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Abstract:
We observed severe autonomic dysregulation in the form of an
inability of the sympathetic nervous system to establish an
electrodermal baseline in 28 out of 35 autistic children. Also, the
phasic autonomic responses of the autistic children were chaotic
and not sensitive to the significance of the stimulus, especially
with social stimuli. These responses have consequences for
higher-level cognition, in a way similar to those shown by Damasio
(1995; failure of autonomic response causes disinhibition) and
Hirstein and Ramachandran (1997; failure of autonomic response
produces 'impostor' delusion). The autonomic system produces a
'salience landscape' which guides higher-level cognition by
attaching significance values to stimuli, we suggest. In autistic
children the system can alternate between extremely high, chaotic
levels of arousal, in which every perceptual event is given
annoyingly high significance, and low, non-responsive levels, in
which the child is calm, but unreachable. Bachevalier has argued
that the central problem in the autistic brain is amygdala
damage/malfunction (Bachevalier, 1994). The central route to the
amygdala in visual perception is via the temporal lobe's 'ventral'
visual stream. The autistic brain may 'prefer' activity in the
other, 'dorsal' stream (generated by tactile or somesthetic
activity) to activity in the ventral stream with its concomitant
sympathetic overexcitation. We observed that certain forms of
tactile stimulation cause steep reductions in sympathetic activity,
which may explain why autistic children seek to engage in such
behavior: they are themselves attempting to regulate a system which
should be self-regulating.
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