Arbor vitae (tree of life): distinctive treelike pattern of the white matter
FoliumFolium
CerebellumCerebellum
Regulation of muscle tone,coordination of skilled voluntary movement
Planning and initiation of voluntary activity
Maintenance of balance, control of eye movements
Vestibulocerebellum
Spinocerebellum
Cerebrocerebelum
Anterior Lobe
Posterior Lobe
Flocculo-Nodular Lobe (FN lobe)
Folia
Primary fissure
CerebellumCerebellum
Lateral part
Intermediate part
Cerebellum:Cerebellum: the Structure the StructureInputs to the cerebellar cortex:Inputs to the cerebellar cortex: Climbing fibers Climbing fibers && Mossy fibers Mossy fibersClimbing fibers:Climbing fibers: originate in the inferior olive of the medulla originate in the inferior olive of the medullaMossy fibers:Mossy fibers: originate in all the cerebellar afferent tracts apart from inferior olive originate in all the cerebellar afferent tracts apart from inferior olivePurkinje cells:Purkinje cells: The The finalfinal output of the cerebellar cortex output of the cerebellar cortex
Climbing fibers:Climbing fibers: excite the Purkinje cells excite the Purkinje cells Mossy fibers:Mossy fibers: excite the granule cells excite the granule cells Granule cells:Granule cells: make excitatory contact with the Purkinje cells make excitatory contact with the Purkinje cellsPurkinje cells:Purkinje cells: Tonic Tonic inhibitioninhibition on the activity of the neurons of the cerebellar nuclei on the activity of the neurons of the cerebellar nuclei =>=> All excitatory inputs will be converted to the inhibition All excitatory inputs will be converted to the inhibition =>=> Removing the excitatory influence of the cerebellar inputs ( Removing the excitatory influence of the cerebellar inputs (erasingerasing))
Cerebellar PedunclesCerebellar PedunclesThree 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.
CerebellarPeduncles
Cerebellar PedunclesCerebellar 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)
Cerebellar InputCerebellar Input
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.
Cerebellar InputsCerebellar InputsVermis 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
Outputs of the CerebellumOutputs of the Cerebellum
Dentate nuclei: project contralaterally through the superior cerebellar peduncle to neurons in the contralateral thalamus & from thalamus to motor cortexFunc.: 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
Inputs and outputs of the CerebellumInputs and outputs of the Cerebellum
Clinical Findings and Localization of Cerebellar LesionsClinical Findings and Localization of Cerebellar Lesions
AtaxiaAtaxia refers to disordered contractions of agonist and antagonist refers to disordered contractions of agonist and antagonistmuscles and lack of coordination between movements at muscles and lack of coordination between movements at different joints typically seen in patients with cerebellar lesions.different joints typically seen in patients with cerebellar lesions.
Normal movements require coordination of agonist and antagonistNormal movements require coordination of agonist and antagonistmuscles at different joints in order for movement to have muscles at different joints in order for movement to have
smoothsmoothtrajectory.trajectory.
In ataxia movements have irregular, wavering In ataxia movements have irregular, wavering course consisting of continuous course consisting of continuous overshooting, overcorrecting and overshooting, overcorrecting and then overshooting then overshooting
again around the intended trajectory.again around the intended trajectory.
Dysmetria =Dysmetria = abnormal undershoot or overshoot abnormal undershoot or overshoot during movements toward a target during movements toward a target (finger-nose-finger test).(finger-nose-finger test).
Cerebellum and Motor LearningCerebellum 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
Cerebellum: Control of Voluntary MovementCerebellum: Control of Voluntary Movement
Information sources: lesions & damages & experimental stimulation of cerebellar nuclei
Primary function: 1. To supplement & correlate the activities of other motor areas2. Control of posture 3. Correction of rapid movements initiated by cerebral cortex4. Motor learning
Frequency of nerve impulses in the climbing fibers almost doubles when a monkey learns a new task
Movement Control:a. Inputs from motor cortex inform the cerebellum of an intended
movement before it is initiatedb. Sensory information is then received via the
spinocerebellar tractc. An error signal is generated and is fed back to the cortex
Cerebellum has no direct connection to the spinal motoneurons (indirect effect).
