Brain research by PolyU and CAS published in Nature journals

A neuroscience research jointly conducted by The Hong Kong Polytechnic University (PolyU) and the Chinese Academy of Science (CAS) has led to the discovery of a previously unknown feature of the human brain – the novelty detection mechanism in the gateway to the cerebral cortex. The finding was reported in the latest issue (September 2009) of Nature Neuroscience and highlighted by Nature (China), both being publications of the Nature Publishing Group.

This sophisticated research was being undertaken at the University's Applied Neuroscience Laboratory by a team led by Prof. He Jufang of PolyU Department of Rehabilitation Sciences and his student and Prof. He Shigang in CAS Institute of Biophysics. The study found that the thalamic reticular neurons which reside in the position as the guardian of the gateway to the cerebral cortex, responded to novel stimulus a lot better than to the repeated stimulus.

The researchers presented a two-tone melody repeatedly to rats during the experiment, pitching the sound mostly at a standard frequency and occasionally at a deviant frequency. This oddball procedure showed that the auditory sector of thalamic reticular neurons – which are inhibitory and control the ascending sensory information in the thalamus – has a deviance preference. The structure has been hypothesized to performing a great role in sensory attention.

The present finding advanced our understanding of its potential roles and the mechanism in attention shift, which could happen across sensory modalities. Malfunction of these neurons might cause attention deficit disorders and tinnitus, the perception of sound within the human ear in the absence of corresponding external sound.

Earlier, the Applied Neuroscience Laboratory has collaborated with Prof. Poo Mu-ming and Zhang Xiaohui of CAS Institute of Neuroscience and made another major finding in the auditory thalamus which was published in The Journal of Neuroscience (May 2009). In that study, they found that the auditory thalamic neurons can respond to sound of low frequency or slow oscillations at frequencies of less than one Hertz. More importantly, the auditory thalamic neurons can pick up and retain the sound beat for a while even after the sound has stopped. This interesting finding has shed new light on the mechanism of attention and understanding the sensitivity of our brains to certain sounds.

In carrying out this study, researchers presented repetitive sound stimuli and analyzed the response of their auditory neurons with sophisticated measuring tools. The study showed that the sensory neurons remained active after termination of the sound stimuli, and even a weak sound could trigger the sustaining response for at least 10 seconds. The study also found that the thalamic neurons responded to rhythmic sound stimuli during slow wave sleep, as confirmed by extracellular recordings. Such effects may help retain the information of stimulus interval in order of seconds.

The principal investigator Prof. He Jufang is one of the leading neuroscientists in the hearing research and thalamocortical system, especially in the corticofugal modulation. With research interest focusing on systems neuroscience, he combines electrophysiological, anatomical and engineering approaches to investigate the fundamental questions of hearing, sleep, learning and memory. Prof. He has recently been named a Croucher Senior Research Fellow 2009 in recognition of distinguished research accomplishment.

The Applied Neuroscience Laboratory was set up by PolyU in 2006 to support research work and investigate fundamental questions in neuroscience. A part of this laboratory in the line of visuo-auditory integration was entitled in 2008 as a Joint-Laboratory between the Chinese Academy of Sciences and PolyU.