The Journal of Neuroscience, March 1, 2002, 22(5):1922-1928
Spatial Working Memory and the Brainstem Cholinergic Innervation
to the Anterior Thalamus
Anna S.
Mitchell,
John C.
Dalrymple-Alford, and
Michael A.
Christie
Christchurch Movement Disorders and Brain Research Group Psychology
Department, University of Canterbury, Christchurch, New Zealand
8001
The anteroventral thalamic nucleus (AV) has a role in spatial
memory, but the influence of the prominent brainstem cholinergic projection to this region is unknown. Here, spatial memory in a 12-arm
radial maze was examined after 0.15 µl bilateral AV infusions of
scopolamine. In part one, rats visited six arms singly (the phase 1 arms) and, after a 10 min delay, were allowed free choice to
both phase 1 arms and the remaining six baited arms (phase 2 arms).
Scopolamine (10 µg) administered during the delay increased errors to
both phase 1 and phase 2 arms, whereas PBS infusions increased
phase 1 arm errors only. The PBS effect was the result of inserting the
internal cannulas alone and not the infusion. The same dose of
scopolamine (10 µg) infused before maze testing (part two: no phase 1 arms, no delay) also impaired spatial memory over and above the effects
of both PBS and no-infusion, which did not differ markedly. Part two
also showed that choice latency and choice strategies were unaffected
by PBS and scopolamine. Cannulation and infusion procedures in both
parts one and two did not produce any negative carryover effects across
multiple control (no internal cannula) sessions, and a trypan blue
manipulation indicated that infusions were restricted to the AV region.
This study provides the first direct evidence that the brainstem
cholinergic innervation to the limbic thalamus influences learning and
memory, which may have important implications for human neurological
conditions such as alcohol-related disorders and schizophrenia.
Key words:
anterior thalamic nuclei; cholinergic systems; laterodorsal tegmental nucleus; scopolamine; spatial working memory; alcohol disorders; schizophrenia
Copyright © 2002 Society for Neuroscience 0270-6474/02/2251922-07$05.00/0