The hippocampus plays a key role in the formation of emotion-laden, long-term memories based on emotional input from the amygdala. The left temporal lobe holds the primary auditory cortex, which is important for processing the semantics of speech. The occipital lobe contains most of the visual cortex and is the visual processing center of the brain. Cells on the posterior side of the occipital lobe are arranged as a spatial map of the retinal field.
The visual cortex receives raw sensory information through sensors in the retina of the eyes, which is then conveyed through the optic tracts to the visual cortex.
Other areas of the occipital lobe are specialized for different visual tasks, such as visuospatial processing, color discrimination, and motion perception. Damage to the primary visual cortex located on the surface of the posterior occipital lobe can cause blindness, due to the holes in the visual map on the surface of the cortex caused by the lesions.
The parietal lobe is associated with sensory skills. It integrates different types of sensory information and is particularly useful in spatial processing and navigation. The parietal lobe plays an important role in integrating sensory information from various parts of the body, understanding numbers and their relations, and manipulating objects.
Its also processes information related to the sense of touch. The parietal lobe is comprised of the somatosensory cortex and part of the visual system. Several portions of the parietal lobe are important to language and visuospatial processing; the left parietal lobe is involved in symbolic functions in language and mathematics, while the right parietal lobe is specialized to process images and interpretation of maps i.
The limbic system is a complex set of structures found on the central underside of the cerebrum, comprising inner sections of the temporal lobes and the bottom of the frontal lobe. It combines higher mental functions and primitive emotion into a single system often referred to as the emotional nervous system.
It is not only responsible for our emotional lives but also our higher mental functions, such as learning and formation of memories. The limbic system is the reason that some physical things such as eating seem so pleasurable to us, and the reason why some medical conditions, such as high blood pressure, are caused by mental stress. There are several important structures within the limbic system: the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus.
The amygdala is a small almond-shaped structure; there is one located in each of the left and right temporal lobes. Known as the emotional center of the brain, the amygdala is involved in evaluating the emotional valence of situations e.
It helps the brain recognize potential threats and helps prepare the body for fight-or-flight reactions by increasing heart and breathing rate. The amygdala is also responsible for learning on the basis of reward or punishment. The amygdala : The figure shows the location of the amygdala from the underside ventral view of the human brain, with the front of the brain at the top of the image.
Due to its close proximity to the hippocampus, the amygdala is involved in the modulation of memory consolidation, particularly emotionally-laden memories. In fact, experiments have shown that administering stress hormones to individuals immediately after they learn something enhances their retention when they are tested two weeks later.
The hippocampus is found deep in the temporal lobe, and is shaped like a seahorse. It consists of two horns curving back from the amygdala. Psychologists and neuroscientists dispute the precise role of the hippocampus, but generally agree that it plays an essential role in the formation of new memories about past experiences.
Some researchers consider the hippocampus to be responsible for general declarative memory memories that can be explicitly verbalized, such as memory of facts and episodic memory. Damage to the hippocampus usually results in profound difficulties in forming new memories anterograde amnesia , and may also affect access to memories formed prior to the damage retrograde amnesia.
Although the retrograde effect normally extends some years prior to the brain damage, in some cases older memories remain intact; this leads to the idea that over time the hippocampus becomes less important in the storage of memory.
Hippocampus : This image shows the horned hippocampus deep within the temporal lobe. Both the thalamus and hypothalamus are associated with changes in emotional reactivity. The hypothalamus is a small part of the brain located just below the thalamus on both sides of the third ventricle. Lesions of the hypothalamus interfere with several unconscious functions such as respiration and metabolism and some so-called motivated behaviors like sexuality, combativeness, and hunger. The lateral parts of the hypothalamus seem to be involved with pleasure and rage, while the medial part is linked to aversion, displeasure, and a tendency for uncontrollable and loud laughter.
The cingulate gyrus is located in the medial side of the brain next to the corpus callosum. There is still much to be learned about this gyrus, but it is known that its frontal part links smells and sights with pleasant memories of previous emotions. This region also participates in our emotional reaction to pain and in the regulation of aggressive behavior.
