(see, e.g., Miller and Buschman 2007, Antzoulatos and Mil ler 2011, Kotz and
Schwartze 2010, Ullman 2001, 2004, 2006), the th alamus cannot be ignored,
as it provides the way for these other subcortical structures to interface with
the cortex in a reciprocal fashion (for recent suggestive evidence of this fruitful-
ness of this perspective, see Teichmann et al. 20 15). In fact, the data to be
reviewed below pertaining to the involvement of the thalamus in mental health
suggest that the thalamus may well be the answer to Friederici’s (2006) ques-
tion: ‘What’s in control of language?’
3 The thalamus: far more than a relay station
It is common to regard the thalamus as a mere relay station (relay bias). Indeed,
the thalamus has traditionally been thought of as a necessary link in the flow of
information from the periphery to the cortex. But there are good reasons to
view the higher-order nuclei making up the dorsal thalamus as crucially implicated
in higher cognition. This is what we wish to highlight in this section.
As we have already pointed out, the function most commonly attributed to
the thalamus is that of ‘channeling’ information from the subcortical parts to
the neocortex. Indeed, every sensory system (with the exception of the olfactory
system) includes a thalamic nucleus that receives sensory signals and sends them
to the associated primary cortical areas. If we were to stop here, we could say
that the thalamus essentially determines the bandwidth capacity of the brain.
But its role is far more complex. In fact, the thalamus evaluates all the incoming
stimuli and segregates them, so that they can proceed to the neocortex. And
this early segregation of input to modality-specific information is actually respon-
sible for the localization of functional systems in the neocortex. That is, the
thalamic performance justifies to a great extent the designations of the cortical
systems as visual, auditory, somatosensory, motor etc. So, on the basis of this
alone, it is impossible to inspect issues related to lateralization and the distribu-
tion of the neocortical loci without taking into serious consideration the role
of the thalamus.
Building on considerations of the sort just mentioned, Buzsáki (2006: 177)
regar ds the thalamus as the ‘afferent and efferent expansion’ of the neocortex.
But this efferent-afferent function is far from random; rather, it is both ‘eco-
nomical’ and ‘sophisticated’. The ‘economy’ of the thalamus can be construed
in two senses: firstly, as ‘selectivity’, in that its efferent function is expressed
subcortically, relaying important inputs from the hippocampus, the cerebellum,
the amygdala, the basal ganglia, the brainstem and the superior colliculus, and
its afferent function towards the neocortex; secondly, the thalamus is ‘economi-
cal’ as far as its location in the brain is concerned, especially in the context of
a globular brain. Being equidistant from all the cortical areas, it is the most
adequate and flexible spatiotemporal gate of information, in as much as spatial
wiring length entails temporal axonal communication.
But the thalamus is not a mere segregator-distributor of information. It acts
as an oscillatory pacemaker, or better put, it is the part of the brain assigned
The central role of the thalamus 235