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P D Beck

Publications and source records attributed to P D Beck.

16 recordsLinked to original sources
PubMed2000

Real-time prediction of hand trajectory by ensembles of cortical neurons in primates.

Signals derived from the rat motor cortex can be used for controlling one-dimensional movements of a robot arm. It remains unknown, however, whether real-time processing of cortical signals can be employed to reproduce, in a robotic device, the kind of complex arm movements used by primates to reach objects in space. Here we recorded the simultaneous activity of large populations of neurons, distributed in the premotor, primary motor and posterior parietal cortical areas, as non-human primates performed two distinct motor tasks. Accurate real-time predictions of one- and three-dimensional arm movement trajectories were obtained by applying both linear and nonlinear algorithms to cortical neuronal ensemble activity recorded from each animal. In addition, cortically derived signals were successfully used for real-time control of robotic devices, both locally and through the Internet. These results suggest that long-term control of complex prosthetic robot arm movements can be achieved by simple real-time transformations of neuronal population signals derived from multiple cortical areas in primates.

Animals↗
PubMed1999

Cortical connections of the dorsomedial visual area in old world macaque monkeys.

The connections of a wedge of densely myelinated cortex along the dorsomedial border of V2 were determined by injecting tracers into this region in macaque monkeys. According to previous descriptions, this cortex would constitute parts of dorsal V3 and V3A, or a dorsomedial visual area, DM, homologous to the DM described in prosimians and New World monkeys. Injections of wheat germ agglutinin conjugated to horseradish peroxidase or various fluorescent tracers demonstrated connections with architectonically defined V1, V2, and the middle temporal area, as well as regions of visual areas known as the ventral posterior parietal area, the rostral dorsolateral area or rostral V4, ventral posterior cortex and more rostral cortex in the ventral temporal lobe, and medial and dorsointermediate areas. Other sparser and less consistently revealed connections were with the medial superior temporal area, the area of the fundus of the superior temporal sulcus, and the caudal dorsolateral area. Distributions of labeled cells in V1 varied in relationship to the pattern of cytochrome oxidase blobs and interblobs in a manner suggesting a heterogeneous pattern of terminations from blob and interblob regions within DM. Major similarities in overall connections of the DM region in macaques with DM connections described in New World monkeys and prosimian galagos support the conclusion that the same visual area, DM, has been identified in all these primates.

Animals↗
PubMed1998

Cortical connections of the dorsomedial visual area in new world owl monkeys (Aotus trivirgatus) and squirrel monkeys (Saimiri sciureus).

The dorsomedial visual area (DM) is an extrastriate area that was originally described in owl monkeys as a complete representation of the visual hemifield in a heavily myelinated wedge of cortex just rostral to dorsomedial visual area V2. More recently, connections of DM in owl monkeys have been described (Krubitzer and Kaas [1993] J. Comp. Neurol 334:497-528). As part of an effort to determine whether DM exists in other primates, we compared the architecture, connections, and visual topography of DM in owl monkeys and the presumptive DM in squirrel monkeys. In both species of New World monkeys, the DM region was more heavily myelinated than adjacent cortex, and this region was connected with the first and second visual areas, the middle temporal area (MT), the medial area, the ventral posterior parietal area, the dorsointermediate area, the dorsolateral area, the ventral posterior and ventral anterior areas, the medial superior temporal area, the fundal area of the superior temporal sulcus, the inferior temporal cortex, and frontal cortex in or near the frontal eye field. In squirrel monkeys, both blob and interblob regions of V1 contributed equally to DM, whereas the blob regions provided most of the projections to V1 in owl monkeys. In squirrel monkeys, connections were also found with cortex on the ventral surface in the ventral occipital temporal sulcus. In owl monkeys and squirrel monkeys, connections were with both the upper and lower visual field representations in V1, V2, and MT, demonstrating that DM contains a complete representation of the visual field. These similarities in architecture, connections, and retinotopy argue that DM is a visual area of both owl and squirrel monkeys.

Animals↗
PubMed1998

Cortical connections of the dorsomedial visual area in prosimian primates.

