Womelsdorf et al found that bursts of neural activity in the prefrontal cortex and anterior cingulate synchronize at gamma and beta frequencies during focused attention. Non-burst activity did not show long-range synchronization. Burst synchronization may underlie the formation of long-range networks.
-
Ruff and Cohen report evidence that attention can increase or decrease neural correlations depending on whether the neurons have the same or different functions.
-
Goal-direction and top-down control
Timothy J. Buschman and Earl K. MillerWe review the neural mechanisms that support top-down control of behavior. We suggest that goal-directed behavior utilizes two systems that work in concert. A basal ganglia-centered system quickly learns simple, fixed goal-directed behaviors while a prefrontal cortex-centered system gradually learns more complex (abstract or long-term) goal-directed behaviors. Interactions between these two systems allows top-down control mechanisms to learn how to direct behavior towards a goal but also how to guide behavior when faced with a novel situation.
-
Womeldorf et al observed bursts of firing in the anterior cingulate and prefrontal cortex during shifts of attention. These bursts (but not non-burst firing) synchronized over long distances (between the AC and PFC) to local field field potentials at beta and gamma frequencies. These bursts were proceeded by bursts of inhibitory neurons. The authors propose burst firing mechanisms help form functional networks to coordinate shifts of attention.
-
At this risk of kvelling, in 2011 we published a paper (Buschman et al., 2011) showing independent visual working memory capacities in the right vs left visual hemifields. We were told “no way” and “that’s impossible”. Since then, a bunch of papers have supported this. Here’s another one.
Wang et al used FMRI and found that brain networks primarily interact with ipsilateral, not contralateral networks. Thus, the brain emphasizes processing within each hemisphere (visual hemifield) and minimizes across-hemisphere processing.
Also see:
Buschman,T.J., Siegel, M., Roy, J.E. and Miller, E.K. (2011) Neural substrates of cognitive capacity limitations. Proceedings of the National Academy of Sciences. 108(27):11252-5. View PDF » -
Zhang et al optogenetically activated the mouse cingulate region and found that it enhanced activity in primary visual cortex (V1), improved visual discrimination and increased center-surround effects. This modulation was mediated by long-range projections that activated GABAergic (inhibitory) circuits in V1. Thus, long-range projection from the frontal lobe may modulate sensory cortex via excitatory action on local inhibitory circuits.
-
Bob Desimone and crew find that removal of the prefrontal cortex (PFC) reduces (but, notably, does not eliminate) the effects of attention on neurons in visual cortical area V4. The modulation of attention on firing rates was weaker and onset was delayed relative to the hemisphere with an intact PFC and there was a reduction of gamma power and synchrony. Thus, PFC is an important, but not the only, source of top-down modulation on visual cortex.
-
Chan et al show that the prefrontal cortex (PFC) may exert top-down influences on the superior colliculus (SC) via oscillatory synchrony. Animals performed both pro- and anti-saccade trials. Anti-saccades are highly dependent on the PFC because they involve inhibiting a highly prepotent response (a pro-saccade). Bilateral deactivation of the PFC attenuated beta and gamma power in the SC around the time the animals were preparing to respond. The gamma power was correlated with spiking activity whereas beta was tonic (and reduced after PFC deactivation) and may facilitate communication between the PFC and SC.
-
The evidence is mounting that the primate brain has separate, independent attentional/working memory capacities in the right and left visual hemifields. In this study, Matushima and Tanaka trained monkeys to track single or multiple objects across both visual hemifields. Neural activity to a given object was only degraded when another object was in the same hemifield, not when another object was in the opposite hemifield. This could not be explained by distance between objects; there was no difference between upper and lower visual fields, for example. This suggests that the anatomical separation of the right and left visual hemifields into the left vs right cerebral hemispheres results in separate cognitive capacities for the right vs left sides of vision. Buschman et al (2011) found similar effects for object identity.
For further reading:
Buschman,T.J., Siegel, M., Roy, J.E. and Miller, E.K. (2011) Neural substrates of cognitive capacity limitations. Proceedings of the National Academy of Sciences. 108(27):11252-5. View PDF » -
Huffington Post article about the evils of multitasking.
You’re Not Busy, You Just Think You Are: 7 Ways To Find More Time The Huffington Post UK | By Georgia James Posted: 13/06/2014 15:00 BST
(with quotes from Earl Miller)