PT  - JOURNAL ARTICLE
AU  - Pennartz, C. M. A.
AU  - Lee, E.
AU  - Verheul, J.
AU  - Lipa, P.
AU  - Barnes, C. A.
AU  - McNaughton, B. L.
TI  - The Ventral Striatum in Off-Line Processing: Ensemble Reactivation during Sleep and Modulation by Hippocampal Ripples
AID  - 10.1523/JNEUROSCI.0575-04.2004
DP  - 2004 Jul 21
TA  - The Journal of Neuroscience
PG  - 6446--6456
VI  - 24
IP  - 29
4099  - http://www.jneurosci.org/content/24/29/6446.short
4100  - http://www.jneurosci.org/content/24/29/6446.full
SO  - J. Neurosci.2004 Jul 21; 24
AB  - Previously it has been shown that the hippocampus and neocortex can spontaneously reactivate ensemble activity patterns during post-behavioral sleep and rest periods. Here we examined whether such reactivation also occurs in a subcortical structure, the ventral striatum, which receives a direct input from the hippocampal formation and has been implicated in guidance of consummatory and conditioned behaviors. During a reward-searching task on a T-maze, flanked by sleep and rest periods, parallel recordings were made from ventral striatal ensembles while EEG signals were derived from the hippocampus. Statistical measures indicated a significant amount of reactivation in the ventral striatum. In line with hippocampal data, reactivation was especially prominent during post-behavioral slow-wave sleep, but unlike the hippocampus, no decay in pattern recurrence was visible in the ventral striatum across the first 40 min of post-behavioral rest. We next studied the relationship between ensemble firing patterns in ventral striatum and hippocampal ripples-sharp waves, which have been implicated in pattern replay. Firing rates were significantly modulated in close temporal association with hippocampal ripples in 25% of the units, showing a marked transient enhancement in the average response profile. Strikingly, ripple-modulated neurons in ventral striatum showed a clear reactivation, whereas nonmodulated cells did not. These data suggest, first, the occurrence of pattern replay in a subcortical structure implied in the processing and prediction of reward and, second, a functional linkage between ventral striatal reactivation and a specific type of high-frequency population activity associated with hippocampal replay.