lobes of brain ( parietal, temporal, occipital)

Lobes of brain

1. LOBES OF BRAIN-II DR HARI RAM SEDAI 1 ST YEAR RESIDENT PSYCHIATRY

2. TOPIC OF DISCUSSION PARIETAL LOBE - Location , Functions & Clinical importance OCCIPITAL LOBE - Location & Functions & Clinical importance TEMORAL LOBE - Location & Functions & Clinical importance

3. PARIETAL LOBE L ies posterior to the central sulcus on the superolateral and medial surfaces of the cerebral hemisphere Anterior border - formed by the central sulcus Posterior border - formed by the imaginary line extending between the parieto -occipital sulcus (superiorly) and the pre-occipital notch (inferiorly) Inferior border - formed by the lateral fissure of Sylvius Superior border - formed by the medial longitudinal fissure that separates the two hemispheres

4. PRIMARY SOMATOSENSORY CORTEX

5. PRIMARY SOMATOSENSORY CORTEX Occupies the post central gyrus on on the lateral surface of the hemisphere and the posterior part of the paracentral lobule on the medial surface ( Brodmann areas 3, 1 & 2 ) R eceives projection fibers from the ventral posterior lateral and ventral posterior medial nuclei of the thalamus The pharyngeal region, tongue & Jaws are represented in the most inferior part of the postcentral gyrus ; this is followed by the face, fingers, hand, arm, trunk, and thigh Concerned with the perception of exteroceptive (pain, touch, temperature) & proprioceptive (vibration, muscle & joint sense)

6. SOMATOSENSORY ASSOCIATION AREA Occupies the superior parietal lobule extending onto the medial surface of the hemisphere ( Brodmann areas 5 and 7 ) M ain function is to receive and integrate different sensory modalities Concerned with perception of shape, size, roughness & texture of object Processing, analysing & memory of somatic sensation It enables one to recognize objects placed in the hand without the help of vision ( stereogenosis )

7. POSTERIOR ASSOCIATION AREA Lies in the superior lip of the posterior limb of the lateral fissure Multi modal association area (visual, auditory & somatic sensation) F ace area lies most anterior and the leg area is posterior The body is bilaterally represented with the contralateral side dominant S ensory impulses come from the primary area and many signals are transmitted from the brainstem N eurons respond particularly to transient cutaneous stimuli, such as brush strokes or tapping of the skin This area relates more to the pain perception The ablation of this area may relieve intractable pain

8. LESION OF PARIETAL LOBE Lesions in the angular gyrus of the dominant (usually left) parietal lobe can cause: Gerstmann’s syndrome : left- right confusion inability to count ( acalculia ) inability to name the fingers (finger agnosia ) inability to write ( agraphia )

9. Sensory and Perceptual Deficits : Parietal lobe damage can lead to difficulties in processing sensory information and piecing together experiences, resulting in problems with spatial awareness, visual processing, hand-eye coordination, and body awareness. Apraxia and Agnosia : Parietal lobe damage can cause constructional apraxia (difficulty with complex movements), visuospatial agnosia (difficulty recognizing objects), and topographical disorientation (getting lost, inability to learn new routes ) Impaired Spatial Cognition : The parietal lobe plays a key role in spatial orientation, attention, and understanding one's relationship to the environment. Damage can lead to difficulties with left-right discrimination, body part localization, and navigational skills.

10. PARIETAL LOBE IMPLICATIONS IN PSYCHIATRY Schizophrenia : Abnormalities in parietal lobe function have been associated with psychotic-like experiences and cognitive deficits in schizophrenia. Functional imaging studies have shown parietal hypoactivation and prefrontal hyperactivity during working memory tasks in patients with schizophrenia Anxiety : Stimulation of the right inferior parietal lobe has been found to increase anxiety in humans. The right inferior parietal lobe may help attenuate stress by recruiting attentional resources to cope with threat situations

11. OCCIPITAL LOBE The primary visual area ( Brodmann area 17) is situated In the walls of the posterior part of the calcarine sulcus O ccasionally extends around the occipital pole onto the lateral surface of the hemisphere The secondary visual area ( Brodmann areas 18 and 19 ) surrounds the primary visual area on the medial and lateral surfaces of the hemisphere . This area receives afferent fibers from area 17 and other cortical areas as well as from the thalamus

12. O ccipital eye field (Area 19) is thought to exist in the secondary visual area in humans Stimulation produces conjugate deviation of the eyes, especially to the opposite side F unction of this eye field is believed to be reflex and associated with movements of the eye when it is following an object O ccipital eye fields of both hemispheres are connected by nervous pathways and also are thought to be connected to the superior colliculus F rontal eye field controls voluntary scanning movements of the eye and is independent of visual stimuli

13. Functions of Occipital Lobe Primary visual area (area 17) is concerned with perception of visual sensation Secondary visual area (area 18) is concerned with interpretation of visual sensation and storage of memories of visual symbols Occipital eye field (area 19) is concerned with reflex movement of eyeballs. It is also concerned with associated movements of eyeballs while following a moving object

