In the Light of Evolution Volume VI: Brain and Behavior (2013) / Chapter Skim
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7 Evolution of Columns, Modules, and Domains in the Neocortex of Primates--Jon H. Kaas
7 Evolution of Columns, Modules, and Domains in the Neocortex of Primates--Jon H. Kaas
Pages 113-126
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From page 113... ...
Larger regions of posterior parietal cortex and frontal motor cortex are parts of networks devoted to producing different sequences of movements. We distinguish these larger functionally distinct regions as domains.
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From page 114... ...
. As a result, neurons in narrow vertical arrays share many response properties, especially the location of the receptor fields of neurons on the sensory receptor surface.
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From page 115... ...
. Minicolumns are thought to be 30–50 μm in diameter, although functional boundaries between them are not likely to be sharp owing to the spread of apical dendrites of pyramidal cells and the extents of axon arbors of cortical neurons and subcortical activating inputs.
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From page 116... ...
introduced the concept of cortical columns after reporting that recordings along microelectrode trajectories tangential to the surface of somatosensory cortex encountered short sequences of neurons that responded either to light touch on the skin (superficial skin receptors) or touch with pressure (deep receptors)
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From page 117... ...
. Although the CO-dense stripes are not consistently distinguishable as thick or thin, they can be identified by functional differences, with neurons in the thick stripes sensitive to binocular disparities and stimulus orientation, the neurons in the thin stripes sensitive to luminance and color, and neurons
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From page 118... ...
. Groups of neurons most sensitive to one stimulus orientation or another can be selectively activated, the activity pattern optically imaged, and regions of cortex sensitive to different orientations color coded to produce colorful illustrations of arrays of orientation "columns." These "columns" differ from classic columns in that they have no borders because the orientations of stimuli change continuously without disruption.
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From page 119... ...
Thus, the extrastriate hypercolumns for stimulus orientation may have emerged with the first primates. Other proposed modules of V2 in primates include subregions of thin stripes selective for different hues (Xiao et al., 2003; Roe, 2004)
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From page 120... ...
. In cortex, the ocular dominance "columns" in primary visual cortex of primates fall into the category of modules based on disruptions of the sensory surface, because the retina of the two eyes have independent activity patterns prenatally.
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From page 121... ...
in a flat surface view of primary visual cortex (V1) of an Old World macaque monkey as reflected by distribution of terminations of lateral geniculate axons related to each eye in cortical layer 4.
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From page 122... ...
Domains: Larger Functional Divisions of Cortical Areas Primary motor cortex and dorsal and ventral premotor areas are widely recognized as valid cortical areas, and each of these areas has a somatotopic representation of small movements of body parts that are revealed by brief trains of near-threshold pulses of electrical current. However, cortical motor areas representing major body parts, such as the forelimb, have a locally fractured somatotopy so that different movement zones, roughly the size of minicolumns, are mixed and repeated (Fig.
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From page 123... ...
Functionally matched domains for at least some of the complex movement patterns of primary motor cortex also exist in premotor cortex and in posterior parietal cortex. The domains in posterior parietal cortex may be parts of larger cortical areas.
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From page 124... ...
The projections from each of these eyes respond to molecular signals that tend to produce the same retinotopic pattern in the optic tectum, but local groups of tectal neurons favor inputs from one eye or the other. The result is that the afferents from the two eyes form alternating bands or stripes that resemble the ocular dominance bands in cats and anthropoid primates.
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From page 125... ...
Columns, Modules, and Domains in the Neocortex of Primates / 125 question. Instead, we might ask, what else is achieved in neural tissue by the mix of activity-dependent and position-dependent factors that select and group synaptic contacts when these factors coexist at particular developmental times?
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