Dr Ingvars Birznieks


Senior Research Fellow, NeuRA Senior Lecturer, Physiology, School of Medical Sciences, UNSW Medicine
Adjunct Fellow, School of Science and Health, UWS

+612 9399 1672

Dr Ingvars Birznieks is a sensory neurophysiologist interested in sensory information encoding mechanisms. He received his PhD training at Umeå University in Sweden and the University of Melbourne. After his postdoc studies, he was offered a position of senior research officer at NeuRA to contribute to the large scale cross-organisational project supported by Australian Government Special Research Initiative “Thinking Systems” – the project bringing together neuroscientists, biomedical engineers and roboticists. He established his own research network centred around the studies on neuronal information encoding mechanisms in the somatosensory system. His current focus is cross-disciplinary projects linking neuroscience, clinical neurology, and biomedical engineering.

Projects Dr Ingvars Birznieks is currently involved with


The encoding of friction by tactile mechanoreceptors

Unmatched human ability to control the hand so that brittle objects are gently held without slipping or being crushed by excessive force rely on sophisticated tactile sense in the fingertips. Our aim is to uncover some of the fundamental sensory mechanisms underlying unique human capabilities to manipulate objects and use tools. Our findings will enhance the future development of next generation sensory-controlled prosthetic and robotic manipulators.


The encoding of friction by tactile mechanoreceptors – the key to fingertip force control during dexterous object manipulation by humans

Information encoding by temporal structure of afferent spike trains

Our ability to sense, discriminate and interpret vibrotactile stimuli underpins some of the most crucial functions of the human hand that relate to object exploration and manipulation. This project has one branch focusing on prosthetic development of a non-invasive prosthetic system that can restore tactile perception in patients and potentially could be used in brain-machine interfaces (BMIs).


Information encoding by temporal structure of afferent spike trains evoked by complex vibrotactile stimuli

The effects of tonic muscle pain on the sympathetic and somatic motor systems

Chronic pain, defined as pain lasting for >3 months, typically develops from injuries to deep tissues such as muscle, yet little is known about how long-lasting pain affects a person's blood pressure or capacity to control their muscles. This project assesses the effects of tonic muscle pain on sympathetic nerve activity and stretch sensitivity of muscle spindles.


The effects of tonic muscle pain on the sympathetic and somatic motor systems in human subjects

Adaptation and aftereffects in perception of tactile motion

The hand's exquisite sensitivity depends to a large extent on its motion relative to the objects it touches or manipulates. Tactile motion is analysed using mechanisms we do not understand, and the aim of the proposed research is to contribute to their better understanding. We use psychophysical and neurophysiological methods to study adaptation to motion in touch. This is basic research that contributes to the knowledge underlying applications in the fields of clinical neurology, robotics and virtual reality systems.


Adaptation and aftereffects in perception of tactile motion

Restoring sensitivity in peripheral neuropathy

The elderly and patients with diabetes are at high risk of losing sensation in their feet and currently no treatment for this condition exists. This loss of feeling leads to falls, fractures and foot ulcers, which in many cases end with amputation. We have developed a new subsensory stimulation technique which for the first time restores lost sensation.


Restoring sensitivity in peripheral neuropathy

Somatotopic mismatch of hand representation following stroke

We have developed a testing technique that enables us to identify various distortions of somatotopic representation after stroke that are not detected by routine clinical testing and remain unknown to patients themselves. This indicates the need to raise awareness about this pathological condition and identify patients who would potentially benefit from sensory rehabilitation. We suggest that new rehabilitation strategies need to be developed specifically for such patients.


Somatotopic mismatch of hand representation following stroke




Sarah McIntyre






Consistent interindividual increases or decreases in muscle sympathetic nerve activity during experimental muscle pain.

