Cells andcircuits contributing tofunctional properties in areaViofmacaque monkeycerebral cortex: bases for neuroanatomicall y realistic models

Anatomical andphysiological dataobtained frominvestigations ofareaVIofthemacaque monkeyvisual cerebral cortex havebeenusedin3models outlining possible circuitry underlying functional properties of theregion. The3models use, respectively, afully implemented computer neural network, amathematical formulation ofinteractions inadescriptive modelofanatomical circuitry andapurely descriptive account of circuitry that could underlie particular functions. The1st2models involve aspartoftheir design an interpolation principle whereafferents ofopposite physiological property establish spatially offset but adjacent terminal fields andthepostsynaptic neurons' dendrites haveacontinuum ofdifferent degrees of overlap into the2afferent pools andtherefore different synaptic weights fromthe2afferents; this creates a functional andspatial gradient ofresponse properties inthepostsynaptic neurons between theproperties of thedifferent sets ofafferents. The3rdmodelexamines lateral excitatory andinhibitory interactions insuch gradients. Model1addresses thetransformation ofdistinct thalamic axonproperties toagradient of response properties inpostsynaptic spiny stellate neurons inlayer 4CofVI.Model2proposes circuitry producing orientation specificity inVIthatbegins bygenerating specificity ofresponses toorthogonal orientations; this isachieved bymeansoforthogonally oriented lateral axonprojections madebythelayer 4Cspiny stellate neurons; this isfollowed bygeneration ofafull cycle oforientation specificities bymeans ofpyramidal neuron dendritic overlap across spatially separated fields ofspiny stellate neuron axons responding preferentially toorthogonal orientations. Model3describes acircuitry toexplain inhibitory and facilitatory interactions observed tooccur insingle unit responses whentheclassical receptive field is stimulated concurrently withthesurround region. Alltheproposed models makepredictions that canbe tested byfurther anatomical andphysiological experiments inthereal visual cortex.