::: Current research in
Stan Leung’s Laboratory :::
A general
description of research is given in an interview in International Innovation
1. Generation
and significance of neuronal oscillations in the hippocampus. Theta
(4-10Hz) and gamma (30-100Hz) rhythms in the hippocampus are studied in
behaving animals and in brain slices. Computational approach is used to
elucidate the significance of extrinsic and intrinsic oscillations, which can
explain theta-frequency spike precession in the place field. How theta phase
shift within the hippocampus modulates synaptic transmission and plasticity is
studied.
2. Seizures
and physiological and behavioral consequences. Various models of
temporal lobe epilepsy (kindling, kainic acid, pilocarpine) and immature animal
seizures (induced by hyperthermia or GABA-B receptor antagonist) are used. The
physiological consequences of acute and chronic seizure activity are studied.
Changes in neural circuits are studied in vivo using 16-channel electrodes,
field potential recordings, and current source density analysis. Changes in
synaptic properties are studied in vitro using intracellular and whole-cell
recordings from brain slices. Behavioral consequences of experimental seizures
are studied using a variety of cognitive (spatial maze) and motor (prepulse
inhibition, behavioral activity) tasks. Our current emphasis is on psychiatric
symptoms induced by animal models of temporal lobe epilepsy.
3. Long-term
potentiation in the hippocampus and its cholinergic modulation. We
showed the physiological release of endogenous acetylcholine, and its
modulation by histamine, underlies the facilitation of long-term potentiation
of the basal dendritic in the hippocampus of behaving rats.
4. Central
mechanisms mediating general anesthesia. We reported that inactivation
of the hippocampus, medial septum, nucleus accumbens, ventral pallidum and
ventral tegmental area enhanced the potency of various anesthetics, suggesting
the participation of the limbic system in mediating consciousness. Our studies
on the participation of histaminergic tuberomammillary nucleus and nucleus
basalis in general anesthesia, extend the concept that sleep and anesthesia share
common mechanisms.
5. The
septohippocampal system participates in schizophrenia. The symptoms
induced by acute models of schizophrenia (induced by ketamine, MK-801) are
partly mediated by the hippocampus, and alleviated by medial septal
inactivation. The behavioral and electrophysiological assessments include
sensorimotor gating (prepulse inhibition), auditory gating and locomotion.
6. Functional
magnetic resonance imaging and EEG simultaneous recording during normal
and seizure activity in animals are done in collaboration with Matt Hutchison,
Seyed Mirsattari, Joe Gati and Ravi Menon. Recent studies showed a large number
of independent components in the resting state BOLD signal in animals.