Effects of scopolamine on matching to sample paradigm and related tests in human subjects

This was a double-blind placebo-controlled study with a cross-over
design to examine the effects of scopolamine on cognitive functions
in young healthy subjects. Scopolamine hydrobromide was
administered subcutaneously to 12 subjects (mean +/- SD age 23.8
+/- 2.2 years) at doses of 0.3 and 0.6 mg in comparison with two
placebo conditions. Scopolamine at both doses produced marked
sedation as rated by subjects and an observer. In the continuous
performance test, vigilance was impaired by both doses of
scopolamine. The span of apprehension test showed differing results
(only the high dose of scopolamine showed a performance decrement
only in the three-character version of the span of apprehension
test). Significant impairment by both doses of scopolamine was seen
in immediate and delayed free recall, continuous visual
recognition, running word recognition and running picture
recognition. While scopolamine caused a significant slowing in
average reaction times for simultaneous matching as well as for
delayed matching, subjects made more errors under scopolamine
compared to placebo only in delayed matching, not in simultaneous
matching. Also, the main outcome of matching to sample showed
significant effects only in delayed matching, not in simultaneous
matching. Notable in this study is the incongruity between the
simultaneous matching test and the span of apprehension test on the
one hand and the other cognitive tests used on the other. These
results demonstrated that scopolamine has a greater effect on
memory than on attention. Thus, the scopolamine-induced effects in
the present study seem to be more relevant to Alzheimer's disease
in an advanced phase than to normal aging. Copyright (C) 2003 S.
Karger AG, Basel.