RESUMEN
The cytoarchitecture and cortical connections of the ventral motor region are investigated using Nissl, and NeuN staining methods and the fluorescent retrograde tract tracing technique in the rhesus monkey. On the basis of gradual laminar differentiation, it is shown that the ventral motor region stems from the ventral proisocortical area (anterior insula and dorsal Sylvian opercular region). The cytoarchitecture of the ventral motor region is shown to progress in three lines, as we have recently shown for the dorsal motor region. Namely, root (anterior insular and dorsal Sylvian opercular area ProM), belt (ventral premotor cortex) and core (precentral motor cortex) lines. This stepwise architectonic organization is supported by the overall patterns of corticocortical connections. Areas in each line are sequentially interconnected (intralineal connections) and all lines are interconnected (interlinear connections). Moreover, root areas, as well as some of the belt areas of the ventral and dorsal trend are interconnected. The ventral motor region is also connected with the ventral somatosensory areas in a topographic manner. The root and belt areas of ventral motor region are connected with paralimbic, multimodal and prefrontal (outer belt) areas. In contrast, the core area has a comparatively more restricted pattern of corticocortical connections. This architectonic and connectional organization is consistent in part, with the functional organization of the ventral motor region as reported in behavioral and neuroimaging studies which include the mediation of facial expression and emotion, communication, phonic articulation, and language in human.
Asunto(s)
Corteza Cerebral/citología , Macaca mulatta/anatomía & histología , Animales , Mapeo Encefálico/métodos , Corteza Cerebral/fisiología , Estimulación Eléctrica/métodos , Macaca mulatta/fisiología , Vías Nerviosas/citología , Vías Nerviosas/fisiología , Técnicas de Trazados de Vías Neuroanatómicas , FotomicrografíaRESUMEN
The cytoarchitecture and cortical connections of the anterior cingulate, medial and dorsal premotor, and precentral region are investigated using the Nissl and NeuN staining methods and the fluorescent retrograde tract tracing technique. There is a gradual stepwise laminar change in the cytoarchitectonic organization from the proisocortical anterior cingulate region, through the lower and upper banks of the cingulate sulcus, to the dorsolateral isocortical premotor and precentral motor regions of the frontal lobe. These changes are characterized by a gradational emphasis on the lower stratum layers (V and VI) in the proisocortical cingulate region to the upper stratum layers (II and III) in the premotor and precentral motor region. This is accompanied by a progressive widening of layers III and VI, a poorly delineated border between layers III and V and a sequential increase in the size of layer V neurons culminating in the presence of giant Betz cells in the precentral motor region. The overall patterns of corticocortical connections paralleled the sequential changes in cytoarchitectonic organization. The proisocortical areas have connections with cingulate motor, supplementary motor, premotor and precentral motor areas on the one hand and have widespread connections with the frontal, parietal, temporal and multimodal association cortex and limbic regions on the other. The dorsal premotor areas have connections with the proisocortical areas including cingulate motor areas and supplementary motor area on the one hand, and premotor and precentral motor cortex on the other. Additionally, this region has significant connections with posterior parietal cortex and limited connections with prefrontal, limbic and multimodal regions. The precentral motor cortex also has connections with the proisocortical areas and premotor areas. Its other connections are limited to the somatosensory regions of the parietal lobe. Since the isocortical motor areas on the dorsal convexity mediate voluntary motor function, their close connectional relationship with the cingulate areas form a pivotal limbic-motor interface that could provide critical sources of cognitive, emotional and motivational influence on complex motor function.
