The possible correlation of 4-12 Hz hippocampal field oscillations (theta rhythm) with motor and cognitive behavior was studied by recording the hippocampal electroencephalogram in non-locomoting rats as they solved a hippocampus-dependent place recognition task. The electroencephalogram (EEG) during the place recognition task was compared with the EEG during a control task, which had the same ...

Theta frequency oscillations are a prominent feature of the hippocampal EEG during active locomotion and learning. It has also been observed that the relative timing of place cell firing recedes as its place field is traversed – a phenomena known as phase precession. This has led to the development of a theory of theta phase coding, whereby spatial sequences being encountered on a behavioural t...

The hippocampal theta rhythm is required for accurate navigation and spatial memory but its relation to the dynamics of locomotion is poorly understood. We used miniature accelerometers to quantify with high temporal and spatial resolution the oscillatory movements associated with running in rats. Simultaneously, we recorded local field potentials in the CA1 area of the hippocampus. We report t...

The majority of evidence from in vivo studies indicates that theta rhythms are imposed upon cortical structures by projections from the medial septum/diagonal band. Anatomical studies have indicated highly specific target neuronal classes for one branch of this projection (that using GABA as a transmitter) but less specific target specificity for the other branch (that using acetylcholine). In ...

A characteristic feature of the electroencephalogram (EEG) of the hippocampus and rhinal (entorhinal and perirhinal) cortex of the freely moving rat is theta rhythm, a prominent oscillation of approximately 8 Hz. Here we demonstrate that a novel rhythm that occurs at the border between the theta and alpha range of frequencies (10-12 Hz) can also be recorded from these structures. This rhythm (r...

In Korean, a class of lexemes of Chinese origin exhibit both nominal and verbal behavior. Specifically, they can assign lexically idiosyncratic case, but require a semantically vacuous light verb in order to form a sentence and are themselves marked with accusative case. In this paper, we propose a TAG-based account of this behavior, and propose some generalizations towards a pure representatio...

The hippocampal theta and neocortical gamma rhythms are two prominent examples of oscillatory neuronal activity. The hippocampus has often been hypothesized to influence neocortical networks by its theta rhythm, and, recently, evidence for such a direct influence has been found. We examined a possible mechanism for this influence by means of a biophysical model study using conductance-based mod...

Theta-frequency (4-12 Hz) rhythms in the hippocampus play important roles in learning and memory. CA1 interneurons located at the stratum lacunosum-moleculare and radiatum junction (LM/RAD) are thought to contribute to hippocampal theta population activities by rhythmically pacing pyramidal cells with inhibitory postsynaptic potentials. This implies that LM/RAD cells need to fire reliably at th...

During study trials of a recognition memory task, alpha (∼10 Hz) oscillations decrease, and concurrently, theta (4-8 Hz) oscillations increase when later memory is successful versus unsuccessful (subsequent memory effect). Likewise, at test, reduced alpha and increased theta activity are associated with successful memory (retrieval success effect). Here we take an individual-differences approac...

The coordinated activity of hippocampal neurons is reflected by macroscopic patterns, theta and sharp waves (SPW), evident in extracellular field recordings. The importance of these patterns is underscored by the ordered relation of specific neuronal populations to each pattern as well as the relation of each pattern to distinct behavioral states. During awake immobility, consummatory behavior,...