Subcortical Brain Mechanisms in Speech and Language

Abstract

This paper reviews current research and contemporary theories of subcortical participation in the motor control of speech production and language processing. As a necessary precursor to the discussion of the functional roles of the basal ganglia and thalamus, the neuroanatomy of the basal ganglial-thalamocortical circuitry is described. Contemporary models of hypokinetic and hyperkinetic movement disorders based on recent neuroanatomical descriptions of the multi-segmented circuits that characterise basal ganglion anatomy are described. Reported effects of surgically induced lesions in the globus pallidus and thalamus on speech production are reviewed. In addition, contemporary models proposed to explain the possible contribution of various subcortical structures to language processing are described and discussed in the context of evidence gained from observation of the effects of circumscribed surgically induced lesions in the basal ganglia and thalamus on language function. The potential of studies based on examination of the speech/language outcomes of patients undergoing pallidotomy and thalamotomy to further inform the debate relating to the role of subcortical structures in speech motor control and language processing is highlighted.

Bilingualism at the core of the brain. Structural differences between bilinguals and monolinguals revealed by subcortical shape analysis

“…Nevertheless, our greater sample size, the fact that we focused on simultaneous (instead of early) bilinguals, and the use of a more sensitive technique for the analysis of subcortical morphology, likely explain the larger extent and bilaterality of our results. The role of this striatal structure in language production and perception is well documented (Bohland and Guenther 2006;Gil Robles et al 2005;Murdoch 2001;Oberhuber et al 2013;Riecker et al 2005;Seghier and Price 2010;Tettamanti et al 2005), including the monitoring and programming of speech articulations (Chan et al 2008;Dodel et al 2005;Garbin et al 2010;Klein et al 1994Klein et al , 1995Riecker et al 2002;Simmonds, Wise, Leech 2011) and the processing of phonological errors (Tettamanti et al 2005; see also Bitan et al 2005;Booth et al 2002Booth et al , 2007Houk 2005). Given the wider range of speech sounds managed by Catalan-Spanish bilinguals compared to Spanish monolinguals, it is reasonable to expect that the putamen will be more strongly recruited by the former group, which might have an effect at the structural level.…”

Neuropsychological and quality of life outcomes 12 months after unilateral thalamic stimulation for essential tremor

“…Given studies showing that in PD the effects of thalamic stimulation on language and memory vary as a function of stimulation parameters (see Hugdahl and Wester, 21 Johnson and Ojemann, 22 Pillon et al, 23 and Tröster et al 24 ), and the fact that the lexical verbal fluency decrement persists to 12 months (and are accompanied by clinically notable declines in semantic fluency in about 10% of patients), enthusiasm for a microthalamotomy effect explanation is diminished. Indeed, stimulation of subcortical structures has been shown to affect both motor speech 25 and cognitive processes 26 27 involved in verbal fluency task performance, making it more likely that changes in fluency are attributable to stimulation in itself. Notwithstanding intraoperative recording and stimulation for localisation purposes, the absence of radiological verification of electrode location in this and other studies limits statements about the neuroanatomic parameters of stimulation effects on cognition.…”

Variability in aphasia following subcortical hemorrhagic lesion

“…1 However, the subcortical structures were not implicated with linguistic functions until the X-ray-based imaging techniques were applied in neuroscience around the second half of 20 th century. 2 Although aphasia has, ever since then, been reported in patients with subcortical damage, 2 its clinical manifestation shows considerable variability. 3 …”