Though stuttering is manifest in its motor characteristics, the cause of

Though stuttering is manifest in its motor characteristics, the cause of stuttering may not relate purely to impairments in the motor system as stuttering frequency is increased by linguistic factors, such as syntactic complexity and length of utterance, and decreased by changes in perception, such as masking or altering auditory feedback. opercular and sensorimotor cortex bilaterally and Heschls gyrus on the left. These results are consistent with a recent meta-analysis of functional imaging studies in developmental stuttering. Two additional findings emerged from our study. First, we found overactivity in the midbrain, which was at the level of the substantia nigra and extended to the pedunculopontine nucleus, red nucleus and subthalamic nucleus. This overactivity is consistent with suggestions in previous studies of abnormal function of the basal ganglia or excessive dopamine in people who stutter. Second, we found underactivity of the cortical motor and premotor areas associated with 482-39-3 manufacture articulation and speech production. Analysis of the diffusion data revealed that the integrity of the white matter underlying the underactive areas in ventral premotor cortex was reduced in people who stutter. The white matter tracts in this area via connections with posterior superior temporal and inferior parietal cortex provide a substrate 482-39-3 manufacture for the integration of articulatory planning and sensory feedback, and via connections with primary motor cortex, a substrate for 482-39-3 manufacture execution of articulatory movements. Our data support the conclusion that stuttering is a disorder related primarily to disruption in the cortical and subcortical neural systems supporting the selection, initiation and execution of motor sequences necessary for fluent speech production. hypothesis that the areas of the brain affected in stuttering would be language and motor areas and their homologues in 482-39-3 manufacture the right hemisphere, we report differences in FA in tracts associated with those areas at a threshold of t(28)>3.1 (p<0.0025, one-tail, uncorrected); many of these areas showed group differences bilaterally (see Table 3 and Figure 2). The joint probability of finding these bilateral differences can be considered p<0.00252. The PWS group (N=17) had significantly lower FA compared to the Control group (N=13) in white matter underlying pars orbitalis in the right IFG, left and right posterior IFG, left and right precentral gyrus (middle), left and right ventral premotor cortex, right posterior supramarginal gyrus and left dorsal supramarginal gyrus, in the right and left cerebellar white matter and in white matter tracts such as the right corticospinal tract (at the level of the midbrain), the medial lemniscus and the right middle cerebellar peduncle. The PWS group had higher FA than controls in the white matter underlying left posterior IFG (ventral to the area of decrease described above), right postcentral gyrus and right supramarginal gyrus. Figure 2 Structural white matter differences between controls and people who stutter Table 3 Differences between people who stutter and controls in structural integrity of white matter tracts By superimposing the statistical maps of the comparisons between PWS and Controls we were able to demonstrate the relationship between the functional and structural differences. The reduced functional activations in the left ventral premotor cortex and even more ventrally located right premotor (Rolandic/central opercular) cortex in the PWS group lay directly above regions of white matter showing reduced integrity in that group (see Figure 3). Figure 3 Structural and functional abnormalities in the premotor cortex and underlying white matter in people who stutter Discussion Using a combination of structural and functional brain image analysis Rabbit Polyclonal to EHHADH in people who stutter, we have identified a relationship between abnormal brain function of the ventral premotor cortex in both hemispheres and the integrity of white matter connections lying underneath this area. The affected areas were not perfectly symmetrical in the left and right hemispheres, being more ventral and anterior on the right than on the left (see central operculum in Table 1 and Figure 1). In the monkey, ventral premotor cortex (Brodmanns area 6) and adjacent area 44 receive inputs from the supramarginal gyrus and adjacent parietal operculum (Petrides and Pandya, 2002) and the posterior insula (Mesulam and Mufson, 1982). Also, ventral premotor cortex projects to the primary motor cortex in the precentral sulcus/gyrus (area 4) (Barbas and Pandya, 1987). Disruption of white matter tracts underlying the ventral premotor cortex is likely to interfere with the integration of sensory and motor information necessary for fluent speech production. Brain activity in the left frontal precentral cortex (-48 -4 32), at a location slightly posterior and dorsal to the peak in ventral premotor cortex reported here (-54 2 482-39-3 manufacture 24), is reported to be significantly lower compared to controls in people who stutter prior to therapy (Neumann et al., 2003). When studied at follow-up, after therapy, activity in this region (-46 -2 24; IFG) was significantly increased (Neumann et al., 2003). Functionally, the ventral premotor cortex subserves complex sequences of movements, including those involved in speech (Wise et al., 1999). In the monkey, mirror neurons responding to both production of.