Journal of Neurophysiology, Vol 50, Issue 4 896-909, Copyright © 1983 by APS

ARTICLES

Corticotectal and corticothalamic efferent projections of SIV somatosensory cortex in cat

B. E. Stein, R. F. Spencer and S. B. Edwards

Substantial corticotectal (and corticothalamic) projections from the cortex of the anterior ectosylvian sulcus (AES) were demonstrated in the cat using the axonal transport methods of autoradiography and horseradish peroxidase. The corticotectal projection arises nearly exclusively from medium-large pyramidal cells in lamina V. One of the densest projecting areas of the AES is the rostral aspect of its superior bank, where a fourth somatotopic representation (SIV) has recently been demonstrated. It terminates in the intermediate and deep laminae of the superior colliculus, where somatic cells are located. The pathway is bilateral but much heavier ipsilaterally than contralaterally. In contrast to the substantial corticotectal projection from SIV and adjacent tissue, there was no unequivocal evidence for a corticotectal projection from traditional somatosensory cortex SI-SIII. This finding, that somatosensory projections to the cat superior colliculus arise from an area outside of SI-SIII, was unexpected on the basis of what is known about visual corticotectal projections. However, it is consistent with the patterns of other cortical projections that terminate in the intermediate and deep laminae of this structure and with the absence of demonstrable corticotectal influences from SI to SIII in this animal. These data are in contrast to demonstrations by other investigators that there is a corticotectal projection from SI cortex in rodents. Apparently there is a fundamental species difference in the organization of descending somatosensory pathways. A corticothalamic projection of the AES was also observed. This descending projection appeared to form a shell of labeled cells and fibers around the ventrobasal complex, but unequivocal terminal labeling within the ventrobasal complex could not be demonstrated. Dense terminal labeling was apparent in the posterior group of thalamic nuclei (PO) where thalamocortical afferents to the AES originate.

This article has been cited by other articles:

				V. Fuentes-Santamaria, J. C. Alvarado, B. E. Stein, and J. G. McHaffie Cortex Contacts both Output Neurons and Nitrergic Interneurons in the Superior Colliculus: Direct and Indirect Routes for Multisensory Integration Cereb Cortex, July 1, 2008; 18(7): 1640 - 1652. [Abstract] [Full Text] [PDF]

				J. C. Alvarado, J. W. Vaughan, T. R. Stanford, and B. E. Stein Multisensory Versus Unisensory Integration: Contrasting Modes in the Superior Colliculus J Neurophysiol, May 1, 2007; 97(5): 3193 - 3205. [Abstract] [Full Text] [PDF]

				W. Jiang, H. Jiang, B. A. Rowland, and B. E. Stein Multisensory Orientation Behavior Is Disrupted by Neonatal Cortical Ablation J Neurophysiol, January 1, 2007; 97(1): 557 - 562. [Abstract] [Full Text] [PDF]

				W. Jiang, H. Jiang, and B. E. Stein Neonatal Cortical Ablation Disrupts Multisensory Development in Superior Colliculus J Neurophysiol, March 1, 2006; 95(3): 1380 - 1396. [Abstract] [Full Text] [PDF]

				T. R. Stanford, S. Quessy, and B. E. Stein Evaluating the Operations Underlying Multisensory Integration in the Cat Superior Colliculus J. Neurosci., July 13, 2005; 25(28): 6499 - 6508. [Abstract] [Full Text] [PDF]

				W. Jiang, H. Jiang, and B. E. Stein Two Corticotectal Areas Facilitate Multisensory Orientation Behavior J. Cogn. Neurosci., November 1, 2002; 14(8): 1240 - 1255. [Abstract] [Full Text] [PDF]

				W. Jiang, M. T. Wallace, H. Jiang, J. W. Vaughan, and B. E. Stein Two Cortical Areas Mediate Multisensory Integration in Superior Colliculus Neurons J Neurophysiol, February 1, 2001; 85(2): 506 - 522. [Abstract] [Full Text] [PDF]

				M. T. Wallace and B. E. Stein Onset of Cross-Modal Synthesis in the Neonatal Superior Colliculus is Gated by the Development of Cortical Influences J Neurophysiol, June 1, 2000; 83(6): 3578 - 3582. [Abstract] [Full Text] [PDF]

				D. C. Kadunce, J. W. Vaughan, M. T. Wallace, G. Benedek, and B. E. Stein Mechanisms of Within- and Cross-Modality Suppression in the Superior Colliculus J Neurophysiol, December 1, 1997; 78(6): 2834 - 2847. [Abstract] [Full Text] [PDF]