Tone of Voice and Mind : The Connections between Intonation ...

The brain code 127
speaking. Stated conversely, the information conveyed by the literal meaning
of words strung together in syntactically normal sequences is only part of the
message. Sometimes, literal understanding is sufficient and transfer of the literal
symbolic meaning is the entire message, but other times we are also aware
of or perhaps solely interested in conveying/interpreting an emotional message:
“This is my feeling about X” or “This is my feeling about you” or “This
is how I feel”. And in these cases, the lexical meanings, the sequence of words
and the syntactic regularity of the sentences may be less important than the
tone of voice.
If, in line with the central dogma outlined earlier, there is hemispheric
cooperation during language that involves conventional syntax/semantics in
the LH and the sound-symbolism of intonation in the RH, what form does
the cooperation take at the neuronal level? Three issues must be examined in
some detail to answer that question: the known cortical mechanisms of information
storage, the callosal mechanisms of information transfer between the
hemispheres, and the nature of the information involved.
A. Cortical maps
It is known that the patterns of activation on the sensory organs that detect
external stimuli maintain their topographical structure as they are brought to
the central nervous system – and are there mapped and re-mapped numerous
times (Stein & Meredith 1993). The most studied and best understood of
thesemapsaretheretinotopicmapsofthevisualsystem.Theretinaitselfisa
small two-dimensional surface. When light strikes it and excites retinal neurons,
the pattern of excitation is carried in its entirety to the primary visual
cortex (see Figure 5-1). From there it is copied at least 30 times per hemisphere,
with each retinotopic cortical map presumably carrying out slightly different
information processing on the raw retinal image (Posner & Raichle 1994).
In comparison with vision, the sense of touch has a much larger twodimensional
sensory organ – the entire skin surface, but it too is known to have
a two dimensional representation on the surface of the somatosensory cortex
just posterior of the central sulcus (Figure 5-2). Somatosensory information
is mapped separately several times for the perception of touch, warmth and
pressure, and the existence of secondary and tertiary maps in parietal cortex is
known. The somatosensory maps cover the bulk of the cortical surface of the
parietal lobe (in both hemispheres), just as the visual maps cover most of the
bilateral occipital cortex.