Asunto(s)
Encéfalo/citología , Vías Nerviosas/citología , Animales , Inmunohistoquímica , Macaca mulattaRESUMEN
An understanding of visual function at the cerebral cortical level requires detailed knowledge of anatomical connectivity. Cortical association pathways and terminations of preoccipital visual areas were investigated in rhesus monkeys by using the autoradiographic tracing technique. Medial and adjacent dorsomedial preoccipital regions project via the occipitofrontal fascicle to the frontal lobe (dorsal area 6, and areas 8Ad, 8B, and 46); via the dorsal portion of the superior longitudinal fascicle (SLF) to dorsal area 6, area 9, and the supplementary motor area; and via the cingulate fascicle to area 24. In addition, medial and dorsomedial preoccipital areas send projections to parietal (areas PGm, PEa, PG-Opt, and POa) and superior temporal (areas MST and MT) regions. In contrast, connections from the dorsolateral, annectant, and ventral preoccipital regions are conveyed via the inferior longitudinal fascicle (ILF) to the parietal lobe (areas POa and IPd), superior temporal sulcus (areas MT, MST, FST, V4t, and IPa), inferotemporal region (areas TEO and TE1-TE3), and parahippocampal gyrus (areas TF, TH, and TL). The central-lateral preoccipital region projects via an ILF-SLF pathway to frontal area 8Av. The preoccipital areas also have caudal connections to occipital areas V1, V2, and V3. Finally, preoccipital regions are interconnected via different intrinsic pathways. These findings provide further insight into the nature of preoccipital fiber pathways and the connectional organization of the visual system.
Asunto(s)
Macaca mulatta/anatomía & histología , Corteza Visual/anatomía & histología , Vías Visuales/anatomía & histología , Animales , Lóbulo Frontal/anatomía & histología , Lóbulo Frontal/metabolismo , Marcaje Isotópico/métodos , Macaca mulatta/metabolismo , Lóbulo Occipital/anatomía & histología , Lóbulo Occipital/metabolismo , Lóbulo Parietal/anatomía & histología , Lóbulo Parietal/metabolismo , Corteza Visual/metabolismo , Vías Visuales/metabolismoRESUMEN
MRI tractography is the mapping of neural fiber pathways based on diffusion MRI of tissue diffusion anisotropy. Tractography based on diffusion tensor imaging (DTI) cannot directly image multiple fiber orientations within a single voxel. To address this limitation, diffusion spectrum MRI (DSI) and related methods were developed to image complex distributions of intravoxel fiber orientation. Here we demonstrate that tractography based on DSI has the capacity to image crossing fibers in neural tissue. DSI was performed in formalin-fixed brains of adult macaque and in the brains of healthy human subjects. Fiber tract solutions were constructed by a streamline procedure, following directions of maximum diffusion at every point, and analyzed in an interactive visualization environment (TrackVis). We report that DSI tractography accurately shows the known anatomic fiber crossings in optic chiasm, centrum semiovale, and brainstem; fiber intersections in gray matter, including cerebellar folia and the caudate nucleus; and radial fiber architecture in cerebral cortex. In contrast, none of these examples of fiber crossing and complex structure was identified by DTI analysis of the same data sets. These findings indicate that DSI tractography is able to image crossing fibers in neural tissue, an essential step toward non-invasive imaging of connectional neuroanatomy.
Asunto(s)
Imagen de Difusión por Resonancia Magnética/métodos , Fibras Nerviosas/fisiología , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiología , Adulto , Algoritmos , Animales , Encéfalo/anatomía & histología , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Macaca fascicularis , Masculino , Persona de Mediana EdadRESUMEN
The efferent association fibers from the caudal part of the prefrontal cortex to posterior cortical areas course via several pathways: the three components of the superior longitudinal fasciculus (SLF I, SLF II, and SLF III), the arcuate fasciculus (AF), the fronto-occipital fasciculus (FOF), the cingulate fasciculus (CING F), and the extreme capsule (Extm C). Fibers from area 8Av course via FOF and SLF II, merging in the white matter of the inferior parietal lobule (IPL) and terminating in the caudal intraparietal sulcus (IPS). A group of these fibers turns ventrally to terminate in the caudal superior temporal sulcus (STS). Fibers from the rostral part of area 8Ad course via FOF and SLF II to the IPS and IPL and via the AF to the caudal superior temporal gyrus and STS. Some fibers from the rostral part of area 8Ad are conveyed to the medial parieto-occipital region via FOF, to the STS via Extm C, and to the caudal cingulate gyrus via CING F. Fibers from area 8B travel via SLF I to the supplementary motor area and area 31 in the caudal dorsal cingulate region and via the CING F to cingulate areas 24 and 23 and the cingulate motor areas. Fibers from area 9/46d course via SLF I to the superior parietal lobule and medial parieto-occipital region, via SLF II to the IPL. Fibers from area 9/46v travel via SLF III to the rostral IPL and the frontoparietal opercular region and via the CING F to the cingulate gyrus.
