Chris J. Tinsley

Duncan

Funahashi

Liang

Frontiers in Systems Neuroscience

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Editorial: Structural and Functional Organisation of the Prefrontal Cortex

Tinsley, CJ

Nottingham Trent Institutional Repository (IRep)

EDITORIALpublished: 09 November 2016doi: 10.3389/fnsys.2016.00087Frontiers in Systems Neuroscience | www.frontiersin.org 1 November 2016 | Volume 10 | Article 87Edited and reviewed by:Maria V. Sanchez-Vives,Consorci Institut D’InvestigacionsBiomediques August Pi I Sunyer,Spain*Correspondence:Chris J. Tinsleychris.tinsley@ntu.ac.ukReceived: 30 June 2016Accepted: 26 October 2016Published: 09 November 2016Citation:Tinsley CJ (2016) Editorial: Structuraland Functional Organisation of thePrefrontal Cortex.Front. Syst. Neurosci. 10:87.doi: 10.3389/fnsys.2016.00087Editorial: Structural and FunctionalOrganisation of the Prefrontal CortexChris J. Tinsley*School of Science and Technology, Nottingham Trent University, Nottingham, UKKeywords: prefrontal cortex, structure, cortical function, cognition, connectivityThe Editorial on the Research TopicStructural and Functional Organisation of the Prefrontal CortexPrefrontal cortex (PFC) has long been known to be a region of the brain crucially important forcognitive processes. Major progress has been made in understanding the functions of this part ofthe brain however when it comes to brain organization there are still unanswered questions. Inparticular, if we compare known prefrontal cortex organization to that seen in sensory cortices, itis not currently clear whether PFC organization is essentially the same or different. This researchtopic focuses on the structural and functional organization of the prefrontal cortex in rodents andprimates and makes a contribution to current research and debate within this field of neuroscience.In the articles by Bedwell et al.; Bedwell et al., neuroanatomical tracers were employed toinvestigate PFC cortical connections. These studies illuminate a connectional feature common toPFC and other cortical regions: topological/topographical organization of connections. In addition,these studies provided evidence at a fine microscopic resolution for both reciprocal and non-reciprocal PFC connections. The finding of fine-scale non-reciprocity is unexpected, especiallywhen one considers that other cortical regions (such as sensory cortices) are well-known for theirdetailed reciprocity. The study by Nguyen et al. uses electrophysiological approaches to exploreimportant functional questions about the anatomical connections between PFC and primary visualcortex. Such links may be important for mediating attentional and other top-down signals. Theexperiments provided evidence for a functional link between infralimbic and prelimbic cortexand V1, but they found that this link was not mediated strongly via basalo-cortical cholinergicprojections. Another feature of anatomical organization is the columnar organization present inPFC and in other regions of the mammalian cerebral cortex. Several previous anatomical studieshave provided evidence for columnar or modular organization within PFC, in this topic Opris et al.investigated the functional aspects of this organization during exposure to cocaine. The results helpto show how cocaine interrupts complex cognitive processing within columns and layers of themonkey prefrontal cortex.Prefrontal cortex is perhaps best well-known for its role in cognitive function. The classicexperiments of Funahashi and colleagues in the late 1980s and early 1990s (Funahashi et al., 1989,1993) helped to define a role for the primate dorsolateral prefrontal cortex in spatial workingmemory processes. These studies were ground-breaking in terms of their contribution to ourunderstanding of memory processes but also to the organization of neuronal responses within thePFC. In the review paper by Funahashi in this research topic, the interpretation of delay periodactivity in relation to visual memory tasks in primates is explored. The article presents previous andhistorical findings on the subject and discusses different interpretations of these important results.Another important function ascribed to the PFC is fear processing. PFC is known to have stronganatomical links with the amygdala, which is an important structure for mediating fear responses.This research topic features two articles which indicate that PFC plays a role in the processingTinsley Prefrontal Cortex Structure and Functionof fear-related stimuli (Sharpe and Kilcross; Shiba et al.). Sharpeand