1. Functional Areas of Cerebral Cortex 1
Anatomically the cortex is divided into 6 lobes: frontal, parietal, temporal, occipital, limbic and insular
Each lobe has several gyri
Functionally the cortex is divided into numbered areas first proposed by Brodmann in 1909
Brodmann’s areas were described based on cytoarchitecture; later they were found to be functionally significant

2. Functional Areas of Cerebral Cortex 2
Cytoarchitecture is based on the density of different cortical neurons and thickness of layers

3. Frontal Lobe Makes up 1/3 of all cerebral cortex Primary motor
Premotor
Frontal eye field
Supplementary motor
Prefrontal
Broca’s area

4. Primary Motor Cortex: Area 4
Somatotopic organization
Size of areas is proportional to the degree of skill involved with movement
Lesions of motor cortex result in paralysis/paresis of contralateral body area

5. Premotor Cortex: Area 6 Contains programming for movements
Electrical stimulation produces slower movements of larger groups of muscles compared to area 4
Lesion produces apraxia - inability to perform voluntary movement in the absence of paralysis

6. Frontal Eye Field: Inferior Part of Area 8
Stimulation produces conjugate eye movement to contralateral side
Lesion produces transient deviation of eyes to ipsilateral side and paralysis of contralateral gaze

7. Supplementary Motor Area: Parts of Areas 6 and 8
Medial surface
Stimulation produces posturing responses such as turning head and eyes toward moving arm
Programming for complex movements involving several parts of the body

8. Prefrontal Cortex: Areas 9, 10, 11, 12, 32, 46, and 47
Nearly 1/4 of all cortex
Orbitofrontal area functions in visceral and emotional activities
Dorsolateral area functions in intellectual activities such as planning, judgement, problem solving and conceptualizing

9. Prefrontal Cortex 2
Lesions cause loss of initiative, careless dress, loss of sense of acceptable social behavior
Prefrontal leucotomy or prefrontal lobotomy were once common surgical procedures to treat patients with severe behavioral disorders
Now drugs are used

10. Broca’s Area: Area 44 & 45 Part of the inferior frontal gyrus
Functions in speech

11. Parietal Lobe Includes over 1/5 of total cortex Primary somatosensory
Secondary somatosensory
Gustatory
Association

12. Primary Somatosensory Area: 1,2,3
Somatotopically organized
Areas of cortex proportional to sensory discrimination of the area not to amount of surface area
Stimulation produces contralateral tingling or numbness but never pain
Lesions cause contralateral loss of tactile discrimination and position sense but no relief of pain

13. Secondary Somatosensory Area
Parietal operculum into posterior insula; posterior part of area 43
Bilateral input
Somatotopy poorly defined
Pain is perceived here

14. Primary Gustatory Cortex: Area 43
Anterior part of parietal operculum
Lesion results in contralateral (mostly) ageusia

15. Parietal Association Cortex : Areas 5,7,39,40
5 input from S1
7 input from visual and motor cortex
39&40 input from all association areas
function in hand performance
neglect syndrome
astereognosis

16. Parietal Neglect Syndrome Clinical Illustration
Failure to recognize side of body contralateral to injury
May not bathe contralateral side of body or shave contralateral side of face
Deny own limbs
Objects in contralateral visual field ignored

17. Temporal Lobe 1/4 of total cortex Primary auditory
Auditory association
Visual association
Limbic

18. Primary Auditory Cortex: Areas 41 &42
Transverse temporal gyrus
Tonotopic organization
High freq posteromedial and low freq anterolateral
Lesion causes difficulty in recognizing distance and direction of sound, especially when the sound comes from the contralateral side

19. Auditory Association Cortex: Area 22
Wernicke’s area (posterior part of 22)
Language understanding and formulation
Damage can result in aphasia

20. Limbic Temporal Cortex: Areas 20,21, 27,28,29,30, 34,36,38
Visceral function, emotions, behavior, memory
Stimulation can elicit past events
Left posterior area memory of verbal info
Right posterior area memory of visual info
Bilateral lesion of 20,21 causes prosopagnosia, loss of facial recognition
Often damaged in Alzheimer’s disease

21. Occipital Lobe: Areas 17,18,19
17 striate cortex, primary visual cortex
Macular vision in posterior part
Lesion causes homonymous hemianopsia

22. Occipital Lobe: Areas 18 & 19
18 parastriate cortex
19 peristriate cortex
Receive visual info from 17 bilaterally
Complex processing for color, movement, direction, visual interpretation
Lesion can cause visual agnosia

23. Hemispheric Lateralization of Function
Hemisphere with language function is termed “dominant”
10% of population is left-handed
13% male, 9% female are left-handed
95% of right-handers have language in left hemisphere
75% of left-handers have language in left hemisphere
Handedness and language dominance develop before speech begins
Dominant hemisphere also excels in analytical thinking and calculation
Nondominant hemisphere excels in sensory discrimination, emotional/nonverbal thinking, artistic skill, music, spatial perception and perhaps face recognition

24. Language Areas of the Brain 1
Broca’s area, 44 & 45 is the motor speech center
Motor programs for speech production
Projects to motor cortex areas controlling vocal cords, tongue and lips
Lesion causes expressive aphasia with poor articulation, short sentences, slow speech

25. Language Areas of the Brain 2
Wernicke’s area, posterior part of 22
Functions in comprehension and formulation of language
Lesion causes receptive aphasia with defective use of words, meaningless verbiage, lack of comprehension

26. Spoken Description of Visualized Scene
Visual input to 17 with further processing in 18 & 19
On to area 39 where objects named and recognized
Then to 22 where words are assembled into sentences
Then to Broca’s area 44 & 45
Then to adjacent motor cortex for expression