Abstract
Area 10, located in the frontal pole, is a unique specialization of the primate cortex. We studied the cortical connections of area 10 in the New World Cebus monkey, using injections of ...retrograde tracers in different parts of this area. We found that injections throughout area 10 labeled neurons in a consistent set of areas in the dorsolateral, ventrolateral, orbital, and medial parts of the frontal cortex, superior temporal association cortex, and posterior cingulate/retrosplenial region. However, sites on the midline surface of area 10 received more substantial projections from the temporal lobe, including clear auditory connections, whereas those in more lateral parts received >90% of their afferents from other frontal areas. This difference in anatomical connectivity reflects functional connectivity findings in the human brain. The pattern of connections in Cebus is very similar to that observed in the Old World macaque monkey, despite >40 million years of evolutionary separation, but lacks some of the connections reported in the more closely related but smaller marmoset monkey. These findings suggest that the clearer segregation observed in the human frontal pole reflects regional differences already present in early simian primates, and that overall brain mass influences the pattern of cortico-cortical connectivity.
Abstract Abstract: We studied the multiunit responses to moving and static stimuli from 585 cell clusters in area MT using multi-electrode arrays. Our aim was to explore if MT columns exhibit any ...larger-scale tangential organization or clustering based on their response properties. Neurons showing both motion and orientation selectivity were classified into four categories: 1- Type I (orientation selectivity orthogonal to the axis of motion); 2- Type II (orientation selectivity coaxial to the axis of motion); 3- Type DS (significant response to moving stimuli, but non-significant response to static stimuli); and 4- Type OS (significant orientation selectivity, but non-significant direction selectivity). Type I (34%), Type II (24%) and Type DS (32%) clusters were the most predominant and may be associated with different stages of motion processing in MT. On the other hand, the rarer Type OS (9%) may be integrating motion and form processing. Type I and unidirectional sites were the only classes to exhibit significant clustering. Type OS sites showed a trend for clustering, which did not reach statistical significance. We also found a trend for unidirectional sites to have bidirectional sites as neighbors. In conclusion, neuronal clustering associated with these four categories may be related to distinct MT functional circuits.
The claustrum is a surprisingly large, sheet-like neuronal structure hidden beneath the inner surface of the neocortex. We found that the portions of the claustrum connected with V4 appear to overlap ...considerably with those portions connected with other cortical visual areas, including V1, V2, MT, MST and FST, TEO and TE. We found extensive reciprocal connections between V4 and the ventral portion of the claustrum (vCl), which extended through at least half of the rostrocaudal extent of the structure. Additionally, in approximately 75% of the cases, we found reciprocal connections between V4 and a more restricted region located farther dorsal, near the middle of the structure (mCl). Both vCl and mCl appear to have at least a crude topographic organization. Based on the projection of these claustrum subdivisions to the amygdala, we propose that vCl and mCl are gateways for the transmission of visual information to the memory system. In addition to these crude visuotopically organized regions, there are other parts of the claustrum that obey the topographical proximity principle, with considerable overlap of their connections. There is only an overall segregation of claustrum regions reciprocally connected to the occipital, parietal, temporal and frontal lobes. The portion of the claustrum connected to the visual cortex is located ventral and posterior; the one connected to the auditory cortex is located dorsal and posterior; the one connected to the somatosensory cortex is located dorsal and medial; the one connected to the frontal premotor and motor cortices is located dorsal and anterior; while the one connected to the temporal cortex is located ventral and anterior. The extensive reciprocal connections of the claustrum with almost the entire neocortex and its projections to the hippocampus, amygdala and basal ganglia prompt us to propose its role as a gateway for perceptual information to the memory system.
We propose a partitioning of the primate intraparietal sulcus (IPS) using immunoarchitectural and connectivity criteria. We studied the immunoarchitecture of the IPS areas in the capuchin monkey ...using Cat‐301 and SMI‐32 immunohistochemistry. In addition, we investigated the IPS projections to areas V4, TEO, PO, and MT using retrograde tracer injections in nine hemispheres of seven animals. The pattern and distribution of Cat‐301 and SMI‐32 immunostaining revealed multiple areas in the IPS, in the adjoining PO cleft and in the annectant gyrus, with differential staining patterns found for areas V3d, DM, V3A, DI, PO, POd, CIP‐1, CIP‐2, VIPa, VIPp, LIPva, LIPvp, LIPda, LIPdp, PIPv, PIPd, MIPv, MIPd, AIPda, AIPdp, and AIPv. Areas V4, TEO, PO, MT, which belong to different cortical streams of visual information processing, receive projections from at least twenty different areas within the IPS and adjoining regions. In six animals, we analyzed the distribution of retrogradely labeled cells in tangential sections of flat‐mount IPS preparations. The lateral bank of the IPS projects to regions belonging both to the ventral (V4 and TEO) and dorsal (PO and MT) streams. The region on the floor of the IPS (i.e., VIP) projects predominantly to dorsal stream areas. Finally, the medial bank of the IPS (i.e., MIP) projects solely to the dorsalmedial stream (PO). Therefore, our data suggest that ventral and dorsal streams remain segregated within the IPS, and that its projections to the dorsal stream can be further segregated based on those targeting the dorsolateral versus the dorsomedial subdivisions.
