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.
DR HEBA KHAMIS
DR SARAH MCINTYRE
DR TATJANA SIZOVA–CAJIC
DR STEPHEN REDMOND
DR RICHARD VICKERY
Skin vibrations sensed by tactile receptors contribute significantly to the perception of object properties during tactile exploration [1-4] and to sensorimotor control during object manipulation . Sustained low-frequency skin vibration (<60 Hz) evokes a distinct tactile sensation referred to as flutter whose frequency can be clearly perceived . How afferent spiking activity translates into the perception of frequency is still unknown. Measures based on mean spike rates of neurons in the primary somatosensory cortex are sufficient to explain performance in some frequency discrimination tasks [7-11]; however, there is emerging evidence that stimuli can be distinguished based also on temporal features of neural activity [12, 13]. Our study's advance is to demonstrate that temporal features are fundamental for vibrotactile frequency perception. Pulsatile mechanical stimuli were used to elicit specified temporal spike train patterns in tactile afferents, and subsequently psychophysical methods were employed to characterize human frequency perception. Remarkably, the most salient temporal feature determining vibrotactile frequency was not the underlying periodicity but, rather, the duration of the silent gap between successive bursts of neural activity. This burst gap code for frequency represents a previously unknown form of neural coding in the tactile sensory system, which parallels auditory pitch perception mechanisms based on purely temporal information where longer inter-pulse intervals receive higher perceptual weights than short intervals . Our study also demonstrates that human perception of stimuli can be determined exclusively by temporal features of spike trains independent of the mean spike rate and without contribution from population response factors.
The authors examined whether feedforward video self-modeling (FF VSM) would improve control over the affected limb, movement self-confidence, movement self-consciousness, and well-being in 18 stroke survivors. Participants completed a cup transport task and 2 questionnaires related to psychological processes pre- and postintervention. Pretest video footage of the unaffected limb performing the task was edited to create a best-of or mirror-reversed training DVD, creating the illusion that patients were performing proficiently with the affected limb. The training yielded significant improvements for the forward movement of the affected limb compared to the unaffected limb. Significant improvements were also seen in movement self-confidence, movement self-consciousness, and well-being. FF VSM appears to be a viable way to improve motor ability in populations with movement disorders.