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Centrally synthesized maps of sensory space

Konishi, Masakazu (1986) Centrally synthesized maps of sensory space. Trends in Neurosciences, 9 . pp. 163-168. ISSN 0166-2236. doi:10.1016/0166-2236(86)90053-6.

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When central neurons are arranged so that their spatial relationships conserve wholly or partially those in the peripheral sensory epithelium, the relevant portion or feature of the sensory epithelium is said to be mapped topographically. Retinotopic, tonotopic, and somatotopic maps are all examples of topographic projections. Here these maps will be termed ‘projectional maps’. The functional role of these maps is difficult to establish, because the coding of spatial information may not be the factor determining their topographic organisation. For example, a topographic map might also be a by-product of embryological and anatomical processes that have nothing directly to do with neural coding. A second class of brain maps exist which are not topographically related to their corresponding sensory epithelia. For example, neurons selective for sound-source locations form a map of auditory space in the external nucleus of the owl's inferior colliculus (see Fig. 1). Similarly, neurons selective for echo delays are systematically distributed in the auditory cortex of the mustached bat. The distribution of orientation-selective neurons in the monkey's visual cortex also belongs to this class of maps. In these cases, primary sensory cells neither register nor extract the location, delay, or orientation of a stimulus. The selectivity for these cues is created by neuronal circuits in which the neurons forming the maps are nodal points. In this way, neuronal selectivity for stimulus orientation is not generated in the eye but ‘synthesized’ in the cortex. Similarly, neuronal selectivity for binaural disparities is obviously not present in the ear. Tuning to a particular range of echo delays is also a property of central neurons. In this review these maps will be referred to as ‘centrally synthesized’ rather than ‘computational’ maps as they were named elsewhere, because the new term is more descriptive. The study of these maps may cast light on the significance of mapping in general as a method of neural coding.

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Additional Information:© 1986, Elsevier Science Publishers B.V. I thank C. E. Carr, W. E. Sullivan, T. Takahashi, S. Volman, Van Essen and H. Wagner for critically reading and correcting the manuscript. C. E. Carr (Figs 3 and 7) and W. E. Sullivan (Figs 5 and 6) kindly prepared the illustrations. This work was supported by NIH grant NS14619.
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Deposited By: Ruth Sustaita
Deposited On:25 Nov 2015 18:12
Last Modified:10 Nov 2021 23:01

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