Editing Human brain (section)

====Cerebrum====
{{Main|Cerebrum|Cerebral cortex}}
[[File:Gray726.png|thumb|Major gyri and sulci on the lateral surface of the cortex]]
[[File:Gehirn, medial - Lobi en.svg|thumb|Lobes of the brain]]

The cerebrum is the largest part of the brain and is divided into nearly [[Symmetry in biology#Bilateral symmetry|symmetrical]] left and right [[cerebral hemisphere|hemisphere]]s by a deep groove, the [[longitudinal fissure]].<ref name="Davey">{{cite book |author=Davey, G. |title=Applied Psychology |isbn=978-1-4443-3121-9 |publisher=[[John Wiley & Sons]] |year=2011 |page=153 |url=https://books.google.com/books?id=K1qq1SsgoxUC&pg=PA153}}</ref> Asymmetry between the lobes is noted as a [[Paleoneurobiology#Asymmetry|petalia]].<ref>{{cite journal|pmid=30601110|year=2019|last1=Arsava|first1=E. Y.|title=Occipital petalia as a predictive imaging sign for transverse sinus dominance|journal=Neurological Research|volume=41|issue=4|pages=306–311|last2=Arsava|first2=E. M.|last3=Oguz|first3=K. K.|last4=Topcuoglu|first4=M. A.|doi=10.1080/01616412.2018.1560643|s2cid=58546404}}</ref> The hemispheres are connected by five [[Commissural fiber#Structure|commissures]] that span the longitudinal fissure, the largest of these is the [[corpus callosum]].{{sfn|Gray's Anatomy|2008|pp=227-9}}
Each hemisphere is conventionally divided into four main [[lobes of the brain|lobes]]; the [[frontal lobe]], [[parietal lobe]], [[temporal lobe]], and [[occipital lobe]], named according to the [[skull |skull bones]] that overlie them.{{sfn|Gray's Anatomy|2008|pp=335-7}} Each lobe is associated with one or two specialised functions though there is some functional overlap between them.<ref name=Ackerman/> The surface of the brain is [[gyrification|folded]] into ridges ([[gyrus|gyri]]) and grooves ([[sulcus (neuroanatomy)|sulci]]), many of which are named, usually according to their position, such as the [[frontal gyrus]] of the frontal lobe or the [[central sulcus]] separating the central regions of the hemispheres. There are many small variations in the secondary and tertiary folds.{{sfn|Larsen|2001|pp=455–456}}

The outer part of the cerebrum is the [[cerebral cortex]], made up of [[grey matter]] arranged in layers. It is {{convert|2 |to |4 |mm}} thick, and deeply folded to give a convoluted appearance.<ref>{{cite book |last=Kandel |first=E.R. |author2=Schwartz, J.H. |author3=Jessel T.M. |title=Principles of Neural Science |year=2000 |publisher=McGraw-Hill Professional |isbn=978-0-8385-7701-1 |page=[https://archive.org/details/isbn_9780838577011/page/324 324] |url=https://archive.org/details/isbn_9780838577011/page/324 }}</ref> Beneath the cortex is the cerebral [[white matter]]. The largest part of the cerebral cortex is the [[neocortex]], which has six neuronal layers. The rest of the cortex is of [[allocortex]], which has three or four layers.{{sfn|Gray's Anatomy|2008|pp=227–9}}

