Annotated interictal discharges in intracranial EEG sleep data and related machine learning detection scheme.

Interictal epileptiform discharges (IEDs) such as spikes and sharp waves represent pathological electrophysiological activities occurring in epilepsy patients between seizures. IEDs occur preferentially during non-rapid eye movement (NREM) sleep and are associated with impaired memory and cognition. Despite growing interest, most studies involving IED detections rely on visual annotations or employ simple amplitude threshold approaches.

Flexible coding of time or distance in hippocampal cells.

Analysis of neuronal activity in the hippocampus of behaving animals has revealed cells acting as 'Time Cells', which exhibit selective spiking patterns at specific time intervals since a triggering event, and 'Distance Cells', which encode the traversal of specific distances. Other neurons exhibit a combination of these features, alongside place selectivity. This study aims to investigate how the task performed by animals during recording sessions influences the formation of these representations.

Active experience, not time, determines within-day representational drift in dorsal CA1.

Memories of past events can be recalled long after the event, indicating stability. But new experiences are also integrated into existing memories, indicating plasticity. In the hippocampus, spatial representations are known to remain stable but have also been shown to drift over long periods of time.

The chicken and egg problem of grid cells and place cells.

Place cells and grid cells are major building blocks of the hippocampal cognitive map. The prominent forward model postulates that grid-cell modules are generated by a continuous attractor network; that a velocity signal evoked during locomotion moves entorhinal activity bumps; and that place-cell activity constitutes summation of entorhinal grid-cell modules. Experimental data support the first postulate, but not the latter two.

Hippocampal sub-networks exhibit distinct spatial representation deficits in Alzheimer's disease model mice.

Not much is known about how the dentate gyrus (DG) and hippocampal CA3 networks, critical for memory and spatial processing, malfunction in Alzheimer's disease (AD). While studies of associative memory deficits in AD have focused mainly on behavior, here, we directly measured neurophysiological network dysfunction. We asked what the pattern of deterioration of different networks is during disease progression.

Individual differences in experienced and observational decision-making illuminate interactions between reinforcement learning and declarative memory.

Decision making can be shaped both by trial-and-error experiences and by memory of unique contextual information. Moreover, these types of information can be acquired either by means of active experience or by observing others behave in similar situations. The interactions between reinforcement learning parameters that inform decision updating and memory formation of declarative information in experienced and observational learning settings are, however, unknown.

Striatal cholinergic interneurons exert inhibition on competing default behaviours controlled by the nucleus accumbens and dorsolateral striatum.

With repeated practice, learned actions become more skilled, and eventually highly stereotypical. This transition is accompanied by a shift in striatal control over behaviour from ventral and dorsomedial striatum to dorsolateral striatum. The cholinergic interneurons (CINs) in the striatum are central to striatal computation.

Dissociation between Postrhinal Cortex and Downstream Parahippocampal Regions in the Representation of Egocentric Boundaries.

Navigation requires the integration of many sensory inputs to form a multi-modal cognitive map of the environment, which is believed to be implemented in the hippocampal region by spatially tuned cells [1-10]. These cells encode various aspects of the environment in a world-based (allocentric) reference frame. Although the cognitive map is represented in allocentric coordinates, the environment is sensed through diverse sensory organs, mostly situated in the animal's head, and therefore represented in sensory and parietal cortices in head-centered egocentric coordinates.

Odor Concentration Change Coding in the Olfactory Bulb.

Dynamical changes in the environment strongly impact our perception. Likewise, sensory systems preferentially represent stimulus changes, enhancing temporal contrast. In olfaction, odor concentration changes across consecutive inhalations ( ) can guide odor source localization, yet the neural representation of has not been studied in vertebrates.

A Cellular Mechanism Underlying Enhanced Capability for Complex Olfactory Discrimination Learning.

The biological mechanisms underlying complex forms of learning requiring the understanding of rules based on previous experience are not yet known. Previous studies have raised the intriguing possibility that improvement in complex learning tasks requires the long-term modulation of intrinsic neuronal excitability, induced by reducing the conductance of the slow calcium-dependent potassium current (sI) simultaneously in most neurons in the relevant neuronal networks in several key brain areas. Such sI reduction is expressed in attenuation of the postburst afterhyperpolarization (AHP) potential, and thus in enhanced repetitive action potential firing.

Animal Learning in a Multidimensional Discrimination Task as Explained by Dimension-Specific Allocation of Attention.

Reinforcement learning describes the process by which during a series of trial-and-error attempts, actions that culminate in reward are reinforced, becoming more likely to be chosen in similar circumstances. When decisions are based on sensory stimuli, an association is formed between the stimulus, the action and the reward. Computational, behavioral and neurobiological accounts of this process successfully explain simple learning of stimuli that differ in one aspect, or along a single stimulus dimension.

Spatial Rule Learning and Corresponding CA1 Place Cell Reorientation Depend on Local Dopamine Release.

Incentives drive goal-directed behavior; however, how they impact the formation and stabilization of goal-relevant hippocampal maps remains unknown. Since dopamine is involved in reward processing, affects hippocampal-dependent behavior, and modulates hippocampal plasticity, we hypothesized that local dopaminergic transmission in the hippocampus serves to mold the formation and updating of hippocampal cognitive maps to adaptively represent reward-predicting space of sensory inputs. We recorded CA1 place cells of rats throughout training on a spatial extra-dimensional set-shift task.

