1. Some Terminologies Folia : Leaves Vermis: Worm
White matter : myelinated fibre tracts
Gray matter : areas of neuronal cell bodies
Tracts : collections of axons subserving similar function or location in CNS
Nerves : peripheral axons
Nucleus : collection of neurons subserving similar function in CNS – e.g., caudate nucleus, red nuclei
Brainstem: Midbrain (Mesencephalon) + Pons Medulla Oblongata
Folia : Leaves
Vermis: Worm

2. Table 5.3 (1) Page 144 Brain components Cerebral cortex Thalamus
Hypothalamus
Brain stem
Cerebral cortex
Thalamus
(medial)
Basal nuclei
(lateral to thalamus)
Cerebellum
Spinal cord
Midbrain (Mesencephalon)
Pons
Medulla oblongata
Brain components
(midbrain, pons,
and medulla)
Diencephalon

3. The Cerebellum Located dorsal to the pons and medulla
Makes up 11% of the brain’s mass
Cerebellar activity occurs subconsciously
Provides precise timing and appropriate patterns of skeletal muscle contraction Programming ballistic movements
Acts as comparator for movements Comparing intended and actual movement
Correction of ongoing movements Internal & external feedback Deviations from intended movement
Motor learning Shift from conscious ---> unconscious

4. Anatomy of the Cerebellum
2 symmetrical hemispheres connected medially by the Vermis
Folia: Transversely oriented gyri
3 lobes in each hemisphere: Anterior, Posterior, Flocculonodular (FN)
Neural arrangement: Gray matter (Cortex), White matter (Internal), Scattered cerebellar nuclei: dentate, globose, emboliform, fastigial
Arbor vitae (tree of life): distinctive treelike pattern of the white matter
Folium

5. Cerebellum Anterior Lobe Posterior Lobe
Primary fissure
Anterior Lobe
Regulation of
muscle tone,
coordination of
skilled voluntary
movement
Posterior Lobe
Planning and
initiation of
voluntary activity
Flocculo-Nodular Lobe (FN lobe)
Maintenance of
balance, control
of eye movements
Vestibulocerebellum
Spinocerebellum
Cerebrocerebelum
Folia

6. Cerebellum
Lateral part
Intermediate part

7. Cerebellum: the Structure
Inputs to the cerebellar cortex: Climbing fibers & Mossy fibers
Climbing fibers: originate in the inferior olive of the medulla
Mossy fibers: originate in all the cerebellar afferent tracts apart from inferior olive
Purkinje cells: The final output of the cerebellar cortex
3 Layered Cerebellar Cortex

8. Cerebellum: 3 layered cortex
Climbing fibers: excite the Purkinje cells
Mossy fibers: excite the granule cells
Granule cells: make excitatory contact with the Purkinje cells
Purkinje cells: Tonic inhibition on the activity of the neurons of the cerebellar nuclei
=> All excitatory inputs will be converted to the inhibition
=> Removing the excitatory influence of the cerebellar inputs (erasing)

9. Cerebellar Peduncles
Three paired fiber tracts connect the cerebellum to the brainstem:
Superior peduncles connect the cerebellum to the midbrain;
Middle peduncles connect the cerebellum to the pons and to the axis of the brainstem;
Inferior peduncles connect the cerebellum to the medulla.
Cerebellar Peduncles

10. Cerebellar Peduncles Superior peduncles (to the midbrain):
Fibers originate from neurons in the deep cerebellar nuclei & communicates with the motor cortex via the midbrain and the diencephalon (thalamus)
Middle peduncles (to the pons):
Cerebellum receives information advising it of voluntary motor activities initiated by motor cortex
Inferior peduncles (to the medulla):
Afferents conveying sensory information from muscle proprioceptors throughout the body & from the vestibular nuclei of the brainstem (Spinal cord)

11. Cerebellar Input

12. Inputs to cerebellum from spinocerebellar tracts have a somatotopic organization.
2 maps of body
Primary fissure
Signals from the motor cortex, which is also arranged somatotopically,
project to corresponding points in the sensory maps of the cerebellum.

