Corticostriate projections from area 6 in the raccoon

Summary Corticostriate projections from area 6 in the raccoon were studied using the autoradiographic tracing method. Following injections of tritiated amino acids into two different cytoarchitectonic subdivisions of area 6, widespread and dense anterograde label was found in both the ipsilateral and contralateral caudate nucleus and putamen. The densest label was located adjacent to the internal capsule in the lateral part of the head of the caudate nucleus. This bilateral projection pattern from area 6 to the caudate nucleus and putamen is consistent with the hypothesis that the neostriatum maintains a close anatomical and functional relationship with area 6.     

Corticospinal projections from areas 4 and 6 in the raccoon

Summary The corticospinal projections from areas 4 and 6 were investigated in the raccoon using the horseradish peroxidase (HRP) retrograde tracing technique. Multiple injections of lectin bound HRP and HRP were made into either the cervical or lumbar cord in 7 anesthetized raccoons. Retrogradely labeled neurons were observed throughout a wide extent of areas 4 and 6a. The HRP positive cells were most numerous within the dorsal bank of the cruciate sulcus within area 4 and continued around the fundus to occupy the lateral two-thirds of the ventral bank of the cruciate sulcus within area 6a. No labeled cells were observed in the more medially located area 6a. Although the HRP positive cells observed following the lumbar cord injections were situated slightly more medial and caudal to those observed following the cervical cord injections, considerable overlap between the two projections was noted. The corticospinal projections arising from areas 4 and 6a in the raccoon largely correspond in location to the regions functionally defined as the primary motor cortex and the supplementary motor area, respectively.     

Nigrotectal projections in the primate Galago crassicaudatus

Summary The pattern of the nigrotectal projection in Galago crassicaudatus was determined using retrograde and anterograde transport methods. These experiments revealed that pars reticulata and pars lateralis of the substantia nigra project to all layers of the ipsilateral and contralateral superior colliculus, except to layer I. The nigrotectal projection is not homogeneous, but is concentrated in particular collicular layers and sublayers, and the intensity and laminar distribution of the projection varies along the rostral-caudal dimension of the superior colliculus. The ipsilateral and contralateral nigrotectal projections are generally similar, except that a tier of dense label which is prominent in the ventral part of much of the ipsilateral layer IV is not obvious contralaterally; moreover, the contralateral projection is much sparser than the ipsilateral. Deposits of tracers at different medial-lateral locations within the substantia nigra did not result in different laminar patterns of anterogradely transported label in the superior colliculus. Based on the known connections and functions of the collicular layers and sublayers, the pattern and distribution of the nigrotectal projection suggests that the substantia nigra may use this pathway to gain access to particular components of vision- and visuomotor-related networks.Abbreviations Cd Caudate - CG Central gray - CP Cerebral peduncle - D Dorsal - FEF Frontal eye field - IC Internal capsule - ICo Inferior colliculus - IP Interpeduncular nucleus - L Lateral - LG Lateral geniculate - MDmf Medial dorsal nucleus, pars multiformis - MG Medial geniculate - MI Mammillary body, lateral nucleus - Mm Mammillary body, medial nucleus - MRF Mesencephalic reticular formation - nIII Oculomotor nerve - OT Optic tract - PG Pontine gray - Pg Pregeniculate nucleus - Pt Pretectal complex - Pulv Pulvinar nuclei - Put Putamen - R Red nucleus rostral - SCi,d Superior colliculus, intermediate and deep layers - SCs Superior colliculus, superficial layers - SEF Supplementary eye field - SNc Substantia nigra, pars compacta - SNr Substantia nigra, pars reticulata - SNr, 1 Substantia nigra, pars reticulata and pars lateralis - St Subthalamic nucleus - VAmc Ventral anterior nucleus, pars magnocellularis - V Cort Visual cortical areas - ZI Zona incerta - II Layer II of the superior colliculus - III Layer III of the superior colliculus - IV Layer IV of the superior colliculus - V Layer V of the superior colliculus - VI Layer VI of the superior colliculus     

Age-dependent changes in dopaminergic projections from the substantia nigra pars compacta to the neostriatum

Age-dependent changes in dopaminergic (DA) innervation of the neostriatum (Str) were studied in male F344/N rats. Projections from the substantia nigra pars compacta (SNc) to the neostriatum were quantified using electrophysiological methods at age points from 6 to 24 months. The percentage of DA neurons activated antidromically by electrical stimulation (P-index) of Str increased between 18 and 24 months. Additionally, the percentage of DA neurons showing multiple antidromic latencies from striatal stimulation (M-index), which suggests axonal branching of individual DA neurons, increased significantly between 6 and 12 months and 6 and 24 months. These results suggest that DA neurons exhibit increased axonal branching in the aged brain.     