Killcross investigated how cues modulate conditioned fearusing inactivation of the rat prelimbic cortex. The authors foundevidence for a prelimbic cortex role in the processing of thesebehavioral cues so that responses can be modulated accordingly.Shiba et al. explored how PFC lesions alter innate fear in theprimate brain. Here the authors found that lesions to eitherventrolateral PFC and orbitofrontal PFC caused heightened fearin response to predatory stimuli.Some of the most sophisticated brain functions are now beingallocated to the PFC. In a review of human neuroimaging studiesJeon discusses the progress made in understanding hierarchicalprocessing within Prefrontal cortex. This review argues forimportance of a small region of PFC in this high level brainfunction, namely Brodmann’s area 44.Another crucial cognitive function is attention and thereis substantial and increasing evidence for the role of PFC inattention. In the imaging case study by Japee et al. the role ofthe right middle frontal gyrus (MFG) in reorienting attentionwas investigated. In this study a patient with MFG resection wascompared to healthy volunteers and the results showed that, incertain tasks, the patient found it difficult in switching to top-down attentional control. In the review article by Cassaday et al.,PFC studies involving attention are discussed in relation to themethodology employed and the results from different regions ofPFC. This article covers studies of both rodent and primate PFCand outlines the evidence for distinct PFC regions having a role inboth attention and executive processes. Remaining on the subjectof methodology is the field of optogenetics which has become anincreasingly important approach used in the arena of cognitiveneuroscience. In the review article by Riga et al., the subject ofhow optogenetic tools have been used to study the prefrontalcortex in animal models is explored and discussed. The articlehighlights how these tools have been used to effectively study thefunctional circuitry of PFC in rodents. Optogenetics continuesto be developed rapidly and successfully combined with existingtechniques, such as fMRI (Liang et al., 2015).This research topic provides a snapshot of current PFCresearch and highlights some of the progress made inunderstanding PFC anatomy and function. Many of thesestudies also point to the important role of PFC microcircuitryin cognitive processing. Clearly there are still important andfundamental gaps in our understanding of PFC structure andfunction. There are many similarities between the anatomicalorganization of PFC and other cortical regions yet functionallyPFC may be unique, possibly having a multifunctional rolewhich is difficult to define (Duncan, 2001). We still do notunderstand in detail how information flows ormediates cognitiveprocessing in this crucial region however the new molecularbiology techniques are helping scientists to address thisquestion.AUTHOR CONTRIBUTIONSThe author confirms being the sole contributor of this work andapproved it for publication.REFERENCESDuncan, J. (2001). An adaptive coding model of neural function inprefrontal cortex. Nat. Rev. Neurosci. 2, 820–829. doi: 10.1038/35097557Funahashi, S., Bruce, C. J., and Goldman-Rakic, P. S. (1993). Dorsolateralprefrontal lesions and oculomotor delayed-response performance: evidence formnemonic “scotomas.” J. Neurosci. 13, 1479–1497.Funahashi, S., Bruce, C. J., and Goldman-Rakic, P. S. (1989). Mnemonic coding ofvisual space in the monkey’s dorsolateral prefrontal cortex. J. Neurophysiol. 61,331–349.Liang, Z., Watson, G. D., Alloway, K. D., Lee, G., Neuberger, T., and Zhang,N. (2015). Mapping the functional network of medial prefrontal cortex bycombining optogenetics and fMRI in awake rats.Neuroimage 117, 114–123. doi:10.1016/j.neuroimage.2015.05.036Conflict of Interest Statement: The author declares that the research wasconducted in the absence of any commercial or financial relationships that couldbe construed as a potential conflict of interest.Copyright © 2016 Tinsley. This is an open-access article distributed under the termsof the Creative Commons Attribution License (CC BY). The use, distribution orreproduction in other forums is permitted, provided the original author(s) or licensorare credited and that the original publication in this journal is cited, in accordancewith accepted academic practice. No use, distribution or reproduction is permittedwhich does not comply with these terms.Frontiers in Systems Neuroscience | www.frontiersin.org 2 November 2016 | Volume 10 | Article 87