Asunto(s)
Vías Eferentes/anatomía & histología , Macaca/anatomía & histología , Corteza Prefrontal/anatomía & histología , Aminoácidos/química , Aminoácidos/metabolismo , Animales , Vías Eferentes/metabolismo , Isótopos/química , Isótopos/metabolismo , Macaca/metabolismo , Imagen por Resonancia Magnética , Corteza Prefrontal/metabolismoRESUMEN
The cytoarchitecture and connections of the caudal cingulate and medial somatosensory areas were investigated in the rhesus monkey. There is a stepwise laminar differentiation starting from retrosplenial area 30 towards the isocortical regions of the medial parietal cortex. This includes a gradational emphasis on supragranular laminar organization and general reduction of the infragranular neurons as one proceeds from area 30 toward the medial parietal regions, including areas 3, 1, 2, 5, 31, and the supplementary sensory area (SSA). This trend includes a progressive increase in layer IV neurons. Area 23c in the lower bank and transitional somatosensory area (TSA) in the upper bank of the cingulate sulcus appear as nodal points. From area 23c and TSA the architectonic progression can be traced in three directions: one culminates in areas 3a and 3b (core line), the second in areas 1, 2, and 5 (belt line), and the third in areas 31 and SSA (root line). These architectonic gradients are reflected in the connections of these regions. Thus, cingulate areas (30, 23a, and 23b) are connected with area 23c and TSA on the one hand and have widespread connections with parieto-temporal, frontal, and parahippocampal (limbic) regions on the other. Area 23c has connections with areas 30, 23a and b, and TSA as well as with medial somatosensory areas 3, 1, 2, 5, and SSA. Area 23c also has connections with parietotemporal, frontal, and limbic areas similar to areas 30, 23a, and 23b. Area TSA, like area 23c, has connections with areas 3, 1, 2, 5, and SSA. However, it has only limited connections with the parietotemporal and frontal regions and none with the parahippocampal gyrus. Medial area 3 is mainly connected to medial and dorsal sensory areas 3, 1, 2, 5, and SSA and to areas 4 and 6 as well as to supplementary (M2 or area 6m), rostral cingulate (M3 or areas 24c and d), and caudal cingulate (M4 or areas 23c and d) motor cortices. Thus, in parallel with the architectonic gradient of laminar differentiation, there is also a progressive shift in the pattern of corticocortical connections. Cingulate areas have widespread connections with limbic, parietotemporal, and frontal association areas, whereas parietal area 3 has more restricted connections with adjacent somatosensory and motor cortices. TSA is primarily related to the somatosensory-motor areas and has limited connections with the parietotemporal and frontal association cortices.
Asunto(s)
Giro del Cíngulo/citología , Giro del Cíngulo/fisiología , Corteza Somatosensorial/citología , Corteza Somatosensorial/fisiología , Animales , Macaca mulatta , Vías Nerviosas/citología , Vías Nerviosas/fisiologíaRESUMEN
A comparison of the cytoarchitecture of the human and the macaque monkey ventrolateral prefrontal cortex demonstrated a region in the monkey that exhibits the architectonic characteristic of area 45 in the human brain. This region occupies the dorsal part of the ventrolateral prefrontal convexity just below area 9/46v. Rostroventral to area 45 in the human brain lies a large cortical region labelled as area 47 by Brodmann. The ventrolateral component of this region extending as far as the lateral orbital sulcus has architectonic characteristics similar to those of the ventrolateral prefrontal region labelled by Walker as area 12 in the macaque monkey. We designated this region in both the human and the monkey ventrolateral prefrontal cortex as area 47/12. Thus, area 47/12 designates the specific part of the zone previously labelled as area 47 in the human brain that has the same overall architectonic pattern as that of Walker's area 12 in the macaque monkey brain. The cortical connections of these two areas were examined in the monkey by injecting fluorescent retrograde tracers. Although both area 45 and area 47/12 as defined here had complex multimodal input, they could be differentiated in terms of some of their inputs. Retrograde tracers restricted to area 47/12 resulted in heavy labelling of neurons in the rostral inferotemporal visual association cortex and in temporal limbic areas (i.e. perirhinal and parahippocampal cortex). In contrast, injections of tracers into dorsally adjacent area 45 demonstrated strong labelling in the superior temporal gyrus (i.e. the auditory association cortex) and the multimodal cortex in the upper bank of the superior temporal sulcus.