Corticospinal projections from areas 4 and 6 in the raccoon

The corticospinal projections from areas 4 and 6 were investigated in the raccoon using the horseradish peroxidase (HRP) retrograde tracing technique. Multiple injections of lectin bound HRP and HRP were made into either the cervical or lumbar cord in 7 anesthetized raccoons. Retrogradely labeled neurons were observed throughout a wide extent of areas 4 and 6a beta. The HRP positive cells were most numerous within the dorsal bank of the cruciate sulcus within area 4 and continued around the fundus to occupy the lateral two-thirds of the ventral bank of the cruciate sulcus within area 6a beta. No labeled cells were observed in the more medially located area 6a alpha. Although the HRP positive cells observed following the lumbar cord injections were situated slightly more medial and caudal to those observed following the cervical cord injections, considerable overlap between the two projections was noted. The corticospinal projections arising from areas 4 and 6a beta in the raccoon largely correspond in location to the regions functionally defined as the primary motor cortex and the supplementary motor area, respectively.     

重复注射6-羟多巴胺建立帕金森病动物模型

目的探讨通过大鼠中脑内重复注射 6-羟多巴胺 (6-hydroxydopamine,6-OHDA)建立高效、稳定、可靠的帕金森病动物模型。方法将 60 只雄性 SD 大鼠随机分为一次打击组和二次打击组,经腹腔注射 4%水合氯醛(40 mg / 100g)麻醉,脑立体定位仪固定,于左侧黑质致密部(SNC)和中脑腹侧被盖区(VTA)分别注射 6-羟多巴胺 (6-OHDA,2 g / L,2μl),二次打击组一周后在相同位置重复注射同剂量的 6-OHDA,建立帕金森模型,观察其行为改变,通过 HE、TH 和 DIG-dUTP 染色观察其细胞形态的改变及凋亡情况。结果经过二次打击的大鼠,模型成功率(旋转周数 >7 r / min)为 86.7%,明显多于一次打击组的 33.3%;HE 染色显示,二次打击组凋亡细胞的阳性率(37.12%)明显多于一次打击组(21.25%);DIG-dUTP 染色显示,一次打击组大鼠左侧中脑黑质区神经细胞肿胀的数量多 ,凋亡数量少,凋亡细胞阳性率为 20.73%,二次打击组细胞凋亡数显著增多,凋亡细胞阳性率达 36.03%;TH 染色显示,二次打击组 TH 阳性细胞数明显减少,TH 细胞阳性率(18.61%)显著低于一次打击组(36.55%)。结论通过二次打击建立帕金森病动物模型成功率高于一次打击。     

γ-Aminobutyric acid release in the globus pallidus in vivo after a 6-hydroxydopamine lesion in the substantia nigra of the rat

This experiment was designed to determine whether the release of γ-aminobutyric acid (GABA) in the globus pallidus (GP) is affected by a lesion of the nigrostriatal pathway. Rats were lesioned with 6-hydroxydopamine 4 weeks prior to study of the in vivo release of GABA. A microdialysis probe was stereotaxically implanted in halothane-anesthetized animals in a vertical position on both GPs. The perfusates were analyzed for their GABA content with a high performance liquid chromatography technique. Compared to unlesioned controls, a marked decrease in the overflow of GABA was observed in the GP contralateral to the lesion, whereas the ipsilateral GP showed a slight increase. The differences between the sides were exaggerated after KCl (100 mmol) administration. The results are discussed in terms of a possible bilateral influence of dopamine terminals in the striatum on GABA transmission.     