Visual areas of the intraparietal sulcus in the capuchin monkey. Two‐dimensional reconstruction of the monkey cortex, showing the location of the extra‐striate visual areas revealed by Cat‐301 and SMI‐32 immunohistochemistry. Most of these areas are differentially labeled after injections in V4, TEO, MT, and PO.
Abstract
In trace fear conditioning, the prelimbic cortex exhibits persistent activity during the interval between the conditioned and unconditioned stimuli, which maintains a conditioned stimulus ...representation. Regions cooperating for this function or encoding the conditioned stimulus before the interval could send inputs to the prelimbic cortex, supporting learning. The basolateral amygdala has conditioned stimulus- and unconditioned stimulus-responsive neurons, convergently activated. The prelimbic cortex could directly project to the basolateral amygdala to associate the transient memory of the conditioned stimulus with the unconditioned stimulus. We investigated the neuronal circuit supporting temporal associations using contextual fear conditioning with a 5-s interval, in which 5 s separates the contextual conditioned stimulus from the unconditioned stimulus. Injecting retrobeads, we quantified c-Fos in prelimbic cortex- or basolateral amygdala-projecting neurons from 9 regions after contextual fear conditioning with a 5-s interval or contextual fear conditioning, in which the conditioned and unconditioned stimuli overlap. The contextual fear conditioning with a 5-s interval activated ventral CA1 and perirhinal cortex neurons projecting to the prelimbic cortex and prelimbic cortex neurons projecting to basolateral amygdala. Both fear conditioning activated ventral CA1 and lateral entorhinal cortex neurons projecting to basolateral amygdala and basolateral amygdala neurons projecting to prelimbic cortex. The perirhinal cortex → prelimbic cortex and ventral CA1 → prelimbic cortex connections are the first identified prelimbic cortex afferent projections participating in temporal associations. These results help to understand time-linked memories, a process required in episodic and working memories.
We studied the time course of changes of cytochrome oxidase (CytOx) blob spatial density and blob cross‐sectional area of deprived (D) and nondeprived (ND) portions of V1 in four capuchin monkeys ...after massive and restricted retinal laser lesions. Laser shots at the border of the optic disc produced massive retinal lesions, while low power laser shots in the retina produced restricted retinal lesions. These massive and restricted retinal lesions were intended to simulate glaucoma and diabetic retinopathy, respectively. We used a Neodymium‐YAG dual frequency laser to make the lesions. We measured Layer III blobs in CytOx‐reacted tangential sections of flat‐mounted preparations of V1. The plasticity of the blob system and that of the ocular dominance columns (ODC) varied with the degree of retinal lesions. We found that changes in the blob system were different from that of the ODC. Blob sizes changed drastically in the region corresponding to the retinal lesion. Blobs were larger and subjectively darker above and below the non deprived ODC than in the deprived columns. With restricted lesions, blobs corresponding to the ND columns had sizes similar to those from non‐lesioned areas. In contrast, blobs corresponding to the deprived columns were smaller than those from nonlesioned areas. With massive lesions, ND blobs were larger than the deprived blobs. Plastic changes in blobs described here occur much earlier than previously described.
Variation of cytochrome oxidase blob cross sectional area of deprived and nondeprived regions of V1 in cases with restricted (light blue and red) and massive (dark blue and orange) retinal lesions. Insert show a schematic diagram of the fiber track of the retinal surface illustrating the lesions used in this study. Note an extensive ganglion cell axons degeneration after the optic disc laser lesions (red arrow).
•Fast and precise automatic algorithm that allows receptive field mapping.•The method allows bias free automatic mapping of visual receptive fields.•Algorithm reveals receptive field location and ...boundaries.•Comprehensive: automatic mapping of a wide (30°×30°) visual field area.•Scalable receptive field mapping that works with multi-electrodes.
