Spatio-temporal structure of network oscillations in the prefrontal cortex of neonatal and pre-juvenile rat
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1
University Medical Center Hamburg, Center for Molecular Neurobiology Hamburg, Germany
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2
Forschungszentrum Juelich, Institute of Neuroscience and Medicine (INM-6), Germany
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3
RWTH Aachen University, Theoretical Systems Neurobiology, Germany
The interactions between the prefrontal cortex (PFC) and hippocampus are critical for attentional and mnemonic abilities, yet their maturation is poorly understood. We previously showed that the neonatal PFC displays discontinuous oscillatory patterns that with ongoing maturation are replaced by continuous rhythms (Brockmann et al., 2011). The generation of these prefrontal oscillations is driven by hippocampal theta bursts. The intricate spatio-temporal relationship of slow and fast oscillatory components during various stages of development may reveal changes in the flow of activity within and between different brain structures.
We performed extracellular recordings of the local field potential (LFP) and multiple unit activity in postnatal day 7-15 rats in vivo using four-shank 32-channel Michigan electrodes. The recording sites were separated by 200 µm in horizontal and 50 or 100 µm in vertical direction. In our experiments, electrodes were inserted in parallel to the cortical surface, giving us access to neuronal activity at different cortical locations at 4 different depths. Here, we investigate in detail the spontaneous activity patterns (i) across and (ii) within cortical layers of the PFC.
We applied a clustering technique based on amplitude and frequency of the LFP to differentiate between two initial patterns of discontinuous oscillatory activity that are present at the end of the first postnatal week – spindle bursts (SBs) and nested gamma spindle bursts (NGs). In the following, we analyze and compare the features exhibited by neuronal recordings belonging to these two classes of oscillatory events, which are commonly separated by longer periods of quiescent activity. While both patterns exhibit spectral peaks at 4-12 Hz and 16-40 Hz, only NGs in upper layers are accompanied by phase locked spikes and display an additional frequency component above 100 Hz. We calculate the coherence within vs. across layers for the slower rhythms. The maximal coherence is observed within layers for the 4-12 Hz rhythm of SBs, and across layers for the 16-40 Hz rhythm of NGs. NGs show a stronger phase shift across layers. The direction of the shift is opposite for the two rhythms. Moreover, the amplitude of the fast rhythm (>100 Hz) appears strongly phase-coupled to the slower oscillations during NGs.
Towards the end of the second postnatal week the PFC switches to continuous oscillatory activity. At this age the signals are more coherent over the whole PFC and the phase shift of slower rhythms across layers diminishes. The power of fast rhythm (>100 Hz) decreases, whereas firing rates increase. The age- and layer-dependent differences may mirror the functional maturation of the PFC under the influence of hippocampal inputs.
Acknowledgements
Supported by DFG (Emmy Noether), BMBF and Helmholtz Alliance on Systems Biology.
References
Brockmann MD, Pöschel B, Cichon N, Hanganu-Opatz IL (2011). Coupled Oscillations Mediate Directed Interactions between Prefrontal Cortex and Hippocampus of the Neonatal Rat. Neuron 71:332–347.
Keywords:
development,
oscillations,
Prefrontal Cortex
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Other
Citation:
Cichon
N,
Denker
M,
Hanganu-Opatz
IL and
Gruen
S
(2012). Spatio-temporal structure of network oscillations in the prefrontal cortex of neonatal and pre-juvenile rat.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00061
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Received:
18 Sep 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Ms. Nicole Cichon, University Medical Center Hamburg, Center for Molecular Neurobiology Hamburg, Hamburg, 20251, Germany, nicole.cichon@zmnh.uni-hamburg.de