Feel that sight
New Scientist, 21 February 1998
key in your pocket is almost like seeing it on a table: you can pick
out its shape almost as if you can see it. But how does tactile
information produce a visual mental image? Neuroscientists in Sweden
say they may have found the part of the brain that allows different
senses to swap information.
Nouchine Hadjikhani and Per Roland
at the Karolinska Institute in Stockholm used positron emission
tomography to scan the brains of a group of subjects while they decided
if two similar objects were identical. In two of the tasks, they made
comparisons using a single sense: touching both or seeing both. In the
third task, they were asked to compare an object they touched with an
object they saw.
In the third task alone, a structure in the
frontal lobe called the insula-claustrum became active (The Journal of
Neuroscience, vol 18, p 1072). "The claustrum has some role in binding
these two separate processes together," Roland concludes.
findings are very interesting and very reasonable," says Eraldo
Paulesu, a neuroscientist at the Scientific Institute of San Raffaele
in Milan. His earlier work on synaesthesiathe mixing of the
sensessupports the new findings. Synaesthetes, who often perceive
sounds as colours, also have unusual activity in the insula-claustrum
area, unlike normal controls.
However, Paulesu cautions that
more parts of the brain are probably involved. "To circumscribe the
multimodal integration to this area alone would be unwise," he says.