Article

Functional magnetic resonance imaging of delay and trace eyeblink conditioning in the primary visual cortex of the rabbit.

Biomedical Engineering Department, Northwestern University, Evanston, Illinois 60201, USA.
Journal of Neuroscience (impact factor: 7.11). 06/2008; 28(19):4974-81. DOI:10.1523/JNEUROSCI.5622-07.2008 pp.4974-81
Source: PubMed

ABSTRACT The primary sensory cortices have been shown in recent years to undergo experience- and learning-related plasticity under a variety of experimental circumstances. In this study, we used functional magnetic resonance imaging (fMRI) in parallel with both delay and trace eyeblink conditioning to image the learning-related functional activation within the primary visual cortex (V1) of awake, behaving rabbits. We expected that the differing level of forebrain dependence between these two conditioning paradigms should produce a differential blood oxygenation level-dependent (BOLD) functional response in V1. Our results showed a significant expansion of activated volume within V1, particularly early in learning, after training with the more cognitively demanding trace paradigm. In contrast, the simpler delay paradigm produced an increase in the magnitude of the BOLD response in activated voxels, but no significant change in activated volume. No accompanying learning-related changes were observed in the primary somatosensory cortex, which mediates the unconditioned stimulus. These results suggest that the recruitment of additional neurons within V1 is necessary to support the more demanding memory imposed by the trace interval. To our knowledge, this work is the first functional imaging study to compare directly trace and delay eyeblink conditioning in an animal model.

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Keywords

accompanying learning-related changes
 
activated volume
 
additional neurons
 
animal model
 
BOLD response
 
delay eyeblink conditioning
 
demanding memory
 
differential blood oxygenation level-dependent
 
first functional imaging study
 
learning-related functional activation
 
primary sensory cortices
 
primary somatosensory cortex
 
primary visual cortex
 
significant change
 
simpler delay paradigm
 
trace eyeblink conditioning
 
trace interval
 
trace paradigm
 
two conditioning paradigms
 
unconditioned stimulus