Previous research points to an association between retrieval-related activity in the medial prefrontal cortex (mPFC) and preservation of emotional information compared with co-occurring neutral information following sleep. Although the role of the mPFC in emotional memory likely begins at encoding, little research has examined how mPFC activity during encoding interacts with consolidation processes to enhance emotional memory. This issue was addressed in the present study using transcranial magnetic stimulation in conjunction with an emotional memory paradigm. Healthy young adults encoded negative and neutral scenes while undergoing concurrent TMS with a modified short intermittent theta burst stimulation (sTBS) protocol. Participants received stimulation to either the mPFC or an active control site (motor cortex) during the encoding phase. Recognition memory for scene components (objects and backgrounds) was assessed after a short delay (30 min) and a long delay [24 h (including a night of sleep)] to obta...

Learning to recognize and filter familiar, irrelevant sensory stimuli eases the computational burden on the cerebral cortex. Inhibition is a candidate mechanism in this filtration process, and oscillations in the cortical local field potential (LFP) serve as markers of the engagement of different inhibitory neurons. We show here that LFP oscillatory activity in visual cortex is profoundly altered as male and female mice learn to recognize an oriented grating stimulus—low-frequency (∼15 Hz peak) power sharply increases, whereas high-frequency (∼65 Hz peak) power decreases. These changes report recognition of the familiar pattern as they disappear when the stimulus is rotated to a novel orientation. Two-photon imaging of neuronal activity reveals that parvalbumin-expressing inhibitory neurons disengage with familiar stimuli and reactivate to novelty, whereas somatostatin-expressing inhibitory neurons show opposing activity patterns. We propose a model in which the balance of two interacting interneuron circu...

Brian J. Bondy, David B. Haimes, and Nace L. Golding (see pages [6234–6245][1]) Birds and mammals can localize sounds in the horizontal plane by comparing the time of arrival of the sound at each ear. In mammals, interaural time differences are detected by neurons in the medial superior olive (

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide. It is characterized by cognitive decline and concomitant dementia, primarily resulting from progressive degeneration of cortical and hippocampal neurons. AD is definitively diagnosed postmortem by the analysis of two

Functional magnetic resonance imaging (fMRI) is among the foremost methods for mapping human brain function but provides only an indirect measure of underlying neural activity. Recent findings suggest that the neurophysiological correlates of the fMRI blood oxygenation level-dependent (BOLD) signal might be regionally specific. We examined the neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex, where differences in neural architecture might result in a different relationship between the respective signals. Fifteen human neurosurgical patients (10 female, 5 male) implanted with depth electrodes performed a verbal free recall task while electrophysiological activity was recorded simultaneously from hippocampal and neocortical sites. The same patients subsequently performed a similar version of the task during a later fMRI session. Subsequent memory effects (SMEs) were computed for both imaging modalities as patterns of encoding-related brain activity predictive of later fr...

Post tetanic potentiation (PTP) is a form of short-term plasticity that lasts for tens of seconds following a burst of presynaptic activity. It has been proposed that PTP arises from protein kinase C (PKC) phosphorylation of Munc18-1, an SM (Sec1/Munc-18 like) family protein that is essential for release. To test this model, we made a knockin mouse in which all Munc18-1 PKC phosphorylation sites were eliminated through serine-to-alanine point mutations (Munc18-1SA mice) and we studied mice of either sex. Expression of Munc18-1 was not altered in Munc18-1SA mice, and there were no obvious behavioral phenotypes. At the hippocampal CA3 to CA1 synapse, and the granule cell parallel fiber to Purkinje cell (PF to PC) synapse, basal transmission was largely normal except for small decreases in paired-pulse facilitation that are consistent with a slight elevation in release probability. Phorbol esters that mimic activation of PKC by diacylglycerol still increased synaptic transmission in Munc18-1SA mice. In Munc18...

Alzheimer’s disease (AD) is associated with poor sleep, but the impact of tau and β-amyloid (Aβ) pathology on sleep remains largely unknown. Here, we test the hypothesis that tau and Aβ predict unique impairments in objective and self-perceived human sleep under real-life, free-living conditions. Eighty-nine male and female cognitively healthy older adults received 18F-FTP-tau and 11C-PIB-Aβ PET imaging, 7 nights of sleep actigraphy and questionnaire measures, and neurocognitive assessment. Tau burden, but not Aβ, was associated with markedly worse objective sleep. In contrast, Aβ and tau were associated with worse self-reported sleep quality. Of clinical relevance, Aβ burden predicted a unique perceptual mismatch between objective and subject sleep evaluation, with individuals under-estimating their sleep. The magnitude of this mismatch was further predicted by worse executive function. Thus, early-stage tau and Aβ deposition are linked with distinct phenotypes of real-world sleep impairment, one that inc...

Alzheimer’s disease (AD) is a progressive neurodegenerative disease marked by the accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles. Aβ oligomers cause synaptic dysfunction early in AD by enhancing long-term depression (LTD, a paradigm for forgetfulness) via metabotropic glutamate receptor (mGluR)-dependent regulation of striatal enriched tyrosine phosphatase (STEP61). Reelin is a neuromodulator that signals through ApoE receptors to protect the synapse against Aβ toxicity (Durakoglugil et al., 2009) Reelin signaling is impaired by ApoE4, the most important genetic risk factor for AD, and Aβ-oligomers activate metabotropic glutamate receptors (Renner et al., 2010). We therefore asked whether Reelin might also affect mGluR-LTD. To this end, we induced chemical mGluR-LTD using DHPG (Dihydroxyphenylglycine), a selective mGluR5 agonist. We found that exogenous Reelin reduces the DHPG-induced increase in STEP61, prevents the dephosphorylation of GluA2 and concomitantly blocks mGluR-mediated LTD...

Hyperphosphorylation of the microtubule associated protein tau (tau) is inextricably linked to several neurodegenerative diseases, collectively termed tauopathies, in which synapse dysfunction occurs through largely unidentified mechanisms. Our research aimed to uncover molecular mechanisms by which phosphorylation of tau (pTau) affects synapse function. Using combined molecular and electrophysiological analysis with in vitro genetic knock-in of phosphorylation mutant human tau in male rat CA1 hippocampal neurons, we show an interplay between tau and protein kinase C and casein kinase substrate in neurons protein 1 (PACSIN1) that regulates synapse function. pTau at serine residues 396/404 decreases tau:PACSIN1 binding and evokes PACSIN1-dependent functional and structural synapse weakening. Knockdown of tau or PACSIN1 increases AMPA receptor-mediated current at extrasynaptic regions, supporting a role for these proteins in affecting AMPA receptor trafficking. The pTau-induced PACSIN1 dissociation may repre...

Cortical pyramidal neurons possess a persistent Na+ current ( I NaP), which, in contrast to the larger transient current, does not undergo rapid inactivation. Although relatively quite small, I NaP is active at subthreshold voltages and therefore plays an important role in neuronal input–output processing. The subcellular distribution of channels responsible for I NaP and the mechanisms that render them persistent are not known. Using high-speed fluorescence Na+ imaging and whole-cell recordings in brain slices obtained from mice of either sex, we reconstructed the I NaP elicited by slow voltage ramps in soma and processes of cortical pyramidal neurons. We found that in all neuronal compartments, the relationship between persistent Na+ conductance and membrane voltage has the shape of a Boltzmann function. Although the density of channels underlying I NaP was about twofold lower in the axon initial segment (AIS) than in the soma, the axonal channels were activated by ∼10 mV less depolarization than were so...