exploring the neural basis of higher cognitive functions. That is, many studies
ignore the role of subcortical structures.” But there are signs that the role of
subcortical structures is being appreciated again. Recently, Lieberman’s work
has done much to draw attention to the role of the basal ganglia (Lieber man
2002, 2009, 2013). As he puts it:
The traditional theory equating the brain bases of language with Broca’s
and Wernicke’s neocortical areas is wrong. Neural circuits linking activity
in anatomically segregated populations of neurons in subcortical structures
and the neocortex throughout the human brain regulate complex behaviors
such as walking, talking, and comprehending the meaning of sentences.
(Lieberma n 2002: 36)Likewise, the role of the cerebellum, another subcortical structure, is also being
reappreciated (Barton 2 012, Barton a nd Venditti 2014, Murdoch 2010, Beaton
a nd Mariën 2010), as is the role of the hippocampus (Rubin et al. 2014, Duff
and Brown-Schmidt 2012). The shift of focus towards subcortical structures is
in fact part of a larger sea-change in neurolinguistics, which calls for the need
to operate with an “extended language network” (Ferstl et al. 2008), one that
goes much beyond the classical, Broca-Wernicke model.
The present contribution is to be seen in this light. We will focus on the
thalamus, thanks to which the basal ganglia, the cerebellum, and the hippocam-
pus interface with the cortex in a reciprocal fashion. As a matter of fact, this
reciprocal linkage should, by the logic of co-evolution, lead us to adopt a more
balanced view of cortical expansion, and view it as part of a cortical-subcortical
network reorganization. Paraphrasing Buzsáki (2006: 179), we can say that the
neocortex co-evolved with thalamic connectivity.
Of all the subcortical structures, the thalamus is perhaps the one that has
figured less prominently in the literature. But, as a recent special issue in Brain
& Language (2013, vol. 126) devoted to the role of the thalamus in language
shows, this has been a mistake. The Brain & Language issue in part revisits the
importance of the early work by Bruce Crosson and George Ojemann, who
pioneered deep brain stimulation approaches to examine the impact of selective
silencing or stimulation of the thalamus on performance of language tasks.
Tellingly, the editor of the special issue, Daniel A. Llano, closes his editorial
with the following words (p. 21):
The idea that understanding the thalamus will pay broad scientific dividends
is not new. A. Earl Wal ker, in his groundbreaking monograph about the
thalamus in 1938 (Walker 1 938), made this very point to us many years
ago: “The thalamus holds the secret of much that goes on within the
cerebral cortex.”We second this opinion, and will tr y to demonstrate in the rest of the ar ticle
why the thalamus is critical to capturing the role of language in cognition.
The central role of the thalamus 231