The dorsomedial visual area (DM) was originally identified in New World owl monkeys as an area rostral to dorsomedial visual area 2 (V2) that is heavily myelinated, contains a complete representation of the visual field, and has a unique distribution of connections with other visual areas. A DM homologue has been proposed in prosimian galagos on the basis of physiological mapping. We determined the pattern of connections of the proposed DM with other cortical visual areas in galagos by placing injections of several different neuroanatomical tracers into DM and locating the resulting label in relation to areal boundaries and modules by using architecture from cytochrome oxidase and myelin preparations. We found that DM is connected with V1, V2, the middle temporal area, and regions of the medial area, the middle superior temporal area, the dorsointermediate area, the ventral posterior area, and the ventral posterior parietal area. Following some injections, label was also found in the fundal superior temporal sulcus area and in the frontal eye field. Connections with V1 were patchy. Although the majority of labeled neurons were in cytochrome oxidase blobs of V1, many labeled neurons were located in interblob regions as well. Similarities in the connections and the architecture of DM of galagos and owl monkeys suggest that the same area has been identified in both groups of primates.

Amidines↗
PubMed1998

Thalamic connections of the dorsomedial visual area in primates.

The dorsomedial visual area (DM) of owl monkeys is a cortical area that has been described recently in a range of primate species. To study the thalamic connections of this area, injections of several distinguishable neuroanatomical tracers were placed into DM in galagos, owl monkeys, squirrel monkeys, and macaque monkeys. The distribution of label was remarkably consistent across these diverse primate species. Labeled connections were densest within the pulvinar complex. Both the lateral and inferior divisions of the pulvinar, but not the medial division, had connections with DM. Within the inferior pulvinar of monkeys, central lateral and central medial nuclei had dense connections, and the medial and posterior nuclei had sparse connections with DM. Sparser connections were revealed in the lateral geniculate nucleus and the nucleus limitans. Anterograde label was also found in the superior colliculus. The consistencies in the pattern of subcortical projections across prosimian primates, New World monkeys, and Old World monkeys support the concept that DM is a visual area common to all primates. In addition, these results provide further evidence for proposed subdivisions of the inferior pulvinar.

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PubMed1996

Central reorganization of sensory pathways following peripheral nerve regeneration in fetal monkeys.

Transection of a sensory nerve in adults results in profound abnormalities in sensory perception, even if the severed nerve is surgically repaired to facilitate accurate nerve regeneration. In marked contrast, fewer perceptual errors follow nerve transection and surgical repair in children. The basis for this superior recovery in children was unknown. Here we show that there is little or no topographic order in the median nerve to the hand after median nerve section and surgical repair in immature macaque monkeys. Remarkably, however, in the same animals the representation of the reinnervated hand in primary somatosensory cortex area (area 3b) is quite orderly. This indicates that there are mechanisms in the developing brain that can create cortical topography, despite disordered sensory inputs. Presumably the superior recovery of perceptual abilities after peripheral nerve transection in children depends on this restoration of somatotopy in the central sensory maps.

Afferent Pathways↗
PubMed1996

Topography, architecture, and connections of somatosensory cortex in opossums: evidence for five somatosensory areas.

Microelectrode maps of somatosensory inputs were related to cortical architecture and patterns of cortical connections to provide evidence for five subdivisions of the somatosensory or sensorimotor cortex in North American opossums (Didelphis marsupialis). Microelectrode recordings revealed three systematic representations of the body surface. A large mediolaterally oriented representation was identified as the primary somatosensory area (S1) by its relative position, somatotopy, architecture, and connections. S1 represented the hindlimb, trunk, forelimb, and face in a mediolateral sequence. Two additional representations of cutaneous receptors were found caudolateral to S1, each with face representations adjacent to the border of lateral S1 and other body-part representations progressing more caudally toward the auditory cortex. We identified the more dorsal field as the second somatosensory area (S2) and the more ventral field as the parietal ventral area (PV). Tracers injected into S1 labeled neurons and terminals in architectonically distinct fields rostral and caudal to S1, the somatosensory caudal area (SC) and the somatosensory rostral area (SR). Movements could be evoked by microstimulation from sites scattered over S1, SR, and the frontal cortex, but thresholds were high and uncharacteristic of motor cortex. S2 and PV merged caudally with the cortex responsive to auditory stimuli, possibly A1, and neurons in some caudal recording sites in PV were activated by both auditory and cutaneous stimuli. Primary (V1) and secondary (V2) visual areas were also identified by microelectrode mapping, architecture, and connections. In addition, at least part of the cortex between V2 and the somatosensory cortex had visual connections. Thus, most of the dorsolateral cortex of opossums appears to be somatosensory, auditory, or visual.

Animals↗
PubMed1994

Interhemispheric connections in neonatal owl monkeys (Aotus trivirgatus) and galagos (Galago crassicaudatus).