The basal ganglia is a group of nuclei lying deep in the subcortical white matter of the frontal lobes that organizes motor behavior. The caudate , putamen, and globus pallidus are major components of the basal ganglia. The basal ganglia appears to serve as a gating mechanism for physical movements, inhibiting potential movements until they are fully appropriate for the circumstances in which they are to be executed.
The basal ganglia is also involved with:. The brain is constantly adapting throughout a lifetime, though sometimes over critical, genetically determined periods of time. It refers to changes in neural pathways and synapses that result from changes in behavior, environmental and neural processes, and changes resulting from bodily injury. Neuroplasticity has replaced the formerly held theory that the brain is a physiologically static organ, and explores how the brain changes throughout life.
Neuroplasticity occurs on a variety of levels, ranging from minute cellular changes resulting from learning to large-scale cortical remapping in response to injury. The role of neuroplasticity is widely recognized in healthy development, learning, memory, and recovery from brain damage.
During most of the 20th century, the consensus among neuroscientists was that brain structure is relatively immutable after a critical period during early childhood. However, recent findings show that many aspects of the brain remain plastic even into adulthood. Plasticity can be demonstrated over the course of virtually any form of learning. For one to remember an experience, the circuitry of the brain must change.
Learning takes place when there is either a change in the internal structure of neurons or a heightened number of synapses between neurons. Studies conducted using rats illustrate how the brain changes in response to experience: rats who lived in more enriched environments had larger neurons, more DNA and RNA, heavier cerebral cortices, and larger synapses compared to rats who lived in sparse environments.
A surprising consequence of neuroplasticity is that the brain activity associated with a given function can move to a different location; this can result from normal experience, and also occurs in the process of recovery from brain injury. Download the pdf. Download printable poster. Skip to menu Skip to content Skip to footer. Site search Search. Site search Search Menu.
The limbic system. Home The Brain Brain anatomy. Hippocampus The hippocampus, like many other structures in the brain, comes as a pair, one in each hemisphere of the brain. And you may have noticed there's one sense that I didn't mention. And that's a sense of smell.
And the sense of smell actually is the only sense that you have that actually bypasses this thalamus. And instead, it has its own private relay station that, when it comes from the nose, it goes to a certain area in the brain. And that area of the brain actually happens to be very close to other areas that regulate emotion, which explains why sometimes certain scents can evoke very powerful memories and bring you back to a certain moment in time.
But in terms of emotion, I mentioned thalamus because of how the senses play an important role in your emotions. Now, you see here there's these two purple structures. And this is known as an amygdala. Now, the amygdala is sometimes called the aggression center. And experiments have actually shown that if you stimulate the amygdala, you can produce feelings of anger and violence, as well as fear and anxiety.
I'm going to put "stimulate" and represent it as dark green plus sign. So you stimulate the amygdala. It evokes feelings of anger, violence, fear, and anxiety. On the other hand, if you've destroyed your amygdala-- and I'll represent destruction as a negative sign-- if you destroy the amygdala, it can cause a very mellowing effect.
I'll write "mellow. Kluver and a neurosurgeon by the name of Dr. And I mention Kluver and Bucy because in medicine there's actually a syndrome known as Kluver-Bucy syndrome. And that's when there's a bilateral destruction of your amygdala. And "bilateral" means both. And if you have bilateral destruction of the amygdalas, that can result in certain symptoms that are often seen, like hyperorality, which means you put things in their mouth a lot; also hypersexuality; as well as disinhibited behavior.
And disinhibited behavior is when you ignore social conventions. You can act very impulsively. You don't consider the risks of your behavior. So you do dangerous, reckless things. So that's Kluver-Bucy syndrome. And that's again when you destroy both sides of your amygdalas. And the way I remember this is I think if you stimulate the amygdalas, that can cause fear and anxiety. And people who have anxiety disorders or experiencing an anxiety attack sometimes are given a medication known as a benzodiazepine.
Sometimes they're called "benzos. And think of what happens when people consume too much alcohol. The dorsal part of the telencephalon, or pallium, develops into the cerebral cortex, while the ventral telencephalon, or subpallium, forms the basal ganglia.
The diencephalon encompasses the thalamus, metathalamus, hypothalamus, epithalamus, prethalamus or subthalamus and pretectum. The midbrain is centrally located below the cerebral cortex and above the pons. It includes the tectum, the tegmentum, the ventricular mesocoelia, and the cerebral peduncles.
