Brodmann area 47
Brodmann area 47, or BA47, is part of the frontal cortex in the human brain. Curving from the lateral surface of the frontal lobe into the ventral frontal cortex, it is below areas BA10 and BA45, beside BA11. This cytoarchitectonic region most corresponds to the gyral region the orbital part of inferior frontal gyrus, although these regions are not equivalent. Pars orbitalis is not based on cytoarchitectonic distinctions, rather is defined according to gross anatomical landmarks. Despite a clear distinction, these two terms are used liberally in peer-reviewed research journals. BA47 is known as orbital area 47. In the human, on the orbital surface it surrounds the caudal portion of the orbital sulcus from which it extends laterally into the orbital part of inferior frontal gyrus. Cytoarchitectonically it is bounded caudally by the triangular area 45, medially by the prefrontal area 11 of Brodmann-1909, rostrally by the frontopolar area 10, it incorporates the region that Brodmann identified as "Area 12" in the monkey, therefore, following the suggestion of Michael Petrides, some contemporary neuroscientists refer to the region as "BA47/12".
BA47 has been implicated in the processing of syntax in oral and sign languages, musical syntax, semantic aspects of language. Brodmann area List of regions in the human brain Petrides, M. "Comparative cytoarchitectonic analysis of the human and the macaque ventrolateral prefrontal cortex and corticocortical connection patterns in the monkey". European Journal of Neuroscience. 16: 291–310. Doi:10.1046/j.1460-9568.2001.02090.x. PMID 12169111. Levitin, DJ. "Musical structure is processed in "language" areas of the brain: A possible role for Brodmann Area 47 in temporal coherence". NeuroImage. 20: 242–252. Archived from the original on 2007-04-27. For Neuroanatomy of this area visit BrainInfo
Brodmann area 8
Brodmann area 8 is one of Brodmann's cytologically defined regions of the brain. It is involved in planning complex movements. Brodmann area 8, or BA8, is part of the frontal cortex in the human brain. Situated just anterior to the premotor cortex, it includes the frontal eye fields. Damage to this area, by stroke, trauma or infection, causes tonic deviation of the eyes towards the side of the injury; this finding occurs during the first few hours of an acute event such as cerebrovascular infarct or hemorrhage. The term Brodmann area 8 refers to a cytoarchitecturally defined portion of the frontal lobe of the guenon. Located rostral to the arcuate sulcus, it was not considered by Brodmann-1909 to be topographically homologous to the intermediate frontal area 8 of the human. Distinctive features: compared to Brodmann area 6-1909, area 8 has a diffuse but present internal granular layer; the area is involved in the management of uncertainty. A functional magnetic resonance imaging study demonstrated that brodmann area 8 activation occurs when test subjects experience uncertainty, that with increasing uncertainty there is increasing activation.
An alternative interpretation is that this activation in frontal cortex encodes hope, a higher-order expectation positively correlated with uncertainty. Brodmann area List of regions in the human brain
The frontal lobe is the largest of the four major lobes of the brain in mammals, is located at the front of each hemisphere. It is separated from the parietal lobe by a groove between tissues called the central sulcus, from the temporal lobe by a deeper groove called the lateral sulcus; the most anterior rounded part of the frontal lobe is known as the frontal pole, one of the three poles of the cerebrum. The frontal lobe is covered by the frontal cortex; the frontal cortex includes the premotor cortex, the primary motor cortex – cortical parts of the motor cortex. The front part of the frontal lobe is covered by the prefrontal cortex. There are four principal gyri in the frontal lobe; the precentral gyrus, is directly anterior to the central sulcus, running parallel to it and contains the primary motor cortex, which controls voluntary movements of specific body parts. Three horizontally arranged subsections of the frontal gyrus are the superior frontal gyrus, the middle frontal gyrus, the inferior frontal gyrus.
The inferior frontal gyrus is divided into three parts – the orbital part, the triangular part, the opercular part. The frontal lobe contains most of the dopamine neurons in the cerebral cortex; the dopaminergic pathways are associated with reward, short-term memory tasks and motivation. Dopamine tends to select sensory information arriving from the thalamus to the forebrain; the frontal lobe is the largest lobe of the brain and makes up about a third of the surface area of each hemisphere. On the lateral surface of each hemisphere, the central sulcus separates the frontal lobe from the parietal lobe; the lateral sulcus separates the frontal lobe from the temporal lobe. The frontal lobe can be divided into a lateral, polar and medial part; each of these parts consists of a particular gyrus: Lateral part: lateral part of the superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus. Polar part: Transverse frontopolar gyri, frontomarginal gyrus. Orbital part: Lateral orbital gyrus, anterior orbital gyrus, posterior orbital gyrus, medial orbital gyrus, gyrus rectus.
