Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.59 (MIP)
 4,906 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the origin and topography of cortical projections to area PO, an extrastriate visual area located in the parieto-occipital sulcus of the macaque. Distinguishable retrograde fluorescent tracers were injected into area PO at separate retinotopic loci identified by single-neuron recording. The results indicate that area PO receives retinotopically organized inputs from visual areas V1, V2, V3, V4, and MT. In each of these areas the projection to PO arises from the representation of the periphery of the visual field. This finding is consistent with neurophysiological data indicating that the representation of the periphery is emphasized in PO. Additional projections arise from area MST, the frontal eye fields, and several divisions of parietal cortex, including four zones within the intraparietal sulcus and a region on the medial dorsal surface of the hemisphere (MDP). On the basis of the laminar distribution of labeled cells we conclude that area PO receives an ascending input from V1, V2, and V3 and receives descending or lateral inputs from all other areas. Thus, area PO is at approximately the same level in the hierarchy of visual areas as areas V4 and MT. Area PO is connected both directly and indirectly, via MT and MST, to parietal cortex. Within parietal cortex, area PO is linked to particular regions of the intraparietal sulcus including VIP and LIP and two newly recognized zones termed here MIP and PIP. The wealth of connections with parietal cortex suggests that area PO provides a relatively direct route over which information concerning the visual field periphery can be transmitted from striate and prestriate cortex to parietal cortex. In contrast, area PO has few links with areas projecting to inferior temporal cortex. The pattern of connections revealed in this study is consistent with the view that area PO is primarily involved in visuospatial functioning.
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PMID:Topographical organization of cortical afferents to extrastriate visual area PO in the macaque: a dual tracer study. 245 34

The role of the posterior parietal cortex (PPC) in the visual guidance of movements was studied in monkeys trained to use a joystick to guide a spot to a target. Visual and motor influences were dissociated by transiently occluding the spot and by varying the relationship between the direction of joystick and spot movements. We found a strong segregation of function in PPC during visual guidance. Neurons in area MST were selectively modulated by the direction of visible moving stimuli, whereas neurons in area MIP were selectively modulated by the direction of hand movement. In contrast, the selectivity of cells in the lateral intraparietal area (LIP) did not directly depend on either visual input or motor output, but rather seemed to encode a predictive representation of stimulus movement. These predictive signals may be an important link in visuomotor transformations.
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PMID:Dissociation of visual, motor and predictive signals in parietal cortex during visual guidance. 1019 85

The anatomical and physiological substrata of eye-hand coordination during reaching were studied through combined anatomical and physiological techniques. The association connections of parietal areas V6A and PEc, and those of dorso-rostral (F7) and dorso-caudal (F2) premotor cortex were studied in monkeys, after physiological characterization of the parietal regions where retrograde tracers were injected. The results show that parieto-occipital area V6A is reciprocally connected with F7, and receives a smaller projection from F2. Local parietal projections to V6A arise from areas MIP and, to a lesser extent, 7m, PEa and PEC: On the contrary, parietal area PEc is strongly and reciprocally connected with the part of F2 located close to the pre-central dimple (pre-CD). Local parietal projections to PEc come from a distributed network, including PEa, MIP, PEci and, to a lesser extent, 7m, V6A, 7a and MST. Premotor area F7 receives parietal projections mainly from 7m and V6A, and local frontal projections mainly from F2. On the contrary, premotor area F2 in the pre-CD zone receives parietal inputs from PEc and, to a lesser extent, PEci, while in the peri-arcuate zone F2 receives parietal projections from PEa and MIP. Local frontal projections to F2 pre-CD mostly stem from F4, and, to a lesser extent, from F7 and F3, and CMAd; those addressed to peri-arcuate zone of F2 arise mainly from F5 and, to a lesser extent, from F7, F4, dorsal (CMAd) and ventral (CMAv) cingulate motor areas, pre-supplementary (F6) and supplementary (F3) motor areas. The distribution of association cells in both frontal and parietal cortex was characterized through a spectral analysis that revealed an arrangement of these cells in the form of bands, composed of cell clusters, or 'columns'. The reciprocal connections linking parietal and frontal cortex might explain the presence of visually related and eye-position signals in premotor cortex, as well as the influence of information about arm position and movement direction in V6A and PEC: The association connections identified in this study might carry sensory as well motor information that presumably provides a basis for a re-entrant signaling. This might be necessary to match retinal-, eye- and hand-related information underlying eye-hand coordination during reaching.
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PMID:Eye-hand coordination during reaching. I. Anatomical relationships between parietal and frontal cortex. 1137 13