The pons, or metencephalon, in association with the myelencephalon and additional subunits called rhombomeres, form the rhombencephalon or hindbrain , which represents a transition to the spinal cord. Some regions of the mesencephalon, diencephalon, and telencephalon are structurally and functionally interrelated so that they can be considered as a unique functional complex, the so-called limbic system [ 4 ].
Subsequently; however, the limbic lobe started to be called rhinencephalon, which means olfactory brain, due to its apparent involvement with the olfactory process and behaviours generated by olfaction [ 6 ]. In order to understand the concept of limbic system, it is important to understand the term rhinencephalon, whose origins are difficult to trace [ 12 ]. The term was firstly used by Saint-Hillarie to name a one-eyed monster. Soon after, Owen — used the term which means cerebral nose in a neuroanatomical context, referring to the olfactory bulb and the peduncle [ 12 ].
Later, Turner — extended its meaning to include the pyriform lobe. In fact, some neuroscientists consider many of the limbic structures as integrant parts of the rhinencephalon, which is entirely confined to the telencephalon [ 4 ].
However, after a long-lasting hegemony of the Aristotelian theories, some changes took place, which allowed for a better understanding of human psychic foundations. These changes occurred as a result of increasing interest in the dissection of corpses and the resulting progress in the understanding of human anatomy [ 14 , 15 ]. He also developed the most sophisticated investigations into cerebral functions before the Renaissance period.
Among others contributions, Galen developed theories on the somatic senses, having described the anatomy of the cranial nerves and the autonomic nervous system [ 14 ].
Later, with the anatomical contributions put forward by Galen, the cerebral ventricles were considered the centres of reason and emotions [ 14 ]. This was how the emotional process was thought to be generated. A ventricular theory of emotions was also proposed by Saint Augustine in AD [ 6 ]. Although the exact date when this theory was conceived is unknown, it certainly evolved from Galen's fundamental theories of brain anatomy [ 14 , 15 ]. Da Vinci — made significant contributions to the development of neuroscience, particularly in neuroanatomy and neurophysiology.
Regarding the development of human emotional processes, he directed his research to the quest for a biological explanation of the brain processes responsible for visual perception, as well as other sensorial modalities, trying to integrate these senses with an understanding of the mind [ 16 , 17 ]. Da Vinci correlated cerebral structures to superior cerebral functions, and, for this reason, he can be considered the forerunner of the theory developed centuries later by a Viennese doctor named Franz J.
Gall, called phrenology [ 5 ]. The printing press, invented by the Johannes Gutenberg around , made possible for the first time the rapid creation of metal movable type in large quantities, which subsequently led to a boom in printing activities in Europe between and The ability to publish manuscripts was an important technological advance that contributed to the understanding of neuroanatomy and neurology, as known today [ 15 , 18 ]. Thus, in Peyligk graphically described part of the cerebral anatomy, including the dura mater and the pia mater, as well as the ventricles, in his work entitled Compendium philosophiae naturalis.
In , the publication of the groundbreaking work De humani corporis fabrica libri septem by Vesalius — truly revolutionized neuroanatomy. It was the most complete and detailed work in this field and corrected several inaccuracies from the works of Galen. It revealed details about the cerebral ventricles, cranial and peripheral nerves, pituitary gland, meninges, ocular structures, cerebral vascular supply, and spinal cord [ 15 ]. As a corollary to the evolution of the medical sciences, it became evident that the advancement of scientific knowledge, specifically neuroanatomy, depended on the capacity to create accurate reproduction of images.
Some scholars believe that one reason that accounted for a lack of a major advance in Medicine during the Renaissance was the inability to reproduce with graphical perfection the scientific and anatomical findings [ 15 ]. The study of anatomy flourished in the 17th and 18th centuries, given that famous artists, including Michelangelo and Rembrandt, studied anatomy, attended dissections, and published their drawings.
Certified anatomists were allowed to perform dissections in many European cities, depending on the availability of fresh bodies [ 19 ]. These developments enabled a more accurate description of complex structures of the nervous system. Moreover, the rise of neurochemistry took place in the s in France.