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EDITORIAL
published: 09 November 2016
doi: 10.3389/fnsys.2016.00087
Frontiers in Systems Neuroscience | www.frontiersin.org 1 November 2016 | Volume 10 | Article 87
Edited and reviewed by:
Maria V. Sanchez-Vives,
Consorci Institut D’Investigacions
Biomediques August Pi I Sunyer,
Spain
*Correspondence:
Chris J. Tinsley
chris.tinsley@ntu.ac.uk
Received: 30 June 2016
Accepted: 26 October 2016
Published: 09 November 2016
Citation:
Tinsley CJ (2016) Editorial: Structural
and Functional Organisation of the
Prefrontal Cortex.
Front. Syst. Neurosci. 10:87.
doi: 10.3389/fnsys.2016.00087
Editorial: Structural and Functional
Organisation of the Prefrontal Cortex
Chris J. Tinsley*
School of Science and Technology, Nottingham Trent University, Nottingham, UK
Keywords: prefrontal cortex, structure, cortical function, cognition, connectivity
The Editorial on the Research Topic
Structural and Functional Organisation of the Prefrontal Cortex
Prefrontal cortex (PFC) has long been known to be a region of the brain crucially important for
cognitive processes. Major progress has been made in understanding the functions of this part of
the brain however when it comes to brain organization there are still unanswered questions. In
particular, if we compare known prefrontal cortex organization to that seen in sensory cortices, it
is not currently clear whether PFC organization is essentially the same or different. This research
topic focuses on the structural and functional organization of the prefrontal cortex in rodents and
primates and makes a contribution to current research and debate within this field of neuroscience.
In the articles by Bedwell et al.; Bedwell et al., neuroanatomical tracers were employed to
investigate PFC cortical connections. These studies illuminate a connectional feature common to
PFC and other cortical regions: topological/topographical organization of connections. In addition,
these studies provided evidence at a fine microscopic resolution for both reciprocal and non-
reciprocal PFC connections. The finding of fine-scale non-reciprocity is unexpected, especially
when one considers that other cortical regions (such as sensory cortices) are well-known for their
detailed reciprocity. The study by Nguyen et al. uses electrophysiological approaches to explore
important functional questions about the anatomical connections between PFC and primary visual
cortex. Such links may be important for mediating attentional and other top-down signals. The
experiments provided evidence for a functional link between infralimbic and prelimbic cortex
and V1, but they found that this link was not mediated strongly via basalo-cortical cholinergic
projections. Another feature of anatomical organization is the columnar organization present in
PFC and in other regions of the mammalian cerebral cortex. Several previous anatomical studies
have provided evidence for columnar or modular organization within PFC, in this topic Opris et al.
investigated the functional aspects of this organization during exposure to cocaine. The results help
to show how cocaine interrupts complex cognitive processing within columns and layers of the
monkey prefrontal cortex.
Prefrontal cortex is perhaps best well-known for its role in cognitive function. The classic
experiments of Funahashi and colleagues in the late 1980s and early 1990s (Funahashi et al., 1989,
1993) helped to define a role for the primate dorsolateral prefrontal cortex in spatial working
memory processes. These studies were ground-breaking in terms of their contribution to our
understanding of memory processes but also to the organization of neuronal responses within the
PFC. In the review paper by Funahashi in this research topic, the interpretation of delay period
activity in relation to visual memory tasks in primates is explored. The article presents previous and
historical findings on the subject and discusses different interpretations of these important results.
Another important function ascribed to the PFC is fear processing. PFC is known to have strong
anatomical links with the amygdala, which is an important structure for mediating fear responses.
This research topic features two articles which indicate that PFC plays a role in the processing
Tinsley Prefrontal Cortex Structure and Function
of fear-related stimuli (Sharpe and Kilcross; Shiba et al.). Sharpe
and Killcross investigated how cues modulate conditioned fear
using inactivation of the rat prelimbic cortex. The authors found