Cerebellar ProcessingCerebellar Processing• Cerebellum receives impulses of the intent Cerebellum receives impulses of the intent
to initiate voluntary muscle contractionto initiate voluntary muscle contraction• Proprioceptors and visual signals “inform” Proprioceptors and visual signals “inform”
the cerebellum of the body’s conditionthe cerebellum of the body’s condition• Cerebellar cortex calculates the best way Cerebellar cortex calculates the best way
to perform a movementto perform a movement• A “blueprint” of coordinated movement is A “blueprint” of coordinated movement is
sent to the cerebral motor cortexsent to the cerebral motor cortex
Cerebellar Cognitive FunctionCerebellar Cognitive Function• Plays a role in language and problem solvingPlays a role in language and problem solving• Recognizes and predicts sequences of eventsRecognizes and predicts sequences of events
DiencephalonDiencephalon
• Central core of the forebrainCentral core of the forebrain
• Consists of three paired structures – Consists of three paired structures – thalamus, hypothalamus, and epithalamusthalamus, hypothalamus, and epithalamus
• Encloses the third ventricleEncloses the third ventricle
Table 5.3 (1)Page 144
Hypothalamus
Thalamus(medial)
DiencephalonDiencephalon
ThalamusThalamus
Paired, egg-shaped masses that form the Paired, egg-shaped masses that form the superolateral walls of the third ventriclesuperolateral walls of the third ventricle
Contains four groups of nuclei : Contains four groups of nuclei : anterior, ventral, dorsal, and posterioranterior, ventral, dorsal, and posterior
Nuclei project and receive fibers from the Nuclei project and receive fibers from the cerebral cortexcerebral cortex
Table 5.3 (1)Page 144
Hypothalamus
Thalamus(medial)
Thalamus
Thalamic FunctionThalamic Function
• Afferent impulses from Afferent impulses from all sensesall senses converge and synapse in the thalamusconverge and synapse in the thalamus
• Impulses of similar function are sorted out, Impulses of similar function are sorted out, edited, and relayed as a groupedited, and relayed as a group
• All inputs ascending to the cerebral cortex All inputs ascending to the cerebral cortex pass through the thalamuspass through the thalamus
• Plays a key role in mediating sensation, Plays a key role in mediating sensation, motor activities, cortical arousal, learning, motor activities, cortical arousal, learning, and memoryand memory
Hypothalamic NucleiTable 5.3 (1)Page 144
Hypothalamus
Thalamus(medial)
Hypothalamic FunctionHypothalamic Function• Regulates blood pressure, rate and force of Regulates blood pressure, rate and force of
heartbeat, digestive tract motility, rate and depth heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activitiesof breathing, and many other visceral activities
• Is involved with perception of pleasure, fear, and Is involved with perception of pleasure, fear, and ragerage
• Controls mechanisms needed to maintain Controls mechanisms needed to maintain normal body temperaturenormal body temperature
• Regulates feelings of hunger and satiety Regulates feelings of hunger and satiety • Regulates sleep and the sleep cycleRegulates sleep and the sleep cycle• Endocrine Functions of the HypothalamusEndocrine Functions of the Hypothalamus
Frontallobe
Central sulcus
Parietallobe
Parietooccipitalnotch
Occipitallobe
Preoccipitalnotch
Temporallobe
Lateralfissure
The Cerebral CortexThe Cerebral Cortex
The cerebral cortexThe cerebral cortex• Cerebral Cortex : outer layer of gray matter Cerebral Cortex : outer layer of gray matter • It covers an inner core of white matter It covers an inner core of white matter • The gross structure has gyri and sulci The gross structure has gyri and sulci
Different Lobes:Different Lobes: Frontal :Frontal : voluntary motor activity, speaking ability, and voluntary motor activity, speaking ability, and
elaboration of thought; stimulation of different areas of its elaboration of thought; stimulation of different areas of its primary motor cortex moves different body regions, again primary motor cortex moves different body regions, again primarily on the opposite side of the body.primarily on the opposite side of the body.
Parietal :Parietal : somatosensory processing; each region of its cortex somatosensory processing; each region of its cortex receives somaesthetic and proprioceptive input from a specific receives somaesthetic and proprioceptive input from a specific body area, primarily from the opposite body side.body area, primarily from the opposite body side.
