1.4: Parts of the Forebrain

Thalamus

a structure within the forebrain that serves as an important relay station for incoming sensory information including all senses except for smell. After receiving incoming sensory impulses, this sorts and transmits them to the appropriate areas of the cerebral cortex. This is therefore a sensory “way station”.

Hypothalamus

This is subdivided into the lateral, ventromedial, and anterior sections, serves homeostatic functions, and is a key player in emotional experiences during high arousal stages, aggressive behavior, and sexual behavior. It also helps control some endocrine functions, as well as the autonomic nervous system. It serves many homeostatic functions, which are self-regulatory processes that maintain a stable balance within the body. Receptors in this regulate metabolism, temperature, and water balance. When any of these functions are out of balance, this detects the problem and signals the body to correct the imbalance. This is also the primary regulator of the autonomic nervous system and is important in drive behaviors: hunger, thirst, and sexual behavior.

Lateral Hypothalamus (LH)

referred to as the hunger center because it has special receptors throughout to detect when the body needs more food or fluids. This triggers eating and drinking. When this part is removed in lab rats, they refuse to eat and drink and must be force-fed with tubes to survive

Ventromedial Hypothalamus (VMH)

identified as the “satiety center”, and provides signals to stop eating. Brain lesions to this area usually lead to obesity

Anterior Hypothalamus

controls sexual behavior. When this is stimulated, lab animals will mount just about anything (including inanimate objects). In many species, damage to this leads to permanent inhibition of sexual activity This also regulates sleep and body temperature.

Posterior Pituitary

comprised of axonal projections from the hypothalamus and is the site of release for the hypothalamic hormones antidiuretic hormone (ADH, also called vasopressin) and oxytocin.

Pineal Gland

is the key player in several biological rhythms. It secretes a hormone called melatonin. It receives direct signals from the retina for coordination with sunlight

Melatonin

regulates circadian rhythms; secreted by the pineal gland

Basal Ganglia

coordinate muscle movement as they receive information from the cortex and relay this information (via the extrapyramidal motor system) to the brain and the spinal cord. It also helps make out movements smooth and our posture steady

Extrapyramidal System

gathers information about body position and carries this information to the central nervous system, but does not unction directly through motor neurons.

Parkinson’s Disease

is one chronic illness associated with destruction of portions of the basal ganglia. This disease is characterized by jerky movements and uncontrolled resting tremors.

Limbic System

comprises a group of interconnected structures looping around the central portion of the brain and is primarily associated with emotion and memory. Its primary components include the septal nuclei, amygdala, hippocampus, and anterior cingulate cortex.

Septal Nuclei

contain one of the primary pleasure centers in the brain. Mild stimulation of this is reported to be intensely pleasurable; there is association between this and addictive behavior

Amygdala

A structure that plays an important role in defensive and aggressive behaviors, including fear and rage. When this is damaged, aggression and fear reactions are markedly reduced. Lesions to this result in docility and hypersexual states.

Hippocampus

Plays a vital role in learning and memory processes, specifically it helps consolidate information to form long-term memories, and can redistribute remote memories to the cerebral cortex. This communicates with other portions of the Limbic system through the fornix.

Fornix

A long projection that allows the hippocampus and other portions of the Limbic system to communicate

Anterograde Amnesia

Characterized by not being able to establish new long-term memories, whereas memory for events that occurred before brain injury is usually intact.

Retrograde Amnesia

Refers to memory loss of events that transpired before brain injury

Anterior Cingulate Cortex

Due to the connection of this with the frontal and parietal lobes, this functions in higher order cognitive processes, including regulation of impulse control and decision making. It also maintains connections to other parts of the Limbic system, and thus plays a role in emotion and motivation.

Cerebral Cortex

The outer surface of the brain. The most recent brain region to evolve. Rather than having a smooth surface, it has numerous bumps and folds. The convoluted structure of the brain provides increased surface area. It is divided into two cerebral hemispheres. The surface is divided into four lobes: frontal, parietal, occipital, and temporal lobes.

Neocortex

Another name for the cerebral cortex

Gyri

Bumps of the brain

Sulci

Folds of the brain

Cerebral Hemispheres

The cerebrum is divided into ?

