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The Neural Basis for Auditory Temporal Processing

Karolinska Institutet

Whether to hear simple sounds, such as a tone, or perceive more complex meaningful sound patterns, such as human speech, the ear has to extract the spectro-temporal components and convey the signals to the brain where they are further processed with respect to different acoustic cues. However, we still lack an understanding of how the brain can extract the most basic physical parameters, such as amplitude fluctuations and sound gaps from complex segmented acoustic signals. Our research explores how the first central processing stations of the auditory system extract the coarse temporal structure from the acoustic scene, which is important for communication processing.

Current projects in our laboratory are focused on the Superior Paraolivary Nucleus (SPON), a prominent nucleus in the mammalian auditory brainstem. SPON neurons exhibit great sensitivity in signaling temporal cues with spiking responses that are extremely precise compared to other auditory nuclei. Our group has recently demonstrated that SPON neurons are tuned to respond to recurring sound features, such as periodically driven rhythm and pitch. In addition, SPON neurons are sensitive to singular features like abrupt starts and stops or gaps in acoustic stimuli. Our working hypothesis is that the SPON is extracting temporal information contained in natural sounds, and that it is an early locus in a "communication pathway".

IMMUNOHISTOCHEMISTRY

 

A typical SPON neuron visualized using fluorescence immunohistochemistry.

PATCH-CLAMP

 

Voltage-clamp recording of a SPON neuron.

 

MORPHOLOGY

 

Reconstruction of a SPON neuron that was labeled by an intracellular injection.

 

ELECTROPHYSIOLOGY

 

SPON fires in synchrony with the rhythm of the signal.

Our technical approaches combine electrophysiological, anatomical, molecular and behavioral methods to shed light on the SPON. We also make use of transgenic mouse models to target specific inputs to the SPON. Through the combined use of these techniques, and collaboration with mathematicians and neuroethologists, we anticipate to be able to both explore and define the specific role of the SPON for hearing and communication perception.

Anna K Magnusson Karolinska Institutet Alfred Nobels Allé 10, 141 83 Huddinge, Sweden +46 85-248 89 05 anna.magnusson@ki.se

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