Asunto(s)
Macaca mulatta/anatomía & histología , Vías Nerviosas/fisiología , Neuronas/citología , Neuronas/fisiología , Corteza Prefrontal/citología , Corteza Prefrontal/fisiología , Anciano , Animales , Mapeo Encefálico , Colorantes , Colorantes Fluorescentes , Humanos , Macaca mulatta/fisiología , MasculinoRESUMEN
Because of the sharp curvature of the retrosplenial region around the splenium of the corpus callosum, standard coronal sections are not appropriate for architectonic analysis of its posteroventral part. In the present study, examination of the posteroventral retrosplenial region of the rhesus monkey in sections that were orthogonal to its axis of curvature (and therefore appropriate for architectonic analysis) has permitted definition of its architecture and precise extent. This analysis demonstrated that areas 29 and 30 of the retrosplenial cortex, as well as adjacent area 23 of the posterior cingulate cortex, extend together as an arch around the splenium of the corpus callosum and maintain their topographical relationship with one another throughout their entire course. Injections of anterograde and retrograde tracers confined to retrosplenial area 30 revealed that this area has reciprocal connections with adjacent areas 23, 19 and PGm, with the mid-dorsolateral part of the prefrontal cortex (areas 9, 9/46 and 46), with multimodal area TPO in the superior temporal sulcus, as well as the posterior parahippocampal cortex, the presubiculum and the entorhinal cortex. There are also bidirectional connections with the lateroposterior thalamic nucleus, as well as the laterodorsal and the anteroventral limbic thalamic nuclei. The connectivity of area 30 suggests that it may play a role in working memory processes subserved by the mid-dorsolateral frontal cortex in interaction with the hippocampal system.
Asunto(s)
Mapeo Encefálico , Corteza Cerebral/anatomía & histología , Corteza Cerebral/fisiología , Cuerpo Calloso/fisiología , Macaca mulatta/anatomía & histología , Macaca mulatta/fisiología , Animales , Cuerpo Calloso/anatomía & histología , Giro del Cíngulo/anatomía & histología , Giro del Cíngulo/citología , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiologíaRESUMEN
The cytoarchitecture of the human and the macaque monkey dorsolateral prefrontal cortex has been examined in a strictly comparative manner in order to resolve major discrepancies between the available segmentations of this cortical region in the human and the monkey brain. In addition, the connections of the dorsolateral prefrontal cortical areas were re-examined in the monkey. The present analysis showed that only a restricted portion of what had previously been labelled as area 46 in the monkey has the same characteristics as area 46 of the human brain; the remaining part of this monkey region has the characteristics of a portion of the middle frontal gyrus in the human brain that had previously been included as part of area 9. We have labelled this cortical area as 9/46 in both species. These two areas (i.e. 46 and 9/46), which constitute the lower half of the mid-dorsolateral frontal cortex, have a well-developed granular layer IV, and can easily be distinguished from area 9, on the upper part of the mid-dorsolateral region, which does not have a well-developed granular layer IV. Area 9 has the same basic pattern of connections as areas 46 and 9/46, but, unlike the latter areas, it does not receive input from the lateral parietal cortex. Caudal to area 9, on the dorsomedial portion of the frontal cortex, there is a distinct strip of cortex (area 8B) which, unlike area 9, receives significant input from the prestriate cortex and the medial parietal cortex. The present results provide a basis for a closer integration of findings from functional neuroimaging studies in human subjects with experimental work in the monkey.
