Example components groups of electrodes connected by

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Example: Components – groups of electrodes connected by edges trivial components – not connected to any node red components – largest one – with the most connections yellow components – smaller one onset: one dominant component → middle: dominant component fractures → end: one dominant component Microscale Data: local field potential, LFP microelectrode array (4mm x 4mm) records voltage from small neural populations Temporal scales: LFP rhythms example: one microelectrode Ictal chirp
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time-frequency spectrum Hypothesis: rhythms slow at microscale during seizures Spatial interactions: waves Suggests microscale spatial organization What's happening dynamically at the end of the seizure? ASIDE: Critical transitions A tipping point at which the system shifts abruptly from one state to another Example: potential well change parameters until number of fixed points changes Propose: seizures terminate by crossing a tipping point Warning signs (I) Critical transitions can be preceded by dynamical signatures: Critical slowing downstream: Near the transition, the system becomes increasingly slow in recovering from small pertubations. Far from tipping point – move back to position quickly Close to tipping point – move back to position more slowly Flickering: The system moves back and forth between two alternative attractors just before the tipping point. Small kicks – stays in same position Big kicks – go back to a different tipping point December 7, 2012: How the Brain Thinks – Putting the Pieces Together Basic Common Principles Receptive Fields Internal unit of external world, gradually reconstructed Representation of External World Streams of Processing Receptive Fields Retina: Photoreceptors (rods and cones) connect to bipolar/ganglion cells many photoreceptors connect to fewer bipolar/ganglion cells that connect to fewer V1 cells Primary Visual Cortex: simple/complex cells sees a straight line Secondary Visual cortex: shape Tertiary Visual Cortex: form and color Unimodal Association Cortex: whole objects (inferotemporal cortex) Visual processing of faces occurs in ventral stream – more objects dorsal stream has more of a “map” Unimodal Association Cortices Whole objects (vision) + voice (audition) Multimodal Association Cortex: Assign meaning behind information – put modalities together Example: Voice is associated with face Relation Memory (context)
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Declarative: episodic memory What you were doing Where you were When it was happening Streams of Processing Ventral Stream Object Recognition (faces, houses, animals, etc...) Perceptual Constancy Allocentric space = “body independent” space (cardinal directions) Relationships between objects Dorsal stream Maps of the external world Representation of External World Allocentric space: what defines a space? What is a room?
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