24 th Lecture ∣ The Physiology Team

Cerebral hemisphere function

Objectives:

❖ is divided into four lobes by central and . E.g. frontal , , and . ❖ Know the terms categorical hemisphere and representational hemisphere. ❖ Be able to summarize the difference between these hemispheres.

Done by :

❖ Team leader: Rahaf AlShammari, Fatima Balsharf, Abdulelah AlDossari, Ali AlAmmari. ❖ Team members: Reem AlQarni, Abdullah AlSergani, Shahad AlZahrani, Faisal AlTahan, Shahad AlTayash, Hisham AlShaya, Maha AlAmri, Saif AlMeshari. Colour index: ● Important ● Numbers ● Extra

وَ أَن ﻟﻴْﺲَ ﻟِﻺْ ِﻧﺴَ ﺎنِ إِﻻ ﻣَﺎ ﺳَ ﻌَ ﻰٰ Introduction

● The is the largest part of the with two hemisphere, linked by commissural fibres of . ● Each cerebral hemisphere contains externally highly convoluted cortex of and internal mass of ● The cerebral hemispheres contains motor and sensory areas and the limbic system.

Cerebral Cortex ● The outermost layer of gray matter making up the superficial aspect of the cerebrum. ● Microscopically the cortex consists of six layers or laminae lying parallel to the surface. ● From outside to inside the layers are: I. Molecular layer II. The external granular layer III. Layer of pyramidal cell IV. Internal granular layer V. Large pyramidal cell layer VI. Layer of fusiform or polymorphic cells.

Cerebral Cortex Layers 1. The incoming sensory signal excites neuronal layer IV first; then the signal spreads toward the surface of the cortex and also toward deeper layers. 2. Layers I and II & III perform most of intracortical association function. 3. The neurons in layers II and III making short horizontal connections with adjacent cortical areas. 4. The neurons in layers V and VI send output signals to brain stem, spinal cord (V) & (VI). 2 There are three main types of functional areas in the cerebral cortex

1) Primary Areas:

○ The primary motor areas have direct connections with specific muscles for causing discrete muscle movements. ○ The detect specific sensations - visual, auditory, or somatic- transmitted directly to the brain from peripheral sensory organs. ○ Association Areas they receive and analyze signals simultaneously from multiple regions of both the motor and sensory cortices as well as from subcortical structures.

2) Associated areas:

These areas receive and analyze signals simultaneously from multiple regions of both the motor and sensory cortices as well as from subcortical structures.

The most important association areas are 1. Parieto-occipitotemporal association area 2. Prefrontal association area 3. Limbic association area.

Parieto-occipitotemporal association areas

1. Analysis of the Spatial Coordinates of the Body. 2. Language Comprehension. 3. Initials Processing of Visual Language (Reading). 4. Area for Naming Objects.

3 1. Parieto-Occipitotemporal association areas

Area Site Function

Beginning in the Computes the 1) Analysis of the posterior parietal cortex coordinates if the spatial coordinates of and extending into the visual, auditory, and the body superior occipital cortex body surroundings.

Wernicke’s area, lies behind the primary 2) Area for language in the Higher intellectual comprehension posterior part of the function superior of the temporal lobe

Make meaning out of 3) Area for Initial the visually perceived processing of visual area words (lesion causes learning (Reading) Dyslexia or word blindness)

Lateral portion of 4) Area for naming anterior occipital lobe Naming objects objects and posterior temporal lobe

4 2. Prefrontal Association Area

Definition Function Lesion

Is the anterior pole of 1. Planning of complex pattern of (Lesions in this area . movements. lead to change in 2. Personality characteristics and personality and social relationship. behavior) 3. Production of deep, more abstract and logically sequenced thoughts which enable attainment of goals. 4. Working (ability to tie thoughts together in a logical sequence by comparing many bits of information with appropriate stored knowledge and be able to instantly recall this information for future planning).

