Abstract
Sensory thalami are central sensory pathway stations for information processing. Their role for human cognition and perception, however, remains unclear. Recent evidence suggests an involvement of the sensory thalami in speech recognition. In particular, the auditory thalamus (medial geniculate body, MGB) response is modulated by speech recognition tasks and the amount of this task-dependent modulation is associated with speech recognition abilities. Here, we tested the specific hypothesis that this behaviorally relevant modulation is present in the MGB subsection that corresponds to the primary auditory pathway (i.e., the ventral MGB [vMGB]). We used ultra-high field 7T fMRI to identify the vMGB, and found a significant positive correlation between the amount of task-dependent modulation and the speech recognition performance across participants within left vMGB, but not within the other MGB subsections. These results imply that modulation of thalamic driving input to the auditory cortex facilitates speech recognition.
Highlights
Human communication relies on fast and accurate decoding of speech—the most important tool available to us for exchanging information
Voxels would have values from 1 to 10 corresponding to the frequency bin that they best represented. This resulted in a map of frequency distributions from low to high frequencies in the left and right MGB for each participant
Using ultra-high field functional magnetic resonance imaging (fMRI) we showed that it is the left auditory first-order sensory thalamus – the left ventral subdivision of the MGB – that is modulated during speech recognition
Summary
Human communication relies on fast and accurate decoding of speech—the most important tool available to us for exchanging information. Understanding the neural decoding mechanisms for speech recognition is important for understanding human brain function (Rauschecker and Scott, 2009), and for understanding communication disorders such as developmental dyslexia (Galaburda et al, 1994; Muller-Axt et al, 2017). The classic view, that the sensory thalamus is a passive relay station has been by-and-large abandoned over the last two decades. It is well known that there are strong corticofugal projections to the sensory thalamus (Sherman and Guillery, 2006; Winer and Prieto, 2001; Lee and Sherman, 2012; Lee and Winer, 2011).
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