The Journal of Neuroscience, November 28, 2007, 27(48):13108-13116; doi:10.1523/JNEUROSCI.1892-07.2007
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Behavioral/Systems/Cognitive
The TLC: A Novel Auditory Nucleus of the Mammalian Brain
Enrique Saldaña,1,2
Antonio Viñuela,1,2
Allen F. Marshall,3
Douglas C. Fitzpatrick,3 and
M.-Auxiliadora Aparicio1,2
1Laboratory for the Neurobiology of Hearing, Department of Cell Biology and Pathology, Medical School, University of Salamanca, 37007-Salamanca, Spain, 2Neuroscience Institute of Castilla y León (INCyL), University of Salamanca, 37007-Salamanca, Spain, and 3Department of Otolaryngology–Head and Neck Surgery, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7070
Correspondence should be addressed to Dr. Enrique Saldaña, Laboratorio de Neurobiología de la Audición, Departamento de Biología Celular y Patología, Facultad de Medicina, Universidad de Salamanca, 37007 Salamanca, Spain. Email: saldana{at}usal.es
We have identified a novel nucleus of the mammalian brain and termed it the tectal longitudinal column (TLC). Basic histologic stains, tract-tracing techniques and three-dimensional reconstructions reveal that the rat TLC is a narrow, elongated structure spanning the midbrain tectum longitudinally. This paired nucleus is located close to the midline, immediately dorsal to the periaqueductal gray matter. It occupies what has traditionally been considered the most medial region of the deep superior colliculus and the most medial region of the inferior colliculus. The TLC differs from the neighboring nuclei of the superior and inferior colliculi and the periaqueductal gray by its distinct connections and cytoarchitecture. Extracellular electrophysiological recordings show that TLC neurons respond to auditory stimuli with physiologic properties that differ from those of neurons in the inferior or superior colliculi. We have identified the TLC in rodents, lagomorphs, carnivores, nonhuman primates, and humans, which indicates that the nucleus is conserved across mammals. The discovery of the TLC reveals an unexpected level of longitudinal organization in the mammalian tectum and raises questions as to the participation of this mesencephalic region in essential, yet completely unexplored, aspects of multisensory and/or sensorimotor integration.
Key words: superior colliculus; inferior colliculus; auditory; periaqueductal gray; midbrain tectum; multisensory; sensorimotor; tract-tracing; electrophysiology; 3D reconstruction; rat; human
Received April 26, 2007;
revised Oct. 10, 2007;
accepted Oct. 11, 2007.
Correspondence should be addressed to Dr. Enrique Saldaña, Laboratorio de Neurobiología de la Audición, Departamento de Biología Celular y Patología, Facultad de Medicina, Universidad de Salamanca, 37007 Salamanca, Spain. Email: saldana{at}usal.es