Ahissar, Hochstein (1997) Nature Task difficulty and specificity of perceptual learning 1 st third 2nd third Final session Task difficulty Stimulus-to-mask onset asynchrony

Easy task: Learning was general, Complete transfer when swapping -> position non-specific

Classical view of visual hierarchy: 1.Complexity of receptive field - hierarchical 2.Parallel stream – dorsal vs ventral 3.Learning (experience)-, attention (context)- dependent processing (feedback) only at higher areas, but recently down to V1

Rapid, generalized perception “ vision at a glance ” Slow detailed perception “ vision with scrutiny ” Automatic, implicit Categorical scene interpretation : pop-out Conscious, attentive Attention to details Learning effect transferCondition-specific Feedforward processing Hierarchical Feedback processing Reverse hierarchical Reverse Hierarchy Theory of Visual Perception Two modes of perception Reverse hierarchy theory 1 2 3

Common view: Vision at a glance – effortless simple feature detection - low-level mechanism Vision with scrutiny – high-level Pop-out for complex feature (shading, etc) challenge this idea Reverse Hierarchy Theory: Vision at a glance – initial, crude, global percept, e.g., pop-out – high-level cortical mechanism - early spread attention – large receptive field Vision with scrutiny – focused attention, low-level - when focused attention, inattentional blindness

Early spread attention, high cortical level determination of initial conscious perception

Change blindness Initial conscious perception acquire gist of scene. Later focused attention grasps low-level detail. Vision at a glance vs vision w/ scrutiny

Pop-out for complex features Problem: what is high and low level?

Problems Reverse Hierarchy Theory: 1.Hierarchy is poorly defined from connection pattern. Low-level vs high-level Pop-out with shading may be still low-level. 2.Sharp tuning for feature/space is not necessarily mean superior discrimination. See population coding. 3. Attention effects with large receptive fields - Desimone

by M. Sereno Perception – parallel processing

Two streams of visual processing

Neural activity in early visual cortex reflects behavioral experience and higher-order perceptual saliency Nature Neuroscience (2002)

Top-down reentry of later involvement of low-level area