Attention-like modulation of hippocampus place cell discharge.

Hippocampus place cell discharge is an important model system for understanding cognition, but evidence is missing that the place code is under the kind of dynamic attentional control characterized in primates as selective activation of one neural representation and suppression of another, competing representation. We investigated the apparent noise ("overdispersion") in the CA1 place code, hypothesizing that overdispersion results from discharge fluctuations as spatial attention alternates between distal cues and local/self-motion cues. The hypothesis predicts that: (1) preferential use of distal cues will decrease overdispersion; (2) global, attention-like states can be decoded from ensemble discharge such that both the discharge rates and the spatial firing patterns of individual cells will be distinct in the two states; (3) identifying attention-like states improves reconstructions of the rat's path from ensemble discharge.

Specific features of sensorimotor cerebral cortex activity modulation by dopamine releaser amantadine.

The modulatory effects of amantadine (1-adamantanamine) on the activity of sensorimotor cerebral cortex neurones during microiontophoretic application of agonists of glutamatergic and GABA-ergic (gamma-aminobutyric acid) transmission were studied. In non-anaesthetised cats, dopamine (DA) released by amantadine application in a small area of the neocortex increased baseline and evoked neuronal activity, providing stabilization and optimum course of both the neuronal and the conditioned responses of the animal. Amantadine eliminates a decrease in the level of neuronal baseline and evoked activity and marked increase in the latency of neuronal activation and conditioned movement mediated by D2 receptor antagonist sulpiride ((S)-5-aminosulfonyl-N-[(1-ethyl-2-pyrrolidinyl) methyl]-2-methoamantadineybenzamide) or GABA.

Inhibition of kainate receptors reduces the frequency of hippocampal theta oscillations.

We investigated the role of kainate receptors in the generation of theta oscillations using (S)-1-(2-amino-2-carboxyethyl)-3-(2-carboxythiophene-3-yl-methyl)pyrimidine-2,4-dione (UBP304), a novel, potent and highly selective antagonist of GLU(K5)-containing kainate receptors. EEG and single-unit recordings were made from the dorsal hippocampus of awake, freely moving rats trained to forage for food. Bilateral intracerebroventricular injections of UBP304 (2.

The formation of cognitive maps of adjacent environments: evidence from the head direction cell system.

In 2 experiments the authors tested whether the head direction (HD) cell system underlies a sense of direction maintained across environments. In Experiment 1, HD neurons failed to maintain their firing directions across T mazes in adjacent environments but rather reoriented to the T maze within each environment. Such reorientation suggests that familiar landmarks override an internal directional sense, so in Experiment 2 the authors recorded HD neurons as rats walked between novel and familiar "rooms" of a 4-chamber apparatus.