Asunto(s)
Mapeo Encefálico , Interneuronas/fisiología , Macaca mulatta/anatomía & histología , Corteza Prefrontal/anatomía & histología , Corteza Prefrontal/citología , Animales , Humanos , Vías NerviosasRESUMEN
The present study investigated the origin, course, and terminations of the association fiber system linking the frontal cortex with the hippocampal system by means of the cingulum bundle. Injections of tritiated amino acids were placed within individual cytoarchitectonic areas of the frontal cortex in the rhesus monkey. It was demonstrated that the mid-dorsolateral frontal cortex (areas 46, 9/46, and 9) and its medial extension (medial areas 9 and 9/32) is the origin of a specific fiber pathway, running posteriorly as part of the cingulum bundle, and terminating mainly in the retrosplenial area 30 and the posterior presubiculum. This fiber bundle therefore provides the anatomical substrate of a functional interaction between the mid-dorsolateral frontal cortex and the hippocampal memory system for the monitoring of information within working memory.
Asunto(s)
Lóbulo Frontal/anatomía & histología , Giro del Cíngulo/anatomía & histología , Hipocampo/anatomía & histología , Macaca mulatta/anatomía & histología , Fibras Nerviosas/ultraestructura , Animales , Transporte Axonal , Lóbulo Frontal/fisiología , Giro del Cíngulo/fisiología , Hipocampo/fisiología , Leucina/farmacocinética , Neuronas/citología , Neuronas/fisiología , Prolina/farmacocinética , TritioRESUMEN
The connections of the frontoparietal opercular areas were studied in rhesus monkeys by using antero- and retrograde tracer techniques. The rostral opercular cortex including the gustatory and proisocortical motor (ProM) areas is connected with precentral areas 3, 1, and 2 as well as with the rostral portion of the opercular area which resembles the second somatosensory type of cortex (area SII) and the ventral portion of area 6. Its distant connections are with the ventral portion of prefrontal areas 46, 11, 12, and 13 as well as with the rostral insula and cingulate motor area (CMAr). The mid opercular region (areas 1 and 2) is connected with pre- and postcentral areas 3, 1, and 2 as well as SII. Additionally, it is connected with the ventral portion of area 6, area 44, area ProM, the gustatory area, and the rostral insula. Its distant connections are with area 4, the ventral portion of area 46, area 7b, and area POa in the intraparietal sulcus (IPS). The rostral parietal opercular region is connected with the postcentral portions of areas 3, 1, and 2; areas 5, 7, and SII; the gustatory area; and the vestibular area. Its other connections are with area 4, area 44, the ventral portion of area 46, area ProM, CMAr, and the supplementary motor area (SMA). The caudal opercular region is connected with the dorsal portion of area 3; areas 2, 5, and 7a; and areas PEa as well as IPd of IPS. It is also connected with area SII, insula, and the superior temporal sulcus. Its distant connections are with area 44; the dorsal portion of area 8 and the ventral portion of area 46; as well as CMAr, SMA, and the supplementary sensory area. This connectivity suggests that the ventral somatosensory areas are involved in sensorimotor activities mainly related to head, neck, and face structures as well as to taste. Additionally, these areas may have a role in frontal (working) and temporal (tactile) memory systems.
Asunto(s)
Corteza Cerebral/anatomía & histología , Lóbulo Frontal/anatomía & histología , Macaca mulatta/anatomía & histología , Lóbulo Parietal/anatomía & histología , Vías Aferentes/anatomía & histología , Vías Aferentes/fisiología , Amidinas , Animales , Transporte Axonal , Corteza Cerebral/fisiología , Vías Eferentes/anatomía & histología , Vías Eferentes/fisiología , Colorantes Fluorescentes , Lóbulo Frontal/fisiología , Lóbulo Parietal/fisiologíaRESUMEN
Corticostriatal connections of auditory areas within the supratemporal plane and in rostral and caudal portions of the superior temporal gyrus were studied by the autoradiographic anterograde tracing technique. The results show that the primary auditory cortex has limited projections to the caudoventral putamen and to the tail of the caudate nucleus. In contrast, the second auditory area within the circular sulcus has connections to the rostral and the caudal putamen and to the body of the caudate nucleus and the tail. The association areas of the superior temporal gyrus collectively have widespread corticostriatal projections characterized by differential topographic distributions. The rostral part of the gyrus projects to ventral portions of the head of the caudate nucleus and of the body and to the tail. In addition, there are connections to rostroventral and caudoventral portions of the putamen. The mid-portion of the gyrus projects to similar striatal regions, but the connections to the head of the caudate nucleus are less extensive. Compared with the rostral and middle parts of the superior temporal gyrus, the caudal portion has little connectivity to the tail of the caudate nucleus. It projects more dorsally within the head and the body and also more dorsally within the caudal putamen. These differential patterns of corticostriatal connectivity are consistent with functional specialization at the cortical level.
