OADES, R. D., ROEPCKE,
B., & SCHEPKER, R. (1996). A test
of conditioned blocking and its development in childhood and adolescence:
relationship to personality and monoamine metabolism. Developmental
Neuropsychology, 12, 207-230.
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Introduction:
Conditioned blocking (CB) is the undermining of
conditioning to a stimulus by conjoint exposure to a stimulus already
associated with the unconditioned stimulus. CB is one of several tests
of "learned inattention" in which performance has been found to depend
on certain features of personality and on monoamine activity recorded
in animals performing CB.
Methods:
In part 1, the performance of 25 healthy young
adults (mean age 21.6 years) on a new test form for demonstrating CB
is described ("mouse-in-house"). The personality inventories used included
the Hamburger neuroticism/extroversion scale (HANES) and the short version
of the Minnesota multiphasic personality inventory (MMPI). From 24h
urine samples collected at the time of testing the levels of four monoamine
and three of their metabolites were measured as an indicator of the
overall level of neurotransmitter activity. In part 2, the development
of CB was studied across children and adolescents clustered into 4 age
groups (means 10, 14, 17 and 22 years of age).
Results:
Part 1 demonstrated
CB in normal healthy young adults and the expression of CB correlated
with extroversion and increased catecholamine utilisation (turnover).
Part 2 showed CB was least marked prepubertally,
but developed across adolescence independent of IQ. Although performance
did not correlate with developing personality features, like the adults,
CB was positively correlated with dopamine activity. Unlike adults CB
was inversely correlated with noradrenaline activity. Figure 1
shows the development of CB in the 4 age-groups and correlations with
monoamine activity.
Figure 2 shows how the measures of the 3 monoamines,
their metabolites and their activity (turnover) develops across age-groups.
Conclusions:
The maturation of attention related information
processing was discussed in terms of the development and maturation
of structures in the limbic part of the central nervous system and,
in particular, the separate function of dopamine in switching between
and noradrenaline in tuning in/out stimulus features during selection
processes.
We reported on CB in children with ADHD and complex
tics in 1997.
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