Fazalbhoy A, Birznieks I, Macefield VG

We recently showed that long-lasting muscle pain, induced by intramuscular infusion of hypertonic saline, evoked two patterns of cardiovascular responses across subjects: one group showed parallel increases in muscle sympathetic nerve activity (MSNA), blood pressure, and heart rate, while the other group showed parallel decreases. Given that MSNA is consistent day to day, we tested the hypothesis that individuals who show increases in MSNA during experimental muscle pain will show consistent responses over time. MSNA was recorded from the peroneal nerve, together with blood pressure and heart rate, during an intramuscular infusion of hypertonic saline causing pain for an hour in 15 subjects on two occasions, 2-27 weeks apart. Pain intensity ratings were not significantly different between the first (5.8 ± 0.4/10) and second (6.1 ± 0.2) recording sessions. While four subjects showed significant decreases in the first session (46.6 ± 9.2% of baseline) and significant increases in the second (159.6 ± 8.9%), in 11 subjects, there was consistency in the changes in MSNA over time: either a sustained decrease (55.6 ± 6.8%, n = 6) or a sustained increase (143.5 ± 6.1%, n = 5) occurred in both recording sessions. There were no differences in pain ratings between sessions for any subjects. We conclude that the changes in MSNA during long-lasting muscle pain are consistent over time in the majority of individuals, reflecting the importance of studying interindividual differences in physiology.

Single tactile afferents outperform human subjects in a vibrotactile intensity discrimination task.

Arabzadeh E, Clifford CW, Harris JA, Mahns DA, Macefield VG, Birznieks I

We simultaneously compared the sensitivity of single primary afferent neurons supplying the glabrous skin of the hand and the psychophysical amplitude discrimination thresholds in human subjects for a set of vibrotactile stimuli delivered to the receptive field. All recorded afferents had a dynamic range narrower than the range of amplitudes across which the subjects could discriminate. However, when the vibration amplitude was chosen to be within the steepest part of the afferent's stimulus-response function the response of single afferents, defined as the spike count over the vibration duration (500 ms), was often more sensitive in discriminating vibration amplitude than the perceptual judgment of the participants. We quantified how the neuronal performance depended on the integration window: for short windows the neuronal performance was inferior to the performance of the subject. The neuronal performance progressively improved with increasing spike count duration and reached a level significantly above that of the subjects when the integration window was 250 ms or longer. The superiority in performance of individual neurons over observers could reflect a nonoptimal integration window or be due to the presence of noise between the sensory periphery and the cortical decision stage. Additionally, it could indicate that the range of perceptual sensitivity comes at the cost of discrimination through pooling across neurons with different response functions.

Effects of changing skin mechanics on the differential sensitivity to surface compliance by tactile afferents in the human finger pad.

Hudson KM, Condon M, Ackerley R, McGlone F, Olausson H, Macefield VG, Birznieks I

It is not known how changes in skin mechanics affect the responses of cutaneous mechanoreceptors in the finger pads to compression forces. We used venous occlusion to change the stiffness of the fingers and investigated whether this influenced the firing of low-threshold mechanoreceptors to surfaces of differing stiffness. Unitary recordings were made from 10 slowly adapting type I (SAI), 10 fast adapting type I (FAI) and 9 slowly adapting type II (SAII) units via tungsten microelectrodes inserted into the median nerve at the wrist. A servo-controlled stimulator applied ramp-and-hold forces (1, 2, and 4 N) at a constant loading and unloading rate (2 N/s) via a flat 2.5-cm-diameter silicone disk over the center of the finger pad. Nine silicone disks (objects), varying in compliance, were used. Venous occlusion, produced by inflating a sphygmomanometer cuff around the upper arm to 40 ± 5 mmHg, was used to induce swelling of the fingers and increase the compliance of the finger pulp. Venous occlusion had no effect on the firing rates of the SAI afferents, nor on the slopes of the relationship between mean firing rate and object compliance at each amplitude, but did significantly reduce the slopes for the FAI afferents. Although the SAII afferents possess a poor capacity to encode changes in object compliance, mean firing rates were significantly lower during venous occlusion. The finding that venous occlusion had no effect on the firing properties of SAI afferents indicates that these afferents preserve their capacity to encode changes in object compliance, despite changes in skin mechanics.

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