Medial part: Medial part of the superior frontal gyrus, cingulate gyrus. The gyri are separated by sulci. E.g. the precentral gyrus is in front of the central sulcus, behind the precentral sulcus. The superior and middle frontal gyri are divided by the superior frontal sulcus; the middle and inferior frontal gyri are divided by the inferior frontal sulcus. In humans, the frontal lobe reaches full maturity around the late 20s, marking the cognitive maturity associated with adulthood. A small amount of atrophy, however, is normal in the aging person’s frontal lobe. Fjell, in 2009, studied atrophy of the brain in people aged 60–91 years; the 142 healthy participants were scanned using MRI. Their results were compared to those of 122 participants with Alzheimer's disease. A follow-up one year showed there to have been a marked volumetric decline in those with Alzheimer's and a much smaller decline in the healthy group; these findings corroborate those of Coffey, who in 1992 indicated that the frontal lobe decreases in volume 0.5%–1% per year.
The frontal lobe plays a large role in voluntary movement. It houses the primary motor cortex; the function of the frontal lobe involves the ability to project future consequences resulting from current actions. Frontal lobe functions include override and suppression of unacceptable response as well as differentiation tasks; the frontal lobe plays an important part in integrating longer non-task based memories stored across the brain. These are memories associated with emotions derived from input from the brain's limbic system; the frontal lobe modifies those emotions to fit acceptable norms. Psychological tests that measure frontal lobe function include finger tapping, the Wisconsin Card Sorting Test, measures of language and numeracy skills. Damage to the frontal lobe can result in many different consequences. Transient ischemic attacks known as mini-strokes, strokes are common causes of frontal lobe damage in older adults; these strokes and mini-strokes can occur due to the blockage of blood flow to the brain or as a result of the rupturing of an aneurysm in a cerebral artery.
Other ways in which injury can occur include head injuries such as traumatic brain injuries incurred following accidents, diagnoses such as Alzheimer's disease or Parkinson's disease, frontal lobe epilepsy. Common effects of damage to the frontal lobe are varied. Patients who have experienced frontal lobe trauma may know the appropriate response to a situation but display inappropriate responses to those same situations in "real life". Emotions that are felt may not be expressed in the face or voice. For example, someone, feeling happy would not smile, the voice would be devoid of emotion. Along the same lines, the person may exhibit excessive, unwarranted displays of emotion. Depression is common in stroke patients. Common is a loss of or decrease in motivation. Someone might not want to carry out normal daily activities and would not feel "up to it"; those who are close to the person who has experienced the damage may notice changes in behavior. This personality change is characteristic of damage to the frontal lobe and was exemplified in the case of Phineas Gage.
The frontal lobe is the same part of the brain, responsible for executive functions
Broca's area or the Broca area or is a region in the frontal lobe of the dominant hemisphere the left, of the brain with functions linked to speech production. Language processing has been linked to Broca's area since Pierre Paul Broca reported impairments in two patients, they had lost the ability to speak after injury to the posterior inferior frontal gyrus of the brain. Since the approximate region he identified has become known as Broca's area, the deficit in language production as Broca's aphasia called expressive aphasia. Broca's area is now defined in terms of the pars opercularis and pars triangularis of the inferior frontal gyrus, represented in Brodmann's cytoarchitectonic map as Brodmann area 44 and Brodmann area 45 of the dominant hemisphere. Functional magnetic resonance imaging has shown language processing to involve the third part of the inferior frontal gyrus the pars orbitalis, as well as the ventral part of BA6 and these are now included in a larger area called Broca's region.