The cortex is [[brain mapping|mapped]] by divisions into about fifty different functional areas known as [[Brodmann's areas]]. These areas are distinctly different when [[Histology|seen under a microscope]].{{sfn|Guyton & Hall|2011|p=574}} The cortex is divided into two main functional areas – a [[motor cortex]] and a [[sensory cortex]].{{sfn|Guyton & Hall|2011|p=667}} The [[primary motor cortex]], which sends axons down to [[motor neuron]]s in the brainstem and spinal cord, occupies the rear portion of the frontal lobe, directly in front of the somatosensory area. The [[primary sensory areas]] receive signals from the [[sensory nerve]]s and [[nerve tract|tracts]] by way of [[Thalamus#Thalamic nuclei|relay nuclei]] in the [[thalamus]]. Primary sensory areas include the [[visual cortex]] of the [[occipital lobe]], the [[auditory cortex]] in parts of the [[temporal lobe]] and [[insular cortex]], and the [[somatosensory cortex]] in the [[parietal lobe]]. The remaining parts of the cortex are called the [[association areas]]. These areas receive input from the sensory areas and lower parts of the brain and are involved in the complex [[cognition|cognitive processes]] of [[perception]], [[thought]], and [[decision-making]].<ref>Principles of Anatomy and Physiology 12th Edition – Tortora, p. 519.</ref> The main functions of the frontal lobe are to [[Attentional control|control attention]], abstract thinking, behaviour, problem-solving tasks, and physical reactions and personality.<ref name="Freberg">{{cite book |author=Freberg, L. |title=Discovering Biological Psychology |publisher=[[Cengage Learning]] |year=2009 |pages=44–46 |isbn=978-0-547-17779-3 |url=https://books.google.com/books?id=-zyTMXAjzQsC&pg=PA44}}</ref><ref name="Kolb">{{cite book |last1=Kolb |first1=B. |last2=Whishaw |first2=I. |title=Fundamentals of Human Neuropsychology |publisher=[[Macmillan Publishers|Macmillan]] |year=2009 |pages=73–75 |isbn=978-0-7167-9586-5 |url=https://books.google.com/books?id=z0DThNQqdL4C&pg=PA73}}</ref> The occipital lobe is the smallest lobe; its main functions are visual reception, visual-spatial processing, movement, and [[Color vision#Color in the human brain|colour recognition]].<ref name="Freberg"/><ref name="Kolb"/> There is a smaller occipital lobule in the lobe known as the [[cuneus]]. The temporal lobe controls [[Echoic memory|auditory]] and [[visual memory|visual memories]], [[Language processing in the brain|language]], and some hearing and speech.<ref name="Freberg"/>

[[File:Visible Human head slice.jpg|thumb|upright|Cortical folds and white matter in horizontal bisection of head]]

<!--Ventricles and subcortical detail is here.-->The cerebrum contains the [[ventricular system|ventricles]] where the cerebrospinal fluid is produced and circulated. Below the corpus callosum is the [[septum pellucidum]], a membrane that separates the [[lateral ventricles]]. Beneath the lateral ventricles is the [[thalamus]] and to the front and below is the [[hypothalamus]]. The hypothalamus leads on to the [[pituitary gland]]. At the back of the thalamus is the brainstem.{{sfn|Pocock|2006|p=64}}

The [[basal ganglia]], also called basal nuclei, are a set of structures deep within the hemispheres involved in behaviour and movement regulation.{{sfn|Purves|2012|p=399}} The largest component is the [[striatum]], others are the [[globus pallidus]], the [[substantia nigra]] and the [[subthalamic nucleus]].{{sfn|Purves|2012|p=399}} The striatum is divided into a ventral striatum, and dorsal striatum, subdivisions that are based upon function and connections. The ventral striatum consists of the [[nucleus accumbens]] and the [[olfactory tubercle]] whereas the dorsal striatum consists of the [[caudate nucleus]] and the [[putamen]]. The putamen and the globus pallidus lie separated from the lateral ventricles and thalamus by the [[internal capsule]], whereas the caudate nucleus stretches around and abuts the lateral ventricles on their outer sides.{{sfn|Gray's Anatomy|2008|pp=325-6}} At the deepest part of the [[lateral sulcus]] between the [[insular cortex]] and the striatum is a thin neuronal sheet called the [[claustrum]].<ref name="Goll">{{cite journal |last1=Goll |first1=Y. |last2=Atlan |first2=G. |last3=Citri |first3=A. |title=Attention: the claustrum |journal=Trends in Neurosciences |date=August 2015 |volume=38 |issue=8 |pages=486–95 |doi=10.1016/j.tins.2015.05.006 |pmid=26116988|s2cid=38353825 }}</ref>

Below and in front of the striatum are a number of [[basal forebrain]] structures. These include the [[nucleus basalis]], [[diagonal band of Broca]], [[substantia innominata]], and the [[medial septal nucleus]]. These structures are important in producing the [[neurotransmitter]], [[acetylcholine]], which is then distributed widely throughout the brain. The basal forebrain, in particular the nucleus basalis, is considered to be the major [[cholinergic]] output of the central nervous system to the striatum and neocortex.<ref name="Goard">{{cite journal |last1=Goard |first1=M. |last2=Dan |first2=Y. |title=Basal forebrain activation enhances cortical coding of natural scenes |journal=Nature Neuroscience |date=October 4, 2009 |volume=12 |issue=11 |pages=1444–1449 |doi=10.1038/nn.2402|pmid=19801988 |pmc=3576925 }}</ref>