Modulation of CA3 Afferent Inputs by Novelty and Theta Rhythm

@article{citeulike:2066258, abstract = {Models of hippocampal function suggest that the modulation of CA3 afferent input during theta rhythm allows for a rapid alternation between encoding and retrieval states, with each phase enhancing either extrinsic or intrinsic CA3 afferents, favoring either encoding or retrieval, respectively. Here, we show that during the initial exploration of a novel environment by rats, intrinsic CA3-CA3 synaptic inputs are attenuated on CA3 theta peaks, favoring extrinsic CA3 inputs, whereas extrinsic perforant path-CA3 synaptic inputs are attenuated on CA3 theta troughs, favoring intrinsic CA3 inputs. This modulation is absent when animals are re-exposed to the same environment 2 or 48 h later and thus habituates with familiarity, suggesting a process involved in learning. Modulation of CA3 synaptic inputs during novelty was blocked by atropine at a dose that blocks type 2 theta rhythm. Re-exposure to the same novel environment 48 h later in the absence of atropine did not result in habituation, but instead modulated CA3 synaptic responses as though the environment were novel and explored for the first time. The NMDA receptor antagonist ({+/-})-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), administered in a dose that blocks long-term potentiation induction, did not alter CA3 synaptic modulation during initial exploration. However, like atropine, CPP blocked the habituation of synaptic modulation normally observed with re-exposure, as though the environment were novel and explored for the first time. Thus, as predicted theoretically, recurrent and cortical CA3 afferents are differentially modulated during phases of theta rhythm. This modulation is atropine sensitive and habituates in an NMDA receptor-dependent manner, suggesting an NMDA receptor-dependent process that, in conjunction with theta rhythm, contributes to encoding of novel information in the hippocampus. 10.1523/JNEUROSCI.3702-07.2007}, author = {Villarreal, Desiree M. and Gross, Amanda L. and Derrick, Brian E. }, citeulike-article-id = {2066258}, doi = {10.1523/JNEUROSCI.3702-07.2007}, journal = {J. Neurosci.}, keywords = {acetylcholine, ca3, hippocampus, memory, oscillations, theta}, month = {December}, number = {49}, pages = {13457--13467}, posted-at = {2007-12-06 10:24:53}, priority = {2}, title = {Modulation of CA3 Afferent Inputs by Novelty and Theta Rhythm}, url = {http://dx.doi.org/10.1523/JNEUROSCI.3702-07.2007}, volume = {27}, year = {2007} }

TY - JOUR ID - citeulike:2066258 L3 - citeulike-article-id:2066258 TI - Modulation of CA3 Afferent Inputs by Novelty and Theta Rhythm JF - J. Neurosci. VL - 27 IS - 49 SP - 13457 EP - 13467 N2 - Models of hippocampal function suggest that the modulation of CA3 afferent input during theta rhythm allows for a rapid alternation between encoding and retrieval states, with each phase enhancing either extrinsic or intrinsic CA3 afferents, favoring either encoding or retrieval, respectively. Here, we show that during the initial exploration of a novel environment by rats, intrinsic CA3-CA3 synaptic inputs are attenuated on CA3 theta peaks, favoring extrinsic CA3 inputs, whereas extrinsic perforant path-CA3 synaptic inputs are attenuated on CA3 theta troughs, favoring intrinsic CA3 inputs. This modulation is absent when animals are re-exposed to the same environment 2 or 48 h later and thus habituates with familiarity, suggesting a process involved in learning. Modulation of CA3 synaptic inputs during novelty was blocked by atropine at a dose that blocks type 2 theta rhythm. Re-exposure to the same novel environment 48 h later in the absence of atropine did not result in habituation, but instead modulated CA3 synaptic responses as though the environment were novel and explored for the first time. The NMDA receptor antagonist ({+/-})-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), administered in a dose that blocks long-term potentiation induction, did not alter CA3 synaptic modulation during initial exploration. However, like atropine, CPP blocked the habituation of synaptic modulation normally observed with re-exposure, as though the environment were novel and explored for the first time. Thus, as predicted theoretically, recurrent and cortical CA3 afferents are differentially modulated during phases of theta rhythm. This modulation is atropine sensitive and habituates in an NMDA receptor-dependent manner, suggesting an NMDA receptor-dependent process that, in conjunction with theta rhythm, contributes to encoding of novel information in the hippocampus. 10.1523/JNEUROSCI.3702-07.2007 KW - acetylcholine KW - ca3 KW - hippocampus KW - memory KW - oscillations KW - theta AU - Villarreal, Desiree AU - Gross, Amanda AU - Derrick, Brian PY - 2007/12/05/ UR - http://dx.doi.org/10.1523/JNEUROSCI.3702-07.2007 ER -