Forebrain: Cortical Structures

Question 1

FOREBRAIN

CORTICAL STRUCTURES

Answer 1

Cortical Structures of the Forebrain

1. two hemispheres of the cerebral cortex
   
   1. contralateral representation
   2. brain lateralization
2. Lobes of the Cerebral Cortex
   
   1. Frontal Lobe
   2. Parietal Lobe
   3. Temporal Lobe
   4. Occipital Lobe

Question 2

Cerebral Cortex

Forebrain: cortical structures

Answer 2

Cerebral Cortex makes up more than 80% of brain’s weight and is responsible for the regulation of:

1. cognitive, emotional, and motor functions.
2. divided into 2 hemispheres and each hemisphere consists of 4 lobes
3. corpus callosum: right and left hemispheres of the cerebral cortex are connected by bundles of fibers, the largest being the corpus callosum.
   
   1. allows information sent directly from one hemisphere to another, and if severed, the hemispheres operate as two separate, independent brains!

Question 3

2 hemispheres of the Cerebral Cortex

contralateral representation

Answer 3

Contralateral Representation: for most sensory and motor functions, the cortex left hemisphere controls the functions of the right side of the body and vice versa.

1. except olfaction: right nostril go directly to the right hemisphere and left to the left brain
2. visual: information from each eye goes to both sides of the brain.
   
   1. Information from the right visual field of each eye going to the left hemisphere
   2. information from the left visual field of each eye going to the right hemisphere

Question 4

Brain Lateralization

Answer 4

Both hemispheres play a role in most bx, each hemisphere tends to specialize.

brain lateralization or hemispheric specialization is apparent at birth.

For 95-99% of right handed people, and 50-60% of left handed people:

1. written and spoken language and logical, analytical thinking are left (dominant) hemisphere functions
2. spatial relationships, creativity, and facial recognition are right (non-dominant) hemisphere functions.
3. for remaining 50-40% of lefties, language is controlled by the right hemisphere or is controlled bilaterally.

newborns: electrical activity in the left, and right for nonspeech sounds.

Question 5

Brain Lateralization Functions Left/Right

Answer 5

Left Hemisphere (dominant)

1. letters, words,
2. language-related sounds,
3. verbal memory
4. speech, reading, writing, arithmetic
5. positive emotions
6. analytic, logical

Right Hemisphere (non-domiant)

1. complex geometric patterns/design and visual recognition
2. music and other non-language sounds
3. nonverbal memory
4. emotional content of language
5. geometry, sense of direction
6. negative emotions
7. holistic and intuitive

Question 6

Split Brain Patients

Answer 6

Information about brain lateralization initially obtained by severing the corpus callosum as tratment for severe epilepsy. Although the seisures decreased and no effect on intelligence, memory, motivation or groww motor control: it did affect certail kinds of responses.

Sperry and Gazzaniga: split brain patient’s

1. project image to left visual field (goes to right hemisphere only). Patient can pick the object out of 10 objects hidden behind a screen using his left hand. BUT, patient not able to name or describe the object AND unable to pick the object from the 10 choices with his right hand.
2. project image to right visual field (goes to left hemisphere only). Patient CAN name it and pick it out with the right hand BUT can not select with left hand.

Question 7

1.Frontal Lobe

Forebrain-Cortical Structures-Cerebral Cortex

Answer 7

Frontal Lobe: occupies the major portion of the cortex and includes the primary motor cortex, supplementary motor area, premotor cortex, Broca’s area, and prefrontal cortex.

1. _Primary Motor Cortex: _precentral gyrus and involved in the execurion of movement. fingers, lips, jaw, precise control of muscles. Damage= loss of reflexes and flaccid hemiplegia (loss of muscle tone) in the areas of the body conralateral to the damage.
2. Supplementary Motor Area (SMA): planning and conrol of movement. learning new motor sequences and mental representation of movement (dance/corregraphy)
3. Premotor Cortex: just anterior to the primary motor cortex and controls movement in response to external sensory stimuli (jump, bug!)
4. Broca’s Area: Major motor spech area locatedin the inferior frontal region (left side). Damage= Broca’s aphasia (expressive) difficulties in producing spoken and written language.
5. Prefontal Cortex: Emotion, memory, attention, self-awareness, and higher-order cognitive functions. Damage= impair performance on measures of problem-solving and creativity but have little effect on IQ test scores.
   
