Hypercomplex cell

Abstract: In addition to the asymmetry of the spatial coupling and of the specific temporal combination of excitation and inhibition, the non-linearity is very pronounced in area 18. Taking the sequence of a linear operation and a stationary nonlinear characteristic as a model, the experimental findings can be systematized and a cell classification specified which departs from the customary ones. The hypercomplex cell system probably originates in recurrent inhibition and leads to differentiation of the patterns along their contour line. Problems of cell classification and of the type of parallelism in the visual cortex are discussed.

Abstract: Single unit recording has revealed the same orientation sensitive cell classes in cat area 18 as are to be found in area 17. These include particularly the various types of hypercomplex cell belonging to the S, C, and B cell families.

Abstract: Part 1. Concepts of Brain Theory 1. Lettvin's challenge 2. Issues concerning the nature of neuronal response 3. 'Events' in the brain 4. Cell assemblies 5. Surprise, statistical inference, and conceptual notes 6. A new term: ignitions which 'reach' or 'don't reach' a neuron 7. Confirmation loops, powered by self-ignitions 8. Communicating 'relatedness' through time-linked ignitions 9. Relational firing: broadcasting a shape through time-linked ignitions Part 2. Contour strings and the contour wave 10. Enter the contour string 11. Drift of the retinal image 12. Theory of the simple cell 13. Theory of the complex cell 14. Corner processing: theory of the hypercomplex cell Part 3. Nodes, links, bridgeheads 15. Nodes on contour strings 16. Custom-made unstable networks made to support tracking 17. Why is the drifting retinal image helpful in perception? 18. The maintenance of moving nodes and bridgeheads Part 4. Firing games and the integration of contours 19. Making the first links by crawling along a contour string 20. Using existing links to make new links on the same contour 21. Completing a triangle of links

Abstract: Length tuning was first described for the “hypercomplex cell category” in the visual cortex. However it has subsequently become apparent that cells in the dorsal lateral geniculate nucleus (dLGN) also exhibit a high degree of length tuning and that for the majority of the population this matches or exceeds that associated with cortical hypercomplex cells (Cleland et al. 1983; Jones and Sillito 1987). In this paper we describe a distinct subpopulation of dLGN Y cells that lack length tuning. These cells were also characterised by poor centre-surround antagonism, and tended to be located close to laminar borders. They appeared to constitute 25% of the Y cell population. Following recent evidence showing relay cells to be powerfully excited by acetylcholine, and inhibitory interneurones to be inhibited, we have examined the responses of these non-length tuned cells to iontophoretic application of acetylcholine. Their brisk excitatory responses suggest that these cells are in fact relay cells. Their presence raises the possibility of a discrete non-length tuned component to the geniculate input to the cortex, and has potentially important implications for the way in which synaptic processes contributing to the length tuning profiles of visual cortical cells are modelled.