Kemmerer’s critical review of my book The Myth of Mirror Neurons raises some important points regarding the relation between motor-centric and motor-modulatory models of perception and understanding. In addressing his critiques I hope to clarify that there is growing agreement that motor-centric models are untenable, while motor-modulatory models are viable but still face theoretical and empirical hurdles.

There is little doubt that predictive coding is an important mechanism in language processing–indeed, in information processing generally. However, it is less clear whether the action system is the source of such predictions during perception. Here I summarize the computational problem with motor prediction for perceptual processes and argue instead for a dual-stream model of predictive coding.

In the verbal domain, there is only very weak evidence favoring the view that working memory is an active state of long-term memory. We strengthen existing evidence by reviewing two recent fMRI studies of verbal working memory, which clearly demonstrate activation in the superior temporal lobe, a region known to be involved in processing speech during comprehension tasks.

Grodzinsky's localization claim can be questioned on empirical grounds. The Trace Deletion Hypothesis fails to account for a number of comprehension facts in Broca's aphasia and conduction aphasics show similar comprehension patterns. Frontoparietal systems are recruited during sentence comprehension only under conditions of increased processing load and/or attentional demands.