We have developed a neurocomputational model of some attentional e!ects of nicotine. Our simulations reproduce results showing smoking abstinence to impair performance on a rapid visual information processing task involving detecting sequences of even or odd digits. Our model treats presence of nicotine as enhancement of modulatory acetylcholine signals, which focus attention on task-relevant s...

Recent experiments support the theoretical hypothesis that recurrent connectivity plays a central role within the medial entorhinal cortex, by shaping activity of large neural populations, such that their joint activity lies within a continuous attractor. This conjecture involves dynamics within each population (module) of cells that share the same grid spacing. In addition, recent theoretical ...

We investigated the structural development of superficial-layers of medial entorhinal cortex and parasubiculum in rats. The grid-layout and cholinergic-innervation of calbindin-positive pyramidal-cells in layer-2 emerged around birth while reelin-positive stellate-cells were scattered throughout development. Layer-3 and parasubiculum neurons had a transient calbindin-expression, which declined ...

Interactions between the hippocampus, parahippocampal regions and the prefrontal cortex are thought to underlie the formation, consolidation, and retrieval of short term memories and play an important role in the learning processes. To date, only conceptual models have been offered to explain the potential interactions among these regions, but their connectivity and synaptic regulation remain u...

The rhinal cortices play a critical role in high-order perceptual/mnemonic functions and constitute the main route for impulse traffic to and from the hippocampus. However, previous work has revealed that neocortical stimuli that activate a large proportion of perirhinal neurons are unable to discharge entorhinal cells. In search of mechanisms that might facilitate impulse transfer from the neo...

Gamma frequency (30-80 Hz) oscillations are recordable from human and rodent entorhinal cortex. A number of mechanisms used by neuronal networks to generate such oscillations in the hippocampus have been characterized. However, it is as yet unclear as to whether these mechanisms apply to other anatomically disparate brain regions. Here we show that the medial entorhinal cortex (mEC) in isolatio...

Whereas recent studies have elucidated principles for representation of information within the entorhinal cortex, less is known about the molecular basis for information processing by entorhinal neurons. The HCN1 gene encodes ion channels that mediate hyperpolarization-activated currents (I(h)) that control synaptic integration and influence several forms of learning and memory. We asked whethe...

Anticipating the future is a key motif of the brain, possibly supported by mental simulation of upcoming events. Rodent single-cell recordings suggest the ability of spatially tuned cells to represent subsequent locations. Grid-like representations have been observed in the human entorhinal cortex during virtual and imagined navigation. However, hitherto it remains unknown if grid-like represen...

Gamma frequency field oscillations (40-100 Hz) are nested within theta oscillations in the dentate-hilar and CA1-CA3 regions of the hippocampus during exploratory behaviors. These oscillations reflect synchronized synaptic potentials that entrain the discharge of neuronal populations within the approximately 10-25 msec range. Using multisite recordings in freely behaving rats, we examined gamma...

Slow (<1 Hz) periodic activity is a distinctive discharge pattern observed in different cortical and sub-cortical structures during sleep and anesthesia. By performing field and cellular recordings, we demonstrated that slow periodic events (0.02-0.4 Hz) are spontaneously generated in the entorhinal cortex of the in vitro isolated whole brain of the guinea pig. These events were characterized b...