The Functional Organization and Cortical Connections of Motor Cortex in Squirrels

Cooke, Dylan F.; Padberg, Jeffrey; Zahner, Tony; Krubitzer, Leah

doi:10.1093/cercor/bhr228

Cited by 43 publications

(49 citation statements)

References 88 publications

(147 reference statements)

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“…First, the appearance and response properties of DZ in rats [Chapin and Lin, 1984] and 3a in squirrels [Slutsky et al, 2000;Cooke et al, 2011] are similar. Second, the connections of the granular zone (GZ) and DZ within S1 are substantially different.…”

Section: Mousementioning

confidence: 91%

“…We therefore proposed that this field plus the unresponsive zone (UZ) is homologous to area 3a in primates and other species [ fig. 20 , Wong and Kaas, 2008;Cooke et al, 2011]. In rats, there appears to be no field in the precise location of area 3a except for the small transitional zone (TZ) described in previous studies.…”

Section: Mousementioning

confidence: 94%

“…In recent studies in ground squirrels in our laboratory, intracortical microstimulation combined with electrophysiological recording revealed that movements of the body could be evoked from this rostral region ( fig. 22) [Cooke et al, 2011]. We therefore proposed that this field plus the unresponsive zone (UZ) is homologous to area 3a in primates and other species [ fig.…”

Section: Mousementioning

confidence: 99%

See 2 more Smart Citations

All Rodents Are Not the Same: A Modern Synthesis of Cortical Organization

Krubitzer

Campi²,

Cooke³

2011

Brain Behav Evol

126

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Rodents are a major order of mammals that is highly diverse in distribution and lifestyle. Five suborders, 34 families, and 2,277 species within this order occupy a number of different niches and vary along several lifestyle dimensions such as diel pattern (diurnal vs. nocturnal), terrain niche, and diet. For example, the terrain niche of rodents includes arboreal, aerial, terrestrial, semi-aquatic, burrowing, and rock dwelling. Not surprisingly, the behaviors associated with particular lifestyles are also highly variable and thus the neocortex, which generates these behaviors, has undergone corresponding alterations across species. Studies of cortical organization in species that vary along several dimensions such as terrain niche, diel pattern, and rearing conditions demonstrate that the size and number of cortical fields can be highly variable within this order. The internal organization of a cortical field also reflects lifestyle differences between species and exaggerates behaviorally relevant effectors such as vibrissae, teeth, or lips. Finally, at a cellular level, neuronal number and density varies for the same cortical field in different species and is even different for the same species reared in different conditions (laboratory vs. wild-caught). These very large differences across and within rodent species indicate that there is no generic rodent model. Rather, there are rodent models suited for specific questions regarding the development, function, and evolution of the neocortex.

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Section: Mousementioning

confidence: 91%

Section: Mousementioning

confidence: 94%

Section: Mousementioning

confidence: 99%

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All Rodents Are Not the Same: A Modern Synthesis of Cortical Organization

Krubitzer

Campi²,

Cooke³

2011

Brain Behav Evol

126

View full text Add to dashboard Cite

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“…Thus, they likely exist in all primates. Such domains for complex movements may also exist in motor cortex of the relatives of primates, tree shrews and rodents, where M1 also has a fractured somatotopy (78,79). However, posterior parietal cortex is no more than a narrow strip of cortex in tree shrews and rodents and is unlikely to contain a series of primate-like domains.…”

Section: Domains: Larger Functional Divisions Of Cortical Areasmentioning

confidence: 99%

Evolution of columns, modules, and domains in the neocortex of primates

Kaas

2012

Proc. Natl. Acad. Sci. U.S.A.

126

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The specialized regions of neocortex of mammals, called areas, have been divided into smaller functional units called minicolumns, columns, modules, and domains. Here we describe some of these functional subdivisions of areas in primates and suggest when they emerged in mammalian evolution. We distinguish several types of these smaller subdivisions. Minicolumns, vertical arrays of neurons that are more densely interconnected with each other than with laterally neighboring neurons, are present in all cortical areas. Classic columns are defined by a repeating pattern of two or more types of cortex distinguished by having different inputs and neurons with different response properties. Sensory stimuli that continuously vary along a stimulus dimension may activate groups of neurons that vary continuously in location, producing “columns” without specific boundaries. Other groups or columns of cortical neurons are separated by narrow septa of fibers that reflect discontinuities in the receptor sheet. 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. Columns of several types have evolved independently a number of times. Some of the columns found in primates likely emerged with the first primates, whereas others likely were present in earlier ancestors. The sizes and shapes of columns seem to depend on the balance of neuron activation patterns and molecular signals during development.

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“…Finally, when similar microstimulation parameters are used across animals, the functional organization of primary motor cortex (M1) is highly variable within many species, including mice (41) (Fig. 5A), rats (42), squirrels (43), and owl monkeys (44).…”

Section: Within-species Variabilitymentioning

confidence: 99%

Cortical evolution in mammals: The bane and beauty of phenotypic variability

Krubitzer

Seelke

2012

Proc. Natl. Acad. Sci. U.S.A.

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Evolution by natural selection, the unifying theory of all biological sciences, provides a basis for understanding how phenotypic variability is generated at all levels of organization from genes to behavior. However, it is important to distinguish what is the target of selection vs. what is transmitted across generations. Physical traits, behaviors, and the extended phenotype are all selected features of an individual, but genes that covary with different aspects of the targets of selection are inherited. Here we review the variability in cortical organization, morphology, and behavior that have been observed across species and describe similar types of variability within species. We examine sources of variability and the constraints that limit the types of changes that evolution has and can produce. Finally, we underscore the importance of how genes and genetic regulatory networks are deployed and interact within an individual, and their relationship to external, physical forces within the environment that shape the ultimate phenotype.E volution is the change in heritable, phenotypic characteristics within a population that occurs over successive generations. The notion that biological life evolves and that animal forms descend from ancient predecessors has been considered for centuries and, in fact, predates Aristotle (1). However, Charles Darwin was the first to articulate a scientific argument based on extensive observations for a theory of evolution through natural selection. Darwin's theory contains three basic tenets: individuals within a group are variable, variations are heritable, and not all individuals survive (2). Survival is based on selective advantages that particular phenotypic characteristics or behaviors confer to some individuals within a given environmental context. Although in Darwin's time our understanding of the brain was in its infancy and Mendel's Laws of Inheritance were little appreciated, Darwin's assertions regarding evolution through natural selection of adaptive traits, was, and still is, compelling.Recently our understanding of the mechanisms underlying evolution has become more sophisticated, and we appreciate that slight variations in gene sequence can be correlated with alterations of traits and behaviors within and across species. However, an important but often overlooked distinction is the difference between the targets of selection (i.e., phenotypic variations) vs. what natural selection passes on to the next generation (i.e., genes). Although genes are the heritable part of the equation and have a causal, although not always direct, link with some characteristic of the phenotype, genes are not the targets of selection. Genes are indirectly selected for because they covary with the targets of selection, and if the target of selection is adaptive, then genes or portions of the genome replicate and produce a long line of descendants. The direct target of selection is multilayered but can be thought to center around the individual and the unique phenotypic characteristics a...

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The Functional Organization and Cortical Connections of Motor Cortex in Squirrels

Cited by 43 publications

References 88 publications

All Rodents Are Not the Same: A Modern Synthesis of Cortical Organization

All Rodents Are Not the Same: A Modern Synthesis of Cortical Organization

Evolution of columns, modules, and domains in the neocortex of primates

Cortical evolution in mammals: The bane and beauty of phenotypic variability

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