correlation between thalamus volume and cognitive abilities; see, e.g., Scharinger
et al. 2014.)
4 The thalamus, lang uage, and mental health
If we are right in ascribing to the thalamus such a leading role in cognition, we
ought to expect to find numerous associations between thalamic damage and
cognitive disorders. This section shows that this expectation appears to be met.
There is indeed rapidly accumulating evidence that cognitive disorders that
are routinely associated with language and the distinctive mode of thought it
entails, such as schizophrenia, autism, dementia, major depression, verbal work-
ing memory impairments, etc., crucially involve thalamic disorders, especially as
they affect the higher-order nuclei, such as the mediodorsal nucleus and the
pulvinar.
Some of this evidence goes as far back as Stern (1939), where a case of severe
dementia was associated with bilateral symmetrical degeneration of the thalamus,
but likely due to the reigning cortico-centrism of the time, the significance of
this finding appeared to have been lost on its contemporaries. Recently, thalamic
damage has been reported for a variety of cognitive disorders. Let us list some
salient examples here, before examining what this might tell us about the neu-
robiological nature of linguistic cognition.
In the context of schizophrenia, Agarwal et al. (2008) report “microstructural
thalamic changes”; Kemether et al. (2003), Alelú-Paz and Giméne z-Amaya
(2008) and Byne et al. (2009), abnormal thalamic volume (reduction); Thong
et al. (2013), thalamic shape abnormali ties; Popken et al. (2000) and Harms
et al. (2007), neuron loss; and Pinault (2011), “dysfunctional thalamus-relat ed
networks”. Martinsde Souza et al. (2010) consider the th alamus a potential
biomarker candidate for schizophrenia (see also Brucato et al. 2015). At a more
general level , Andreasen (1997) discusses the role of the th alamus in the patho-
genesis of schizophrenia, building on original insights from Jones (1997).
Given Goldman-Rakic’s (1994) cl aim that a defect in working memory may
be the fundamental impairment leading to schizophrenic thought disorder, it
may not come as a surprise to find reports of thalamic damage in the context
of working memory impairments, in the context of schizophrenia and beyond
(Dagenbach et al. 2001, Vigren et al. 2013, Par naudeau et al. 2013).
I n the context of aut ism, a similar state of affairs obtains: Egawa et al. (2011)
and Tsatsanis et al. (2003 ) report reduced thalami c volume; Nair et al. (2013),
impaired thalami-cortical connectivity; and Shi et al. (2013), gray and white
matter abnor malities in the thalamus.
Thalamic atrophy is also reported following severe brain injury, and is found
to correlate with cognitive impairment (Lutkenhoff et al. 2013). Abnormal
neuron numbe rs in thalamus nuclei are found in cases of major depression
(Young et al. 2004), and finally, thalamic dama ge is also reported in leukoma-
lacia (Ligam et al. 2009), attention deficit hyperact ivity disorder (Mills et al.
2012), dementia (Kovacs et al. 20 13), multiple sclerosis (Cifel li et al. 2002),
The central role of the thalamus 237