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Spike-time encoding of gas concentrations using neuromorphic analog sensory front-end

Shavika Rastogi, Nik Dennler, Michael Schmuker, André van Schaik

TL;DR

It is shown that in the setting of controlled airflow-embedded gas injections, the time difference between the two generated pulses varies inversely with gas concentration, which is in agreement with the spike timing difference between tufted cells and mitral cells of the mammalian olfactory bulb.

Abstract

Gas concentration detection is important for applications such as gas leakage monitoring. Metal Oxide (MOx) sensors show high sensitivities for specific gases, which makes them particularly useful for such monitoring applications. However, how to efficiently sample and further process the sensor responses remains an open question. Here we propose a simple analog circuit design inspired by the spiking output of the mammalian olfactory bulb and by event-based vision sensors. Our circuit encodes the gas concentration in the time difference between the pulses of two separate pathways. We show that in the setting of controlled airflow-embedded gas injections, the time difference between the two generated pulses varies inversely with gas concentration, which is in agreement with the spike timing difference between tufted cells and mitral cells of the mammalian olfactory bulb. Encoding concentration information in analog spike timings may pave the way for rapid and efficient gas detection, and ultimately lead to data- and power-efficient monitoring devices to be deployed in uncontrolled and turbulent environments.

Spike-time encoding of gas concentrations using neuromorphic analog sensory front-end

TL;DR

It is shown that in the setting of controlled airflow-embedded gas injections, the time difference between the two generated pulses varies inversely with gas concentration, which is in agreement with the spike timing difference between tufted cells and mitral cells of the mammalian olfactory bulb.

Abstract

Gas concentration detection is important for applications such as gas leakage monitoring. Metal Oxide (MOx) sensors show high sensitivities for specific gases, which makes them particularly useful for such monitoring applications. However, how to efficiently sample and further process the sensor responses remains an open question. Here we propose a simple analog circuit design inspired by the spiking output of the mammalian olfactory bulb and by event-based vision sensors. Our circuit encodes the gas concentration in the time difference between the pulses of two separate pathways. We show that in the setting of controlled airflow-embedded gas injections, the time difference between the two generated pulses varies inversely with gas concentration, which is in agreement with the spike timing difference between tufted cells and mitral cells of the mammalian olfactory bulb. Encoding concentration information in analog spike timings may pave the way for rapid and efficient gas detection, and ultimately lead to data- and power-efficient monitoring devices to be deployed in uncontrolled and turbulent environments.
Paper Structure (8 sections, 5 figures)

This paper contains 8 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Experimental Setup for MOx Sensor Recordings
  3. Proposed Analog Circuit Design
  4. Concentration Encoding in Mammalian Olfactory Bulb
  5. ATIS Pixel Mechanism
  6. Proposed Circuit Design
  7. Results
  8. Discussion and Future Work

Figures (5)

  • Figure 1: Mean load voltage over all trials obtained for the sensor for four different gases at five different concentration levels. Gas stimulus is indicated by the shaded region, with the gas type indicated in the title of each panel. C1 to C5 indicate 5 concentration levels of each gas such that C1 is the lowest and C5 is the highest concentration level, and each colored curve indicates the mean response at these concentrations. The individual trials are shown in grey.
  • Figure 2: (a) Baseline firing of MCs and TCs. Both cells fire in opposite phases of the sniff cycle. (b) Variation in MC and TC firing with increasing odor concentration, as indicated by the arrows. Figures adapted from Fukunaga2012.
  • Figure 3: Proposed gas concentration measurement circuit.
  • Figure 4: Output of circuit for Eucalyptol (Eu) gas at concentration level 5
  • Figure 5: Inverse of the time difference between CD and EM pulse activation with respect to concentration level. Dots and error bars represent the mean and standard deviation across 20 trials respectively. For one trial for 2H at C1, the EM pulse was not observed and thus the trial was discarded.