3. Limbic Association Area

Definition Function Lesion

Anterior and inner Is primarily concerned with (Lesion of this area may portion of temporal emotion , behavior and lead to decreased lobe. motivational drive for aggression, lack of different tasks most emotion, hyper sexuality importantly learning. & hyperphagia)

Area of Recognition of

Location Function Lesion

The underside of The occipital portion is Inability to recognize the brain on the contiguous with , faces is called medial occipital and while the temporal one is temporal lobe closely associated with limbic (Patient with prosopagnosia can’t recognize faces even his or her own system in the mirror, they can recognize people with their voices)

5 ❏ Frontal ❏ Parietal ❏ Occipital ❏ Tempora

Frontal lobe

Location Function Cortical region

Deep to the -Memory ● Primary () Frontal Bone formation Cortical site involved with controlling movements of the . -Emotions of the body. -Decision ● Broca’s Area making plan of motor pattern for expressing of individual -Reasoning words. Located on Left Frontal Lobe -Personality ● Broca’s Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words. ● Site of Frontal Lobotomies ● Olfactory Bulb Cranial Nerve I, Responsible for sensation of Smell

Frontal Lobotomies

Desired effects Possible side effects

Diminished rage Epilepsy

Decreased aggression Poor emotional responses

Poor emotional responses Perseveration (Uncontrolled, repetitive actions, gestures, or words) 6 Parietal lobe

Located Deep inside the parietal bone of the skull

Function Cortical region Lesions

-Sensing and A. Primary somatosensory ● Parietal lobe is essential integration of cortex for our feeling of touch, the sensation. () :It is the warmth/heat , cold, -Spatial site involved in processing , body position and awareness and tactile and proprioceptive appreciation of shapes of → information) ( to this area palpated objects causes loss of sensation ) ● When damaged , the which is person loses the ability awareness of B. Somatosensory to recognize shapes of the body or its association cortex complex objects by parts in space Assists with the integration palpation ( Palpation = also develops , ( اﻟﻠﻤﺲ and its relation and interpretation of to one another sensations relative to body Sensory Inattention on position and orientation in opposite side space () ● إذا ﻛﺎن اﻟﺸﺨﺺ ﻣﺼﺎب ﻓﻲ ﻫﺬه اﻟﻤﻨﻄﻘﺔ Sensory Inattention ﺑﺎﻟﺘﺎﻟﻲ ﻫﻮ ﻳﻘﺪر ﻳﺤﺲ ﺑﺲ ﻣﺎ ﻳﻘﺪر ﻳﻔﺴﺮ The inability to feel a tactile اﻻﺷﻴﺎء اﻟﻲ ﺣﺲ ﺑﻬﺎ وراح ﻳﻜﻮن ﻋﻨﺪه ﻣﺸﻜﻠﺔ when a similar ﺑﺘﻨﻈﻴﻢ وﺗﻨﺴﻴﻖ اﻟﺤﺮﻛﺔ stimulus, presented C. Primary gustatory simultaneously in a cortex The are involved homologous area of the body, in interpretation of the is perceived. sensation

7 Occipital lobe

Location Function Cortical region

Deep inside Its primary ● Primary visual cortex : the occipital function is the ● This is the primary ( main ) area of the bone of the processing, brain responsible for detection of the skull integration, visual stimuli (injury to this area causes interpretation of blindness) vision and visual ● stimuli Visual association cortex : ● Interprets the visual information obtained from the primary visual اﻟﻤﺮﻳﺾ ﻟﺴﻰ ﻳﻘﺪر ﻳﺸﻮف اﻷﺷﻴﺎء ﺑﺲ ﻟﻸﺳﻒ cortex ﻣﺎ ﻳﻘﺪر ﻳﻔﻬﻢ او ﻳﻔﺴﺮ اﻳﺶ اﻟﻲ ﻗﺎﻋﺪ ﻳﺸﻮﻓﻪ

8 Temporal Lobe :

located on the sides of the brain deep to the Temporal Bones of the skull

Function Cortical region Lesions

A. Primary Auditory Cortex ● Wernicke’s Aphasia - -Organization/ Responsible for hearing Language comprehension is Comprehension inhibited. The individuals have difficulty understanding of language written and spoken language Information B. ● Memory impairment Retrieval Interprets the of smell ● Can be associated with (Memory and once it reaches the cortex via Memory the olfactory bulbs. (Not Formation) visible on the superficial cortex)