Interactions between inputs from adjacent digits in somatosensory thalamus and cortex of the raccoon

Interactions between somatosensory afferents arriving from different points in the periphery play an important role in sensory discrimination and also provide the substrate for plasticity following peripheral injury. To examine the extent and time course of such interactions, extracellular recordings were made from neurons in the primary somatosensory cortex and the ventroposterior lateral thalamus of anesthetized raccoons. Interactions between adjacent digits were studied using the conditioning-test paradigm in which a test pulse was delivered to the digit containing the neuron's receptive field (the on-focus digit) at various intervals following conditioning stimulation of an adjacent, off-focus digit. Off-focus stimulation produced predominantly inhibition of the test response with a maximum effect at 20–40 ms in both cortex and thalamus. The mean inhibition was approximately twice as large in the thalamus as in the cortex. Recordings were made in other animals after unmyelinated C fibers had been destroyed in the on-focus digit by subcutaneous injection of capsaicin. This resulted in a doubling of the responses evoked by the test stimulus in both regions, but the spontaneous discharge rate was not changed. The amount of inhibition produced in the cortex was unchanged by capsaicin treatment, but was reduced in the thalamus compared to control animals. This indicates that capsaicin-sensitive peripheral afferents provide a tonic control over interdigit inhibition in the thalamus.     

Collateral projections of neurons of the rat globus pallidus to the striatum and substantia nigra

Summary Double retrograde fluorescent tracing techniques were used to evaluate the possibility that ascending and descending projections from the globus pallidus arise from divergent axon collaterals. Appropriately placed injections of different tracers (True Blue, Nuclear Yellow) into the substantia nigra and the striatum resulted in the double labelling of neurons in the globus pallidus. Conversely, simultaneous injection of two different sites within the striatum did not produce significant double labelling of globus pallidus neurons. These results indicate that at least a portion of the neurons of the globus pallidus project to both the striatum and substantia nigra, and that individual pallidal neurons do not have widespread projections to the striatum.     

Methamphetamine-induced Fos expression in the substantia nigra pars reticulata in rats with a unilateral 6-OHDA lesion of the nigrostriatal fibers

In rats with a unilateral 6-hydroxydopamine (6-OHDA)-induced lesion in the nigrostriatal fibers, methamphetamine (3 mg/kg, i.p.) induced Fos-like immunoreactivity (FLI), which was inhibited by pretreatment with N-methyl-

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-aspartate antagonist MK-801 (1 mg/kg, i.p.), not only in the medial striatum contralateral to the lesion but also in the substantia nigra pars reticulata (SNr) ipsilateral to the lesion. Thus, hemispheric asymmetries in FLI were induced by methamphetamine in the medial striatum and the SNr in the 6-OHDA model of turning which may be related to the altered function of glutamatergic transmission.     

Cholinergic stimulation of substantia nigra: abolition of carbachol-induced eating by unilateral 6-hydroxydopamine lesion of nigrostriatal dopamine neurones

Summary Microinjection of cholinergic agonists into the substantia nigra is known to elicit increases in eating, drinking and sexual behaviour under appropriate circumstances. It has been suggested that these effects are dependent on stimulation of nigrostriatal dopamine-containing neurones in the substantia nigra pars compacta, but no direct evidence has confirmed this. The present experiment was therefore undertaken to determine whether unilateral lesions of nigrostriatal dopamine neurones made by 6-hydroxydopamine would attenuate or abolish eating in satiated rats elicited by intranigral microinjection of the muscarinic agonist carbachol. Two groups of rats were tested: a 6-hydroxydopamine- and a sham-lesion group. Before lesions were made intranigral microinjection of 0.5 g/0.5 l carbachol stimulated significantly more eating than control microinjections in both groups. After 6-hydroxydopamine lesions, microinjection of carbachol elicited no more eating than vehicle alone. Rats given sham lesions (ascorbate-saline vehicle only) showed increased feeding to intra-nigral carbachol before and after sham-lesioning. Post-mortem analysis by HPLC was used to determine the concentration of dopamine, DOPAC, HVA, serotonin and 5-HIAA in the lesioned and nonlesioned hemispheres of both 6-hydroxydopamine- and sham-lesioned rats. In caudate-putamen there were significant reductions in the concentration of DA (to 50.03% of the level in control sides), DOPAC (to 49.34%) and HVA (to 63.98%) in the 6-hydroxydopamine-lesioned but not sham-lesioned rats. The concentration of dopamine, DOPAC and HVA were not affected in the nucleus accumbens. The turnover of dopamine (assessed by calculating the ratio of dopamine to DOPAC) in the caudateputamen but not nucleus accumbens was also altered by the 6-hydroxydopamine lesions. The concentration and turnover of serotonin was not affected in either the caudate-putamen or nucleus accumbens in either group of rats. These data show that loss of dopamine from the caudate-putamen but not nucleus accumbens is sufficient to abolish completely the eating stimulated by intranigral carbachol.     

