The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of allocortex. It is separated into two cortices, by the longitudinal fissure that divides the cerebrum into the left and right cerebral hemispheres. The two hemispheres are joined beneath the cortex by the corpus callosum. The cerebral cortex is the largest site of neural integration in the central nervous system. It plays a key role in attention, perception, awareness, thought, memory, language, and consciousness. The cerebral cortex is part of the brain responsible for cognition.
The thalamus is a large mass of gray matter located in the dorsal part of the diencephalon. Nerve fibers project out of the thalamus to the cerebral cortex in all directions, allowing hub-like exchanges of information. It has several functions, such as the relaying of sensory signals, including motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.
In neuroanatomy, the lateral geniculate nucleus is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve. There are two LGNs, one on the left and another on the right side of the thalamus. In humans, both LGNs have six layers of neurons alternating with optic fibers.
The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.
The dorsal column–medial lemniscus pathway (DCML) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints. It transmits information from the body to the primary somatosensory cortex in the postcentral gyrus of the parietal lobe of the brain. The pathway receives information from sensory receptors throughout the body, and carries this in nerve tracts in the white matter of the dorsal column of the spinal cord to the medulla, where it is continued in the medial lemniscus, on to the thalamus and relayed from there through the internal capsule and transmitted to the somatosensory cortex. The name dorsal-column medial lemniscus comes from the two structures that carry the sensory information: the dorsal columns of the spinal cord, and the medial lemniscus in the brainstem.
The pulvinar nuclei or nuclei of the pulvinar are the nuclei located in the thalamus. As a group they make up the collection called the pulvinar of the thalamus, usually just called the pulvinar.
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. The reticular formation includes ascending pathways to the cortex in the ascending reticular activating system (ARAS) and descending pathways to the spinal cord via the reticulospinal tracts.
In neuroanatomy, thalamocortical radiations also known as thalamocortical fibres, are the efferent fibres that project from the thalamus to distinct areas of the cerebral cortex. They form fibre bundles that emerge from the lateral surface of the thalamus.
The dentate nucleus is a cluster of neurons, or nerve cells, in the central nervous system that has a dentate – tooth-like or serrated – edge. It is located within the deep white matter of each cerebellar hemisphere, and it is the largest single structure linking the cerebellum to the rest of the brain. It is the largest and most lateral, or farthest from the midline, of the four pairs of deep cerebellar nuclei, the others being the globose and emboliform nuclei, which together are referred to as the interposed nucleus, and the fastigial nucleus. The dentate nucleus is responsible for the planning, initiation and control of voluntary movements. The dorsal region of the dentate nucleus contains output channels involved in motor function, which is the movement of skeletal muscle, while the ventral region contains output channels involved in nonmotor function, such as conscious thought and visuospatial function.
The medial geniculate nucleus (MGN) or medial geniculate body (MGB) is part of the auditory thalamus and represents the thalamic relay between the inferior colliculus (IC) and the auditory cortex (AC). It is made up of a number of sub-nuclei that are distinguished by their neuronal morphology and density, by their afferent and efferent connections, and by the coding properties of their neurons. It is thought that the MGN influences the direction and maintenance of attention.
The septal area, consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum.
The zona incerta (ZI) is a horizontally elongated region of gray matter in the subthalamus below the thalamus. Its connections project extensively over the brain from the cerebral cortex down into the spinal cord.
The basal ganglia form a major brain system in all species of vertebrates, but in primates there are special features that justify a separate consideration. As in other vertebrates, the primate basal ganglia can be divided into striatal, pallidal, nigral, and subthalamic components. In primates, however, there are two pallidal subdivisions called the external globus pallidus (GPe) and internal globus pallidus (GPi). Also in primates, the dorsal striatum is divided by a large tract called the internal capsule into two masses named the caudate nucleus and the putamen—in most other species no such division exists, and only the striatum as a whole is recognized. Beyond this, there is a complex circuitry of connections between the striatum and cortex that is specific to primates. This complexity reflects the difference in functioning of different cortical areas in the primate brain.
The amygdalofugal pathway is one of the three major efferent pathways of the amygdala, meaning that it is one of the three principal pathways by which fibers leave the amygdala. It leads from the basolateral nucleus and central nucleus of the amygdala. The amygdala is a limbic structure in the medial temporal lobe of the brain. The other main efferent pathways from the amygdala are the stria terminalis and anterior commissure.
The mammillothalamic tract arises from cells in both the medial and lateral nuclei of the mammillary body and by fibers that are directly continued from the fornix.
The isothalamus is a division used by some researchers in describing the thalamus.
Synaptic gating is the ability of neural circuits to gate inputs by either suppressing or facilitating specific synaptic activity. Selective inhibition of certain synapses has been studied thoroughly, and recent studies have supported the existence of permissively gated synaptic transmission. In general, synaptic gating involves a mechanism of central control over neuronal output. It includes a sort of gatekeeper neuron, which has the ability to influence transmission of information to selected targets independently of the parts of the synapse upon which it exerts its action.
The trisynaptic circuit, or trisynaptic loop is a relay of synaptic transmission in the hippocampus. The circuit was initially described by the neuroanatomist Santiago Ramon y Cajal, in the early twentieth century, using the Golgi staining method. After the discovery of the trisynaptic circuit, a series of research has been conducted to determine the mechanisms driving this circuit. Today, research is focused on how this loop interacts with other parts of the brain, and how it influences human physiology and behaviour. For example, it has been shown that disruptions within the trisynaptic circuit leads to behavioural changes in rodent and feline models.
The parabrachial nuclei, also known as the parabrachial complex, are a group of nuclei in the dorsolateral pons that surrounds the superior cerebellar peduncle as it enters the brainstem from the cerebellum. They are named from the Latin term for the superior cerebellar peduncle, the brachium conjunctivum. In the human brain, the expansion of the superior cerebellar peduncle expands the parabrachial nuclei, which form a thin strip of grey matter over most of the peduncle. The parabrachial nuclei are typically divided along the lines suggested by Baxter and Olszewski in humans, into a medial parabrachial nucleus and lateral parabrachial nucleus. These have in turn been subdivided into a dozen subnuclei: the superior, dorsal, ventral, internal, external and extreme lateral subnuclei; the lateral crescent and subparabrachial nucleus along the ventrolateral margin of the lateral parabrachial complex; and the medial and external medial subnuclei
