Cerebral Cortex
The Cerebrum are the two large hemispheres that contribute 85% of brain weight
The Cerebral Cortex covers those hemispheres and is located in the forebrain
Gray matter on outside is actually only gray in preserved brain. In a live brain, it is pink.
Neural networks within the cerebrum produce higher order functions like language, information processing, judgment, perception, and personality
A sheet of neural cells typically 2-3 mm thick. It is folded to fit (which allows a lot more area to fit into our skulls). This produces the “wrinkles” we envision when we think about a brain. o The creases are the sulci and the bulges are the gyri o Particular sulci and gyri often consist of groups of neurons with well-defined functions. There are major connections between areas that tend to work together and as the brain develops and the cortex expands, these connections force the cortex to fold in certain ways
Each hemisphere has 4 Lobes that are separated by prominent fissures (folds). These have different functions but the usually work in concert, not in isolation
The more advanced and complex the animal, the larger and more adaptable their cerebral cortex, offering increased capacity for learning and thinking. [A frog has a small cortex which operates extensively on preprogrammed genetic instructions]
The thickness of different cortical areas varies. In general, sensory cortex is thinner and motor cortex is thicker. One study has found some positive association between the cortical thickness and intelligence. Another study has found that the somatosensory cortex is thicker in migraine sufferers.
4 Cortical Lobes
OCCIPITAL LOBES - Vision
- Concerned entirely with different aspects of vision
Most of the fibers from the eyes lead to it
If you are hit in the back of the head hard enough, you will see “stars”
Many separate areas work together to specify visual properties such as shape, color, and motion
Damage

partial or total blindness o Remove left occipital and the person will be unable to see things in their right visual field
Contains the Primary Visual Cortex also called the Striate cortex
TEMPORAL LOBES
Involved in processing sound, entering new information into memory (why do you think these two things are grouped together in the same area?), storing visual memories, and comprehending language.
Connections between temporal and occipital lobes  visual information transmitted from occipital lobe to temporal lobe where visual memories are stored and compared to input. Damage to the connections between temporal and occipital lobes
 only small amount of information reaches the temporal lobe and things may be perceived one piece at a time, rather than as a whole. Think about

how hard it would be to read if you could only perceive each part of a letter and not the letter as a whole.
PARIETAL LOBES
Processes information about space and position
Includes the somatosensory strip or the Primary sensory cortex – registers sensation from the body, with each area of the body having a corresponding space on the sensory cortex and more space devoted to more sensitive body parts (lips, fingertips)
Judging distance, doing math, imagining objects in space
Proprioception, or sense of our body position and orientation
-
Einstein’s were 15% larger than normal
Also plays role in consciousness (and sense of self) – damage to right parietal lobe
 unilateral
visual neglect often with anosognosia (lack of awareness that anything is wrong – doctor’s third arm)
FRONTAL LOBES
The part of the brain that makes us uniquely human and makes us each who we are
Contains the motor strip or Primary motor cortex on gyrus immediately in front of the central sulcus o Controls fine movements, larger areas dedicated to body parts we control with precision
Phineas Gage  before: responsible, organized; after: disorderly, indecisive, lacking self-control, used profanity
Damage

difficulty reasoning and making decisions, trouble controlling emotions, personality changes.
The four lobes contain sensory, motor, and association areas
ASSOCIATION AREAS
-
The ¾ of the cortex, across all four lobes not devoted to sensory or muscle activity.
Interpret, integrate information processed by the sensory areas, link sensory inputs with stored memories  more complex functions than primary sensory or motor cortex
In the frontal lobes enable judgment, planning, processing memories, inhibitions, and personality
In parietal lobes, enable mathematical and spatial reasoning
In right temporal, enable facial recognition.
Sensory association areas are usually adjacent to or very close to the sensory area they are involved with and I will talk about these in relation to the areas they are associated with
SENSORY AREAS
– Areas that receive and process information from the senses
Primary Sensory Areas – sensory areas that receive sensory inputs from thalamus