大鼠大脑皮层－尾壳核和尾壳核－黑质间的往返定位投射

用霍乱毒素Ｂ亚单位（ＣＢ）追踪法系统地研究了大鼠大脑皮层与尾壳核和尾壳核与黑质之间的定位投射。将ＣＢ分别泳入尾壳核不同节段的不同区域后，大脑皮层内的逆标胞体和顺标终末主要见于额叶１区和２区、顶叶１区和２区以及颗粒岛皮质；黑质内的顺标终末主要见于网状带的不同部位，而逆标胞体则主要见于致密带和腹侧被盖区。本研究结果说明在大鼠大脑皮层－尾壳核和尾壳核－黑质之间存在着且有点对点定位特征的往返联系。这种定位投射对躯体运动的精细调节提供了形态学基础。     

The effect of aging on the neuronal population within area 17 of adult rat cerebral cortex

The brains of Sprague-Dawley rats in various age groups from 3 to 33 months were fixed by perfusion with standard aldehyde solutions in order to determine the effects of aging on neuronal numbers. Several indices of cortical volume were then measured to determine whether neuronal packing densities were affected by age-related change in cortical volume. The lengths, heights and widths of individual hemispheres for 160 animals ranging in age from 1 day to 36 months were first determined, after which blocks of tissue were removed from area 17 of some of the brains. These blocks were osmicated, embedded in Araldite and sectioned at 1 micrometer to ascertain, in the vertical plane, the thickness of area 17 and, in the tangential plane, the packing density of the clusters of apical dendrites extending from layer V pyramidal neurons. Results indicate the overall dimensions of the cerebral hemispheres increased until 3 months of age, after which there was no further increase in size. Between 3 and 33 months of age there was no age-related change in either the thickness of area 17 or in the separation between dendritic clusters, indicating the volume of area 17 did not change after 3 months of age. Within individual age groups the amount of variation present is greater than that among age groups. Since the number of nucleus-containing neuronal profiles per unit area of layers II/III, IV, V, VIa and VIb was similar in two groups of three animals at 3 and 33 months of age and the diameters of neuronal nuclei were unchanged, there seems to be no significant change in the number of neurons contained in these layers of rat visual cortex between 3 and 33 months of age. It is therefore concluded that no neurons are lost from area 17 as the mature cerebral cortex ages.     

The effect of aging on the neuronal population within area 17 of adult rat cerebral cortex

The brains of Sprague-Dawley rats in various age groups from 3 to 33 months were fixed by perfusion with standard aldehyde solutions in order to determine the effects of aging on neuronal numbers. Several indices of cortical volume were then measured to determine whether neuronal packing densities were affected by age-related change in cortical volume. The lengths, heights and widths of individual hemispheres for 160 animals ranging in age from 1 day to 36 months were first determined, after which blocks of tissue were removed from area 17 of some of the brains. These blocks were osmicated, embedded in Araldite and sectioned at 1 micrometer to ascertain, in the vertical plane, the thickness of area 17 and, in the tangential plane, the packing density of the clusters of apical dendrites extending from layer V pyramidal neurons. Results indicate the overall dimensions of the cerebral hemispheres increased until 3 months of age, after which there was no further increase in size. Between 3 and 33 months of age there was no age-related change in either the thickness of area 17 or in the separation between dendritic clusters, indicating the volume of area 17 did not change after 3 months of age. Within individual age groups the amount of variation present is greater than that among age groups. Since the number of nucleus-containing neuronal profiles per unit area of layers II/III, IV, V, VIa and VIb was similar in two groups of three animals at 3 and 33 months of age and the diameters of neuronal nuclei were unchanged, there seems to be no significant change in the number of neurons contained in these layers of rat visual cortex between 3 and 33 months of age. It is therefore concluded that no neurons are lost from area 17 as the mature cerebral cortex ages.     