Asunto(s)
Corteza Auditiva/citología , Macaca mulatta/anatomía & histología , Neostriado/citología , Lóbulo Temporal/citología , Animales , Vías Auditivas , Autorradiografía , MicroinyeccionesRESUMEN
The precise characterization of cortical connectivity is important for the understanding of brain morphological and functional organization. Such connectivity is conveyed by specific pathways or tracts in the white matter. Diffusion-weighted magnetic resonance imaging detects the diffusivity of water molecules in three dimensions. Diffusivity is anisotropic in oriented tissues such as fiber tracts. In the present study, we used this method to map (in terms of orientation, location, and size) the "stem" (compact portion) of the principal association, projection, and commissural white matter pathways of the human brain in vivo, in 3 normal subjects. In addition, its use in clinical neurology is illustrated in a patient with left inferior parietal lobule embolic infarction in whom a significant reduction in relative size of the stem of the left superior longitudinal fasciculus was observed. This represents an important method for the characterization of major association pathways in the living human that are not discernible by conventional magnetic resonance imaging. In the clinical domain, this method will have a potential impact on the understanding of the diseases that involve white matter such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, head injury, and spinal cord injury.
Asunto(s)
Corteza Cerebral/anatomía & histología , Corteza Cerebral/metabolismo , Difusión , Imagen por Resonancia Magnética/métodos , Corteza Cerebral/patología , Trastornos Cerebrovasculares/metabolismo , Trastornos Cerebrovasculares/patología , HumanosRESUMEN
Corticothalamic connections of extrastriate visual areas were studied by using the autoradiographic anterograde tracing technique. The results show that the medial extrastriate region above the calcarine sulcus projects mainly to the lateral pulvinar (PL), medial pulvinar (PM), and lateral posterior (LP) nuclei. In addition, the dorsal portion of the medial region has connections to the lateral dorsal (LD) as well as to intralaminar nuclei. The dorsolateral extrastriate region projects strongly to the PL and LP nuclei, to the PM and inferior pulvinar (PI) nuclei, and to the LD and intralaminar nuclei. The lateral extrastriate region above the inferior occipital sulcus (IOS) has strong connections to both the PL and PI nuclei and has minor projections to the PM and oral pulvinar nuclei. The ventrolateral extrastriate region below the IOS projects mainly to the PI nucleus and to the caudal portion of the PL nucleus and has some projections to the PM nucleus. The ventromedial extrastriate region medial to the occipitotemporal sulcus has strong connections with the ventral and medial sectors of the PI nucleus. This region also projects to the caudal portion of the PL nucleus and has minor connections to the LP nucleus. Finally, the annectant gyrus projects to the PL nucleus and to the rostral portion of the PI nucleus and has minor connections to the PM nucleus. Thus, the medial and dorsolateral extrastriate regions are related mainly to the PL and LP nuclei as well as to intralaminar nuclei. In contrast, the ventrolateral and ventromedial regions are connected strongly with the PI nucleus. This connectional organization appears to reflect functional differentiation at the cortical level.
Asunto(s)
Corteza Cerebral/fisiología , Macaca mulatta/fisiología , Tálamo/fisiología , Vías Visuales/fisiología , Animales , Autorradiografía , Mapeo EncefálicoRESUMEN
If there is a cerebellar contribution to nonmotor function, particularly to cognitive abilities and affective states, then there must be corresponding anatomic substrates that support this. The cerebellum is strongly interconnected with the cerebral hemispheres in both feedforward (cerebral hemispheres to cerebellum) and feedback directions. This relationship has long been recognized, particularly with respect to the motor and sensory cortices. Investigations performed over the last decade however, have demonstrated for the first time the organization and strength of the connections that link the cerebellum with areas of the cerebral cortex known to be concerned with higher order behavior rather than with motor control. The feedforward projections from these higher order areas, namely the associative and paralimbic cortices, seem to be matched, at least in the limited but definite demonstrations to date, by cerebellar projections back to these same areas. These observations are important because they are congruent with the notion that cognitive functions are distributed among multiple cortical and subcortical nodes, each of which functions in concert but in a unique manner to produce an ultimate behavior pattern. This chapter describes the neural circuitry postulated to subserve the cerebellar contribution to nonmotor processing, particularly cognitive and affective modulation, and discusses the theoretical implications of these anatomic findings.
