Several aspects of the human nervous system and associated motor and cognitive processes have been reported to be modulated by extremely low-frequency (ELF, < 300 Hz) time-varying Magnetic Fields (MF). Due do their worldwide prevalence; power-line frequencies (60 Hz in North America) are of particular interest. Despite intense research efforts over the last few decades, the potential effects of...

We explore both analytically and numerically an ensemble of coupled phase oscillators governed by a Kuramoto-type system of differential equations. However, we have included the effects of time delay (due to finite signal-propagation speeds) and network plasticity (via dynamic coupling constants) inspired by the Hebbian learning rule in neuroscience. When time delay and learning effects combine...

Virtually all current theories of category learning assume that humans learn new categories by gradually forming associations directly between stimuli and responses. In information-integration category-learning tasks, this purported process is thought to depend on procedural learning implemented via dopamine-dependent cortical-striatal synaptic plasticity. This article proposes a new, neurobiol...

In free operant experiments, subjects alternate at will between targets that yield rewards stochastically. Behavior in these experiments is typically characterized by (1) an exponential distribution of stay durations, (2) matching of the relative time spent at a target to its relative share of the total number of rewards, and (3) adaptation after a change in the reward rates that can be very fa...

The development of precise connections in the mammalian central nervous system requires neural activity. Synchronous patterns of afferent activity, and coincident afferent and target activity are required for specifying the neuronal connectivity that characterizes the adult visual pathway in mammals. During development, postsynaptic target neurons communicate with presynaptic afferents. Recent ...

In this study, the necessary conditions, including those related to behavior, for lasting modifications to occur in correlated activity ('functional plasticity') were examined in the behaving monkey. Previously, in-vitro studies of neuronal plasticity yielded important information about possible mechanisms of synaptic plasticity, but could not be used to test their functionality in the intact, ...

Changes in synaptic strength are important for synaptic development and synaptic plasticity. Most directly responsible for these synaptic changes are alterations in synaptic receptor number and density. Although alterations in receptor density mediated by the insertion, lateral mobility, removal, and recycling of receptors have been extensively studied, the dynamics and regulators of intracellu...

Modulation of intrinsic excitability is an alternative to classical synaptic plasticity for implementing activity-dependent changes in neuronal networks. In this issue of Neuron, Nelson et al. reveal a new form of plasticity of intrinsic excitability that can be triggered rapidly when synaptic inhibition reduces spontaneous firing, resulting in persistent enhancement of firing rate and neuronal...

Neurosteroid dehydropiandrosterone (DHEA) and its sulphate (DHEAS) are reported to have modulatory effects on neuronal excitabillity and synaptic plasticity. DHEA and DHEAS are synthesized in central and peripheral nervous system from cholesterol or steroidal precursors imported from peripheral sources. There is accumulating evidence that alterations in DHEA(S) levels may be involved in the pat...

A fundamental property of the brain is its capacity to change with a wide variety of experiences, including injury. Although there are spontaneous reparative changes following injury, these changes are rarely sufficient to support significant functional recovery. Research on the basic principles of brain plasticity is leading to new approaches to treating the injured brain. We review factors th...