BASAL Ganglia and it's anatomy and functions

About basal ganglia,caudate nucleus

1. CAUDATE NUCLEUS DR.ANISHA MENTOR : DR.MAITHREYI

2. SCHEME OF THE PRESENTATION BASAL GANGLIA Anatomy Blood supply Afferent of basal ganglia Efferent of basal ganglia Functions of basal ganglia Disorders of basal ganglia Psychiatric manifestations of basal ganglia References

3. BASAL GANGLIA The basal ganglia are large masses of grey matter situated in the cerebral hemisphere. They play an important role in regulating movements .

4. Basal ganglia includes structures Anatomical division: Caudate nucleus Putamen lentiform nucleus Corpus striatum Globus pallidus Amygdaloid nuclear complex Claustrum

5. Functional divisions : Corpus striatum Subthalamic nuclei Substantia nigra Ventral striatum Ventral pallidum

6. Neo striatum –Caudate nucleus + Putamen Paleo striatum – Globus pallidii (interna + externa) Archistriatum –formed by Amygdaloid nuclear complex and Claustrum. Corpus striatum – Caudate nucleus + Putamen + Globus pallidus Lentiform nucleus –Putamen + Globus pallidus

7. Caudate nucleus

8. Caudate Nucleus Telencephalic in origin It is a c shaped structure It is divided into 3 parts – head , body and tail RELATIONS : Associated with contour of lateral ventricles. Head – bulges into anterior horn of the ventricle and forms its floor .It is continuous with Putamen . The body –lies in the floor of the central part of ventricle. Tail is the roof of the inferior horn of the ventricle.

9. The anterior part of the head is fused with the lentiform nucleus inferiorly . Thus region is called Fundus striati . Tail lies in close relation with the amygdaloid nucleus . The body is related medially to thalamus and laterally to the internal capsule which separates it from lentiform nucleus .

10. Lentiform nucleus

11. Lentiform nucleus Appears triangular in the coronal section with its tip directed medially Divided into two parts by external medullary lamina (thin lamina of white mater ) lateral part Putamen Medial part globus pallidus

12. Putamen It is telencephalic in nature Bounded laterally by the external capsule Medially by globus pallidus Separated from caudate by the anterior limb of internal capsule

13. Globus Pallidus It is diencephalic in origin Latin word “ pale globe “ also known as paleostriatum Inner component of the lentiform nucleus It is subdivided into external( GPe ) and internal ( GPi ) by internal medullary lamina Cone like structure with top directed medially It is bounded medially by the posterior limb of internal capsule Laterally by putamen

14. Amygdaloid nuclear complex: Lies in temporal lobe close to the temporal pole . Related to the anterior end of inferior horn of lateral ventricle . Claustrum : Thin lamina of grey matter lies lateral to lentiform nucleus. Its connections and functions are not known.

15. Substantia Nigra It is mesencephalic Present in mid brain consists of 2 components Pars reticulata – functionally related to GPi .They use inhibitory neurotransmitter –GABA . Pars compacta –neurons here are pigmented because of the presence of neuromelanin . These cells contain Dopamine.

16. Subthalamic Nuclei It is diencephalic in origin It lies dorsomedial to posterior limb of internal capsule It is situated dorsal to substantial nigra Lesion in this – Hemiballismus .

17. Ventral striatum Masses of grey matter lying in the region of anterior perforated substance. More medially mass of grey matter called nucleus accumbens . It is related to caudate nucleus – superolaterally and to septal nuclei –medially. Ventral striatum consists of Olfactory tubercle and Nucleus accumbens .

18. Dorsal striatum – caudate nucleus & putamen . Ventral striatum –olfactory tubercle & nucleus accumbens . Dorsal pallidum – globus pallidus . Ventral pallidum – part below the anterior perforated substance.

19. Blood supply Lenticulostriate branches of middle and anterior cerebral arteries . Anterior choroidal branches of internal carotid artery . Head of caudate by Recurrent artery of Heubner . Tail of caudate by Anterior Choroidal artery.

20. Internal organization Types of neurons in striatum: Medium spiny neurons Medium aspiny neurons Large spiny neurons Large aspiny neurons

21. Inputs /afferents to basal ganglia Striatum is the major recipient of inputs to basal ganglia 3 major afferent pathways are known to terminate in striatum Cerebral cortex - Corticostriate - glutaminergic Substantia nigra -Nigrostriatal – dopaminergic Thalamus - Thalamostriate – from central median nucleus

22. Corticostriatal pathway Originates from all regions of neocortex Arises mainly from pyramidal cells of the layer 5 and 6 Uses excitatory neurotransmitter –glutamate Afferent from Sensorimotor cortex – putamen Association regions –caudate nucleus Prefrontal regions-head of the caudate nucleus

23. Nigrostriatal PATHWAY Originates from substanstia nigra ( pars compacta) Major neurotransmitter –dopamine Thalamostraiatal pathway Originates from thalamus Thalamic nuclei providing the projections are the intralaminar nuclei , particularly the central median nucleus

24. The afferents from the cerebral cortex and the thalamus provide the striatum with various modalities of sensory information . Disruption of the input pathways is associated with movement disorders like parkinsons disease.

