Auditory activation of 'visual' cortical areas in the blind mole rat (Spalax ehrenbergi)

• Published in: The European journal of neuroscience Vol. 16; no. 2; pp. 311 - 329
• Main Authors: Bronchti, Gilles, Heil, Peter, Sadka, Ronen, Hess, Andreas, Scheich, Henning, Wollberg, Zvi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01.07.2002
• Subjects: 2-deoxyglucose; Acoustic Stimulation; Action Potentials - physiology; Animals; auditory cortex; Auditory Cortex - cytology; Auditory Cortex - physiology; Auditory Pathways - cytology; Auditory Pathways - physiology; Auditory Perception - physiology; Blindness - physiopathology; Brain Mapping; cross-modal compensation; Dark Adaptation - physiology; Deoxyglucose; Evoked Potentials, Auditory - physiology; Evoked Potentials, Somatosensory - physiology; Mechanoreceptors - physiology; Mole Rats - anatomy & histology; Mole Rats - physiology; Neuronal Plasticity - physiology; Neurons - cytology; Neurons - physiology; Physical Stimulation; somatosensory cortex; Somatosensory Cortex - cytology; Somatosensory Cortex - physiology; Spalax ehrenbergi; Vibrissae - physiology; visual cortex; Visual Cortex - cytology; Visual Cortex - physiology; Visual Pathways - cytology; Visual Pathways - physiology
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1046/j.1460-9568.2002.02063.x

The mole rat (Spalax ehrenbergi) is a subterranean rodent whose adaptations to its fossorial life include an extremely reduced peripheral visual system and an auditory system suited for the perception of vibratory stimuli. We have previously shown that in this blind rodent the dorsal lateral geniculate nucleus, the primary visual thalamic nucleus of sighted mammals, is activated by auditory stimuli. In this report we focus on the manifestation of this cross‐modal compensation at the cortical level. Cyto‐ and myeloarchitectural analyses of the occipital area showed that despite the almost total blindness of the mole rat this area has retained the organization of a typical mammalian primary visual cortex. Application of the metabolic marker 2‐deoxyglucose and electrophysiological recording of evoked field potentials and single‐unit activity disclosed that a considerable part of this area is activated by auditory stimuli. Previous neuronal tracing studies had revealed the origin of the bulk of this auditory input to be the dorsal lateral geniculate nucleus which itself receives auditory input from the inferior colliculus.