Frontal Lobe

comprised of two basic regions: the prefrontal cortex and the motor cortex

Prefrontal Cortex

Part of the Frontal Lobe. It manages executive function by supervising and directing the operations of other brain regions. To regulate attention and alertness, it communicates with the reticular formation in the brainstem, telling an individual to either wake up or to relax, depending on the situation. This region also supervises processes associated with perception, memory, emotion, impulse control, and long-term planning. In memory, for instance, the sole of this is not to store any memory traces, but rather to remind individuals that they have something to remember at all.

Damage to this impairs its overall supervisory functions, People this lesions to this may be more impulsive and generally less in control of their behavior. As a result, these individuals can have an increased tendency towards angry outbursts, as well as a higher predisposition to crying. Additionally, it is not unusual for someone with a lesion to this to make vulgar and inappropriate sexual remarks, or to be apathetic to the emotional responses of others.

Association Area

An area that integrates input from diverse regions of the brain. For example, multiple inputs may be necessary to solve a complex puzzle, to plan ahead for the future, or to reach a difficult decision. The prefrontal cortex is a good example of this because it integrates information from different cortical regions.

Projection Areas

Performs more rudimentary perceptual and motor tasks. An example of this would be the primary motor cortex.

Primary Motor Cortex

Part of the Frontal Lobe and located on the precentral gyrus, just in front of the central sulcus that divides the frontal and parietal lobes. The function of this is to initiate voluntary motor movements by sending neural impulses down the spinal cord toward the muscles. As such, it is considered a projection area in the brain. The neurons in this are arranged systemically according to the parts of the body to which they are connected.

Motor Homunculus

The organizational pattern of the neurons in the motor cortex which are arranged systemically according to the parts of the body to which they are connected. Because certain sets of muscles require finer motor control than others, they take up additional space in the cortex relative to their size in the body.

Broca’s Area

Part of the Frontal Lobe. This is vitally important for speech production. This is usually found in only one hemisphere, the so-called “dominant” hemisphere; for most people - both right- and left-handed - this is the left hemisphere.

Parietal Lobe

Located to the rear of the Frontal Lobe. Contains the Somatosensory Cortex. The central region of this is associated with spatial processing and manipulation. This region makes it possible to orient oneself and other objects in three-dimensional space, to do spatial manipulation of objects, and to apply spatial orientation skills such as those required for map reading.

Occipital Lobe

Located at the very rear of the brain, contain the visual cortex, which is sometimes called the striate cortex. The visual cortex is one of the best-understood brain regions, owing to the large amount of research that has been done on visual processing. Areas in this have also been implicated in learning and motor control.

Striate Cortex

Another name for the visual cortex

Temporal Lobes

These are associated with a number of functions. The auditory cortex and Wernicke's area are located here. This also functions in memory processing, emotion, and language. Studies have shown that electrical stimulation of these can evoke memories for past events. This makes sense because the hippocampus is located deep inside this. It is important to note that the lobes, although having seemingly independent functions, are not truly independent of one another. Often, a sensory modality may be represented in more than one area.

Auditory Cortex

This is located in the Temporal Love and is the primary site of most sound processing, including speech, music, and other sound information.

Wernicke’s Area

This is located in the Temporal Lobe and is associated with language reception and comprehension.

Corpus Callosum

connects and shares information between the two cerebral hemispheres

Contralaterally

In most cases, one side of the brain communicates with the opposite side of the body. In such cases, we say a cerebral hemisphere communicates __________. For example, the motor neurons on the left side of the brain activate movements on the right side of the body.

Ipsilaterally

In other cases (for instance, hearing), cerebral hemispheres communicate with the same side of the body. In such cases, the hemispheres communicate ___________.

Dominant Hemisphere

This is typically defined as the one that is more heavily stimulated during language reception and production. This is usually the left and is primarily analytic in function, making it well-suited for managing details. For instance, language, logic, and math skills are all located in this. Language production (Broca's area) and language comprehension (Wernicke’s area) are primarily driven by this.

Left

The dominant hemisphere is usually the ________

Nondominant Hemisphere

This is usually the right and is associated with intuition, creativity, music cognition, and spatial processing. This simultaneously processes the pieces of a stimulus and assembles them into a holistic image. This serves a less prominent role in language. It is more sensitive to the emotional tone of spoken language, and permits us to recognize others' moods based on visual and auditory cues, which adds to communication.

Dominant

Visual System: Letters, words

Auditory System: Language-related sounds

Language: Speech, reading, writing, arithmetic

Movement: Complex voluntary movement

Spatial Processes: -

Nondominant

Visual System: Faces

Auditory System: Music

Language: Emotions

Movement: -

Spatial Processes: Geometry, sense of direction