He led studies to examine the nature of brain substances that could retard putrefaction [ 19 ]. As a result, through the convergence of previously distinct biological disciplines including anatomy and chemistry, it became possible to speculate about the molecular biology of the cerebral systems responsible for the production of emotions [ 20 ].
At the end of the eighteenth century, neurology had developed from a science with poor anatomical groundwork to a more concise, practical, and less philosophical combination of anatomy, pathology, and neurochemistry [ 15 , 21 ]. In the nineteenth century, medical knowledge gained new impetus as important discoveries occurred.
Henle combined anatomy with human biology to create the field of physiology, whereas Virchow and Pasteur established the fields of cellular pathology and microbiology, respectively. In addition, major advancement allowed for safer and painless surgical procedures in that period. Lister advocated for the disinfection of surgical equipment, whereas Morton developed anaesthetic techniques. In addition, new concepts in neuroscience emerged [ 22 ].
Neurology flourished as a discipline and became similar to what it is today: an independent field of research of the complex functions and dysfunctions of the nervous system [ 15 ].
In the nineteenth century Gall believed, similar to several of his precursors, that the brain was organized according to different abilities and physically defined specific functions.
Nowadays it is known that the theories of Gall were not correct. However, phrenology was the first theory to consider the cerebral location of specific functions, being the precursor of modern theories due to its strong emphasis on localization of cerebral function [ 6 ].
The year was marked by discussions about whether the cerebral hemispheres acted as independent units and whether there were specialized regions in the human brain [ 24 ]. In , Broca examined the brain of one of his patients and concluded that the centre of speech was located in the inferior frontal gyrus in the dominant hemisphere. Later, the eponyms Broca's aphasia and Broca's area became widely known [ 24 ].
Broca also studied eight cases of left frontal injuries and subsequently developed the concept of cerebral dominance [ 25 , 26 ]. Substantial progress in the understanding of the association between cortical damage and behavioural changes came from an observation by Harlow in Vermont, USA, in A healthy twenty-five-year-old man suffered an accident, in which an iron bar passed through his skull, affecting the pre-frontal cortex region [ 32 , 33 ].
The patient was purportedly in perfect physical condition less than two months later, except that a bizarre behavioural change had developed. Testing of his executive functioning indicated that he had lost the ability to use anticipatory planning as well as becoming socially awkward [ 32 — 36 ].
Subsequently, a significant revolution in the concept of the emotions took place under the influence of Darwin's seminal ideas. Darwin proposed two major postulates in relation to mammalian emotional processes.
The first was that emotions in animals would be similar to human emotions—a logical extension of his work on the evolution of the species [ 37 , 38 ]. Darwin also proposed that humans expressed vestigial patterns of mammalian emotional behaviour, by exposing the front teeth when expressing sadness through anger or crying [ 37 , 38 ]. The second postulate proposed by Darwin states that there is a set of basic or fundamental emotions that are present throughout distinct species and are independent of cultures or societal norms.
These emotions include anger, fear, surprise, and sadness [ 37 , 38 ]. Both tenets were of great relevance for the field of affective neuroscience, since they have spawned investigations involving animals as a resource to understand human emotions.
Moreover, these ideas generated new research on distinct neural substrates for a series of emotional expressions [ 39 ]. James proposed an innovative theory whereby various human emotions occurred in response to afferent feedback loops from sensory receptors in the skin, muscles, cartilage, and other organs which produced, although unknown at that time, physical changes that were subsequently encoded into the cerebral cortex memory storage to determine the subjective quality of the stimuli being experienced as temperature change, pain, vibration, and so forth [ 37 , 40 , 41 ].
According to James' theory, emotions are just one form of experience of a wider array of physical changes that occur in response to emotional stimuli.
James advocated that a sensorial feedback occurred from the corporal periphery to the cerebral cortex in the context of an emotionally laden behaviour, thus, determining the subjective quality of such a behavioural experience [ 1 ]. James understood that different corporal memory processes encoded different emotions [ 37 , 40 , 41 ].
According to his theory, tremor is the cause of fear and not its consequence, as cry is the cause of sadness [ 6 ]. Similar ideas were proposed in the same period by the Danish physician and psychologist Lange [ 42 ].