14. OCCIPITAL LOBE IMPLICATIONS IN PSYCHIATRY Schizophrenia Structural Changes : R educed grey matter volume in the occipital lobe of people with schizophrenia compared to controls Increased antipsychotic dose was associated with decreased occipital grey matter over time and decreases were associated with lower overall functioning Functional Changes : Reduced activation in the left middle occipital gyrus during executive functioning tasks and reduced activation in the right lingual gyrus and cuneus during episodic memory tasks have been observed in people with schizophrenia compared to controls Visual Hallucinations : The association of visual hallucinations with occipital lobe damage in schizophrenia is well established. Studies have found reduced activation in the left middle occipital gyrus during executive functioning tasks and reduced activation in the right lingual gyrus and cuneus during episodic memory

15. Depression Occipital Bending : Studies have found a higher frequency of abnormal (reversed) asymmetry in the occipital lobe in patients with major depressive disorder (MDD) compared to healthy controls. This phenomenon known as occipital bending may be associated with reduced M2 receptor binding, reduced fractional anisotropy, and reduced magnetization transfer ratios in the occipital lobe Grey Matter Volume : Reduced grey matter volume in the occipital lobe has been observed in patients with major depressive disorder compared to controls

16. Other Implications Visual Processing : The occipital lobe plays a crucial role in visual processing, including object recognition, spatial awareness, and depth perception. Dysfunction in this region can lead to various visual impairments and difficulties in recognizing objects Interactions with Other Brain Regions : The occipital lobe interacts with other brain regions, such as the temporal and parietal lobes to process visual information and assign meaning to objects. Dysfunction in the occipital lobe can impact these interactions and contribute to various psychiatric symptoms

17. TEMPORAL LOBE The primary auditory area ( Brodmann areas 41 and 42) includes the gyrus of Heschl and is situated in the inferior wall of the lateral sulcus Area 41 is a granular type of cortex; area 42 is homotypical and is mainly an auditory association area Projection fibres to the auditory area arise principally in the medial geniculate body and form the auditory radiation of the internal capsule The anterior part of the primary auditory area is concerned with the reception of sounds of low frequency, and the posterior part of the area is concerned with the sounds of high frequency

18. SECONDARY AUDITORY AREA Situated posterior to the primary auditory area in the lateral sulcus and in the superior temporal gyrus ( Brodmann area 22 ) Receives impulses from the primary auditory area and from the thalamus It is necessary for the interpretation of sounds and for the association of the auditory input with other sensory information

19. SENSORY SPEECH AREA OF WERNICKE Localized in the left dominant hemisphere, mainly in the superior temporal gyrus , with extensions around the posterior end of the lateral sulcus into the parietal region The Wernicke area is connected to the Broca area by a bundle of nerve fibers called the arcuate fasciculus Receives fibers from the visual cortex in the occipital lobe and the auditory cortex in the superior temporal gyrus Wernicke area permits understanding of written and spoken language and enables a person to read a sentence, understand it and say it out loud

20. TEMPORAL LOBE SYNDROME Temporal lobe syndrome is otherwise known as Kluver - Bucy syndrome Occurs after the bilateral ablation of temporal lobe along with amygdala and uncus Manifestations of this syndrome are: 1. Aphasia (disturbance in speech) 2. Auditory disturbances such as frequent attacks of tinnitus, auditory hallucinations with sounds like buzzing, ringing or humming 3. Disturbances in smell and taste sensations 4. Dreamy states: The patients are not aware of their own activities and have the feeling of unreality 5. Visual hallucinations associated with hemianopia

21. TEMPORAL LOBE EPILEPSY A) Epilepsy arising in the medial temporal lobe (MTLE) Due to hippocampal sclerosis Clinical Features Past history of prolonged febrile convulsions >30min Seizures longer than frontal lobe seizures (typically > 2 min), with a slower evolution and more gradual onset Auras common typical of medial temporal (rather than lateral temporal origin) are visceral, cephalic, gustatory, affective, perceptual or autonomic auras Partial awareness commonly preserved, especially in early stages and slow evolution of seizure

22. Prominent motor arrest with loss of awareness (motionless stare) Post- ictal confusion and dysphasia common Autonomic changes (e.g. pallor, redness, and tachycardia) Automatisms usually oroalimentary (lip-smacking, chewing, swallowing) R epetitive motor actions like undressing, walking & running Vocalisation also common EEG CHANGES Anterior or mid-temporal spikes/sharp waves Rhythmic temporal alpha or theta activity within 30 seconds of onset

23. B) Epilepsy Arising In The Lateral Temporal lobe O ften a detectable underlying structural pathology G lioma , cavernous angioma , hamartoma , dysembryoplastic neuroepithelial tumour M alformation of cortical development and damage following trauma Clinical features Typically no history of febrile seizure Auras common Hallucinations (especially auditory) or illusions more suggestive of lateral rather than mesial temporal origin The motionless stare and the automatisms are common

24. EEG Spikes and focal discharges from the temporal region Polyspikes are more commonly seen with neocortical generators

25. REFERENCES Snells clinical neuroanatomy 8 th edition Gray’s anatomy 41st edition Kaplan and Sadock's Comprehensive Textbook of Psychiatry 10 th edition Guyton and Hall Textbook of Medical Physiology 14 th edition Brain , Volume 137, Issue 6, June 2014, Pages 1830–1837,  https:// doi.org/10.1093/brain/awu072 Temporal lobe epilepsy BEATE DIEHL and JOHN S. DUNCAN UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery