cognition – Page 2 – The Miller Lab

21

Jan 2015

New paper – Working Memory Capacity: Limits on the Bandwidth of Cognition

Miller Lab

In The News, Miller Laboratory

Miller, E.K. and Buschman, T.J. (2015) Working memory capacity: Limits on the bandwidth of cognition. Daedalus, Vol. 144, No. 1, Pages 112-122. View PDF

Why can your brain store a lifetime of experiences but process only a few thoughts at once? In this article we discuss “cognitive capacity” (the number of items that can be held “in mind” simultaneously) and suggest that the limit is inherent to processing based on oscillatory brain rhythms, or “brain waves,” which may regulate neural communication. Neurons that “hum” together temporarily “wire” together, allowing the brain to form and re-form networks on the fly, which may explain a hallmark of intelligence and cognition: mental flexibility. But this comes at a cost; only a small number of thoughts can fit into each wave. This explains why you should never talk on a mobile phone when driving.
5

Jan 2015

Interareal oscillatory synchronization in top-down neocortical processing

Miller Lab

Neuroscience

Bressler and Richter review evidence that top-down processing in the cortex depends on synchronization of oscillatory rhythms between brain areas. More specifically, they hypothesize that beta band (13-30 Hz) synchrony conveys information about behavioral context (task information) to neurons in sensory cortex.
16

Dec 2014

Frontoparietal networks involved in categorization and item working memory

Miller Lab

Neuroscience

Braunlich et al compared stimulus identity vs categorization tasks using fMRI in humans. They applied a Constrained Principal Components Analysis. They found evidence for two distinct frontoparietal networks. One that rapidly analyzes the stimuli and a second one that more slowly categorizes them.
16

Dec 2014

Attentional Filtering of Visual Information by Neuronal Ensembles in the Primate Lateral Prefrontal Cortex

Miller Lab

Neuroscience

Virtually all studies of the neural basis of attention to date average effects across independently recorded neurons and across multiple trials. This is obviously artificial because attention has to be allocated on-the-fly, from moment-to-moment, not averaged across time. Trembly et al show that the current locus of attention can be decoded from ensembles of simultaneously recorded prefrontal cortex neurons from single trials. Decoding of these ensembles was stable over weeks. Nice.
2

Dec 2014

Communication through coherence with inter-areal delays

Miller Lab

Miller Laboratory, Neuroscience

Andre Bastos and colleagues review an update the communication-through-coherence (CTC) hypothesis. They propose that bi-directional cortical communication involves separate feedforward and feedback mechanisms that are separate both anatomically and spectrally.
26

Nov 2014

New paper: Task Dependence of Visual and Category Representations in Prefrontal and Inferior Temporal Cortices

Miller Lab

Miller Laboratory, Neuroscience

Task Dependence of Visual and Category Representations in Prefrontal and Inferior Temporal Cortices
Jillian L. McKee, Maximilian Riesenhuber, Earl K. Miller, and David J. Freedman

Visual categorization is an essential perceptual and cognitive process for assigning behavioral significance to incoming stimuli. Categorization depends on sensory processing of stimulus features as well as flexible cognitive processing for classifying stimuli according to the current behavioral context. Neurophysiological studies suggest that the prefrontal cortex (PFC) and the inferior temporal cortex (ITC) are involved in visual shape categorization. However, their precise roles in the perceptual and cognitive aspects of the categorization process are unclear, as the two areas have not been directly compared during changing task contexts. To address this, we examined the impact of task relevance on categorization-related activity in PFC and ITC by recording from both areas as monkeys alternated between a shape categorization and passive viewing tasks. As monkeys viewed the same stimuli in both tasks, the impact of task relevance on encoding in each area could be compared. While both areas showed task-dependent modulations of neuronal activity, the patterns of results differed markedly. PFC, but not ITC, neurons showed a modest increase in firing rates when stimuli were task relevant. PFC also showed significantly stronger category selectivity during the task compared with passive viewing, while task-dependent modulations of category selectivity in ITC were weak and occurred with a long latency. Finally, both areas showed an enhancement of stimulus selectivity during the task compared with passive viewing. Together, this suggests that the ITC and PFC show differing degrees of task-dependent flexibility and are preferentially involved in the perceptual and cognitive aspects of the categorization process, respectively.
13

Nov 2014

Frontoparietal Correlation Dynamics Reveal Interplay between Integration and Segregation during Visual Working Memory

Miller Lab

Neuroscience

Dotson et al recorded neural activity in the prefrontal and parietal cortex during a working memory task. As previous studies have reported (e.g., Buschman and Miller, 2007) they found long range synchronization of 8-25 Hz oscillations between the areas. Interestingly, there found both phase synchronization at 0 and 180 degrees suggesting that the 0 deg phase synchrony helped form networks between the areas whereas the 180 deg (anti-phase) synchrony helped segregate different networks.

For further reading:
Buschman, T.J. and Miller, E.K. (2007) Top-down versus bottom-up control of attention in the prefrontal and posterior parietal cortices. Science. 315: 1860-1862 View PDF »
13

Nov 2014

Burst Firing Synchronizes Prefrontal and Anterior Cingulate Cortex during Attentional Control

Miller Lab

Neuroscience

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.
13

Nov 2014

Gamma Oscillations Underlie the Maintenance of Feature-Specific Information and the Contents of Visual Working Memory

Miller Lab

Neuroscience

Gamma-band oscillations have been associated with holding information in working memory. Is it just a general increase in gamma or do gamma oscillations actually maintain and convey specific information? A new study by Honkanen et al suggests that it does contain information. The strength and topography of gamma oscillations reflected memorized visual features as well as the amount of information in working memory.

We’ve also shown that information about two different objects can be carried in different phases of gamma band oscillations:
Siegel, M., Warden, M.R., and Miller, E.K. (2009) Phase-dependent neuronal coding of objects in short-term memory. Proceedings of the National Academy of Sciences, 106: 21341-21346. View PDF »
Read commentary by Vogel and Fukuda
30

Oct 2014

Earl Miller interviewed about consciousness in The Huffington Post

Miller Lab

In The News, Miller Laboratory, Neuroscience

They got my experiment wrong, but spelled my name right:
Biology of Consciousness: Bridging the Mind-Body Gap?
The Huffington Post 10/30/14