褪黑素对6-OHDA诱导大鼠模型黑质神经元和胶质细胞的影响

目的探察褪黑素(melatonin,MT)对6-羟基多巴(6-hydroxydopamine,6-OHDA)诱导的帕金森病(Parkinson’sdisease,PD)模型大鼠黑质神经元和胶质细胞的影响。方法选取35只成年雄性SD大鼠,随机分成正常对照组、6-OHDA处理组和6-OHDA+MT处理组,采用免疫组化染色检测各组大鼠黑质Iba1、GFAP阳性胶质细胞及多巴胺(Dopamine,DA)能神经元的形态结构变化,并进行细胞计数,蛋白印迹技术(Western blotting)检测TH、GFAP、OX42蛋白表达水平的变化。实验数据用统计学软件进行分析,P<0.05为差异具有统计学意义。结果 6-OHDA处理组黑质胶质细胞呈激活状态,且数量明显多于对照组和6-OHDA+MT处理组(P<0.05),TH阳性多巴胺能神经元数量明显少于对照组和6-OHDA+MT处理组(P<0.05),对照组和6-OHDA+MT处理组无明显差异(P>0.05);6-OHDA处理组TH蛋白的表达水平明显下调(P<0.05),OX42、GFAP蛋白的表达水平明显上调(P<0.05),对照组和6-OHDA+MT处理组无明显差异(P>0.05)。结论MT能够抑制6-OHDA帕金森病大鼠模型黑质胶质细胞的增殖和活化,并推测MT可能通过这一抑制作用保护DA能神经元。     

Topographical projections from the cerebral cortex to the nucleus of the solitary tract in the cat

Summary The distribution of cerebral cortical neurons sending projection fibers to the nucleus of the solitary tract (NST), and the topographical distribution of axon terminals of cortico-NST fibers within the NST were examined in the cat by two sets of experiments with horseradish peroxidase (HRP) and HRP conjugated with wheat germ agglutinin (WGA-HRP). First, HRP was injected into the NST. In the cerebral cortex of these cats, neuronal cell bodies were labeled retrogradely in the deep pyramidal cell layer (layer V): After HRP injection centered on the rostral or middle part of the NST, HRP-labeled neuronal cell bodies were distributed mainly in the orbital gyrus and caudal part of the infralimbic cortex, and additionally in the rostral part of the anterior sylvian gyrus. After HRP injection centered on the caudal part of the NST, labeled neuronal cell bodies were seen mainly in the caudoventral part of the infralimbic cortex, and additionally in the orbital gyrus, posterior sigmoid gyrus and rostral part of the anterior sylvian gyrus. The labeling in the infralimbic cortex, orbital gyrus and anterior sylvian gyrus was bilateral with a predominantly ipsilateral distribution, while that in the posterior sigmoid gyrus was bilateral with a clear-cut contralateral dominance. In the second set of experiments, WGA-HRP was injected into the cerebral cortical regions where neuronal cell bodies had been retrogradely labeled with HRP injected into the NST: After WGA-HRP injection into the orbital gyrus, presumed axon terminals in the NST were labeled in the rostral two thirds of the nucleus bilaterally with an ipsilateral predominance. After WGA-HRP injection into the rostral part of the anterior sylvian gyrus, a moderate number of presumed axon terminals were labeled throughout the whole rostrocaudal extent of the NST bilaterally with a slight ipsilateral dominance. After WGA-HRP injection into the middle and caudal parts of the anterior sylvian gyrus, no labeling was found in the NST. After WGA-HRP injection into the caudal part of the infralimbic cortex, presumed terminal labeling in the NST was seen throughout the whole rostrocaudal extent of the nucleus bilaterally with a dominant ipsilateral distribution. After WGA-HRP injection into the posterior sigmoid gyrus, however, no terminal labeling was found in the NST. The results indicate that cortico-NST fibers from the orbital gyrus terminate in the rostral two thirds of the NST, while those from the infralimbic cortex and the rostral part of the anterior sylvian gyrus project to the whole rostrocaudal extent of the NST.     

