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Corticocortical and Collateral Thalamocortical Connections of Postcentral Somatosensory Cortical Areas in Squirrel Monkeys: A Double-Labeling Study with Radiolabeled Wheatgerm Agglutinin and Wheatgerm Agglutinin Conjugated to Horseradish Peroxidase
| Content Provider | Scilit |
|---|---|
| Author | Cusick, C. G. Steindler, D. A. Kaas, J. H. |
| Copyright Year | 1985 |
| Abstract | Experiments were performed to determine whether thalamic neurons send collaterals to more than one subdivision of postcentral somatosensory cortex, and to evaluate the fidelity of somatotopic connections between cortical representations of the body surface. After microelectrode recordings identified the locations of the representations of the fingertips along the border of area 3b with area 3a and along the border of area 1 with area 2, one tracer, tritiated N-acetyl wheatgerm agglutinin $([^{3}$H]WGA), was injected into the rostral representation at the 3a-3b border, and another, wheatgerm agglutinin conjugated to horseradish peroxidase (WGA:HRP), was injected into the caudal representation at the 1-2 border. The results indicate that three thalamic regions are interconnected with both border zones. Regions of overlapping retrograde and anterograde label included the ventromedial portion of the lateral division of the ventroposterior nucleus (VPL), which is known to represent the digits; the medial extent of a dorsal capping zone of VPL that we term the ventroposterior superior nucleus (VPS); and the anterior pulvinar (Pa). Cells labeled with one or the other tracer, as well as cells labeled with both tracers, were found in VPL, VPS, and Pa. Our procedures necessarily underestimated the numbers of cells projecting to both rostral and caudal injection zones, but at least 15-20% of VPL and 20-40% of VPS neurons that were autoradiographically labeled appeared to have such collaterals. While only a few cells in Pa were autoradiographically labeled from injections at the 3a-3b border, the presence of several double-labeled cells suggests that at least some Pa neurons project to both injected zones. By relating the present results to those from studies where connections were determined for single architectonic fields, we conclude that many neurons in VP project to both areas 3b and 1, and that many neurons in VPS project to both areas 3a and 2. In addition, both areas 3a and 2 appear to have interconnections with Pa. Connections of Pa with area 2 have only recently been reported (Pons and Kaas, in press), and connections of Pa with area 3a have not been described. The results imply that, in part, the same information from cutaneous receptors is relayed to areas 3b and 1, and the same information from deep receptors is relayed to areas 3a and 2. The connections of Pa with areas 3a and 2 indicate that this nucleus may have a more direct role in sensory processing than previously thought. Cortical connections were also revealed by the WGA:HRP injections along the 1-2 border. These injections labeled concentrations of terminals and neurons that overlapped the somatotopically matched region along the 3a-3b border. Thus, cortical connections were homo-topic, with the rostral representation of fingertips strongly interconnected with the caudal representation of fingertips. Injections along the 1-2 border also consistently labeled three separate regions of cortex in or near the expected location of the second somatosensory area on the upper bank of the lateral fissure, raising the possibility that multiple representations of the hand exist in this region of cortex. |
| Related Links | https://www.tandfonline.com/doi/pdf/10.3109/07367228509144574 |
| ISSN | 07367244 |
| DOI | 10.3109/07367228509144574 |
| Journal | Somatosensory research |
| Issue Number | 1 |
| Volume Number | 3 |
| Language | English |
| Publisher | Informa UK Limited |
| Publisher Date | 1985-01-01 |
| Access Restriction | Open |
| Subject Keyword | Journal: Somatosensory Research Neurosciences Horseradish Peroxidase Corticocortical Monkeys Collateral Thalamocortical Wheatgerm Agglutinin Thalamocortical Connections |
| Content Type | Text |
| Resource Type | Article |
| Subject | Neuroscience Physiology |