C. Wernicke’s Area – Language comprehension. • Located on the Left Temporal Lobe (dominant hemisphere). •Understand auditory and visual information and send them to Broca's area

9 Functional Principles of the Cerebral hemispheres

1. Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body. 2. The 2 hemispheres have somewhat different functions although their structures are alike. 3. Correspondence between a specific function and a specific region of cerebral cortex is not precise. 4. No functional area acts alone; conscious behavior involves the entire cortex.

Dominant & Nondominant Hemisphere

❖ Functional differences between left and right hemispheres ◇ In most people, left hemisphere (dominant hemisphere) controls: ■ reading, writing, and math, decision-making, logic, speech and language (usually). ◇ Right cerebral hemisphere relates to: ■ Understanding & interpreting music ■ Non verbal visual Experience ■ Spatial relation between the person & their surroundings ■ Body language and intonation of peoples voices

A:

* This graphic representation of the regions of the Primary Motor Cortex and Primary is one example of a HOMUNCULUS:

10 Important points you should focus on:

Summary

★ Cerebral Cortex is The outermost layer of gray matter making up the superficial aspect of the cerebrum.

Cerebral area Functional importance

Primary Areas The primary motor areas have direct connections with specific muscles for causing discrete muscle movements.

Associated areas These areas receive and analyze signals simultaneously from multiple regions of both the motor and sensory cortices as well as from subcortical structures.

★ If the primary is damaged , the person loses the ability to recognize shapes of complex objects by palpation, also develops Sensory Inattention on opposite side (Astereognosis)

★ Q- conscious proprioception contains : somatosensory cortex, parietal lobe , dorsal column except the . ~ Dr. fawzia

11 Questions

1.The , is composed of six layers tangential to the pial surface of the 5.Damage to which of the following brain hemisphere. Which one of the following areas leads to the inability to statement concerning the organization of comprehend the written or the spoken these six layers is correct? word?

A. on the dominant side A. The neurons in layers II and III of the brain form connections with the basal B. Anterior occipital lobe ganglia C. Junction of the parietal, temporal, B. Specific incoming signals from the and occipital lobes cerebellum terminate primarily in D. Medial portion of the precentral layer IV gyrusE) Most anterior portion of C. The neurons in layer V have axons the temporal lobe that extend beyond layer V to 6.Dysfunction of which brain area will subcortical regions and the spinal lead to behavior which is not appropriate cord for the given social occasion? D. The neurons in layer VI send their A. axons to the hippocampus B. Corpus callosum 2. Lesion of which of the following areas C. Fornix cause Dyslexia? D. A. Visual cortex 7.When a person lose the ability to B. Angular gyrus identify an object by touch, this condition C. Broca's area is called? D. Wernicke's area A. Dyslexia 3.A person who has had a traumatic brain B. Prosopagnosia injury seems to be able to understand the C. Astereognosis written and spoken word but cannot D. Ataxia create the correct sounds to be able to 8.Evaluation of a patient reveals the speak a word that is recognizable. is following deficits: (1) decreased person most likely has damage to which aggressiveness and ambition, and area of the brain? inappropriate social responses; (2) A. Wernicke’s area inability to process sequential thoughts in B. Angular gyrus order to solve a problem; and (3) inability C. Broca’s area to process multiple bits of information D. Prefrontal lobe that could then be recalled 4.Primary gustatory cortex is found in instantaneously to complete a thought or which lobe? solve a problem. Damage to which of the A. Frontal lobe following brain regions might be B. Parietal lobe responsible for such deficits? C. Temporal lobe A. Parieto-occipitotemporal D. Occipital lobe association cortex. B. Broca's area C. Limbic association cortex D. Prefrontal association cortex 8. 7. 6. 5. 4. 3. 2. 1. D C A C B C B C

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