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Rat anterodorsal thalamic head direction neurons depend upon dynamic visual signals to select anchoring

Summary: Rat anterodorsal thalamic head direction neurons
depend upon dynamic visual signals to select anchoring
landmark cues
Michaešl B. Zugaro,* Angelo Arleo,* Cyril DeŽjean, Eric Burguie`re, Mehdi Khamassi and Sidney I. Wiener
CNRS-Colle`ge de France, Laboratoire de Physiologie de la Perception et de l'Action, 11 place Marcelin Berthelot, 75231 Paris
CEDEX 05, France
Keywords: cue control, dynamic motion parallax, hippocampus, limbic system, single unit recordings, spatial orientation
Head direction cells, which are functionally coupled to `place' cells of the hippocampus, a structure critically involved in spatial
cognition, are likely neural substrates for the sense of direction. Here we studied the mechanism by which head direction cells are
principally anchored to background visual cues [M.B. Zugaro et al. (2001) J. Neurosci., 21, RC154,1­5]. Anterodorsal thalamic head
direction cells were recorded while the rat foraged on a small elevated platform in a 3-m diameter cylindrical enclosure. A large card
was placed in the background, near the curtain, and a smaller card was placed in the foreground, near the platform. The cards were
identically marked, proportionally dimensioned, subtended the same visual angles from the central vantage point and separated by
90°. The rat was then disoriented in darkness, the cards were rotated by 90° in opposite directions about the center and the rat was
returned. Preferred directions followed either the background card, foreground card or midpoint between the two cards. In continuous
lighting, preferred directions shifted to follow the background cue in most cases (30 of the 53 experiments, Batschelet V-test,
P < 0.01). Stroboscopic illumination, which perturbs dynamic visual signals (e.g. motion parallax), blocked this selectivity. Head
direction cells remained equally anchored to the background card, foreground card or configuration of the two cards (Watson test,
P > 0.1). This shows that dynamic visual signals are critical in distinguishing typically more stable background cues which govern


Source: Arleo, Angelo - Laboratory of Neurobiology of Adaptive Processes, Université Pierre-et-Marie-Curie, Paris 6


Collections: Biology and Medicine