Dr. Mark Sayles
Areas of Research: Sensory neural circuit analysis: in-vivo auditory neurophysiology
- Understanding the impact of hearing loss on signal processing in the auditory brainstem
Our research interests lie at the intersection of engineering, systems neuroscience, audiology and neurosurgery. We use advanced modern techniques in electrophysiology to understand the transfer functions and connectivity patterns of single neurons in auditory brainstem circuits. Our current focus is understanding how these circuits become maladaptive following hearing loss and how implantable device technology might best aid people with severe hearing loss. This exciting area of neuroscience combines intra-cellular neural recording in whole animal models with computational modelling, signal processing, quantitative analysis and acoustics.
We use instrumentation for recording and analyzing electrical signals from individual neurons on milli-volt and micro-second scales. The neurons we study are located in hard-to-reach areas of the ventral brainstem, necessitating specialized neurosurgical approaches. We are part of an active and growing group of neuroscientists at Purdue, and we collaborate with colleagues at the University of Cambridge (UK) and University of Leuven (Belgium).
A, Action potentials (“spikes”) recorded from a single axon in the lateral lemniscus of a chinchilla. Each spike is approximately 8mV in amplitude and 1ms in duration. Spikes occur in bursts, relating to the repetitive auditory motion induced by a “binaural beat” acoustic stimulus.
B, Firing rate as a function of inter-aural time difference (ITD) for a neuron located in the medial superior olive. Firing rate is a damped oscillatory function of ITD, with a peak firing rate at approximately 0.4ms. Firing rate varies between 0 and 220 spikes per second.
C, Anatomical reconstruction of a labeled single neuron (an “octopus cell”) in the ventral cochlear nucleus after intra-cellular recording using the in-vivo patch-clamp technique. The cell was filled with biotin via the recording pipette.
- Looking for a highly motivated PhD students in the area of neuroscience