The diurnal variation of performance of the novel location recognition task in male rats

A large body of literature has shown that the disruption of circadian clock timing has profound effects on mood, memory and complex thinking. Central to this time keeping process is the master circadian pacemaker located within the suprachiasmatic nucleus (SCN). Of note, within the central nervous system, clock timing is not exclusive to the SCN, but rather, ancillary oscillatory capacity has been detected in a wide range of cell types and brain regions, including forebrain circuits that underlie complex cognitive processes. These observations raise questions about the hierarchical and functional relationship between the SCN and forebrain oscillators, and, relatedly, about the underlying clock-gated synaptic circuitry that modulates cognition. Here, we utilized a clock knockout strategy in which the essential circadian timing gene Bmal1 was selectively deleted from excitatory forebrain neurons, whilst the SCN clock remained intact, to test the role of forebrain clock timing in learning, memory, anxiety, and behavioral despair. With this model system, we observed numerous effects on hippocampus-dependent measures of cognition. Mice lacking forebrain Bmal1 exhibited deficits in both acquisition and recall on the Barnes maze. Notably, loss of forebrain Bmal1 abrogated time-of-day dependent novel object location memory. However, the loss of Bmal1 did not alter performance on the elevated plus maze, open field assay, and tail suspension test, indicating that this phenotype specifically impairs cognition but not affect. Together, these data suggest that forebrain clock timing plays a critical role in shaping the efficiency of learning and memory retrieval over the circadian day.

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“…[31] and conducted under 5 lx dim red light. Animals were initially dark-adapted (day 0), and then habituated to an arena for 10 min (day 1).…”

Section: Methodsmentioning

confidence: 99%

Modulation of learning and memory by the targeted deletion of the circadian clock gene Bmal1 in forebrain circuits

Snider

Dziema

Aten

et al. 2016

Behavioural Brain Research

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“…In a report by Valentinuzzi and colleagues [42] wherein phase of fear conditioning was examined in C57BL/6J mice with access to running wheels, animals trained and tested early in subjective night, rather than day, showed higher rates of freezing to context 24 h post-training. In rats, performance on a novel location recognition task, which like the context test in our paradigm is hippocampal-dependent, likewise peaked at night rather than day [43]. Finally, as with any study of daily learning patterns, it is a possibility that freezing levels could be influenced by daily rhythms in locomotor activity as well as by phase or interval effects on learning, per se.…”

Section: Phase Effects Are Found For Control But Not Bifurcated Micementioning

confidence: 84%

Circadian waveform bifurcation, but not phase-shifting, leaves cued fear memory intact

Harrison

Carmack

Block

et al. 2017

Physiology & Behavior

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• The circadian system was experimentally bifurcated into two days and nights per 24 h.• Pavlovian fear conditioning was used to quantify acquisition and retrieval of memory.• Retrieval of cued fear remained intact in bifurcated, but not phase-shifted, mice. a b s t r a c t a r t i c l e i n f o In mammals, memory acquisition and retrieval can be affected by time of day, as well as by manipulations of the light/dark cycle. Under bifurcation, a manipulation of circadian waveform, two subjective days and nights are experimentally induced in rodents. We examined the effect of bifurcation on Pavlovian fear conditioning, a prominent model of learning and memory. Here we demonstrate that bifurcation of the circadian waveform produces a small deficit in acquisition, but not on retrieval of fear memory. In contrast, repeated phase-shifting in a simulated jet-lag protocol impairs retrieval of memory for cued fear. The results have implications for those attempting to adjust to shift-work or other challenging schedules.

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“…For instance, melatonin administration inhibits LTP in the hippocampus [60,61]. In rats, melatonin modulates memory in a phase-specific manner [62]. Genetic deletions of melatonin receptors in mice lead to enhanced cognitive performance [63].…”

Section: Mechanisms Underlying Circadian Regulation Of Learning and Mmentioning

confidence: 99%

What Role do Circadian Rhythms Play in Learning and Memory?

Mou¹

2016

J Neurol Neurophysiol

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Circadian rhythmicity in gene expression and physiological process has been observed both in the central nervous system and in the periphery, including the hippocampus. As a center for memory formation and storage, the hippocampus shows circadian rhythmicity in clock gene expression and synaptic plasticity. Circadian variation in performance of hippocampus-dependent memory task suggests a link between clock gene oscillation and behavioral response. Yet the discrepancy in time scale between fast information encoding during memory acquisition and much slower circadian oscillation in cellular processes casts doubt on the underlying mechanism of circadian regulation of learning and memory. This short review suggests that instead of being a modulator of learning process and memory formation, the time-of-day information itself could be integrated as a component of episodic memory for later consolidation and retrieval.

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The diurnal variation of performance of the novel location recognition task in male rats

Cited by 40 publications

References 27 publications

Modulation of learning and memory by the targeted deletion of the circadian clock gene Bmal1 in forebrain circuits

Modulation of learning and memory by the targeted deletion of the circadian clock gene Bmal1 in forebrain circuits

Circadian waveform bifurcation, but not phase-shifting, leaves cued fear memory intact

What Role do Circadian Rhythms Play in Learning and Memory?

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