Steven L. BresslerCognitive Neurodynamics Laboratory

Center for Complex Systems & Brain SciencesDepartment of PsychologyFlorida Atlantic University

http://www.ccs.fau.edu/~bressler/

• Top-down processing is a tractable problem in cognition

• Neurocognitive networks provide a workable theoretical framework for understanding top-down processing in the brain

• Novel approaches are being developed to investigate top-down processing by neurocognitive networks

• Cognitive Science: Effect of knowledge on sensory processing

• Brain Science: Effect of “higher-level” neurons on “lower-level” neurons

• Attention: selecting items in perception

• Expectation: priming items for perception

• Inference: identifying items in perception

• The Dorsal Attention Network (DAN) is a system of frontal and parietal regions consistently activated by cues indicating where a visual object will appear.

• The DAN is postulated to exert attentional top-down control of visual cortical.

Prestimulus Processing in Visual Expectation

Poststimulus Processing in Visual Inference

Synchronized beta rhythms between V1 & extrastriate cortex (V4, TEO) form a large-scale network in visual cortex before stimulus presentation.

1,2,3 – V1 5 – V4 6 –TEO

A. Prestimulus extrastriate & V1 beta rhythms are synchronized.

B. Synchronized beta rhythms support top-down extrastriate-to-V1, but not bottom-up V1-to-extrastriate, influences.

“The concept of localization of functions … has come to mean a network of complex dynamic structures or combination centers, consisting of mosaics of distant points of the nervous system, united in a common task.”

Higher Cortical Functions in Man, 1962

NeuroCognitive Networks are large-scale systems of distributed and interconnected neuronal populations in the brain organized to perform cognitive functions.

Bressler, Scholarpedia, 2008Bressler & Menon, TICS, 2010Fuster & Bressler, TICS, 2012Meehan & Bressler, NBR, 2012

• Top-down processing in the brain involves the effect that neurons in a “higher” area have on neurons in a “lower” area.

• It can be observed in the brain wherever a hierarchical order exists

• It may involve effects within or between NeuroCognitive Networks (NCNs):

Between NCNs: FEF V4 Within NCN: V4 V1

• A variety of analytic techniques are used to investigate top-down processing in the brain

▶ Stimulation: TMS, TACS, CMS▶ Ablation: clinical analysis of stroke▶ Electrophysiological Time Series Recording▶ BOLD Time Series Recording▶ Causal Time Series Modeling: AR models, DCM▶ Biophysical Modeling: Neural mass models,

integrate-and-fire models

• Multi-Site Recording Modalities

• Improved Causal Modeling Techniques

• Improved Large-Scale Biophysical Modeling

• Graph Theoretic Methods Tailored to Brain Networks

• Top-down processing is essential in cognition• Top-down processing underlies attention,

expectation, and inference – all used in perception• Top-down processing in cognitive science has a

parallel interpretation in neuroscience• Top-down processing in the brain is readily

accommodated by the concept of neurocognitive networks

• Numerous analytic techniques are available, or are being developed, to study top-down processing by neurocognitive networks.