Studies of chronic aphasia have implicated an essential role of Broca's area in various speech and language functions. Further, fMRI studies have identified activation patterns in Broca's area associated with various language tasks. However, slow destruction of the Broca's area by brain tumors can leave speech intact, suggesting its functions can shift to nearby areas in the brain. Broca's area is identified by visual inspection of the topography of the brain either by macrostructural landmarks such as sulci or by the specification of coordinates in a particular reference space; the used Talairach and Tournoux atlas projects Brodmann's cytoarchitectonic map onto a template brain. Because Brodmann's parcelation was based on subjective visual inspection of cytoarchitectonic borders and Brodmann analyzed only one hemisphere of one brain, the result is imprecise. Further, because of considerable variability across brains in terms of shape and position relative to sulcal and gyral structure, a resulting localization precision is limited.
Broca's area in the left hemisphere and its homologue in the right hemisphere are designations used to refer to the triangular part of inferior frontal gyrus and the opercular part of inferior frontal gyrus. The PTr and POp are defined by structural landmarks that only probabilistically divide the inferior frontal gyrus into anterior and posterior cytoarchitectonic areas of 45 and 44 by Brodmann's classification scheme. Area 45 receives more afferent connections from the prefrontal cortex, the superior temporal gyrus, the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor and inferior parietal regions; the differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions. Indeed, recent neuroimaging studies have shown that the PTr and Pop, corresponding to areas 45 and 44 play different functional roles in the human with respect to language comprehension and action recognition/understanding.
For a long time, it was assumed that the role of Broca's area was more devoted to language production than language comprehension. However, there is evidence to demonstrate that Broca's area plays a significant role in language comprehension. Patients with lesions in Broca's area who exhibit agrammatical speech production show inability to use syntactic information to determine the meaning of sentences. A number of neuroimaging studies have implicated an involvement of Broca's area of the pars opercularis of the left inferior frontal gyrus, during the processing of complex sentences. Further, it has been found in functional magnetic resonance imaging experiments involving ambiguous sentences result in a more activated inferior frontal gyrus. Therefore, the activity level in the inferior frontal gyrus and the level of lexical ambiguity are directly proportional to each other, because of the increased retrieval demands associated with ambiguous content. There is specialisation for particular aspects of comprehension within Broca's area.
Work by Devlin et al. showed in a repetitive transcranial magnetic stimulation study that there was an increase in reaction times when performing a semantic task under rTMS aimed at the pars triangularis. The increase in reaction times is indicative that that particular area is responsible for processing that cognitive function. Disrupting these areas via TMS disrupts computations performed in the areas leading to an increase in time needed to perform the computations. Work by Nixon et al. showed that when the pars opercularis was stimulated under rTMS there was an increase in reaction times in a phonological task. Gough et al. performed an experiment combining elements of these previous works in which both phonological and semantic tasks were performed with rTMS stimulation directed at either the anterior or the posterior part of Broca's area. The results from this experiment conclusively distinguished anatomical specialisation within Broca's area for different components of language comprehension.
Here the results showed that under rTMS stimulation: Semantic tasks only showed a decrease in reaction times when stimulation was aimed at the anterior part of Broca's area Phonological tasks showed a decrease in reaction times when stimulation was aimed at the posterior part of Broca's area (where a decrease of 6% was seen compared t
Brodmann area 6
Brodmann area 6 part of the frontal cortex in the human brain. Situated just anterior to the primary motor cortex, it is composed of the premotor cortex and, the supplementary motor area, or SMA; this large area of the frontal cortex is believed to play a role in the planning of complex, coordinated movements. Brodmann area 6 is called agranular frontal area 6 in humans because it lacks an internal granular cortical layer, it is a subdivision of the cytoarchitecturally defined precentral region of cerebral cortex. In the human brain, it is located on the portions of the precentral gyrus that are not occupied by Brodmann area 4, it extends from the cingulate sulcus on the medial aspect of the hemisphere to the lateral sulcus on the lateral aspect. It is bounded rostrally by the granular frontal region and caudally by the gigantopyramidal area 4. Brodmann area 6 is a cytoarchitecturally defined portion of the frontal lobe of the guenon. Brodmann-1909 regarded it as topographically and cytoarchitecturally homologous to the human agranular frontal area 6 and noted that, in the monkey, area 4 is larger than area 6, whereas, in the human, area 6 is larger than area 4.
