# Show Reference: "Dynamic Predictions: Oscillations and Synchrony in Top-down Processing"

Dynamic Predictions: Oscillations and Synchrony in Top-down Processing Nature Reviews. Neuroscience, Vol. 2, No. 10. (01 October 2001), pp. 704-716, doi:10.1038/35094565 by Andreas K. Engel, Pascal Fries, Wolf Singer
@article{engel-et-al-2001,
abstract = {Classical theories of sensory processing view the brain as a passive, stimulus-driven device. By contrast, more recent approaches emphasize the constructive nature of perception, viewing it as an active and highly selective process. Indeed, there is ample evidence that the processing of stimuli is controlled by top-down influences that strongly shape the intrinsic dynamics of thalamocortical networks and constantly create predictions about forthcoming sensory events. We discuss recent experiments indicating that such predictions might be embodied in the temporal structure of both stimulus-evoked and ongoing activity, and that synchronous oscillations are particularly important in this process. Coherence among subthreshold membrane potential fluctuations could be exploited to express selective functional relationships during states of expectancy or attention, and these dynamic patterns could allow the grouping and selection of distributed neuronal responses for further processing.},
address = {Cellular Neurobiology Group, Institute for Medicine, Research Centre J\"{u}lich, 52425 J\"{u}lich, Germany. a.k.engel@fz-juelich.de},
author = {Engel, Andreas K. and Fries, Pascal and Singer, Wolf},
day = {01},
doi = {10.1038/35094565},
issn = {1471-003X},
journal = {Nature Reviews. Neuroscience},
keywords = {biology, oscillation, synchrony, top-down},
month = oct,
number = {10},
pages = {704--716},
pmid = {11584308},
posted-at = {2013-03-01 08:14:47},
priority = {2},
publisher = {Nature Publishing Group},
title = {Dynamic Predictions: Oscillations and Synchrony in Top-down Processing},
url = {http://dx.doi.org/10.1038/35094565},
volume = {2},
year = {2001}
}


Some argue that the main task of cognition is generating the correct actions.

If the main task of cognition is generating the correct actions, then it is not important in itself to recover a perfect representation of the world from perception.

The idea that neural activity does not primarily represent the world but 'action pointers', as put by Engel et al., speaks to the deep SC which is both 'multi-modal' and 'motor'.

The cognitivist interpretation of the terms 'bottom-up' and 'top-down' is that of hypothesis-driven or expectation-driven processing., respectively.

The anatomical interpretation of the terms 'bottom-up' and 'top-down' is that of feedforward vs. feedback connections in a processing hierarchy, respectively.

The terms 'bottom-up' and 'top-down' can mean different, related things depending on context. Engel et al. list four:

• anatomical
• cognitivist
• gestaltist
• (neural) dynamicist

Grossberg's ART and Friston's theory of cortical responses appeal to the anatomical interpretation of 'top-down' and 'bottom-up' processing and stress feedback as well as feedforward connections.

The temporal binding model implies that related activity of neurons across populations leads to binding of different aspects of stimuli.

According to the temporal binding theory, top-down control is realized by top-down influences on synchronization and oscillations in activity. Engel et al. call this model of top-down control the `dynamicist' notion.

The temporal binding theory does not rely on a hierarchical architecture.

The changes to neural responses due to top-down attention are purely caused by intrinsic processes, not a (direct) reaction to external stimuli. They thus support the theory of situatedness.

The concept of situatedness assumes that cognition does not represent a universally correct way, but in one that satisfies the constraints of the current task and environment.

Situatedness and connectionism share the following concepts:

• distributed processing,
• decentralization,
• context dependence.

Much of the activity of cognitive systems is not only due to current stimuli, but also to a large degree to previous experience, specifically due to the expectations following from it.

A precondition for intelligence is the ability to use previous experience to abstract away from current stimulus conditions—to use both information from current sensory input and from past experience and potentially discard one for the other.

Top-down processing is necessary in order to be able to mix current information from sensory input with previous experience.

Many recent neural theories assume that higher-level brain regions form hypotheses about the world and that top-down, or feedback connections carry predictions for low-level stimuli derived from these hypotheses.

Early theories which assume that higher-level brain regions form hypotheses about the world and that top-down, or feedback connections carry predictions for low-level stimuli derived from these hypotheses is Grossberg's ART.