Evidence that the Acquisition of Novel Odour-Context Associations May Instead Reflect Simple Odour-Cue Associations
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1
University of Canterbury, Van der Veer Institute for Parkinsons Disease and Brain Research, New Zealand
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2
University of Canterbury, New Zealand
The acquisition of novel paired associates between two odours and two environmental contexts (each with a unique test cage and unique spatial position) has been employed as a test of “episodic-like” memory in rodents. Transgenic mice with impaired hippocampal CA3 NMDA receptor function are unable to acquire this task (Rajji et al., 2006). We compared acquisition of this task in intact rats and rats with lesions to the anterior thalamic nuclei (AT) and laterodorsal nuclei (LD), two regions believed to influence hippocampal system function. In addition, we examined probe trials that 1) neutralized a proximal visual cue in both contexts (i.e. the white vs black sand-filled cups were changed to unpainted cups), 2) made the colour of the proximal cue conflicted with one of the contexts (white cups present in both contexts), 3) interchanged the spatial position of the two test cages, but the rewarded odours remained consistent with spatial position, not the cage, and 4) used the original spatial position for the two cages, but interchanged the floor texture of the two test cages. No effects of lesions were found. The three groups acquired the task at a similar rate (means of 85-90% correct at by the end of acquisition). There was a mean drop in performance (to 75%) for probe task 1 (p < 0.05), but performance returned to criterion for probe task 2 (versus probe task 1, p < 0.05). When the test cage conflicted with its spatial position (probe task 3), performance fell below chance (30%; p < 0.001), showing that the rats selected odour on the basis of the test cage, not the “global context”. Probe task 4 had no effect. It appears that acquisition of this task is dependent on some test cage cues, but not spatial position or overall context. Performance on this task may rely on a simple odour-cue association rather than an odour-context association. This difference may explain why the thalamic lesions were without effect.
Conference:
41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009.
Presentation Type:
Poster Presentation
Topic:
Poster presentations
Citation:
Varghese
V,
Brett
F,
Harland
B,
Van-Nobelen
M and
Dalrymple-Alford
J
(2009). Evidence that the Acquisition of Novel Odour-Context Associations May Instead Reflect Simple Odour-Cue Associations.
Conference Abstract:
41st European Brain and Behaviour Society Meeting.
doi: 10.3389/conf.neuro.08.2009.09.339
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Received:
15 Jun 2009;
Published Online:
15 Jun 2009.
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Correspondence:
Vineetha Varghese, University of Canterbury, Van der Veer Institute for Parkinsons Disease and Brain Research, Christchurch, New Zealand, vcv11@student.canterbury.ac.nz