The Journal of Neuroscience, July 1, 1999, 19(13):5514-5527
Optic Flow Input to the Hippocampal Formation from the Accessory
Optic System
Douglas R. W.
Wylie1,
Randal G.
Glover1, and
John
D.
Aitchison2
1 Department of Psychology, University of
Alberta, Edmonton, Alberta, Canada, T6G 2E1, and
2 Department of Cell Biology and Anatomy, University of
Alberta, Edmonton, Canada, T6G 2H7
Recent studies in rodents have implicated the hippocampal formation
in "path integration": the ability to use self-motion cues
(ideothesis) to guide spatial behavior. Such models of hippocampal function assume that self-motion information arises from the vestibular system. In the present study we used the retrograde tracer cholera toxin subunit B, the anterograde tracer biotinylated dextran amine, and
standard extracellular recording techniques to investigate whether the
hippocampal formation [which consists of the hippocampus proper and
the area parahippocampalis (Hp/APH) in pigeons] receives information
from the accessory optic system (AOS). The AOS is a visual pathway
dedicated to the analysis of the "optic flow fields" that result
from self-motion. Optic flow constitutes a rich source of ideothetic
information that could be used for navigation. Both the nucleus of the
basal optic root (nBOR) and nucleus lentiformis mesencephali of the AOS
were shown to project to the area ventralis of Tsai (AVT), which in
turn was shown to project to the Hp/APH. A smaller direct projection
from the nBOR pars dorsalis to the hippocampus was also revealed.
During extracellular recording experiments, about half of the cells
within the AVT responded to optic flow stimuli. Together these results
illustrate that the Hp/APH receives information about self-motion from
the AOS. We postulate that this optic flow information is used for path integration. A review of the current literature suggests that an
analogous neuronal circuit exists in mammals, but it has simply been overlooked.
Key words:
hippocampus; optic flow; self-motion; path integration; accessory optic system; area ventralis of Tsai; ideothesis
Copyright © 1999 Society for Neuroscience 0270-6474/99/19135514-14$05.00/0
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