Interhemispheric connections were studied by injecting a mixture of horseradish peroxidase (HRP) and wheatgerm agglutinin conjugated with horseradish peroxidase (WGA-HRP) into multiple sites in dorsolateral occipital and parietal cortex of one cerebral hemisphere of three galagos (Galago crassicaudatus) and two owl monkeys (Aotus trivirgatus) within seven days of birth. Cortex was either separated from the rest of the brain, flattened and cut parallel to the surface to aid reconstructing surface-view patterns of labeled neurons and processes, or cut in standard coronal or parasagittal planes to better reveal laminar patterns of connections. In both primate species, the surface-view pattern of callosal connections in infants was remarkably adult-like. In infant owl monkeys, callosal connections were concentrated along the margin of area 18 with area 17, and only a few labeled cells were found within area 17. Other visual areas including the second visual area, V-II, and the middle temporal visual area, MT, had patchy distributions of labeled neurons that extended over large parts of the visual field representations. Primary motor, auditory, and somatosensory fields also had patchy distributions of labeled neurons, with regions of areas 3b and adjoining somatosensory fields having few callosal connections in portions that appeared to correspond with representations of the hand and foot. Results were very similar in galagos, except that newborn galagos, as in adults, had a patchy distribution of callosally projecting neurons that extended well within area 17. Furthermore, the labeled neurons were concentrated in patches that aligned with the cytochrome oxidase blobs of area 17. Finally, callosal connections were concentrated in cytochrome oxidase poor regions of area 3b.

Animals↗
PubMed1993

Intrinsic connections of layer III of striate cortex in squirrel monkey and bush baby: correlations with patterns of cytochrome oxidase.

This study used biocytin and horseradish peroxidase (HRP) to examine the intrinsic connections of the cytochrome oxidase (CO) rich blob and CO poor nonblob zones within layer III of striate cortex in two primate species, nocturnal prosimian bush babies (Galago crassicaudatus) and diurnal simian squirrel monkeys (Saimiri sciureus). Our main objective was to determine whether separate classes of lateral geniculate nucleus (LGN) cells projected to separate superficial layer zones or layers in either species. There were three significant findings. First, we confirm that layer III consists of three sublayers, IIIA, IIIB, and IIIC in both species. Layer IIIA receives input from layers IIIB, IIIC, and V, with little or no input from LGN recipient layers IV and VI. Layer IIIB receives its input from nearly every cortical layer. Layer IIIC, receives input principally from layers IV alpha [which receives its input from magnocellular (M) LGN cells] and from layers V and VI. Taken together with other findings on the extrinsic connections of these layers, our data suggest that IIIA and IIIC provide output to separate hierarchies of visual areas and IIIB acts as a set of interneurons. Second, we find that, as in macaque monkeys, cells in both IV beta and IV alpha of bush babies and squirrel monkeys project to layer IIIB, converging within the blobs. These results suggest that information from all LGN cell classes [parvocellular (P), M, and the Koniocellular (K) or their equivalents] may be integrated within the blobs. Thus, blobs in all of these primates may perform a function that transcends visual niche differences. Third, our data show a species specific difference in the connections of the IIIB nonblobs; nonblobs receive indirect input via IV alpha from the LGN M pathway in bush babies but receive indirect input via IV beta from the LGN parvocellular (P) pathway in squirrel monkeys. These findings indicate that the role of nonblob zones within striate cortex differs from that of blob zones and takes into account visual niche differences.

Animals↗
PubMed1993

Visual resolution and sensitivity of single cells in the primary visual cortex (V1) of a nocturnal primate (bush baby): correlations with cortical layers and cytochrome oxidase patterns.