• Somesthetic sensationSomesthetic sensation - - sensations from the surface of the body - touch, pain, sensations from the surface of the body - touch, pain, pressure, heat and coldpressure, heat and cold
• This info is projected to the somatosensory cortex - site for initial cortical This info is projected to the somatosensory cortex - site for initial cortical processing and perception of somesthetic and proprioceptive input processing and perception of somesthetic and proprioceptive input
• Body regions are topographically mapped -Body regions are topographically mapped - sensory homunculussensory homunculus
• Sensory cortex - receives information from the opposite side of the bodySensory cortex - receives information from the opposite side of the body (e.g., damage on right side results in sensory loss on left side)(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 Simple awareness of touch, pressure, temp or pain is first detected by the thalamus, but cortex is required for perception - intensity and spatial thalamus, but cortex is required for perception - intensity and spatial discriminationdiscrimination
• This info is then projected (via fibre tracts) to association cortices for analysis This info is then projected (via fibre tracts) to association cortices for analysis and integration of sensory information - eg., perception of texture, firmness, and integration of sensory information - eg., perception of texture, firmness, temp, shape, position, location of an object you are holding)temp, shape, position, location of an object you are holding)
Regions of the Regions of the cortex involved cortex involved in motor controlin motor control
Frontal lobe - Motor cortexFrontal lobe - Motor cortex
• Primary motor cortexPrimary motor cortex - voluntary control for muscle movement - voluntary control for muscle movement
• Motor cortex on each side controls muscles on the opposite side of Motor cortex on each side controls muscles on the opposite side of the bodythe body
• Tracts originating in the cortex cross (at level of pyramids) before Tracts originating in the cortex cross (at level of pyramids) before continuing down spinal cord to terminate on continuing down spinal cord to terminate on -motor neurons that -motor neurons that directly innervate skeletal muscledirectly innervate skeletal muscle
• Body regions are represented topographically - motor homunculusBody regions are represented topographically - motor homunculus
• Extent of representation in the motor cortex is proportional to the Extent of representation in the motor cortex is proportional to the precision and complexity of motor skills required precision and complexity of motor skills required
Other cerebral brain regions Other cerebral brain regions important for motor control important for motor control
Primary motor cortex does not initiate voluntary movement
Premotor cortex (M1)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)Supplementary motor area (SMA) responds to internal cues plays a preparatory role in programming complex sequences of movement
Posterior parietal cortexPosterior parietal cortex It is posterior to the primary somatosensory cortexinforms premotor cortex of position
Temporal lobeTemporal 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
Cortical Association areasCortical Association areas
• Prefrontal association cortexPrefrontal association cortexFunctions: planning for voluntary activity, decision-making, creativity, Functions: planning for voluntary activity, decision-making, creativity, and developing personality traits. and developing personality traits. – Site of operation of working memory - temporary storage and actively Site of operation of working memory - temporary storage and actively
manipulation of information used in reasoning and planningmanipulation of information used in reasoning and planning
• parietal-temporal-occipital association cortexparietal-temporal-occipital association cortex Integrates somatic, auditory, and visual sensations from three lobesIntegrates somatic, auditory, and visual sensations from three lobes
• limbic association cortexlimbic association cortex Being involved with motivation, emotion, and memory Being involved with motivation, emotion, and memory
The cerebral hemispheres The cerebral hemispheres lateralization/dominancelateralization/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
The limbic system 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
Limbic System
Figure 12.18
Limbic systemLimbic system
Plays a key role in emotion and works with the higher Plays a key role in emotion and works with the higher cerebral cortex to control behavioral patterns.cerebral cortex to control behavioral patterns.
Aggression Aggression --> lesions of amygdala produce docility, while --> lesions of amygdala produce docility, while stimulation results in rage and aggression stimulation results in rage and aggression
FearFear --> stimulation of amygdala and hypothalamus can --> stimulation of amygdala and hypothalamus can produce fear, while ablation results in an absence of fearproduce fear, while ablation results in an absence of fear
Goal-directed behaviourGoal-directed behaviour - reward and punishment - reward and punishment system- stimulation of certain areas function as a reward, system- stimulation of certain areas function as a reward, while stimulation of other areas results in a punishment while stimulation of other areas results in a punishment shockshock
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