Dynamic predictions: Oscillations and synchrony in top–down processing

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.

Spikes, synchrony, and attentive learning by laminar thalamocortical circuits

“…It clarifies data about how bottom-up processing and learned tuning of adaptive filters is modulated by top-down attentive learned expectations that embody predictions or hypotheses that focus attention on expected bottom-up stimuli (Salin and Bullier, 1995;Engel et al, 2001;Gao and Suga, 1998;Krupa et al, 1999;Desimone, 1998;Ahissar and Hochstein, 2002;Hermann et al, 2004). These data support predictions of Adaptive Resonance Theory, or ART (Grossberg, 1980(Grossberg, , 2003Carpenter andGrossberg, 1987, 1993) that top-down expectations regulate predictive coding and matching and thereby help to focus attention, synchronize and gain-modulate attended feature representations, and trigger fast learning that is dynamically buffered against catastrophic forgetting.…”

“…Many authors have examined synchronous oscillations within and across brain regions as one way in which behaviorally significant brain states are organized (Engel et al, 2001). Aggregate and single-cell recordings from multiple thalamic and cortical levels of mammals have shown highfrequency and low-frequency rhythmic synchronous activity correlated with cognitive, perceptual and behavioral tasks.…”

“…ART also predicted that matching synchronizes the firing patterns of cells coding matched stimuli and thereby facilitates fast stable learning (cf., Engel et al, 2001;Fries et al, 2001;Grossberg, 1976Grossberg, , 1980Grossberg, , 1999Pollen, 1999;Usrey, 2002). SMART further develops that proposal to include spiking neurons and the role of the higher-order specific and nonspecific thalamic nuclei.…”

When neurons form memories

“…Modified, with permission, from Ref. [14]. q (2001) Nature Publishing Group (http://www.nature.com/).…”

Comparison of spectral analysis methods for characterizing brain oscillations

“…Numerous theories propose that many of the processes that underlie cognition and awareness are sub-served by oscillatory synchrony between brain areas, where, for example, oscillations have to be sustained to carry information (see e.g., Engel et al (2001); Varela et al (2001); Tononi and Edelman (1998)). Because P episode subtracts background activity, it can be much more sensitive than either wavelets or multitapers when conditions differ only slightly from one another, but have distributions that are near the duration or amplitude thresholds of P episode (cf.…”