In primates, the frontal eye field (FEF) contains separate representations of saccadic and smooth-pursuit eye movements. The smooth-pursuit region (FEFsem) in macaque monkeys lies principally in the fundus and deep posterior wall of the arcuate sulcus, between the FEF saccade region (FEFsac) in the anterior wall and somatomotor areas on the posterior wall and convexity. In this study, cortical afferents to FEFsem were mapped by injecting retrograde tracers (WGA-HRP and fast blue) into electrophysiologically identified FEFsem sites in two monkeys. In the frontal lobe, labeled neurons were found mostly on the ipsilateral side in the (1) supplementary eye field region and lateral area F7; (2) area F2 along the superior limb of the arcuate sulcus; and (3) in the buried cortex of the arcuate sulcus extending along the superior and inferior limbs and including FEFsac and adjacent areas 8, 45, and PMv. Labeled cells were also found in the caudal periprincipal cortex (area 46) in one monkey. Labeled cells were found bilaterally in the frontal lobe in the deep posterior walls of the arcuate sulcus and postarcuate spurs and in cingulate motor areas 24 and 24c. In postcentral cortical areas all labeling was ipsilateral and there were two major foci of labeled cells: (1) the depths of the intraparietal sulcus including areas VIP, LIP, and PEa, and (2) the anterior wall and fundus of the superior temporal sulcus including areas PP and MST. Smaller numbers of labeled cells were found in superior temporal sulcal areas FST, MT, and STP, posterior cingulate area 23b, area 3a within the central sulcus, areas SII, RI, Tpt in the lateral sulcus, and parietal areas 7a, 7b, PEc, MIP, DP, and V3A. Many of these posterior afferent cortical areas code visual-motion (MT, MST, and FST) or visual-motion and vestibular (PP, VIP) signals, consistent with the responses of neurons in FEFsem and with the overall physiology and anatomy of the smooth-pursuit eye movement system.
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PMID:Cortical afferents to the smooth-pursuit region of the macaque monkey's frontal eye field. 1594 Apr 95

The goal of the present study was to elucidate the corticocortical afferent connections of area V6Av, the ventral subregion of area V6A, using retrograde neuronal tracers combined with physiological and cytoarchitectonic analyses in the macaque monkey. The results revealed that V6Av receives many of its afferents from extrastriate area V6, and from regions of areas V2, V3, and V4 subserving peripheral vision. Additional extrastriate visual projections originate in dorsal stream areas MT and MST. Area V6Av does not receive projections directly from V1; such connections were only observed when the injection sites crossed into area V6. The strongest parietal lobe afferents originate in fields V6Ad, PGm, MIP (medial intraparaietal), and PG, with frontal lobe afferents originating from the frontal eye field, caudal area 46, and the rostral subdivision of the dorsal premotor area (F7). A comparison of their respective connections supports the view that V6Av is functionally distinct from adjacent areas (V6 and V6Ad). The strong afferents from V6 and other extrastriate areas are consistent with physiological data that suggest that V6Av is primarily a visual area, supporting the notion that V6Av is part of a dorsomedial cortical network performing fast form and motion analyses needed for the visual guidance of action.
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PMID:Cortical connections of area V6Av in the macaque: a visual-input node to the eye/hand coordination system. 2128 89

In both macaque and human brain, information regarding visual motion flows from the extrastriate area V6 along two different paths: a dorsolateral one towards areas MT/V5, MST, V3A, and a dorsomedial one towards the visuomotor areas of the superior parietal lobule (V6A, MIP, VIP). The dorsolateral visual stream is involved in many aspects of visual motion analysis, including the recognition of object motion and self motion. The dorsomedial stream uses visual motion information to continuously monitor the spatial location of objects while we are looking and/or moving around, to allow skilled reaching for and grasping of the objects in structured, dynamically changing environments. Grasping activity is present in two areas of the dorsal stream, AIP and V6A. Area AIP is more involved than V6A in object recognition, V6A in encoding vision for action. We suggest that V6A is involved in the fast control of prehension and plays a critical role in biomechanically selecting appropriate postures during reach to grasp behaviors. In everyday life, numerous functional networks, often involving the same cortical areas, are continuously in action in the dorsal visual stream, with each network dynamically activated or inhibited according to the context. The dorsolateral and dorsomedial streams represent only two examples of these networks. Many others streams have been described in the literature, but it is worthwhile noting that the same cortical area, and even the same neurons within an area, are not specific for just one functional property, being part of networks that encode multiple functional aspects. Our proposal is to conceive the cortical streams not as fixed series of interconnected cortical areas in which each area belongs univocally to one stream and is strictly involved in only one function, but as interconnected neuronal networks, often involving the same neurons, that are involved in a number of functional processes and whose activation changes dynamically according to the context.
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PMID:The dorsal visual stream revisited: Stable circuits or dynamic pathways? 2819 47

Neural activity in the middle temporal (MT) area is modulated by the direction and speed of motion of visual stimuli. The area is buried in a sulcus in the macaque, but exposed to the cortical surface in the marmoset, making the marmoset an ideal animal model for studying MT function. To better understand the details of the roles of this area in cognition, underlying anatomical connections need to be clarified. Because most anatomical tracing studies in marmosets have used retrograde tracers, the axonal projections remain uncharacterized. In order to examine axonal projections from MT, we utilized adeno-associated viral (AAV) tracers, which work as anterograde tracers by expressing either green or red fluorescent protein in infected neurons. AAV tracers were injected into three sites in MT based on retinotopy maps obtained via in vivo optical intrinsic signal imaging. Brains were sectioned and divided into three series, one for fluorescent image scanning and two for myelin and Nissl substance staining to identify specific brain areas. Overall projection patterns were similar across the injections. MT projected to occipital visual areas V1, V2, V3 (VLP) and V4 (VLA) and surrounding areas in the temporal cortex including MTC (V4T), MST, FST, FSTv (PGa/IPa) and TE3. There were also projections to the dorsal visual pathway, V3A (DA), V6 (DM) and V6A, the intraparietal areas AIP, LIP, MIP, frontal A4ab and the prefrontal cortex, A8aV and A8C. There was a visuotopic relationship with occipital visual areas. In a marmoset in which two tracer injections were made, the projection targets did not overlap in A8aV and AIP, suggesting topographic projections from different parts of MT. Most of these areas are known to send projections back to MT, suggesting that they are reciprocally connected with it.
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PMID:Axonal Projections From the Middle Temporal Area in the Common Marmoset. 3042 25