title: Regular theta-firing neurons in the nucleus incertus during sustained hippocampal activation.
abstract: This paper describes the existence of theta-coupled neuronal activity in the nucleus incertus (NI). Theta rhythm is relevant for cognitive processes such as spatial navigation and memory processing, and can be recorded in a number of structures related to the hippocampal activation including the NI. Strong evidence supports the role of this tegmental nucleus in neural circuits integrating behavioural activation with the hippocampal theta rhythm. Theta oscillations have been recorded in the local field potential of the NI, highly coupled to the hippocampal waves, although no rhythmical activity has been reported in neurons of this nucleus. The present work analyses the neuronal activity in the NI in conditions leading to sustained hippocampal theta in the urethane-anaesthetised rat, in order to test whether such activation elicits a differential firing pattern. Wavelet analysis has been used to better define the neuronal activity already described in the nucleus, i.e., non-rhythmical neurons firing at theta frequency (type I neurons) and fast-firing rhythmical neurons (type II). However, the most remarkable finding was that sustained stimulation activated regular-theta neurons (type III), which were almost silent in baseline conditions and have not previously been reported. Thus, we describe the electrophysiological properties of type III neurons, focusing on their coupling to the hippocampal theta. Their spike rate, regularity and phase locking to the oscillations increased at the beginning of the stimulation, suggesting a role in the activation or reset of the oscillation. Further research is needed to address the specific contribution of these neurons to the entire circuit.
authors: Departamento de Anatomia y Embriología Humana, Facultad de Medicina, Universitat de València, Avd. Blasco Ibañez, 15, 46010, Valencia, Spain.
authors: Sergio
authors: S
authors: Martínez-Bellver
authors: Ana
authors: A
authors: Cervera-Ferri
authors: Joana
authors: J
authors: Martínez-Ricós
authors: Amparo
authors: A
authors: Ruiz-Torner
authors: Aina
authors: A
authors: Luque-Garcia
authors: Aina
authors: A
authors: Luque-Martinez
authors: Arantxa
authors: A
authors: Blasco-Serra
authors: Juan
authors: J
authors: Guerrero-Martínez
authors: Manuel
authors: M
authors: Bataller-Mompeán
authors: Vicent
authors: V
authors: Teruel-Martí
mesh_terms: D000200:Action Potentials; D000818:Animals; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D008564:Membrane Potentials; D009474:Neurons / Q000502:physiology*; D011903:Raphe Nuclei / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D013826:Theta Rhythm; D058067:Wavelet Analysis
keywords: arousal; brainstem; hippocampus; rat; theta rhythm