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Age-related Hearing loss and Dementia

20th national competition for scientific and technical research

Aging and neurodegenerative diseases

Senior Researcher : Manuel Sánchez Malmierca

Research Centre or Institution : Instituto de Neurociencias de Castilla y León. Universidad de Salamanca


The mismatch negativity (MMN) and stimulus-specific adaptation (SSA) are the neural correlates of predictive coding. MMN and SSA are automatic responses that occur under anesthesia, sleep or even coma. However, we propose the hypothesis that attention influences predictive coding, so that voluntary attention will regulate the salience of relevant stimuli, and the underlying mechanisms will be disrupted in aging and in Alzheimer Disease (AD). To test this hypothesis, we are running an experiment based on an attentional frequency discrimination task in healthy animals, to correlate single unit SSA and neuronal mismatch responses to a behavioral level.

In first place, we conducted various session of handling while the animals got used to the operational chamber, in this phase we also put them in food restriction. In the next stage they learned the association between the activation of a nose-poke after a cue tone and a reward delivery in the operational cage. Then, they learned to recognize a deviant tone presented cyclically in between periods of silence and progressively reducing the response window. Finally, they will learn to distinguish a deviant tone embedded in an oddball paradigm. To quantify the ability of discrimination of the rats to the deviant sound we calculate the d’ index. Once associative learning is established, we will study the long-term effects on the neuronal activity of primary auditory cortex under anesthesia.

We will compare these results in healthy animals with our animal model of AD (TgF344-AD rats) in a cross-sectional study to look for alterations of the saliency of unexpected sounds along the auditory pathway, which could underlie the neuronal basis of the aberrant perception in aging and AD,

Thus, these early months have been spent in the selection to hire an investigator with the special education (Laura Quintela Vega, BVetM) to conduct the experiments and also to obtain the TgF344-AD rats from the University of Missouri .and set breeding colony at our Institute. 

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