A neural network model of the inferior colliculus with modifiable lateral inhibitory synapses for human echolocation

Abstract

We propose a neural network model of the inferior colliculus (IC) for human echolocation. Neuronal mechanisms for human echolocation were investigated by simulating the model. The model consists of the neural networks of the central nucleus (ICc) and external nucleus (ICx) of the inferior colliculus. The neurons of the ICc receive interaural sound stimuli via multiple contralateral delay lines and a single ipsilateral delay line. The neurons of the ICc send output signals to the neurons of the ICx in a convergent manner. We stimulated the ICc with pairs of a direct sound (a sonar sound) and an echo sound (the reflection from an object). Information about the distance between the model and the object is expressed by the delay time of the echo sound with respect to the direct sound. The results presented here show that neurons of the ICc responsive to interaural onset time differences contribute to the creation of an auditory distance map in the ICx. We trained the model with various pairs of direct-echo sounds and modified synaptic connection strengths of the networks according to the Hebbian rule. It is shown that self-organized long-term depression of lateral inhibitory synaptic connections plays an important role in enhancing echolocation skills.

A Device for Human Ultrasonic Echolocation

“…However, some blind persons have demonstrated the use of active echolocation, interpreting reflections from self-generated tongue clicks for such tasks as obstacle detection [7], distance discrimination [8], and object localization [9], [10]. The underpinnings of human echolocation in blind (and sighted) people remain poorly characterized, though some informative cues [11], neural correlates [12], [13], [14], and models [15] have been proposed. While the practice of active echolocation via tongue clicks is not commonly taught, it is recognized as an orientation and mobility method [16], [17].…”