25. Internal processing Occurs via direct and indirect pathways Direct pathways; Striatal neurons project to GPi and inhibit GPi . Causes facilitation of movement. Indirect pathway; Striatal neurons project to GPe which in turn project to substantia nigra and then to GPi . Causes inhibition of movements.

26. Efferent from basal ganglia The main output is concentrated upon the pallidum and substantia nigra . Output from Globus pallidus from Fasciculus lenticularis ( from GPi and enters subthalamic region ) Ansa Lenticularis (arises from GPe , GPi and enters the subthalamic region where it meets the dentato rubrothalamic fibres and the fasiculus lenticularis . The union of the three tracts is called fasiculus thalamicus which terminates in the ventral anterior , ventral lateral and centro median nuclei of the thalamus. ) Subthalamic fasiculus ( reciprocal connections between globus pallidus and subthalamic nucleus ) Pallidonigral fibres –pass to the substantia nigra .

27. Efferent connections Substantia Nigra Pars compacta ; Sends a dopaminergic projection to the striatum A projection from striatum ends in pars reticularis Pars reticulata receives fibres from pallidum directly or relay in the subthalamic nucleus . Pars reticularis ; Projects to ventral lateral and ventral anterior nucleus of the thalamus . These impulses are relayed to premotor and prefrontal areas of the cortex

28. Functions of basal ganglia Control of voluntary motor activity Control of reflex muscular activity Control of muscle tone Role in arousal mechanism

29. Control of voluntary motor activity : Neural discharge in basal ganglia begins well before the movement begins . Its involved in Planning and programing of movements It is executed through functional neuronal caudate circuit Timing and scaling of intensity of movement – caudate circuit – lesion leads to akinesia and micrographia Subconsious excecution of movements swinging of hands while walking Movements of facial expressions with emotion.

30. Control of reflex muscular activity Has inhibitory effect on spinal reflexes Maintain posture Control of muscle tone Through reticular formation –in BG lesions – rigidity occurs Role in arousal mechanism Through its connection with reticular formation Lesion –drowsiness ,sleep

31. Disorders of basal ganglia Parkinson's disorder Chorea Athetosis Huntington's disease Hemiballismus Wilsons disease Progressive supranuclear palsy

32. Parkinson's disease A neurogenerative disorder associated with loss of dopaminergic neurons in substantia nigra Parkinson's disease affect movements , producing motor symptoms, nonmotor symptoms including autonomic dysfunction, neuropsychiatric problems sensory and sleep difficulties are also common .

33. Chorea Rapid ,semi purposeful ,dance like non patterned involuntary movements involving proximal and distal muscle groups When the movements are of large amplitude and forceful it is called ballism It is due to damage to caudate nucleus. Seen in children as complication to rheumatic fever.

34. Athetosis Slow , rhythmic , twisting ,worm like movements of the extremities Mainly fingers and wrist Due to damage to putamen

35. Huntington's disease It is a autosomal dominant neurodegenerative disorder characterized by middle onset , progressive course with motor , cognitive and psychiatric symptoms This is because of CAG repeat expansion mutation in the huntin gene in chromosome 4

36. Primary involuntary movement abnormality Chorea or choreoathetosis Associated involuntary movement abnormality Fine motor movements Gait disturbance Psychiatric manifestations High rates of suicide Depression Mania Personality change

37. Hemiballismus A violent form of chorea that comprises wild ,flinging, large amplitude movements on one side of the body Because of damage of subthalamic nucleus (commonly haemorrhage ).

38. Wilsons disease Autosomal recessive condition with mutation in ATP 7B results in abnormal copper accumulation in the liver , basal ganglia and other tissues . Copper deposits in the basal ganglia especially in basal ganglia in the putamen .

39. Neurological findings Tremors Dystonia Rigidity Choreoathetosis

40. Basal ganglia in Psychiatric disorders: OCD ; There is a evidence of basal ganglia dysfunction in imaging studies . Both increase and decrease volumes of caudate nucleus is reported Most patients show increase blood flow to the CAUDATE AUTISM : Enlargement of CAUDATE nucleus upto 8 % . The greater caudate volume is proportional to the increased total brain volume . Motor , communicative and social impairments are associated with shape abnormality in the basal ganglia Glutamate dysfunction in basal ganglia is associated with autism.

41. ADHD : Neuroimaging studies show evidence of striatal dysfunction in ADHD . Teicher and colleagues concluded that ADHD maybe related to functional abnormalities in the Putamen . Boys with ADHD showed a significantly smaller volume of basal ganglia compared with typically developed boys .

42. SCHIZOPHRENIA In striatum ,there are anomalies of DOPAMINE ,synthesis , storage and release . Striatal dopaminergic system is overactive ,increase in presynaptic dopamine function indicating increase dopamine synthesis.

43. DEPRESSION Functional imaging studies have shown pathological interactions in AMYGDALA , VENTRAL STRIATUM and PREFRONTAL CORTEX . Nucleus accumbens is also involved in affective disorders. Caudate hyperintensities are found in elderly patients of depression.

44. THANK YOU

45. REFERENCE 1.Comprehensive textbook of psychiatry –Kaplan and Sadocks 2.Textbook of Neuroanatomy – I.B.Singh 3.Postgraduate Textbook of Psychiatry -Ahuja