Neural basis of hearing deficits in Fragile X syndrome
Fragile X syndrome is the most common inherited form of intellectual disability and autism. It is caused by a mutation in the fmr1 gene which leads to a loss of Fmrp, a protein that regulates the expression synaptic proteins in the brain, leading to excessive connectivity of the brain during development. People with Fragile X Syndrome display a number of sensory deficits including hypersensitivity to sounds and other sensory modalities. In most cases, language development and communication is impaired.
The mouse model of Fragile X Syndrome, one of the first transgenic mouse created in the early 1990’s, exhibits similar traits to humans, including hypersensitivity to loud sounds and deficits in acoustic communication. Using a variety of physiological and anatomical methods we study the changes in neural connectivity and neural function underlying these deficits in different parts of the brain. We are also interested to what these sensory abnormalities translate into altered social behavior.
Vocal communication and social behavior of mice
Because of their genotypical, physiological, and biochemical similarities with humans, mice have become the most widely used vertebrates in life sciences. Furthermore, they share various emotional responses and other centrally controlled traits, such as circadian rhythm, memory, or aggression, with us. Due to these similarities, mice are employed in various studies to approximate human behaviors in both physiological and pathological conditions.
Naturally, mice live in social groups, and living in complex social networks requires extensive communication of all its members. Routes of communication may include both visual and olfactory signaling (non-vocal communication), as well as vocal communication. Indeed, mice emit vocalizations both within and above the auditory/frequency range of human hearing. Those vocalizations exceeding the human auditory range are summarized by the term ultrasonic vocalizations (or USVs). Mice possess a USV repertoire comprising of 10 to 12 different syllables. The way mice use these different USV syllables in different social contexts and which properties of these syllables are relevant for the interindividual communication is the focus of current research efforts.
We investigate how vocal communication in mice is affected in models of neurodevelopmental disorders (e.g. Fragile X syndrome) and how USV alterations affect social interactions. Furthermore, we are researching whether mouse USVs can be used to assess the wellbeing of both individual mice as well as social groups of mice.
Hearing under-ground: auditory processing in naked mole-rats
Naked mole-rats live in large eusocial groups in extensive underground burrow systems. With this special life style they evolved a number of adaptations, the most famous and well-studied among them are extreme longevity with reduced physiological aging and resistivity against cancer.
Naked mole-rats also exhibit profound adaptations in sensory perception in response to their underground living. For example, the burrow system provides only limited environmental acoustic information. At the same time naked mole-rats are highly vocal and transmit information about their status and their social interaction using a large repertoire of vocalizations. To accommodate this altered acoustic environment, the ascending auditory system, ranging from the inner ear to the auditory cortex has evolved a number of specialized adaptations ranging from a reduced number of ion channels to altered connectivity in the auditory brainstem.
We are especially interested to what extent voltage-gated ion channels may be adapted the special living conditions and whether these adaptations influence the analysis of sound features these animals encounter in the daily life.