Abstract
To obtain deeper insights into the tactile processing pathway from a population-level point of view, we have modeled three stages of the tactile pathway from the periphery to the cortex in response to indentation and scanned edge stimuli at different orientations. Three stages in the tactile pathway are, (1) the first-order neurons which innervate the cutaneous mechanoreceptors, (2) the cuneate nucleus in the midbrain and (3) the cortical neurons of the somatosensory area. In the proposed network, the first layer mimics the spiking patterns generated by the primary afferents. These afferents have complex skin receptive fields. In the second layer, the role of lateral inhibition on projection neurons in the cuneate nucleus is investigated. The third layer acts as a biomimetic decoder consisting of pyramidal and cortical interneurons that correspond to heterogeneous receptive fields with excitatory and inhibitory sub-regions on the skin. In this way, the activity of pyramidal neurons is tuned to the specific edge orientations. By modifying afferent receptive field size, it is observed that the larger receptive fields convey more information about edge orientation in the first spikes of cortical neurons when edge orientation stimuli move across the patch of skin. In addition, the proposed spiking neural model can detect edge orientation at any location on the simulated mechanoreceptor grid with high accuracy. The results of this research advance our knowledge about tactile information processing and can be employed in prosthetic and bio-robotic applications.
Highlights
To obtain deeper insights into the tactile processing pathway from a population-level point of view, we have modeled three stages of the tactile pathway from the periphery to the cortex in response to indentation and scanned edge stimuli at different orientations
The first stage of the tactile processing pathway consists of the cutaneous mechanoreceptors which are broadly categorized as two cell types with different response characteristics: (1) slowly adapting (SA) mechanoreceptors which produce sustained firing activity in response to a static indentation of the skin, (2) and rapidly adapting (RA) mechanoreceptors which mainly fire at the onset and offset of indentation
We examine the role of lateral inhibition in the projection neurons (PN) population and demonstrate how insufficient inhibitory currents lead to a failure in suppressing skin hypersensitivity
Summary
To obtain deeper insights into the tactile processing pathway from a population-level point of view, we have modeled three stages of the tactile pathway from the periphery to the cortex in response to indentation and scanned edge stimuli at different orientations. The third layer acts as a biomimetic decoder consisting of pyramidal and cortical interneurons that correspond to heterogeneous receptive fields with excitatory and inhibitory sub-regions on the skin In this way, the activity of pyramidal neurons is tuned to the specific edge orientations. A three-layer biophysical model using a spiking neural network is proposed to functionally simulate the tactile processing pathway. The SA-I and RA-I afferents are modeled as they branch into the skin and innervate overlapping receptive fields which provides spatial and temporal information about the tactile s timuli[4,9]. The entire spiking neural network model was built using the Brian[2] simulator with Python version 3.6526
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