D42 Mapping of receptive fields

Topic

A sensory neuron's receptive field defines the specific region of physical space—or, alternatively, of a particular sensory spectrum—to which that neuron responds. In an insect's visual cell, for instance, this region corresponds to a zone of its visual field; in a human mechanosensory cell (specifically a mechanoreceptor), it corresponds to a zone of the cuticle or skin; and in a human olfactory cell, it constitutes a subset of the organism's specific chemical space.

The systematic mapping of these receptive fields reveals the topographic organization of the nervous system: neighboring neurons typically possess adjacent receptive fields, thereby forming an ordered map across the nervous system. The fact that these neighboring neurons maintain a high degree of spatial fidelity between their receptive fields results in an even more precise ordered map of the nervous system.

The spike-triggered averaging technique is particularly efficient for revealing a sensory neuron's receptive field: a random stimulus is presented to the neuron, and the stimulus is averaged over the moments preceding each action potential spike, thereby revealing the linear core of the receptive field. Making the random stimulus presented to the sensory neuron more prolonged results in the final linear kernel revealed by the technique becoming even more precise.

The final orientation selectivity index quantifies whether the sensory neuron prefers a specific angle of the stimulus or responds virtually uniformly to any angle of that stimulus. If the sensory neuron shows a stronger preference for a specific stimulus angle, its final orientation selectivity index moves closer to its maximum selectivity.

The final size of the receptive field determines the final spatial resolution of the entire sensory system—the same resolution established by another model in this set based on its own criteria: a significantly smaller receptive field implies significantly higher final acuity for the sensory system. Further reduction of the sensory neuron's receptive field results in even higher final acuity for the sensory system.

Consequently, regarding the region of space or the sensory spectrum introduced at the beginning, this model relates the sensory neuron's final spatial cutoff frequency—the maximum spatial frequency of the stimulus that the neuron can still transmit—to the aforementioned acuity via the Nyquist theorem (also established by another model in this set). A higher final spatial cutoff frequency for the sensory neuron results in higher final acuity for the sensory system within that specific region of space or the sensory spectrum.

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