Mechanoreceptor vs. cortical neuron receptive field

[Function]

Hello everyone

 

The Princples of Neural Science (Kandel et al.) states that "For example, the receptive fields of SA1 and RA1 fibers innervating the fingertip are tiny spots on the skin, whereas those on the cortical neurons receiving these inputs cover an entire fingertip or several adjacent fingers. The receptive field of a neuron in area 3b represents a composite of inputs from 300 to 400 sensory nerve fibers."

 

My question is: how so are these smaller receptive fields of those sensory nerve fibers innervating e.g. Merkel and Meissner cells, still distinguished as per two-point discrimination, on a conscious level, if they're all merged into 1 perceptive field on the S-I cortex?

 

Only thing I can think of, is that perhaps the smaller perceptive fields are not only connected to 1 cortical perceptive fields, but to multiple ones, and that a balance between different levels of activation of these cortical perceptive fields makes us experience for example two-point discrimination on a conscious level?

 

Thanks!

 

F

 

The following can be read in a thesis by Magnus Johnsson @ Lund University

A receptive field is the area on the skin innervated by a neuron (Gardner & Kandel, 2000; Gardner, Martin & Jessell, 2000), and for the neurons in the dorsal root ganglion the receptive fields delimits the resolution of tactile stimulation, i.e. smaller and more receptive fields in a skin area gives a better resolution. In the dorsal root ganglion, the receptive field of a neuron represents the input from only one receptive field is the area on the skin innervated by a neuron (Gardner & Kandel, 2000; Gardner, Martin & Jessell, 2000), and for the neurons in the dorsal root ganglion the receptive fields delimits the resolution of tactile stimulation, i.e. smaller and more receptive fields in a skin area gives a better resolution. In the dorsal root ganglion, the receptive field of a neuron represents the input from only one receptor, while in the somatosensory cortex the receptive field of a neuron represents the composite input of 300 – 400 receptors. However, the size of a receptive field in cortex or in a relay nucleus is not

fixed, but can be modified by experience or for example, injury to a sensory nerve. In spite of the size of the receptive field of

cortical neurons, fine details can be discriminated.

So what is the difference between a dorsal root afferent sensory neuron and a cortical sensory neuron? And how do they interact? What's the relationship between their receptive fields?

Edited October 17, 2015 by Function