The evolution of prefrontal inputs to the cortico-pontine system: Diffusion imaging evidence from macaque monkeys and humans

Cognitive Neuroscience Laboratory, Department of Psychology, Royal Holloway University of London, UK.
Cerebral Cortex (Impact Factor: 8.67). 07/2006; 16(6):811-8. DOI: 10.1093/cercor/bhj024
Source: PubMed


The cortico-ponto-cerebellar system is one of the largest projection systems in the primate brain, but in the human brain the nature of the information processing in this system remains elusive. Determining the areas of the cerebral cortex which contribute projections to this system will allow us to better understand information processing within it. Information from the cerebral cortex is conveyed to the cerebellum by topographically arranged fibres in the cerebral peduncle - an important fibre system in which all cortical outputs spatially converge on their way to the cerebellum via the pontine nuclei. Little is known of their anatomical organization in the human brain. New in vivo diffusion imaging and probabilistic tractography methods now offer a way in which input tracts in the cerebral peduncle can be characterized in detail. Here we use these methods to contrast their organization in humans and macaque monkeys. We confirm the dominant contribution of the cortical motor areas to the macaque monkey cerebral peduncle. However, we also present novel anatomical evidence for a relatively large prefrontal contribution to the human cortico-ponto-cerebellar system in the cerebral peduncle. These findings suggest the selective evolution of prefrontal inputs to the human cortico-ponto-cerebellar system.

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    • "), a distinction also supported by their connectivity to the basal ganglia and cerebellum (Akkal et al., 2007; Lehericy et al., 2004a; Ramnani et al., 2006). Although less a focus of earlier investigations, the cortex located anterior to pre-SMA (BA 8/9) was distinguished from the pre-SMA in some studies (Lehericy et al., 2004b; Petrides and Pandya, 2007; Zhang et al., 2012). "
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    • "Current cognitive models posit that the basal ganglia (and specifically the caudate) and the cerebrocerebellar circuitry systems ''train'' the prefrontal cortex during the course of development (Antzoulatos & Miller, 2014; Koziol, Budding, & Chidekel, 2012; Koziol & Lutz, 2013). Ramnani has proposed that the cerebellum provides the cerebral cortex with the input necessary for the automation of skilled cognitive operations (Koziol, Budding, Andreasen et al., 2013; Ramnani et al., 2005). "
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    • "Most importantly, however, the finding of NCB/NCX ratios that do not decrease as the rest of brain grains neurons indicates that the relative expansion in numbers of neurons in the cerebral cortex over the rest of brain in primates and artiodactyls is matched by a similar expansion of the neuronal population in the cerebellum. This concerted addition of neurons to the cerebral cortex and cerebellum is consistent with the findings that, in primates, the cerebellum, neocortex, vestibular nuclei and relays between them exhibit concerted volumetric evolution, even after removing the effects of change in other structures (Whiting and Barton, 2003), and that increases in the volume of the prefrontal cerebral cortex are accompanied by increases in the volume of the prefrontal cortico-pontine system and prefrontal-projecting cerebellar lobules (Ramnani et al., 2006; Balsters et al., 2010). The concerted scaling of numbers of neurons in the cerebral cortex and cerebellum also agree with recent models of brain function that consider that these two structures work in conjunction (Leiner et al., 1989; Ramnani, 2006; Ito, 2008), instead of endorsing a functional preponderance of the cerebral cortex over the cerebellum. "
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