Functional organization of inferior area 6 in the macaque monkey

Summary The functional properties of neurons located in the rostral part of inferior area 6 were studied in awake, partially restrained macaque monkeys. The most interesting property of these neurons was that their firing correlated with specific goal-related motor acts rather than with single movements made by the animal. Using the motor acts as the classification criterion we subdivided the neurons into six classes, four related to distal motor acts and two related to proximal motor acts. The distal classes are: Grasping-with-the-hand-and-the-mouth neurons, Grasping-with-the-hand neurons, Holding neurons and Tearing neurons. The proximal classes are: Reaching neurons and Bringing-to-the-mouth-or-to-the-body neurons. The vast majority of the cells belonged to the distal classes. A particularly interesting aspect of distal class neurons was that the discharge of many of them depended on the way in which the hand was shaped during the motor act. Three main groups of neurons were distinguished: Precision grip neurons, Finger prehension neurons, Whole hand prehension neurons. Almost the totality of neurons fired during motor acts performed with either hand. About 50% of the recorded neurons responded to somatosensory stimuli and about 20% to visual stimuli. Visual neurons were more difficult to trigger than the corresponding neurons located in the caudal part of inferior area 6 (area F4). They required motivationally meaningful stimuli and for some of them the size of the stimulus was also critical. In the case of distal neurons there was a relationship between the type of prehension coded by the cells and the size of the stimulus effective in triggering the neurons. It is proposed that the different classes of neurons form a vocabulary of motor acts and that this vocabulary can be accessed by somatosensory and visual stimuli.     

Electrophysiological investigations on the projections from the cerebral cortex to the vermal posterior lobe of the cerebellum

Summary The following cerebrocortical areas have been electrically stimulated in cats under Nembutal anaesthesia: forelimb and hindlimb areas of the primary sensorimotor cortex, primary and secondary acoustic areas and visual area. Stimulation of these regions evokes in the vermal portion of lobuli VI and VII of the cerebellum potentials at a short latency (2.8–3.5 ms) and at a longer latency (12–22 ms), which have been identified as due to mossy and climbing fibre inputs respectively. Each point of the cerebellar cortex receives usually projections by some and never by all the stimulated cerebrocortical areas. The different cortical regions don't project predominantly to separate parts of the cerebellar cortex, but they project in an apparently random manner with a patchy arrangement.In the anterior lobe we have confirmed the known somatotopy from the primary sensorimotor cortex and we have found no projections from the other cerebrocortical areas.This work has been performed in part with a grant given by the Consiglio Nazionale delle Ricerche to the E.U.L.O., Brescia     

Anatomical evidence for the projections from the basal nucleus of the amygdala to the primary visual cortex in the cat

The amygdaloid complex receives information from all sensory systems, especially from vision. In the primate, the amygdala is reciprocally interconnected with some regions of high-order visual cortices such as TE and TEO and only projects to the primary visual cortex (V1, area 17) without direct projection from V1. However, in the cat little is known about the projection from the amygdala to the primary visual cortex. In this study, anatomical study is carried out in cats to determine whether the amygdala sends feedback projection to area 17. FlouroGold, a fluorescent dye was microinjected into area 17 in cats. In the basal nucleus in the amygdala, the retrograde labeled cells (about 30% of total number of the region of interest observed) are distributed widely in an irregular manner, neither in lamina nor in group. The results provide the first anatomical evidence of the amygdale projection to area 17 in the cat, which is a widely used animal model for vision research.     

Autoradiographic study of early neurogenesis in rat neocortex

Summary The early neurogenesis of rat neocortex was analysed by means of light and electron microscopic autoradiography. It was found that the very first preneurons originate probably as early as ED 11. They are the horizontal cells of Cajal-Retzius. The peak of their formation is on ED 13 (surface index estimated on ED 17 after injection of ³H-thymidine on ED 13:21, after injection on ED 12:4, after injection on ED 15:5), whereas no Cajal-Retzius cells could be found to have originated after ED 15. These cells are the developmentally most advanced of the neocortex. The cells second in date of origin and maturation are preneurons which presumably correspond to the presumptive neurons of Layer VII (VI b), and begin to originate on ED 12. The end of their formation could not be defined owing to a lack of ultrastructural differences to other, younger preneurons in later gestational stages. These two cell types are the first cellular components of the primordial plexiform layer (Marin-Padilla, 1978) or pallial anlage (Rickmann, 1977), demonstrating an outside-in gradient within this layer, and are separated by the formation of the cortical plate. This could be proven by their simultaneous labelling above and below the cortical plate after administration of ³H-thymidine before ED 15. These results confirm the hypothesis of a dual origin of the mammalian neocortex (Marin-Padilla, 1978).