Similar effects of medial supramammillary or systemic injection of chlordiazepoxide on both theta frequency and fixed-interval responding

Woodnorth, Mary-Anne; McNaughton, Neil

doi:10.3758/cabn.2.1.76

Cited by 45 publications

(18 citation statements)

References 78 publications

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“…However, recent data have shown that intracranial anxiolytic injections can concurrently change hippocampal theta and behaviour as extensively as systemic injections [164]. Importantly, when theta frequency is specifically changed by intracranial injections, formation of spatial memory is changed to an equivalent extent [124].…”

Section: The Septo-hippocampal Systemmentioning

confidence: 98%

A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance

McNaughton

Corr

2004

Neuroscience & Biobehavioral Reviews

1,129

888

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Section: The Septo-hippocampal Systemmentioning

confidence: 98%

A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance

McNaughton

Corr

2004

Neuroscience & Biobehavioral Reviews

1,129

888

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“…Medial SuM probably determines a slightly greater proportion of benzodiazepine-mediated frequency control during RPO-stimulation, than PH. However, given that even small frequency changes (Յ0.6 Hz) can be behaviourally significant (Pan and McNaughton, 1997;Woodnorth and McNaughton, 2002), the effective PH region must represent an important modulator of hippocampal function.…”

Section: Discussionmentioning

confidence: 99%

Multiple hypothalamic sites control the frequency of hippocampal theta rhythm

et al. 2003

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Stimulation of a neural pathway originating in the brainstem reticular formation, with synapses in the medial hypothalamus, activates the hippocampal theta rhythm. The frequency of reticular-elicited theta is determined in the medial supramammillary nucleus (mSuM) completely in anaesthetised rats, but only partially when the animal is awake. We tested other medial hypothalamic sites for their capacity to control theta frequency in awake rats. Blockade of sodium channels (1 microl fast infusion of the local anaesthetic procaine, experiment 1) or increased inhibition by GABA (Chlordiazepoxide [CDP], experiment 2) was found to reduce or increase the frequency of reticular-elicited theta, depending on the precise site of injection, in the region of the dorsomedial hypothalamic nucleus (DMH) and the posterior hypothalamic nucleus (PH). A band of null sites for CDP was located in the region of the ventral border of PH and dorsal border of mSuM. Using 0.5 and 1 microl CDP, and slow infusions (experiment 3), it was found that effective PH sites were also separate from mSuM in the rostrocaudal direction. In experiment 4, the DMH/PH region was mapped with unilateral and bilateral slow infusions of 0.5 microl CDP. CDP significantly reduced frequency in medial (periventricular) and dorsal PH, but not DMH. Bilateral injections appeared to generally sum the usual effects of unilateral injection, producing effects of intermediate size. However, the absolute frequency change in any given site, or with any pair of sites, did not exceed 1 Hz, which is similar to what is seen with single injections in mSuM. Overall, it appears that at, any one time, theta frequency may be determined by a complex interplay between distinct but interacting modulatory regions in the medial hypothalamus.

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“…Elimination of the spatial pattern of neuronal firing is possibly not a problem when the frequency of theta is reduced by injection of a benzodiazepine receptor agonist into the supramammillary nucleus. This can alter both theta and behavior as much as systemic injection of the same drug (Woodnorth and McNaughton, 2002). However, even in this case, the anatomy of the area (Pan and McNaughton, 2004) leaves open the possibility that adjacent nontheta neurons were affected.…”

Section: Introductionmentioning

confidence: 99%

Restoring theta‐like rhythmicity in rats restores initial learning in the Morris water maze

2006

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Neural activity often becomes rhythmic during mental processing. But there has been no direct proof that rhythmicity, per se, is important for mental function. We assessed this issue in relation to the contribution of hippocampal theta-frequency rhythmicity to learning in the Morris water maze by blocking theta (and other septal inputs to the hippocampus) and then using electrical stimulation to restore rhythmicity. We injected tetracaine into the medial septal area, and so blocked septal input to the hippocampus in rats throughout 16 consecutive trials in a Morris water maze. Rats with no hippocampal theta also showed no initial learning in the maze. Theta rhythmicity in the supramammillary area remained after septal blockade, and we used this to trigger electrical stimulation of the fornix superior. This substantially restored hippocampal theta-like rhythmicity throughout training at a normal frequency but with abnormal wave forms. This treatment applied throughout training substantially restored initial learning. Fixed frequency (7.7 Hz) stimulation produced rhythmic activity and a brief improvement in learning. Irregular stimulation with an average frequency of 7.7 Hz produced little rhythmicity and little improvement in learning. These results demonstrate that brain rhythmicity, per se, can be important for mental processing even when the detailed information originally carried by neurons is lost and when the reinstated pattern of population firing is not normal. The results suggest that the precise frequency of rhythmicity may be important for hippocampal function. Functional rhythmicity needs, therefore, to be included in neural models of cognitive processing. The success of our procedure also suggests that simple alterations of rhythmicity could be used to ameliorate deficits in learning and memory. (c) 2006 Wiley-Liss, Inc.

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Similar effects of medial supramammillary or systemic injection of chlordiazepoxide on both theta frequency and fixed-interval responding

Cited by 45 publications

References 78 publications

A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance

A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance

Multiple hypothalamic sites control the frequency of hippocampal theta rhythm

Restoring theta‐like rhythmicity in rats restores initial learning in the Morris water maze

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