A spatial version of eyeblink conditioning in young and old rats
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1
University of Arizona, United States
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2
Memorial University of Newfoundland, Canada
Hippocampal physiology and function undergo age-related changes that may affect this structure’s role in spatial learning and memory. We developed a spatial version of classical eyeblink conditioning (see Kawahara et al., Society for Neuroscience Abstract, 2003) in order to investigate the effect of age on memory for a specific location. Young (12 month old) and aged (25 month old) rats were trained to shuttle on a circular track for food reward, then were implanted with eyelid EMG and electrical stimulation wires. At two specific locations on the track, rats received blink-inducing trains of electrical stimulation with 50% probability. The time and location of eyelid activity were analyzed from the eyelid EMG recordings. For a control zone on the track in which no blink stimuli were given, the mean and SD of eyelid activity were calculated for each session. We normalized data from zones of the track analyzed for blink behavior by subtracting this control mean and expressing data as z-scores. This method of analysis controls for individual variability in background EMG activity, and ensures that any conditioned responses identified are, in fact, location-specific. Further demonstrating the spatial precision of this conditioned response, blink acitivity increased over the last 500 msec of the approach to the stimulus locations in young and old rats when considering all trials in all sessions. EMG activity 2SD above the control mean was considered to be above threshold, and percentages of activity above threshold were calculated in 100 msec intervals for the 1000 msec before the two stimulus locations. When the first session was compared to the last session of training, both young and old rats showed a significant increase in the amount of blink activity above threshold in the 100 msec before crossing the stimulus locations. When average activity over all sessions was considered, rats expressed significant variability in blinking activity above threshold both within and between groups. In addition, individual rats expressed wide variations in the level of conditioned response expression between sessions. Our data indicate that both young and old rats can learn the locations of the blink stimuli, but also that individuals vary in the rate of learning of the conditioned response. Once acquired, there are also individual differences in the accuracy and consistency of expression of the conditioned response. These behavioral data provide an excellent framework in which to study the neurobiological underpinnings of individual differences and instability in the expression of spatial memory and temporal accuracy of the conditioned response. Further electrophysiological studies will examine hippocampal single unit activity in conjunction with spatial eyeblink conditioning in order to determine whether altered hippocampal information processing underlies deficits in expression of the conditioned response. Supported by AG012609, CIHR SIB-78537, AHFMR 20060436, and McKnight Brain Research Foundation.
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Cognitive Aging
Citation:
Schimanski
L,
Broersma
B,
Harley
C and
Barnes
C
(2008). A spatial version of eyeblink conditioning in young and old rats.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.178
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Received:
08 Dec 2008;
Published Online:
08 Dec 2008.
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Correspondence:
Lesley Schimanski, University of Arizona, Tucson, United States, lesleyschimanski@hotmail.com