Steven L. Bressler

Cognitive Neurodynamics Laboratory Center for Complex Systems & Brain Sciences Department of Psychology Florida 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.

B.

synchronized.

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, 2008 Bressler & Menon, TICS, 2010 Fuster & Bressler, TICS, 2012 Meehan & 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  Within NCN: V4  V1 V 4

• 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.