Asunto(s)
Afecto/fisiología , Cerebelo/fisiología , Corteza Cerebral/fisiología , Cognición/fisiología , Animales , Retroalimentación , Humanos , Fibras Nerviosas/fisiologíaRESUMEN
In our ongoing attempt to determine the anatomic substrates that could support a cerebellar contribution to cognitive processing, we investigated the prefrontal cortical projections to the basilar pons. A detailed understanding of these pathways is needed, because the prefrontal cortex is critical for a number of complex cognitive operations, and the corticopontine projection is the obligatory first step in the corticopontocerebellar circuit. Prefrontopontine connections were studied using the autoradiographic technique in rhesus monkey. The pontine projections were most prominent and occupied the greatest rostrocaudal extent of the pons when derived from the dorsolateral prefrontal convexity, including areas 8Ad, 9/46d, and 10. Lesser pontine projections were observed from the medial prefrontal convexity and area 45B in the inferior limb of the arcuate sulcus. In contrast, ventral prefrontal and orbitofrontal cortices did not demonstrate pontine projections. The prefrontopontine terminations were located preferentially in the paramedian nucleus and in the medial parts of the peripeduncular nucleus, but each cortical area appeared to have a unique complement of pontine nuclei with which it is connected. The existence of these corticopontine pathways from prefrontal areas concerned with multiple domains of higher-order processing is consistent with the hypothesis that the cerebellum is an essential node in the distributed corticosubcortical neural circuits subserving cognitive operations.
Asunto(s)
Macaca mulatta/anatomía & histología , Macaca mulatta/fisiología , Puente/anatomía & histología , Puente/fisiología , Corteza Prefrontal/fisiología , Transmisión Sináptica , Animales , Autorradiografía , Mapeo Encefálico , Vías Nerviosas/anatomía & histologíaRESUMEN
The advent of new technology has led to a proliferation of studies examining the functional roles of discrete prefrontal cortical areas. This has created a need for more precise information regarding the morphological characteristics of this region. Existing architectonic maps of human and monkey brains are not compatible with regard to areal delineations and topography, creating significant difficulty in interpreting comparative data. Therefore, we have re-examined the comparative morphological organization of the prefrontal cortex in humans and rhesus monkeys. Our analysis indicates that the architectonic areas in both species correspond in terms of morphological features as well as topographical locations. We have developed a common organizational schema for these areas, thereby allowing for a resolution of previous discrepancies. Moreover, in monkeys a connectional analysis has revealed that each of the newly designated areas is characterized by a unique pattern of cortical relationships. The present organizational schema provides a framework for interrelating findings such as those obtained from human brain imaging studies with those from behavioural investigations of non-human primates.
Asunto(s)
Corteza Prefrontal/anatomía & histología , Corteza Prefrontal/fisiología , Amidinas , Animales , Corteza Cerebral/anatomía & histología , Corteza Cerebral/fisiología , Haplorrinos , Humanos , Vías Nerviosas/anatomía & histología , Vías Nerviosas/fisiologíaRESUMEN
The feedforward limb of the cerebrocerebellar system is directed largely through the corticopontine pathway. We determined the extent to which higher order corticopontine projections are derived from prefrontal associative cortices by injecting anterograde tracers into multiple prefrontal regions in rhesus monkeys. Most prefrontopontine projections were derived from the dorsolateral and dorsomedial convexities, including areas 8A, 46 dorsal, 9, and 10; and lighter projections arose from medial and ventrolateral cortices. These findings strengthen the observation that the cerebrocerebellar system incorporates associative cerebral regions, and they enhance the notion that the cerebellum participates in the organization of cognitive function.