The James-Lange theory states that the autonomic nervous system generates physiological events as a response to humans' experiential interaction with the world. According to this theory, emotions are feelings that occur as a consequence—instead of being the cause—of physiological changes. Experiments developed by authors such as Exner, Freud, and Waynbaum led to further advancements [ 43 ].
In spite of the then limited knowledge about the cerebral anatomical interconnections, the ideas advocated by these proponents were in line with current tendencies. Sigmund Exner — , a physiologist at the University of Vienna and one of the charter members of the German Society of Psychology, described in a neural circuit model that explained the interactions between sensations of pleasure and aversion in the brain [ 41 , 42 ].
This model, based on his knowledge of animal experimentation, detailed how sensorial events acquire emotional meaning and produce motor and autonomic responses, anticipating what subsequently would be elaborated in recent neurobiological theories [ 41 ]. Thus, the thalamus would function as the centre of sensory integration and as a filter that would direct only intense stimuli to the aversive centre. The aversion would be processed in a structure composed of neuronal bodies, which encompassed, under modern neurobiological perspectives, the amygdala.
This theory underpinned Sigmund Freud's ideas — who, at the beginning of his scientific activities , had described psychological phenomena as forms of nervous energy in neuronal systems, which consisted of diverse cellular types, each with only one function [ 35 , 43 — 45 ]. Thus, aversive reactions would be manifested during the mnemonic representation of the aversive experience.
This is the basis of Freud's neuronal theory [ 43 , 44 ]. Freud's first postulate, called inertia, is similar to what is today known as homeostasis. It states that an organism, when stimulated, attempts to return to the unstimulated condition. Neurologically, the affects result when cathexis increases negative affects or decreases positive affects.
These changes in cortical cathexis follow the activation of traces imprinted in the nuclear system on prior occasions during episodes of negative or positive affects. The affects, consequently, modulate current experiences with imprints from past impressions [ 46 ]. Another model for the understanding of the emotional process was proposed in by the French physician Israel Waynbaum. In the s, physiological laboratory studies began to differentiate the psychological and neurophysiological domains, since previously both specialties had investigated only emotional processes [ 47 ].
Walter Cannon, a Harvard physiologist and pioneer in neurophysiological studies of emotional substrates, highlighted the fact that laboratory investigations of human emotions were partially hindered by the difficulty of inducing emotional states in animals and of maintaining these states for subsequent studies [ 48 , 49 ]. The obstacles to conducting research on human emotions in laboratory settings were emphasized in numerous psychological and physiological studies. There were difficulties both in inducing genuine and intense emotional reactions in laboratories as well as the fact that emotions generated in the laboratory environment were considered extremely artificial [ 50 — 54 ].
In , James suggested that emotions could be mediated by sensory and motor areas of the cerebral cortex. He believed that the sensory areas were essential to the immediate detection of stimuli and that the motor regions were responsible for the production of feedback reactions [ 6 , 40 ]. In the s, Cannon contradicted the prevailing peripheral emotional theory of James. He also proposed a new emotional theory based on investigations from Phillip Bard's laboratory, in which animal brains were longitudinally sectioned in the diencephalon in consecutive inferior anatomical planes [ 1 , 55 ].
The intention was to find a transection plane that would suppress or diminish the emotional expression in the animal model. This region was defined, according to the experiments, as the caudal half of the hypothalamus and the posteroventral thalamus, which revealed to both Cannon and Bard that those structures were essential for the emotional brain [ 1 , 6 ].
Fictitious rage is a term coined by Cannon and Bard to describe the rage produced surgically in decerebrated animals. Consequently, physical and autonomic activities were insufficient to distinguish between distinct emotional states, and physical changes are extremely slow to generate emotions as a result of hormonal activation induced by such physical activity.
They postulated that the hypothalamus could receive afferent impulses from the thalamus at the same time as the thalamus sends information to the cerebral cortex. The hypothalamus would have access to emotions at the same time as the cortex and would, therefore, stimulate behavioural and autonomic bodily reactions typical of affective states.
This would explain, according to Cannon and Bard, why decortication could not prevent the genesis of emotional patterns, a finding that opposed the James-Lange theory [ 1 , 6 , 55 — 58 ].
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