   1. reduced metabolism in the prefrontal cortex (hypofrontality) linked to Schizophrenia, ADHD and dementia.
   2. Dosolateral area damage: dorsal convexity dysexecutive syndrome: impaired EF, concrete, perseverative, neglect hygiene, and little sex interest and apathetic.
   3. Orbitofrontal area damage: orbitofrontal disinhibition syndrome or pseudopsychopathy=emotional lability, distractibility, poor impulse control, and poor social insight. labile mood, unusual or inappropriate sex, rude, …etc.
   4. mediofrontal area demage= mesial frontal apathetic syndrome: pseudodepression= impaired spontaneity, reduced emotional reactions, diminished motor bx and verbal output, lower-extremity weakness and sensory loss. Lack motivation and seem depressed but lack the vegetative symptoms, negative cognitions, and dysphoria that characterize major depression.

Question 8

Parietal Lobe

Answer 8

Contains the somatosensory cortex, located on the postcentral gyrus and governs pressure, temperature, pain, proprioception, and gustation.

Electrical stimulation of the somatosensory cortex = warmth, tingling or other sensation throughout the body.

Damage to Parietal lobe = distrubances in spatial orientation:

1. Apraxia: inability to perform skilled motor movements in the absence of impaired motor functioning,
2. somatosensory agnosia: tactile agnosia: unable to recognize familiar objects by touch
3. asomatognosia: failure to recognize parts of one’s own body
4. anosognosia: inability to recognize one’s own neurological symptoms or disorder
5. Lesions on the right parietal lobe can cause contralateral neglect: lost of knowledge about or interest in the left side of the body.
6. Lesions on the Left Parietal Lobe: ideational apraxia: inability to carry out a sequence of actions.
   
   1. Ideomotor Apraxia: inability to carry out a simple action in response to a command
   2. Gerstmann’s Syndrome: combination of finger agnosia, right-left confusion, agraphia, and acalculia (inability to perform simple math calculations).
   3. Agraphia: dysgraphia and involves the inability to write,

Question 9

Temporal Lobe

Answer 9

Auditory Cortex and Wernicke’s area (usually in the left hemisphere).

1. Lesions in the Auditory Cortex may cause auditory agnosia, auditory hallucinations, and other dx of auditory sensation and perception.
2. Wernicke’s Area: comprehension of language and lesions produce Wernicke’s (receptive) aphasia, or severe deficits in language comprehension and abnormatlities in language productions.
3. Temporal lobe mediates encoding, retrieval, and storage of long-term declarative memories.
4. electrical stimulation: elicit complex, vivid memories that have been previously forgotten.
5. lesions of the temporal lobe: retrograde and anterograde amnesia for semantic and episodic memories.

Question 10

Occipital Lobe

Answer 10

Visual Cortex is responsible for visual perception, recognition and memory.

Posterior portion of the visual cortex: high-resolution macular vision (visual signals received in the central retina)

Anterior portion more with peripheral vision.

Damage: apperceptive or associative Visual agnosia, visual hallucinations, or cortical blindness.

1. Apperceptive Visual Agnosia: person is unable to perceive objects despite intact visual acuity.
2. Associative Visual Agnosia: unable to recognize an object that he is focusing on as the result of impaired memory or inability to access relevant semantic knowledge.
3. Left Occipital Lobe Damage: simultanagnosia = inability to see more than one thing or one aspect of an object at a time.
4. lesions at the junction of the occipital, temporal, and parietal lobes may produce: Prosopagnosia: inability to recognize familiar faces.