Enhance your chance with the TANs: tonically active neurons support learning in the ventral striatum.

The striatum is crucial for the correct learning and control of goal-directed behavior and habitual actions. Here in this issue of Neuron, Atallah et al. (2014) show that both reinforcement-based learning and control parameters are reflected in the neural activity of the ventromedial striatum.

Coherent phasic excitation during hippocampal ripples.

High-frequency hippocampal network oscillations, or "ripples," are thought to be involved in episodic memory. According to current theories, memory traces are represented by assemblies of principal neurons that are activated during ripple-associated network states. Here we performed in vivo and in vitro experiments to investigate the synaptic mechanisms during ripples.

Cannabinoids disrupt hippocampal sharp wave-ripples via inhibition of glutamate release.

Cannabis consumption results in impaired learning. The proper synchronization of neuronal activity in the mammalian hippocampus gives rise to network rhythms that are implicated in memory formation. Here, we have studied the impact of cannabinoids on hippocampal sharp waves and associated ripple oscillations using field- and whole-cell voltage-clamp recordings.

The effects of motivation on response rate: a hidden semi-Markov model analysis of behavioral dynamics.

A central goal of neuroscience is to understand how neural dynamics bring about the dynamics of behavior. However, neural and behavioral measures are noisy, requiring averaging over trials and subjects. Unfortunately, averaging can obscure the very dynamics that we are interested in, masking abrupt changes and artificially creating gradual processes.

Striatal action-learning based on dopamine concentration.

The reinforcement learning hypothesis of dopamine function predicts that dopamine acts as a teaching signal by governing synaptic plasticity in the striatum. Induced changes in synaptic strength enable the cortico-striatal network to learn a mapping between situations and actions that lead to a reward. A review of the relevant neurophysiology of dopamine function in the cortico-striatal network and the machine reinforcement learning hypothesis reveals an apparent mismatch with recent electrophysiological studies.

An approach for reliably investigating hippocampal sharp wave-ripples in vitro.

Background: Among the various hippocampal network patterns, sharp wave-ripples (SPW-R) are currently the mechanistically least understood. Although accurate information on synaptic interactions between the participating neurons is essential for comprehensive understanding of the network function during complex activities like SPW-R, such knowledge is currently notably scarce.

Methodology/principal Findings: We demonstrate an in vitro approach to SPW-R that offers a simple experimental tool allowing detailed analysis of mechanisms governing the sharp wave-state of the hippocampus.

Encoding by response duration in the basal ganglia.

Several models have suggested that information transmission in the basal ganglia (BG) involves gating mechanisms, where neuronal activity modulates the extent of gate aperture and its duration. Here, we demonstrate that BG response duration is informative about a highly abstract stimulus feature and show that the duration of "gate opening" can indeed be used for information transmission through the BG. We analyzed recordings from three BG locations: the external part of the globus pallidus (GPe), the substantia nigra pars reticulata (SNr), and dopaminergic neurons from the substantia nigra pars compacta (SNc) during performance of a probabilistic visuomotor task.

Lack of spike-count and spike-time correlations in the substantia nigra reticulata despite overlap of neural responses.

Previous studies of single neurons in the substantia nigra reticulata (SNr) have shown that many of them respond to similar events. These results, as well as anatomical studies, suggest that SNr neurons share inputs and thus may have correlated activity. Different types of correlation can exist between pairs of neurons.

Statistical properties of pauses of the high-frequency discharge neurons in the external segment of the globus pallidus.

The neurons of many basal ganglia nuclei, including the external and internal globus pallidus (GPe and GPi, respectively) and the substantia nigra pars reticulata (SNr) are characterized by their high-frequency (50-100 spikes/s) tonic discharge (HFD). However, the high firing rate of GPe neurons is interrupted by long pauses. We studied the extracellularly recorded spiking activity of 212 well-isolated HFD GPe and 52 GPi/SNr neurons from five monkeys during different states of behavioral activity.

Midbrain dopamine neurons encode decisions for future action.

Current models of the basal ganglia and dopamine neurons emphasize their role in reinforcement learning. However, the role of dopamine neurons in decision making is still unclear. We recorded from dopamine neurons in monkeys engaged in two types of trial: reference trials in an instructed-choice task and decision trials in a two-armed bandit decision task.

Physiological studies of information processing in the normal and Parkinsonian basal ganglia: pallidal activity in Go/No-Go task and following MPTP treatment.

Understanding the role of the basal ganglia in day to day behavior is critical for a better understanding of the role of these structures in pathological states--such as Parkinson's disease. To elucidate this connection, we studied pallidal activity in a monkey performing a delayed release Go/No-Go task and in monkeys treated with the dopaminergic neurotoxin--MPTP. We compared the results with the predictions of the action selection and reinforcement driven dimensionality reduction models of the basal ganglia.

Independent coding of movement direction and reward prediction by single pallidal neurons.

Associating action with its reward value is a basic ability needed by adaptive organisms and requires the convergence of limbic, motor, and associative information. To chart the basal ganglia (BG) involvement in this association, we recorded the activity of 61 well isolated neurons in the external segment of the globus pallidus (GPe) of two monkeys performing a probabilistic visuomotor task. Our results indicate that most (96%) neurons responded to multiple phases of the task.