evidence for a prelimbic cortex role in the processing of these
behavioral cues so that responses can be modulated accordingly.
Shiba et al. explored how PFC lesions alter innate fear in the
primate brain. Here the authors found that lesions to either
ventrolateral PFC and orbitofrontal PFC caused heightened fear
in response to predatory stimuli.
Some of the most sophisticated brain functions are now being
allocated to the PFC. In a review of human neuroimaging studies
Jeon discusses the progress made in understanding hierarchical
processing within Prefrontal cortex. This review argues for
importance of a small region of PFC in this high level brain
function, namely Brodmann’s area 44.
Another crucial cognitive function is attention and there
is substantial and increasing evidence for the role of PFC in
attention. In the imaging case study by Japee et al. the role of
the right middle frontal gyrus (MFG) in reorienting attention
was investigated. In this study a patient with MFG resection was
compared to healthy volunteers and the results showed that, in
certain tasks, the patient found it difficult in switching to top-
down attentional control. In the review article by Cassaday et al.,
PFC studies involving attention are discussed in relation to the
methodology employed and the results from different regions of
PFC. This article covers studies of both rodent and primate PFC
and outlines the evidence for distinct PFC regions having a role in
both attention and executive processes. Remaining on the subject
of methodology is the field of optogenetics which has become an
increasingly important approach used in the arena of cognitive
neuroscience. In the review article by Riga et al., the subject of
how optogenetic tools have been used to study the prefrontal
cortex in animal models is explored and discussed. The article
highlights how these tools have been used to effectively study the
functional circuitry of PFC in rodents. Optogenetics continues
to be developed rapidly and successfully combined with existing
techniques, such as fMRI (Liang et al., 2015).
This research topic provides a snapshot of current PFC
research and highlights some of the progress made in
understanding PFC anatomy and function. Many of these
studies also point to the important role of PFC microcircuitry
in cognitive processing. Clearly there are still important and
fundamental gaps in our understanding of PFC structure and
function. There are many similarities between the anatomical
organization of PFC and other cortical regions yet functionally
PFC may be unique, possibly having a multifunctional role
which is difficult to define (Duncan, 2001). We still do not
understand in detail how information flows ormediates cognitive
processing in this crucial region however the new molecular
biology techniques are helping scientists to address this
question.
AUTHOR CONTRIBUTIONS
The author confirms being the sole contributor of this work and
approved it for publication.
REFERENCES
Duncan, J. (2001). An adaptive coding model of neural function in
prefrontal cortex. Nat. Rev. Neurosci. 2, 820–829. doi: 10.1038/350
97557
Funahashi, S., Bruce, C. J., and Goldman-Rakic, P. S. (1993). Dorsolateral
prefrontal lesions and oculomotor delayed-response performance: evidence for
mnemonic “scotomas.” J. Neurosci. 13, 1479–1497.
Funahashi, S., Bruce, C. J., and Goldman-Rakic, P. S. (1989). Mnemonic coding of
visual space in the monkey’s dorsolateral prefrontal cortex. J. Neurophysiol. 61,
331–349.
Liang, Z., Watson, G. D., Alloway, K. D., Lee, G., Neuberger, T., and Zhang,
N. (2015). Mapping the functional network of medial prefrontal cortex by
combining optogenetics and fMRI in awake rats.Neuroimage 117, 114–123. doi:
10.1016/j.neuroimage.2015.05.036
Conflict of Interest Statement: The author declares that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Copyright © 2016 Tinsley. This is an open-access article distributed under the terms
of the Creative Commons Attribution License (CC BY). The use, distribution or
reproduction in other forums is permitted, provided the original author(s) or licensor
are credited and that the original publication in this journal is cited, in accordance
with accepted academic practice. No use, distribution or reproduction is permitted
which does not comply with these terms.
Frontiers in Systems Neuroscience | www.frontiersin.org 2 November 2016 | Volume 10 | Article 87


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Editorial: Structural and Functional Organisation of the Prefrontal Cortex

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