13. Cerebellar Inputs Vermis Intermediate Zone Lateral Zone
Receives input from spinal cord regarding somatosensory and kinesthetic information (intrinsic knowledge of the position of the limbs)
Damage leads to difficulty with postural adjustments (cerebellar ataxia)
Intermediate Zone
Receives input from the red nucleus and somatosensory information from the spinal cord
Damage results in rigidity & difficulty in moving limbs
Lateral Zone
Receives input from the motor and association cortices through the pons
Projects to the dentate nucleus, which projects back to primary and premotor cortex
Damage leads to 4 types of deficits: Ballistic movements (cerebellar ataxia) Coordination of multi-joint movement (lack of coordination: asynergia) Muscle learning (loss of muscle tone: hypotonia) Movement timing

14. Outputs of the Cerebellum
Cerebellar nuclei: dentate, globose, emboliform, fastigial
Dentate nuclei: project contralaterally through the superior cerebellar peduncle to neurons in the contralateral thalamus & from thalamus to motor cortex Func.: influence planning and initiation of voluntary movement
Emboliform & Globose nuclei: project mainly to the contralateral red nuclei & a small group is projected to the motor cortex Red Nuclei  Rubrospinal Tract control of proximal limb muscles
Fastigial nuclei: project to the vestibular nuclei & to the pontine and medullary reticular formation Vestibulospinal & Reticulospinal tracts

16. Inputs and outputs of the Cerebellum

17. Clinical Findings and Localization of Cerebellar Lesions
Ataxia refers to disordered contractions of agonist and antagonist
muscles and lack of coordination between movements at
different joints typically seen in patients with cerebellar lesions.
Normal movements require coordination of agonist and antagonist
muscles at different joints in order for movement to have smooth
trajectory.
In ataxia movements have irregular, wavering course consisting of continuous overshooting, overcorrecting and then overshooting
again around the intended trajectory.
Dysmetria = abnormal undershoot or overshoot during movements toward a target (finger-nose-finger test).

18. Cerebellum and Motor Learning
Deficits in learning complex motor tasks after cerebellar lesions
fMRI studies : cerebellum active during learning of novel movements
Postulated that cerebellar nuclei store certain motor memories
May be involved in cognitive functions

19. Cerebellum: Control of Voluntary Movement
Cerebellum has no direct connection to the spinal motoneurons (indirect effect).
Information sources: lesions & damages & experimental stimulation of cerebellar nuclei
Primary function:
To supplement & correlate the activities of other motor areas
Control of posture
Correction of rapid movements initiated by cerebral cortex
Motor learning Frequency of nerve impulses in the climbing fibers almost doubles when a monkey learns a new task
Movement Control:
Inputs from motor cortex inform the cerebellum of an intended movement before it is initiated
Sensory information is then received via the spinocerebellar tract
An error signal is generated and is fed back to the cortex

20. Cerebellar Processing
Cerebellum receives impulses of the intent to initiate voluntary muscle contraction
Proprioceptors and visual signals “inform” the cerebellum of the body’s condition
Cerebellar cortex calculates the best way to perform a movement
A “blueprint” of coordinated movement is sent to the cerebral motor cortex
Cerebellar Cognitive Function
Plays a role in language and problem solving
Recognizes and predicts sequences of events

21. Diencephalon Central core of the forebrain
Table 5.3 (1) Page 144
Hypothalamus
Thalamus
(medial)
Diencephalon
Central core of the forebrain
Consists of three paired structures – thalamus, hypothalamus, and epithalamus
Encloses the third ventricle

22. Diencephalon

23. Table 5.3 (1) Page 144
Hypothalamus
Thalamus
(medial)
Thalamus
Paired, egg-shaped masses that form the superolateral walls of the third ventricle
Contains four groups of nuclei : anterior, ventral, dorsal, and posterior
Nuclei project and receive fibers from the cerebral cortex

24. Thalamus

25. Thalamic Function
Afferent impulses from all senses converge and synapse in the thalamus
Impulses of similar function are sorted out, edited, and relayed as a group
All inputs ascending to the cerebral cortex pass through the thalamus
Plays a key role in mediating sensation, motor activities, cortical arousal, learning, and memory

26. Hypothalamic Nuclei Table 5.3 (1) Page 144 Hypothalamus Thalamus
(medial)

27. Hypothalamic Function
Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activities
Is involved with perception of pleasure, fear, and rage
Controls mechanisms needed to maintain normal body temperature
Regulates feelings of hunger and satiety
Regulates sleep and the sleep cycle
Endocrine Functions of the Hypothalamus

28. The Cerebral Cortex Central sulcus Frontal lobe Parietal
Parietooccipital
notch
Occipital
Preoccipital
Temporal
Lateral
fissure