Asunto(s)
Cerebelo/citología , Cognición/fisiología , Vías Nerviosas/fisiología , Puente/citología , Corteza Prefrontal/citología , Animales , Macaca mulattaRESUMEN
Cortical auditory areas located in the superior temporal region (STR) in monkey and human. The primary auditory area (AI) occupies the cortex of the supratemporal plane (STP) and is surrounded by auditory association areas in circular sulcus and superior temporal gyrus (STG). Architectonic studies have parcellated auditory areas into a number of subregions. Beginning from the temporal polar proisocortex up to the parietal cortex, these areas shows progressive laminar differentiation, and are arranged into three parallel lines. The most medial line occupies the cortex of the circular sulcus. The regions of this line maintains limbic features and is termed as root line. Another line is located in STG. The regions of this line show progressive emphasis in the third and fourth layer neurons and is termed as belt line. Interposed between root and belt line is a core line located in STP. In this line there is greater accumulation of fourth layer neurons. Recent physiological studies have outlined several auditory representations surrounding AI. These auditory representations correspond to above mentioned architectonic subregions of STR. The subregions within each line have bidirectional connectional laminar specificity. The feedforward connections originate from the supragranular layer III and terminate in the around layer IV of the rostrally adjacent region. Feedback projections in contrast stem from the infragranular layers and terminate in layer I. The long association connections of auditory areas are with the prefrontal cortex (PFC), the multimodal areas and the limbic regions, and are derived from belt and root line areas of STR. These projections follow the rostro-caudal architectonic differentiation of STR. Thus the rostral STG areas are mainly connected with orbital and medial PFC areas whereas the caudal STG areas are connected with caudal PFC. The intermediate STG areas are preferentially related to the lateral PFC regions. It seems that STG-PFC connections are between the areas with similar level of architectonic differentiation. The thalamic connections of the subregions of STR also follow the architectonic organizations. The core line areas are preferentially related to ventral nucleus (MGv) of medial geniculate nucleus (MGN) whereas the root and belt line areas are connected respectively to magnocellular (MGmc) and dorsal (MGd) subdivisions of MGN. The root and belt areas share some connections and are also related to pulvinar, suprageniculate, dorsomedial and intralaminar nuclei. It seems therefore that progressive laminar and tripartrate organization of auditory regions of STR is reflected in intrinsic, association and thalamic connections. The feedforward connections may be engaged in analysis of external environmental cues whereas feedback connections may have a role in matching learned or stored information with incoming auditory signals. The preferential core line connectivity with MGv may be involved in spectral analysis of sound whereas the connections of the belt and root areas with MGmc, MGd, and pulvinar may have role in sound pattern recognition, auditory memory, the localization of sound in space as well as matching auditory information with other modalities.
Asunto(s)
Corteza Auditiva/anatomía & histología , Animales , Corteza Auditiva/fisiología , Corteza Auditiva/ultraestructura , Corteza Cerebral/anatomía & histología , Corteza Cerebral/fisiología , Corteza Cerebral/ultraestructura , Humanos , Tálamo/anatomía & histología , Tálamo/fisiología , Tálamo/ultraestructuraRESUMEN
The striatal connections of extrastriate visual areas were examined by the autoradiographic technique in rhesus monkeys. The medial as well as the dorsolateral extrastriate regions project preferentially to dorsal and lateral portions of the head and of the body of the caudate nucleus, as well as to the caudodorsal sector of the putamen. The rostral portion of the annectant gyrus has connections to the caudal sector of the body and to the genu, whereas projections from the caudal portion of the lower bank of the superior temporal sulcus are directed to dorsal and central sectors of the head and the body, to the genu and the tail, as well as to the caudal putamen. The ventrolateral extrastriate region is related mainly to the ventral sector of the body, to the genu and the tail, and to the caudal putamen. In contrast, the striatal projections of the ventromedial extrastriate cortex resemble those of the medial and dorsolateral regions. The caudal inferotemporal cortex is related strongly to the tail of the caudate nucleus and to the ventral putamen. The differential corticostriatal connectivity of the various extrastriate regions may contribute to the specific functional roles of these cortices. Thus, the connections from the dorsomedial, dorsolateral, and ventromedial areas to dorsal portions of the caudate nucleus and of the putamen may serve a visuospatial function. In contrast, the connections from the ventrolateral extrastriate and inferotemporal regions to the tail of the caudate nucleus and to the ventral putamen may have a role in visual object-related processes.