HindbrainMyencelphalon:
Metencephalon:
The hind brain is mainly a continuation of the spinal cord and contains all the ascending and descending fibres connecting the brain and spinal cord. |
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Small but crucial area of the brain with two subdivisions:
Tectum has 4 bumps: The Inferior (auditory) and Superior Colliculi (visual)
Tecmentum is the area below (inferior; verntral) to the tectum.
Primary structures:
DiencephalonPrimary Structures:
Other structures of interest:
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The hypothalamus regulates many ‘primitive functions’ including the response to stress (control of the ANS),has key roles in motivational behaviour (making us find food, water), sexual behaviour. It also houses at least some ‘body clocks’.
Although the hypothalamus is a small area it is extremely important behaviourally.
It regulates the activity of the pituitary gland (literally: Snot gland. Previously called the ‘master gland’).
Mammillary bodies: These represent specific hypothalamic nuclei
The TelencephalonPrimary Structures:
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(From limbus, meaning ring)
From Pinel (1990) the oldest joke in bio-psychology:The limbic system is involved in the fours Fs: Feeding, fighting, fleeing and sexual behaviour.
The limbic and BG are involved in: emotion (e.g. the papez circuit); aggressive behaviour, fear, pleasure and several key aspects of personality.
Components of the limbic system:
Primary Structures
Damage to the BG is associated with Huntington’s and Parkinson’s disease.
“The basal ganglia are regarded as sub-cortical nuclear complexes that play a critical role in the integration of motor activity” (Noback, 1996).
“Overall, there is growing evidence that alterations in basal ganglia circuits with nonmotor areas of cortex occur in a wide variety of neuropsychiatric disorders, including not only schizophrenia and obsessive-compulsive disorder, but also depression, Tourette’s syndrome, autism, and attention deficit disorder..” Middleton and Strick (2000)
Highly convoluted 2D structure divided into four lobes.
The dualists
Marc Dax (1836)
Franz Gall: 1758 - 1822.
1861: Paul Broca and Tan
On September 13, 1848, Phineas Gage was working outside the small town of Cavendish, Vermont on the construction of a railroad track where he was employed as a foreman. One of his duties was to set explosive charges in holes drilled into large pieces of rock so they could be broken up and removed. This involved filling the hole with gunpowder, adding a fuse, and then packing in sand with the aid of a large tamping iron. Gage was momentarily distracted and forgot to pour the sand into one hole. Thus, when he went to tamp the sand down, the tamping iron sparked against the rock and ignited the gunpowder, causing the iron to be blown through Gage’s head with such force that it landed almost thirty yards (27 meters) behind him.
The three foot (1 m) long tamping iron with a diameter of 1.25 inches (3.2 cm) weighing thirteen and a half pounds (6.12 kg) entered his skull below his left cheek bone and exited after passing through the anterior frontal cortex and white matter. Whether the lesion involved both frontal lobes, or was limited only to the left side, remains a matter of controversy. Remarkably, after such a dramatic accident, Gage regained consciousness within a few minutes, was able to speak, and survived a 45-minute ride back to his boarding house sitting in a cart.
As the doctor arrived, he was reportedly conscious, and had a regular pulse of about 60 beats per minute, suggesting that he only suffered minimal blood loss. His left pupil was still reacting to direct light (and stayed that way for the following 10 days), which indicates that the left optic and oculomotor nerves were still functioning, supporting the hypothesis that the tamping iron must have passed laterally to the left optic nerve. After a seemingly complete recovery from such a serious injury, Gage was soon back at work.
While early studies by Antonio Damasio and colleagues suggested a bilateral damage to the medial frontal lobes, a recent study by Ratiu and colleagues, based on a CT scan of Gage’s skull suggests that the extent of Gage’s brain injury must have been more limited than previously thought.
In light of modern medical science, a bilateral damage of the frontal brain by a projectile measuring 1.25 inches in diameter and weighing thirteen pounds, appears to be incompatible with survival, since this would imply an extensive damage to vital vascular structures, such as the superior sagittal sinus. Nevertheless, Gage survived the traumatic event and reportedly developed personality changes.
According to Gage’s physician, Dr J.M. Harlow, whereas previously he had been hard-working, responsible, and popular with the men in his charge, his personality seemed to have been radically altered after the accident. His physician reported that :
Gage was fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’
After his injury, Gage lost his job with the railroad construction company. When he was well enough again in or around 1850, he spent about a year as a sideshow attraction and at P. T. Barnum’s New York museum, putting his injury, and the tamping iron which caused it, on display to anybody willing to pay for the show. He then worked as an assistant in New Hampshire and, for nearly seven years, as a coach driver in Chile. When his health started to fail in 1859, he returned to San Francisco, where he lived with his mother and, for some months before his death, was employed as a farm worker.
Several attempts have been made to map the cytoarchitecture of the neocortex. Campell (1905) divided the neocortex in 13 zones based on myelin and nerve cell properties.
The most popular is Brodman’s Map