Craig and McBain review the role of oscillations in understanding the functional circuitry of the hippocampus with an eye toward bridging in vitro and in vivo studies.
-
Micheli et al find that during sustained attention, successful near-threshold visual detection is predicted by increased phase synchrony between the frontal and temporal/parietal cortex. They suggest that beta coherent states in the prefrontal cortex regulate top-down expectancy and coupling with posterior cortex facilitates the gating of that information.
Evidence for the role of beta in top-down selection continues to mount.
-
Bonnefond and Jenson used MEG in humans to find coupling between alpha and gamma rhythms during an attention-demanding task. High alpha power was associated with weak gamma power at the trough of the alpha cycle. This may provide a mechanism for top-down control of attention.
-
Tremblay et al decode the allocation of attention, stimulus location, and saccade from local field potentials in a frequency-dependent matter. Decoding from LFPs was more stable across time than decoding from spikes.
-
Working memory has long been thought to depend on sustained firing of cortical neurons. However, single neurons showing unbroken sustained activity is rare and average population activity is often only strong near the end of a memory delay. Mark Stokes presents the intriguing hypothesis for activity-silent working memory. He suggests that working memory depends on patterns of functional connectivity between neurons, not sustained activity.
-
Takeda et al show that layer-specific oscillatory synchrony during successful recall of memories. Specifically, there was laminar specific feedback from area 36 to area TE that supported the recall of a paired associate object.
-
Kundu et al recorded EEG from humans during a short-term memory task. They found fronto-parietal coherence in different frequencies were associated with different memory functions. Alpha coherence was associated with maintenance of the information in memory. By contrast, the top-down filtering of distractions was associated with beta coherence. This adds to mounting evidence that specific frequency bands are associated with specific types of cortical processing like, for example, beta and top-down control.
-
Ardid et al use spike shape and firing variability to identify different classes in the primate prefrontal cortex. They ID four classes of broad spiking neurons and three classes of narrow spiking (inhibitory) neurons. These cell classes show different strength of synchrony to local field potential oscillations at specific frequencies. The authors suggest this reflects canonical cortical circuits with different functions.
-
Georgia Gregoriou and colleagues review the role of oscillations in the focusing of attention. They suggest that different frequencies reflect the biophysical properties of different cell types and that synchrony allows selective routing of information through these cell populations.
-
Frequency-specific hippocampal-prefrontal interactions during associative learning
Brincat, S.L. and Miller, E.K. (2015) Nature Neuroscience, advanced online publicationAbstract:
Much of our knowledge of the world depends on learning associations (for example, face-name), for which the hippocampus (HPC) and prefrontal cortex (PFC) are critical. HPC-PFC interactions have rarely been studied in monkeys, whose cognitive and mnemonic abilities are akin to those of humans. We found functional differences and frequency-specific interactions between HPC and PFC of monkeys learning object pair associations, an animal model of human explicit memory. PFC spiking activity reflected learning in parallel with behavioral performance, whereas HPC neurons reflected feedback about whether trial-and-error guesses were correct or incorrect. Theta-band HPC-PFC synchrony was stronger after errors, was driven primarily by PFC to HPC directional influences and decreased with learning. In contrast, alpha/beta-band synchrony was stronger after correct trials, was driven more by HPC and increased with learning. Rapid object associative learning may occur in PFC, whereas HPC may guide neocortical plasticity by signaling success or failure via oscillatory synchrony in different frequency bands.