Dentate gyrus is needed for memory retrieval.

The hippocampus is crucial for acquiring and retrieving episodic and contextual memories. In previous studies, the inactivation of dentate gyrus (DG) neurons by chemogenetic- and optogenetic-mediated hyperpolarization led to opposing conclusions about DG's role in memory retrieval. One study used Designer Receptors Exclusively Activated by Designer Drugs (DREADD)-mediated clozapine N-oxide (CNO)-induced hyperpolarization and reported that the previously formed memory was erased, thus concluding that denate gyrus is needed for memory maintenance.

Pre- and postsynaptic N-methyl-D-aspartate receptors are required for sequential printing of fear memory engrams.

The organization of fear memory involves the participation of multiple brain regions. However, it is largely unknown how fear memory is formed, which circuit pathways are used for "printing" memory engrams across brain regions, and the role of identified brain circuits in memory retrieval. With advanced genetic methods, we combinatorially blocked presynaptic output and manipulated N-methyl-D-aspartate receptor (NMDAR) in the basolateral amygdala (BLA) and medial prefrontal cortex (mPFC) before and after cued fear conditioning.

Microglial phagocytosis dysfunction in stroke is driven by energy depletion and induction of autophagy.

Microglial phagocytosis of apoptotic debris prevents buildup damage of neighbor neurons and inflammatory responses. Whereas microglia are very competent phagocytes under physiological conditions, we report their dysfunction in mouse and preclinical monkey models of stroke (macaques and marmosets) by transient occlusion of the medial cerebral artery (tMCAo). By analyzing recently published bulk and single cell RNA sequencing databases, we show that the phagocytosis dysfunction was not explained by transcriptional changes.

Immediate and after effects of transcranial direct-current stimulation in the mouse primary somatosensory cortex.

Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique consisting in the application of weak electric currents on the scalp. Although previous studies have demonstrated the clinical value of tDCS for modulating sensory, motor, and cognitive functions, there are still huge gaps in the knowledge of the underlying physiological mechanisms. To define the immediate impact as well as the after effects of tDCS on sensory processing, we first performed electrophysiological recordings in primary somatosensory cortex (S1) of alert mice during and after administration of S1-tDCS, and followed up with immunohistochemical analysis of the stimulated brain regions.

Drug-Responsive Inhomogeneous Cortical Modulation by Direct Current Stimulation.

Objective: Cathodal direct current stimulation (cDCS) induces long-term depression (LTD)-like reduction of cortical excitability (DCS-LTD), which has been tested in the treatment of epilepsy with modest effects. In part, this may be due to variable cortical neuron orientation relative to the electric field. We tested, in vivo and in vitro, whether DCS-LTD occurs throughout the cortical thickness, and if not, then whether drug-DCS pairing can enhance the uniformity of the cortical response and the cDCS antiepileptic effect.

Exploring new transcranial electrical stimulation strategies to modulate brain function in animal models.

Transcranial electrical stimulation (tES) refers to a group of non-invasive brain stimulation techniques to induce changes in the excitability of cortical neurons in humans. In recent years, studies in animal models have been shown to be essential for disentangling the neuromodulatory effects of tES, defining safety limits, and exploring potential therapeutic applications in neurological and neuropsychiatric disorders. Testing in animal models is valuable for the development of new unconventional protocols intended to improve tES administration and optimize the desired effects by increasing its focality and enabling deep-brain stimulation.

Involvement of hippocampal inputs and intrinsic circuit in the acquisition of context and cues during classical conditioning in behaving rabbits.

Learning-related changes in strength in selected hippocampal synapses have been described recently. However, information is scarce regarding the spatial-temporal sequence of changes in synaptic weights taking place during the acquisition of a classical conditioning task and the contribution of both context (environmental details) and cues (conditioned and unconditioned stimuli: CS, US) to those activity-dependent changes. We recorded in rabbits the monosynaptic field excitatory postsynaptic potentials (fEPSPs) evoked at 6 different hippocampal synapses during the acquisition and extinction of a classical eyeblink conditioning using trace or delay paradigms, as well as during pseudoconditioning and in the absence of CS and US presentations (context).

Red nucleus neurons actively contribute to the acquisition of classically conditioned eyelid responses in rabbits.

The red nucleus (RN) is a midbrain premotor center that has been suggested as being involved in the acquisition and/or performance of classically conditioned nictitating membrane/eyelid responses. We recorded in rabbits the activity of RN and pararubral neurons during classical eyeblink conditioning using a delay paradigm. Neurons were identified by their antidromic activation from contralateral facial and accessory abducens nuclei and by their synaptic activation from the ipsilateral motor cortex (MC) and the contralateral cerebellar interpositus (IP) nucleus.