Distinctive features: It is thick relative to other cortical areas. Brodmann area List of regions in the human brain Korbinian Brodmann ancil-41 at NeuroNames – agranular frontal area 6 ancil-1044 at NeuroNames – Brodmann area 6
Nociception is the sensory nervous system's response to certain harmful or harmful stimuli. In nociception, intense chemical, mechanical, or thermal stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and results in a subjective experience of pain in sentient beings. Damaging mechanical and chemical stimuli are detected by nerve endings called nociceptors, which are found in the skin, on internal surfaces such as the periosteum, joint surfaces, in some internal organs; the concentration of nociceptors varies throughout the body. Some nociceptors are unspecialized free nerve endings that have their cell bodies outside the spinal column in the dorsal root ganglia. Nociceptors are categorized according to the axons which travel from the receptors to the spinal cord or brain. Nociceptors have a certain threshold. Once this threshold is reached a signal is passed along the axon of the neuron into the spinal cord.
Nociceptive threshold testing deliberately applies a noxious stimulus to a human or animal subject in order to study pain. In animals, the technique is used to study the efficacy of analgesic drugs and to establish dosing levels and period of effect. After establishing a baseline, the drug under test is given and the elevation in threshold recorded at specified time points; when the drug wears off, the threshold should return to the baseline value. In some conditions, excitation of pain fibers becomes greater as the pain stimulus continues, leading to a condition called hyperalgesia; the gate control theory of pain, proposed by Patrick David Wall and Ronald Melzack, postulates that nociception is "gated" by non-nociceptive stimuli such as vibration. Thus, rubbing a bumped knee seems to relieve pain by preventing its transmission to the brain. Pain is "gated" by signals that descend from the brain to the spinal cord to suppress incoming nociception information. Nociception can cause generalized autonomic responses before or without reaching consciousness to cause pallor, tachycardia, lightheadedness and fainting.
This overview discusses proprioception, thermoception and nociception as they are all integrally connected. Proprioception is determined by using standard mechanoreceptors. Proprioception is covered within the somatosensory system as the brain processes them together. Thermoception refers to stimuli of moderate temperatures 24–28 °C, as anything beyond that range is considered pain and moderated by nociceptors. TRP and potassium channels each respond to different temperatures which create action potentials in nerves which join the mechano system in the posterolateral tract. Thermoception, like proprioception, is covered by the somatosensory system. TRP channels that detect noxious stimuli relay that info to nociceptors that generate an action potential. Mechanical TRP channels react to depression of their cells, thermal TRP change shape in different temperatures, chemical TRP act like taste buds, signalling if their receptors bond to certain elements/chemicals. Laminae 3-5 make up nucleus proprius in spinal grey matter.
Lamina 2 makes up substantia gelatinosa of unmyelinated spinal grey matter. Substantia conveys intense, poorly localized pain. Lamina 1 project to the parabrachial area and periaqueductal grey, which begins the suppression of pain via neural and hormonal inhibition. Lamina 1 receive input from thermoreceptors via the posterolateral tract. Marginal nucleus of the spinal cord are the only unsuppressible pain signals; the parabrachial area integrates taste and pain info relays it. Parabrachial checks if the pain is being received in normal temperatures and if the gustatory system is active. Ao fibers synapse on laminae 1 and 5 while Ab synapses on 1, 3, 5, C. C fibers synapse on lamina 2; the amygdala and hippocampus encode the memory and emotion due to pain stimuli. The hypothalamus signals for the release of hormones. Periaqueductal grey hormonally signals reticular formation’s raphe nuclei to produce serotonin that inhibits laminae pain nuclei. Lateral spinothalamic tract aids in localization of pain.
Spinoreticular and spinotectal tracts are relay tracts to the thalamus that aid in the perception of pain and alertness towards it. Fibers cross over via the spinal anterior white commissure. Lateral lemniscus is the first point of integration of pain information. Inferior colliculus aids in sound orienting to pain stimuli. Superior colliculus receives IC’s input, integrates visual orienting info, uses the balance topographical map to orient the body to the pain stimuli. Inferior cerebellar peduncle integrates proprioceptive info and outputs to the vestibulocerebellum; the peduncle is not part of the lateral-spinothalamic-tract-pathway.
Middle frontal gyrus
The middle frontal gyrus makes up about one-third of the frontal lobe of the human brain. The middle frontal gyrus, like the inferior frontal gyrus and the superior frontal gyrus, is more of a region in the frontal gyrus than a true gyrus; the borders of the middle frontal gyrus are the inferior frontal sulcus below.