Primary Auditory Cortex – Hearing
There are tonotopic maps for different tones.
Unilateral cortical lesions do not effect hearing because of completely bilateral sound representation
Auditory Association Areas & Language cortical association areas
Involved in interpretation of sound
In dominant hemisphere (LEFT?)
 Wernicke’s area, required for understanding language, especially dominant meaning of ambiguous words. Damage  Wernicke’s aphasia, inability to understand language (including written language), speech maintains normal sounding rhythm and syntax but is nonsensical (fluent but nonsense)
In nondominant hemisphere/RIGHT homologous area
 subordinate meanings of ambiguous words, understanding tone of voice
-
Also, Broca’s area (language production so it is a motor cortex, not sensory)
Primary Visual Cortex
Striate cortex
Upper part of the world projects to lower part of striate cortex, left visual field projects to right hemisphere striate cortex and right visual field projects to left
Lesions cause cortical blindness or difficulty tracking objects
Visual Association Areas (around striate cortex)
Interpret visual signals and recognize form, colors, and movements
Selective lesions of these areas will produce an inability to recognize objects
Primary Somatosensory Cortex – Touch
If a body part is amputated (such as a finger) there is reorganization with neurons responding to stimulation of adjacent body parts. This can also happen as the result of increased use of a body part.
Damage to the sensory cortex results in decreased sensory thresholds, an inability to discriminate the properties of tactile stimuli or to identify objects by touch.
Somatosensory association cortex
Directly behind the sensory cortex in the superior parietal lobes.
Receives synthesized connections from the primary and secondary sensory cortices.
Respond to several types of inputs and are involved in complex associations.
Damage can affect the ability to recognize objects even though the objects can be felt ( tactile agnosia ). Cortical damage, particularly in the area of cortex where the posterior parietal lobe meets the anterior occipital and the posterior, superior temporal lobe, can cause neglect of the contralateral side of the world. This typically happens with nondominant hemisphere lesions since this hemisphere appears necessary to distribute attention to both sides of the body. The dominant hemisphere appears to only “pay attention” to the associated (usually right) side of the world. Therefore, neglect usually involves the left side and can be so severe that the individual even denies that their left side belongs to them.

MOTOR AREAS
Primary Motor Cortex
Origin of most of the corticospinal tract, also projects to thalamus and basal ganglion
Also receives inputs from sensory cortical areas and premotor cortical areas
Somatotopic organization
Specific movements tend to be represented (such as elbow flexion) rather than specific muscles
Lesions produce weakness or loss of movement or loss of control of movement in the area of the body corresponding to the lesioned area
Premotor Cortex (Association area)
Right in front of the motor cortex
Receives many of the same connections as motor cortex (input from sensory cortex, thalamus, basal ganglia) but most of its outputs go to the motor cortex, and some go to spinal cord and brainstem
Electrical stimulation of this area produces more complex movements and at a higher stimulus intensity than the simple movements from primary motor.
Lesions  less severe weakness but greater spasticity (loss of control of movement) than with lesions to primary motor cortex
Prefrontal Cortex
Extremely well developed in humans (and dolphins)
Two Main portions: o Dorsolateral Prefrontal Cortex (DLPC) – Executive functions (working memory, judgment, planning, sequencing of activity, abstract reasoning, and dividing attention o Orbitomedial Prefrontal Cortex – impulse control, personality, reactivity to the surroundings and mood o These are the areas damaged in Phineas Gage o "The equilibrium or balance, so to speak, between his intellectual faculties and animal propensities, seems to have been destroyed. He is 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 operation, which no sooner arranged than they are abandoned... in this regard his mind was radically changed, so decidedly that is friends and acquaintances said that he was 'no longer
Gage.'" (Harlow, 1868) o The frontal lobes connect to all other cortical regions through association fibers. It receives particularly strong input from limbic cortex, amygdala, areas involved in emotional responses. Patients with lesions in this area are often referred to as having a changed personality.
Anterior Cingulate gyrus – Particularly associated with mood. There is some lateralization between hemispheres but it is less pronounced  lesion in dominant hemisphere tends to produce depression,
in nondominant hemisphere, mania