generated transient neurons that originate in the preplate, respectively. We challenge the classical concept that the striatum is solely derived from the restricted germinal area located in the basal telencephalon by providing evidence that striatal development requires the intermixture of different types of neurons originating from distinct regions of the telencephalon.     

Electrical stimulation of the ventral tegmental area and catecholamine metabolism in discrete regions of the rat brain

Data are presented which show a different pattern of dopamine and noradrenaline utilization in terminal regions of the A9 and A10 dopaminergic systems and in terminal regions of the dorsal noradrenergic bundle after electrical stimulation of the ventral tegmental area and an adjacent area. At the sites of the electrodes an enhanced turnover of noradrenaline was found. These results are discussed relating the location of the electrode sites and the location of the dopaminergic cell bodies A9 and A10 and catecholaminergic fibers passing through the MFB innervating forebrain and limbic structures. It is concluded that activation of parts of the A10 dopaminergic system and the A6 noradrenergic system is correlated with intracranial selfstimulation.     

The role of the dura in conditioned taste avoidance induced by cooling the area postrema of male rats

Experiments were designed to assess the contribution of the dura mater to the formation of conditioned taste avoidance induced by cooling the area postrema. The results of the first experiment verified that the temperature of the dura showed a temperature gradient at various distances from the tip of the cold probe. In the second and third experiments, a circle of dura was cut away so that different amounts of the area postrema could be cooled without cooling the overlying dura. Cooling the dura plus the area postrema did not produce a stronger avoidance than just cooling the area postrema. In the fourth experiment, the cerebellar cortex was cooled with and without cooling the dura. Cooling the cerebellar cortex produced conditioned taste avoidance, and cooling the dura plus the cerebellar cortex did not produce a stronger avoidance. Taken together, these results suggest that cooling the dura mater does not contribute to the conditioned taste avoidance induced by cooling the area postrema. The results of the fifth experiment showed that cooling the area postrema produced a stronger conditioned taste avoidance than cooling the cerebellar cortex. It is suggested that the avoidance induced by cooling both of these structures is the result of physiological changes occurring when neurons in these structures are inactivated and when the subdural meninges are cooled. Furthermore, these changes are more severe when the area postrema is cooled.     

Interrelationship of thermal and sleep-wakefulness changes elicited from the medial preoptic area in rats

The study investigated the possible interrelationship between changes in sleep-wakefulness and body temperature, primarily induced by manipulation of the noradrenergic system in the medial preoptic area. Saline, norepinephrine, and its alpha- and beta-blockers were injected in the medial preoptic area and in some control areas of rats, during their sleeping and active periods. 5-Hydroxytryptamine was injected in the medial preoptic area in another group of animals. Simultaneous changes in sleep-wakefulness and the body temperature were continuously recorded. Norepinephrine produced hypothermia and arousal, whereas alpha-adrenergic blockers induced hyperthermia and sleep. These changes in body temperature and in sleep-wakefulness did not follow an identical time course. 5-Hydroxytryptamine induced hyperthermia without affecting sleep-wakefulness. It is suggested that there are different neuronal mechanisms in the medial preoptic area that bring about the drug-induced changes in temperature and sleep-wakefulness.