Crossmodal plasticity of sensory cortical processing
It might not be a surprise that sensory systems do not work in isolation. Moreover, it is well known that visual deprivation, such as blindness, can lead to improved auditory abilities. However, the underlying mechanisms that contribute to these “supernormal” abilities are largely unknown. For example, it could be that neurons in the visual cortex are recruited to subserve auditory processing, or that neurons in the auditory cortex become better at processing sounds, or some combination of these two mechanisms.
Many studies have investigated changes in the visual cortex in long-term blindness and found crossmodal activation of the visually deprived visual cortex (for example by braille reading). We are interested in investigating what happens to other cortical areas, in particular the auditory cortex when visual experience is altered at older ages. We are looking at how auditory processing and micro-circuits are altered.
Our results show that visual deprivations (simulated blindness) in adults alter auditory processing in that neurons have better frequency discrimination and lower thresholds. Moreover we find that thalamocortical synapses in auditory cortex are strengthened (Petrus et al Neuron 2014, see F1000 review, BBC, NPR, Washington Post, Nature.com, Voice of America). These changes occur not only on the level of single neurons, but also on the network level. Our in vivo studies show that neuronal responses decorrelate and we observe more auditory cortex neurons responding to high or low frequencies (Solarana et al. eNeuro 2019).
Seeing changes in thalamocortical connections is surprising as our visual deprivation occurs after the critical period and suggests that crossmodal influences may be more powerful than unimodal influences in changing cortical circuits. We also find extensive changes in intracortical connections between layres 4 and 2/3 (Petrus et al. 2015, Meng et al. 2015, Meng et al. 2017) indicating that visual deprivation has a powerful influence on the auditory cortex.
The fact that the frequency preference of auditory cortex neurons is shifted (Solarana et al. eNeuro 2019) suggests that maybe the auditory cortex reorganizes to better detect behaviorally important sounds in the dark. Indeed, when we visually deprive mice for 2 weeks they show improved auditory behavioral performance. In particular, mice that develop early age-related hearing loss (C57Bl/6 mice), show a decreased progression of this hearing loss (Jendrichovsky et al. 2024).
Clinical relevance:
While it is too premature to speculate whether this would work in humans (or whether humans would even do this) our results give us hope that there might be the potential for simple treatments for human central hearing problems. Moreover, if this works in humans our findings might help to improve hearing in deaf individuals. Many people are trying to recover their hearing by cochlear implants. These devices work very well in younger children, who recover perfectly. But older individuals who are completely deaf have a difficult time recovering their hearing with these devices. So maybe one can modify training regimes for cochlear implant users to help the brain to be more plastic and improve sound processing with cochlear implants.
We are collaborating closely in this project with the lab of Dr. Hey-Kyoung Lee at JHU.
Key Publications
P. Jendrichovsky, H-K Lee, P.O. Kanold “Brief periods of visual deprivation in adults increase performance on auditory tasks”, iScience 2024
J. Whitt, G. Ewall, D. Chakraborty, A. Adegbesan, R. Lee, P.O. Kanold, H-K Lee “Visual deprivation selectively reduces thalamic reticular nucleus-mediated inhibition of the auditory thalamus in adults”, J. Neuroscience 2022
K. Solarana, J. Liu, Z. Bowen, H.-K. Lee, P.O. Kanold “Temporary visual deprivation causes decorrelation of spatio-temporal population responses in adult mouse auditory cortex” eNeuro 2019
X. Meng, JPY. Kao, H-K. Lee, P.O. Kanold “ Intracortical Circuits in Thalamorecipient Layers of Auditory Cortex Refine after Visual Deprivation”, eNeuro 2017
X. Meng, JPY. Kao, H-K. Lee, P.O. Kanold “Visual Deprivation Causes Refinement of Intracortical Circuits in the Auditory Cortex, Cell Reports 2015
E. Petrus*, A. Isaiah*, AP. Jones, D. Li, H. Wang, H-K Lee, P.O. Kanold ”Crossmodal Induction of Thalamocortical Potentiation Leads to Enhanced Information Processing in the Auditory Cortex”, Neuron 2014 (F1000 review, BBC, NPR, Washington Post, Nature.com, Voice of America)
