Neurons

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Chapter 4 endnote 4, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

Your brain’s 86 billion neurons, which are connected into massive networks, never lie dormant awaiting a jump-start.

The firing of a single neuron (or a small population of neurons) represents the presence or absence of some feature. The feature can be simple, like a line; or a complex summary of multiple simple features, like a face, or the sight, sounds, and tastes of an apple. However, a given neuron (or group of neurons) represents different features from moment to moment;[1][2][3][4] Its receptive field (the feature it represents) is not fixed. Many different neurons synapse onto one neuron (many-to-one connectivity), so that a neuron’s receptive field depends on the information it receives at a given moment in time. Most of these neurons excite each other (speed each other’s firing rates) but some inhibit each other (slow each other’s firing rate);[5] i.e., all neurons have a neural context in the moment that determines their receptive field.[6] Conversely, one neuron also synapses on many other neurons (one-to-many connectivity).[7] Each neuron is connected to over a thousand other neurons, by many thousands of synapses,[8] although on average, a change in one neuron’s firing rate will cause changes in about 15,000 to 17,500 synapses.[9] This is just an estimate, however, because neurons at the front of the brain are more densely connected to each other than those at the back by a systematic factor of five to tenfold from occipital to frontal.[10]


Notes on the Notes

  1. Spillmann, Lothar, Birgitta Dresp-Langley, and Chia-huei Tseng. 2015. "Beyond the classical receptive field: the effect of contextual stimuli." Journal of Vision 15 (9): 7.
  2. Stokes, Mark G., Makoto Kusunoki, Natasha Sigala, Hamed Nili, David Gaffan, and John Duncan. 2013. "Dynamic coding for cognitive control in prefrontal cortex." Neuron 78 (2): 364-375.    
  3. Rigotti, Mattia, Omri Barak, Melissa R. Warden, Xiao-Jing Wang, Nathaniel D. Daw, Earl K. Miller, and Stefano Fusi. 2013. "The importance of mixed selectivity in complex cognitive tasks." Nature 497 (7451): 585-590.
  4. Basole, Amit, Leonard E. White, and David Fitzpatrick. 2003. "Mapping multiple features in the population response of visual cortex." Nature 423 (6943): 986-990.
  5. Sillito, A. M. 1975. "The contribution of inhibitory mechanisms to the receptive field properties of neurones in the striate cortex of the cat." Journal of Physiology 250 (2): 305-329.
  6. McIntosh, Anthony Randal. 2004. "Contexts and catalysts: a resolution of the localization and integration of function in the brain." Neuroinformatics 2 (2): 175-182    
  7. Sporns, Olaf. 2011. Networks of the Brain. Cambridge, MA: MIT Press..
  8. Peters, Alan. 2002. "Examining neocortical circuits: Some background and facts." Journal of Neurocytology 31: 183-193.
  9. Lennie, Peter. 2003. "The cost of cortical computation." Current Biology 13 (6): 493-497.
  10. Charvet, Christine J., and Barbara L. Finlay. 2014. "Evo-devo and the primate isocortex: the central organizing role of intrinsic gradients of neurogenesis." Brain, Behavior and Evolution 84 (2): 81-92.