CiteULike: nelmor's Pennartz

Functional Interaction between the Hippocampus and Nucleus Accumbens Shell Is Necessary for the Acquisition of Appetitive Spatial Context Conditioning

Rutsuko Ito — 2008-07-07T08:13:45-00:00

J. Neurosci., Vol. 28, No. 27. (2 July 2008), pp. 6950-6959.

The nucleus accumbens (NAc) has been implicated in a variety of associative processes that are dependent on the integrity of the amygdala and hippocampus (HPC). However, the extent to which the two subregions of the NAc, the core and shell, form differentiated circuits within the amygdala- and hippocampal-ventral striatal circuitry remains unclear. The present study investigated the effects of selective excitotoxic lesions of the nucleus accumbens shell or core subregion on appetitive elemental cue and context conditioning, shown previously to be dependent on the basolateral amygdala and hippocampus, respectively. Rats were trained sequentially to acquire discrete conditioned stimulus-sucrose conditioning, followed by spatial context-sucrose conditioning in a place preference apparatus characterized by three topographically identical chambers, the chambers being discriminable only on the basis of path integration. NAc shell lesions selectively impaired the acquisition of conditioned place preference and the use of spatial information to retrieve information about a discrete cue, whereas, as expected, NAc core lesions attenuated the acquisition of cue conditioning compared with sham rats. In a subsequent experiment, disconnection of the HPC from the NAc shell using unilateral asymmetric lesions of each structure resulted in a pattern of impairment in place conditioning and context-dependent cue retrieval similar to that produced by NAc shell lesions. These data not only suggest that the NAc core and shell subregions subserve distinct associative processes but also that the NAc shell and HPC are important functional components of a limbic corticostriatal network involved in spatial context conditioning. 10.1523/JNEUROSCI.1615-08.2008

Preferential Reactivation of Motivationally Relevant Information in the Ventral Striatum

Carien Lansink — 2008-06-18T18:22:40-00:00

J. Neurosci., Vol. 28, No. 25. (18 June 2008), pp. 6372-6382.

Spontaneous "off-line" reactivation of neuronal activity patterns may contribute to the consolidation of memory traces. The ventral striatum exhibits reactivation and has been implicated in the processing of motivational information. It is unknown, however, whether reactivating neuronal ensembles specifically recapitulate information relating to rewards that were encountered during wakefulness. We demonstrate a prolonged reactivation in rat ventral striatum during quiet wakefulness and slow-wave but not rapid eye movement sleep. Reactivation of reward-related information processed in this structure was particularly prominent, and this was primarily attributable to spike trains temporally linked to reward sites. It was accounted for by small, strongly correlated subgroups in recorded cell assemblies and can thus be characterized as a sparse phenomenon. Our results indicate that reactivated memory traces may not only comprise feature- and context-specific information but also contain a value component. 10.1523/JNEUROSCI.1054-08.2008

The ventral striatum in off-line processing: ensemble reactivation during sleep and modulation by hippocampal ripples.

CM Pennartz — 2008-01-08T20:16:11-00:00

J Neurosci, Vol. 24, No. 29. (21 July 2004), pp. 6446-6456.

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.

Putting a spin on the dorsal-ventral divide of the striatum.

P Voorn — 2006-01-25T02:36:21-00:00

Trends Neurosci, Vol. 27, No. 8. (August 2004), pp. 468-474.

Since its conception three decades ago, the idea that the striatum consists of a dorsal sensorimotor part and a ventral portion processing limbic information has sparked a quest for functional correlates and anatomical characteristics of the striatal divisions. But this classic dorsal-ventral distinction might not offer the best view of striatal function. Anatomy and neurophysiology show that the two striatal areas have the same basic structure and that sharp boundaries are absent. Behaviorally, a distinction between dorsolateral and ventromedial seems most valid, in accordance with a mediolateral functional zonation imposed on the striatum by its excitatory cortical, thalamic and amygdaloid inputs. Therefore, this review presents a synthesis between the dorsal-ventral distinction and the more mediolateral-oriented functional striatal gradient.

A split microdrive for simultaneous multi-electrode recordings from two brain areas in awake small animals

Carien Lansink — 2007-04-12T11:07:23-00:00

Journal of Neuroscience Methods, Vol. 162, No. 1-2. (15 May 2007), pp. 129-138.

Complex cognitive operations such as memory formation and decision-making are thought to be mediated not by single, isolated brain structures but by multiple, connected brain areas. To facilitate studies on the neural communication between connected brain structures, we developed a multi-electrode microdrive for chronically recording ensembles of neurons in two different brain areas simultaneously. The `split drive' contains 14 independently movable microdrivers that were designed to hold tetrodes and to permit day-to-day adjustment of dorsoventral position in the brain. The limited weight of the drive allowed rats to adjust well to the headstage after recovering from surgery and permitted stable recording sessions across at least several weeks. In addition to describing the design and assembly of the split drive, we also discuss some important individual parts of microdrives used for tetrode recordings in general. Furthermore, the split drive was applied to two widely separated and connected brain structures, the hippocampus and ventral striatum. From these two areas, stable ensemble recordings were conducted in rats performing a reward-searching task on a triangular track, yielding group sizes of about 15 and 25 units in the dorsal hippocampus and ventral striatum, respectively.