That’s right: Sensorimotor Journal Club has been moved to Tuesdays at 4pm!

We’re still meeting in the Keck Conference Room (HSE810)

 

Sensory feedback is not always suppressed

 

At this coming Tuesday’s journal club, we’ll continue disucssing how sensory input is processed when it is feedback from a motor act. From what we’ve talked about so far, it looks like sensory feedback processing = sensory feedback suppression: first we looked at an example of non-specific sensory suppression seen in finger movements, then, in the following week, we reviewed some examples of feedback suppression that appeared highly selective in suppressing mainly the response to expected feedback. This selective suppression lent support to a model of feedback processing where incomming feedback is compared with a prediction of that feedback.

 

This Tuesday, I’ll talk further about this model, and show how, in certain circumstances, the model predicts motor action should cause an enhanced response to sensory input, relative to passive listening. And indeed this appears to be the case, as was seen in some of our recent experiments that I will talk about.

 

Talk title and Abstract:

Cortical responses to feedback perturbations during speaking

Understanding how speech perception interacts with speech production is a longstanding issue that has classically been investigated by looking at how altering auditory feedback affects speech. Recently, however, the advent of functional neuroimaging methods has allowed a new approach to the issue: examining how producing speech affects the neural processes serving auditory perception. Several studies have shown that speaking suppresses the normal response to speech sounds in auditory cortex and associated regions. Our own studies suggest that this suppression reflects a comparison between actual auditory input and a prediction of that auditory input (Houde et al., 2002). Based on these initial studies, we have developed a model for how auditory feedback is processed during speech production. Here, we test this model by using whole-head magnetic source imaging (MSI) to monitor activity in auditory cortex as speakers compensate for brief perturbations of the pitch or amplitude of their speech. Prior studies have shown that such speech perturbations cause compensatory responses in speech motor output (Burnett et al., 1998; Heinks-Maldonado & Houde, 2005). In the speaking session of the experiment, subjects phonated the neutral schwa vowel while sitting in the MSI scanner. At roughly 1.2 second intervals, they experienced 400ms perturbations of the pitch or amplitude of their audio speech feedback. In the listening session of the experiment, subjects passively listened to playback of their audio feedback in the speaking session. Our results reveal that in most subjects making significant compensations for the feedback perturbations, we find areas in the vicinity of auditory cortex that have greater responses to the perturbations during speaking than during passive listening.