29. The cerebral cortex Different Lobes:
Cerebral Cortex : outer layer of gray matter
It covers an inner core of white matter
The gross structure has gyri and sulci
Different Lobes:
Frontal : voluntary motor activity, speaking ability, and elaboration of thought; stimulation of different areas of its primary motor cortex moves different body regions, again primarily on the opposite side of the body.
Parietal : somatosensory processing; each region of its cortex receives somaesthetic and proprioceptive input from a specific body area, primarily from the opposite body side.
Temporal : receives sound sensation
Occipital : initial processing of visual input

30. Parietal lobe Frontal lobe Occipital lobe Temporal lobe
Somatosensory cortex
(Somesthetic sensation and proprioception)
Supplementary motor area
(programming of complex movement)
Primary motor cortex
(Voluntary movement)
Premotor cortex
(coordination of complex
movements)
Central
sulcus
Posterior parietal cortex
(integration of somatosensory and visual input)
Prefrontal association cortex
(planning for voluntary activity; decision making;
personality traits)
Parietal lobe
Wernicke’s area
(speech
understanding)
Frontal lobe
Parietal-temporal-occipital
association cortex
(integraton of all sensory input-
imp in language)
Broca’s area
(speech formation)
Primary auditory cortex
Occipital lobe
Limbic association cortex
(motivation, emotion, memory)
Temporal lobe
Primary visual cortex

31. Parietal Lobe - Somatosensory cortex
Somesthetic sensation - sensations from the surface of the body - touch, pain, pressure, heat and cold
This info is projected to the somatosensory cortex - site for initial cortical processing and perception of somesthetic and proprioceptive input
Body regions are topographically mapped - sensory homunculus
Sensory cortex - receives information from the opposite side of the body (e.g., damage on right side results in sensory loss on left side)
Simple awareness of touch, pressure, temp or pain is first detected by the thalamus, but cortex is required for perception - intensity and spatial discrimination
This info is then projected (via fibre tracts) to association cortices for analysis and integration of sensory information - eg., perception of texture, firmness, temp, shape, position, location of an object you are holding)

32. Regions of the cortex involved in motor control

33. Frontal lobe - Motor cortex
Primary motor cortex - voluntary control for muscle movement
Motor cortex on each side controls muscles on the opposite side of the body
Tracts originating in the cortex cross (at level of pyramids) before continuing down spinal cord to terminate on a-motor neurons that directly innervate skeletal muscle
Body regions are represented topographically - motor homunculus
Extent of representation in the motor cortex is proportional to the precision and complexity of motor skills required

34. Other cerebral brain regions important for motor control
Primary motor cortex does not initiate voluntary movement
Premotor cortex (M1) anterior to the primary motor cortex acts in response to external cues must be informed of body’s position in relation to target
Supplementary motor area (SMA) responds to internal cues plays a preparatory role in programming complex sequences of movement
Posterior parietal cortex It is posterior to the primary somatosensory cortex informs premotor cortex of position

35. Temporal lobe
Contains auditory centres that receive sensory fibres from the cochlea of each ear
Also involved in the interpretation and association of auditory and visual information
Temporal lobe contains the hippocampus and the amygdala
Involves in memory

36. Cortical Association areas
Prefrontal association cortex Functions: planning for voluntary activity, decision-making, creativity, and developing personality traits.
Site of operation of working memory - temporary storage and actively manipulation of information used in reasoning and planning
parietal-temporal-occipital association cortex Integrates somatic, auditory, and visual sensations from three lobes
limbic association cortex Being involved with motivation, emotion, and memory

37. The cerebral hemispheres lateralization/dominance
Each cerebral hemisphere receives information from both sides of the body
The left cerebral hemisphere excels in performing logical, analytical, sequential, and verbal tasks
Better at describing facial appearances
The right cerebral hemisphere excels in spatial perception and artistic and musical talents
Better at recognizing faces

38. The limbic system
Refers to several forebrain structures that function together
Cingulate gyrus
Hippocampus
Amygdala
Septal nuclei
Closed circuit of information flow between the limbic system and the thalamus and hypothalamus
Limbic system and hypothalamus - cooperate in the neural basis of emotional states

39. Limbic System
Figure 12.18

40. Limbic system
Plays a key role in emotion and works with the higher cerebral cortex to control behavioral patterns.
Aggression --> lesions of amygdala produce docility, while stimulation results in rage and aggression
Fear --> stimulation of amygdala and hypothalamus can produce fear, while ablation results in an absence of fear
Goal-directed behaviour - reward and punishment system- stimulation of certain areas function as a reward, while stimulation of other areas results in a punishment shock