An important issue for neurophysiological studies of the visual system is the definition of the region of the visual field that can modify a neuron's activity (i.e., the neuron's receptive field – RF). Usually a trade-off exists between precision and the time required to map a RF. Manual methods (qualitative) are fast but impose a variable degree of imprecision, while quantitative methods are more precise but usually require more time. We describe a rapid quantitative method for mapping visual RFs that is derived from computerized tomography and named back-projection. This method finds the intersection of responsive regions of the visual field based on spike density functions that are generated over time in response to long bars moving in different directions. An algorithm corrects the response profiles for latencies and allows for the conversion of the time domain into a 2D-space domain. The final product is an RF map that shows the distribution of the neuronal activity in visual–spatial coordinates. In addition to mapping the RF, this method also provides functional properties, such as latency, orientation and direction preference indexes. This method exhibits the following beneficial properties: (a) speed; (b) ease of implementation; (c) precise RF localization; (d) sensitivity (this method can map RFs based on few responses); (e) reliability (this method provides consistent information about RF shapes and sizes, which will allow for comparative studies); (f) comprehensiveness (this method can scan for RFs over an extensive area of the visual field); (g) informativeness (it provides functional quantitative data about the RF); and (h) usefulness (this method can map RFs in regions without direct retinal inputs, such as the cortical representations of the optic disc and of retinal lesions, which should allow for studies of functional connectivity, reorganization and neural plasticity). Furthermore, our method allows for precise mapping of RFs in a 30° by 30° area of the visual field for an array of microelectrodes of any size in less than 6min.
This chapter deals with the role of the pulvinar in spatial visual attention. There are at least two aspects in which the pulvinar seems to be instrumental for selective visual processes. The first ...aspect concerns pulvinar connectivity pattern. The pulvinar is connected with brain regions known to be playing a role in attentional mechanisms, such as area V4, the superior colliculus (SC), and the inferior parietal cortex (IP). Additionally, the pulvinar is richly interconnected with multiple cortical areas. This enables the pulvinar to serve as a hub for brain communication, potentially gating the flow of information across different regions. The second aspect concerns neuronal circuits intrinsic to the pulvinar. We claim these circuits are subserving three basic steps regarding the allocation of spatial attention: disengaging from the current focus of attention, moving it to a new target, and engaging it at a new position.
Connectivity of the Pulvinar Gattass, Ricardo; Soares, Juliana G M; Lima, Bruss
Advances in anatomy, embryology and cell biology,
01/2018, Letnik:
225
Journal Article
Recenzirano
Pulvinar connectivity has been studied using a variety of neuroanatomical tracing techniques in both New and Old World monkeys. Connectivity studies have revealed additional maps of the visual field ...other than those described using electrophysiological techniques, such as P3 in the capuchin monkey and P3/P4 in the macaque monkey. In this chapter, we argue that with increasing cortical size, the pulvinar developed new functional subdivisions in order to effectively interconnect and interact with the cortex.
Vision is a major sense for Primates and the ability to perceive colors has great importance for the species ecology and behavior. Visual processing begins with the activation of the visual opsins in ...the retina, and the spectral absorption peaks are highly variable among species. In most Primates, LWS/MWS opsins are responsible for sensitivity to long/middle wavelengths within the visible light spectrum, and SWS1 opsins provide sensitivity to short wavelengths, in the violet region of the spectrum. In this study, we aimed to investigate the genetic variation on the sws1 opsin gene of New World monkeys (NWM) and search for amino acid substitutions that might be associated with the different color vision phenotypes described for a few species. We sequenced the exon 1 of the sws1 opsin gene of seven species from the families Callitrichidae, Cebidae, and Atelidae, and searched for variation at the spectral tuning sites 46, 49, 52, 86, 90, 93, 114, 116, and 118. Among the known spectral tuning sites, only residue 114 was variable. To investigate whether other residues have a functional role in the SWS1 absorption peak, we performed computational modeling of wild‐type SWS1 and mutants A50I and A50V, found naturally among the species investigated. Although in silico analysis did not show any visible effect caused by these substitutions, it is possible that interactions of residue 50 with other sites might have some effect in the spectral shifts in the order of ~14 nm, found among the NWM. We also performed phylogenetic reconstruction of the sws1 gene, which partially recovered the species phylogeny. Further studies will be important to uncover the mutations responsible for the phenotypic variability of the SWS1 of NWM, and how spectral tuning may be associated with specific ecological features such as preferred food items and habitat use.
Spectral variability of sws1 opsin gene in humans and New World monkeys.
Highlights
Spectral tuning sites of the SWS1 opsin are conserved among New World monkeys, with the exception of residue 114.
Interactions among other unknown spectral tuning sites may also play a role in the spectral shifts of the SWS1 opsins of Primates.
Spectral shifts of the violet‐sensitive opsins of New World monkeys might be associated with ecological features such as variations in the preferred food items and habitat selection.
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