Psyc 372 – Physiological Psychology

Overview

• Is located behind the Medulla and • Contains only 10% of the Brain’s volume The • Contains more that 50% of the brain’s Little Brain neurons • Appears similar to the cortex Psychology 372 • Also has two hemispheres • Is connected to the Pons by three bundles of Physiological Psychology axons called the Cerebellar Peduncles. Steven E. Meier, Ph.D. • Superior (Brachium Conjunctivum) Listen to the audio lecture while viewing these slides • Middle (Brachium Po ntis) • Inferior (Restiform Body) 1 2

Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology

Function Overview Has Three Distinct Regions • Cerebellar cortex. • Basically evaluates and adjusts motor •Is the outer covering movement while it is in progress. • Is composed mostly of Gray Matter • Internal • Does a lot of integration and evaluation • Are Myelinated Axons/Fiber Tracts of incoming information. • Three pairs of Deep Nuclei • Is very important for balance and motor •Fastigal •Interposed learning • Globose • Emboliform • Dentate • Nuclei receive information from the cerebellar cortex • Nuclei send information to the cerebellum 3 and to other brain structures. 4

Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology Three Major Tracts of Neurons Connect to the Brain Stem Anatomically

• inferior • Cerebellum surface has many parallel • Middle Cerebellar Peduncle convolutions called Folia (leaves) that • Superior Cerebellar Peduncle run from side to side • Has the most connections • Has three distinct lobes separated by two fissures • Most input begins in deep nuclei

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Posteriolateral fissure Fissures

• Separates the body of the cerebellum • Define a ridge in the midline called the from the Flocculonodular lobe vermis • Is the primary fissure in the body of the • On each side of the vermis are the cerebellum cerebellar hemispheres • Separates the anterior lobe from the • Hemispheres are divided into posterior lobe intermediate and lateral regions. • Lobes are important functionally • Each is important for specific motor functions

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Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology Flocculonodular Lobe (Vestibulocerebellum) Damage

• Is most primitive • Problems with eye movements during head rotations • Gets information from vestibular areas of the brain. • Problems with limbs and body structures during standing or walking • Semicircular canals • Have problems maintaining balance • Otoliths • Is extremely important for balance and • Patients separate legs but the move eye movements their legs irregularly and often fall • Can move arms and legs accurately when lying down or when their head is supported 9 10

Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology

Vermis Intermediate Zone

• Gets information from visual auditory • Gets somatosensory information from and vestibular areas. limbs • Also gets information from somatic • Helps control distal muscles of the limbs sensory areas as well. and fingers • Helps control the proximal muscles of the body and limbs. • Generally governs posture, locomotion, and gaze.

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2 Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology Vermis and Intermediate Zones (Spinocerebellum) Function

• Receives information from the spinal • Influences limb muscles and muscles in cord. the body • Also gets information from ventral and • Don’t get limb deceleration - so you get dorsal spinocerebellar tracts. overshoot of the system • Receives information from the leg • Is especially important for rhythmic muscles and joints activity during locomotion • Sends information to structures that • Also contains inverted somatotopic develop into the rubrospinal and maps that are inverted corticospinal tracts. • E.g., head is at the bottom in the vermis

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Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology

Cerebrocerebellum Damage

• Are lateral parts of the hemispheres • Disrupts motor planning and prolongs • Only receives information from the reaction times cortex • Have to plan out every movement • Is involved with planning and mental before doing it. rehearsal of complex motor actions and • Conscious assessment of movement errors. • Has a very important role in perceptual and cognitive functioning

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Psyc 372 – Physiological Psychology Psyc 372 – Physiological Psychology

Example, tapping tests on Halstad Reitan Question

• Rhythm is irregular and the motions • Is one tone longer than another? vary in duration and force. • Is the speed of an object faster than • Medial cerebellar lesions interfere only another? with accurate execution of the response • Dentate also is important for tasks • Lateral cerebellar lesions interfered with requiring complex spatial and temporal the timing of the events judgments • Timing was also disrupted in other • Is essential for conducting complex cognitive tasks as well motor movements

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Some Disorders e.g., Hand Alternation Task • Lots of disorders • Diagno sis is o ften do ne symptomatically • Have fingers hit alternate palm of the •Examples hand • Hypotonia • Get tremor when you are trying to stop • Knee jerk the movement • You flex but the leg does not come back smoothly • Problem occurs when antagonistic • Instead ossicilates several times muscles are trying to stop the • movement. • Lack of coordination • Also get a delay in initiating responses with the affected limb • Also get errors in the range and regularity of movement 19 20

Psyc 372 – Physiological Psychology

Overall Damage to Cerebellum

• Generally, results in jerky, exaggerated, erratic motor movements. • Movements are also poorly coordinated.

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