1. This study describes the response properties of V1 cortical cells in a nocturnal primate and examines the receptive field organization of these cells in relationship to anatomically defined layers and cytochrome oxidase (CO) rich blobs and CO poor interblob compartments. Visual resolution and contrast sensitivity are consistent with other physiological and behavioral measures in this species. Comparisons are made with response properties of the same zones in macaque monkey, as well as of area 17 of a distantly related species (cat) that also occupies a nocturnal niche. 2. The responses of single cells to drifting sinusoidal gratings were recorded in V1 (striate cortex) of anesthetized, paralyzed bush babies (Galago crassicaudatus). Cells tended to be grouped with respect to ocular dominance, orientation preference, and direction selectivity. There was a high proportion of monocularly driven cells as in macaque monkey. Only 6% of the cells were nonoriented. These were poorly tuned complex cells and bore no resemblance to nonoriented lateral geniculate nucleus (LGN)-like cells reported in layer IV of macaque monkeys. Unidirectional cells were most frequently encountered in cortical layers that receive input from the magnocellular layers of the LGN. 3. Cells were classified as simple (31%) or complex (69%) according to standard criteria. Simple cells were significantly more narrowly tuned than complex cells for both orientation and spatial frequency. Complex cells had significantly higher average optimal spatial frequencies and spatial frequency cutoffs than simple cells. Contrast sensitivity of simple and complex cells averaged 38 and 34, respectively. Spatial resolution and sensitivity of these cells matches behavioral measures in bush baby. The spatial and temporal resolution of bush baby cells are similar to those of cats, which is likely related to the nocturnal niche of both species. 4. Cells in supragranular (I-III) and infragranular (V, VI) layers differed significantly in their response characteristics. The cells in the supragranular layers had significantly higher contrast sensitivity than did the cells in the infragranular layers. Cells in the supragranular layers likewise had higher temporal frequency cutoffs, significantly lower optimal spatial frequencies, lower spatial frequency cutoffs, and tighter orientation tuning than did cells in the infragranular layers. 5. Properties of cells in individual layers and CO blob and interblob compartments also showed differentiation. Layer III had the narrowest orientation and spatial frequency tuning with the tightest tuning in layer IIIC (IVB).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Areal, modular, and connectional organization of visual cortex in a prosimian primate, the slow loris (Nycticebus coucang).

Slow lorises (Nycticebus coucang) are nocturnal prosimian (i.e. strepsirhine) primates, closely related to bushbabies (Galago spp.). We examined the organization of visual cortex in four hemispheres from two slow lorises, using connectional and architectonic techniques. All hemispheres were flattened and sections stained for myelin and cytochrome oxidase (CO). Our results indicate, first, that the primary visual area (V1) in slow lorises has a system of small CO-dense blobs, as has been described in most other anthropoid and prosimian primates examined to date. The second visual area (V2) is characterized by broad, stripe-like zones of dense CO staining separated by zones of lighter staining. Loris V2 stripes are less distinct than those of anthropoid primates, and separate classes of thin and thick dark stripes are not apparent. However, V2 stripes are much better developed than in Galago, where they are virtually absent. Injections of wheat-germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in area V1 revealed reciprocal connections with area V2, and the middle temporal (MT) and dorsolateral (DL) extrastriate areas. Area MT was also identified by its distinctive, dense myelination. As has been reported in anthropoids, DL can be divided into separate caudal and rostral divisions, which differ in myelin and CO staining, and in the strength of their connections with V1. Taken together, our results suggest that many of the features that characterize visual cortex organization in anthropoid primates are present in prosimians and thus probably evolved early in primate history, prior to the diversification of modern primate groups.

Animals↗
PubMed1992

Parallel pathways in macaque monkey striate cortex: anatomically defined columns in layer III.

Visual information reaching striate cortex comes from parallel pathways, and the information is organized, or processed, by the layers and columns of striate cortex. To better understand how this is accomplished anatomically, we asked whether parallel pathways originating in the lateral geniculate nucleus (LGN), and terminating separately in layer IV, remain separate in layer III of macaque monkeys. Layer III is of interest since it may play a special role in color and form vision but not in analysis of visual motion. The chief finding was that cells in "blobs" of layer III that stain densely for cytochrome oxidase receive indirect input, via layer IVC, from both LGN magnocellular (M) and parvocellular (P) cells. This is important because the P and M pathways may represent color/form and motion-processing channels, respectively. Interblob cells receive indirect input, via layers IVC and IVA, from the LGN P cells. Also, as suggested by others, our data demonstrate that layer III can be subdivided. The bottom tier, layer IIIB, receives direct projections from all cortical layers. Output from layer IIIB appears to remain intrinsic to striate cortex. In contrast, the top tier, layer IIIA, receives projections from layer IIIB as well as from layers IVA, IVB (blobs only), and V, but it receives no direct projections from LGN recipient layers IVC and VI. Unlike layer IIIB, the output of layer IIIA reaches extrastriate areas. Thus, impulses arriving from parallel LGN pathways may be recombined through serial stages in striate cortex to produce a set of parallel pathways that are qualitatively different from the original LGN set.

Animals↗