Cerebrum Lundy-Ekman, Chapters 17, 18

Objectives Explain the organization of cerebral cortex and subcortical structures Identify the motor and cognitive functions of the basal ganglia, and the effects of injury on these functions Recognize the cellular and structural organization of the cerebral cortex Describe the anatomical and function meaning of Brodmann’s areas

For the different regions of cerebral cortex Describe the functional significance of the following classifications of regions of cerebral cortex: Primary Sensory Areas, Sensory Association Areas, Primary Motor Areas, Motor Association Areas, and Heteromodal Association Areas For the different regions of cerebral cortex Identify the Brodmann’s area Describe the function of the area Describe the effects of injury on function

For higher cognitive and cerebral functions: Describe the function Identify the side and the region of the brain important for this function Describe the effects of brain injury on the function Identify regions of the brain important for attention and awareness Differentiate between selective and sustained awareness

Identify anatomical structures and pathways important in the ARAS Describe the different types of memory Identify regions of the nervous system important for each type of memory

Cerebrum Diencephalon Thalamus Hypothalamus Epithalamus Subthalamic nucleus Telencephalon Subcortical structures White matter Basal Ganglia Cerebral Cortex

                                                                   

Intralaminar nuclei Midline nuclei Reticular nuclei

Thalamic nuclei Relay nuclei Association nuclei Non-specific nuclei Relay information to cerebral cortex from? Association nuclei Emotional and some memory info Integrate different types of sensation Reciprocal connections with large areas of cortex Non-specific nuclei Multiple inputs, Output to large areas of cortex Consciousness and arousal

Thalamic damage To relay nuclei Thalamic pain syndrome

Hypothalamus

Hypothalamus Homeostasis Body temperature Metabolic rate Blood pressure Water intake and excretion Digestion

Epithalamus Pineal gland Regulate circadian rhythms Regulate pituitary gland, adrenal gland, parathyroid gland and pancreas

Subthalamus

Organization of the Cerebral Cortex Outer layer Cells Deeper layer Basal Nuclei Subcortical White Matter

Subcortical White Matter Thalamus Lenticular nucleus Internal capsule

Subcortical White Matter Projection fibers Commissural fibers Association fibers

Basal Ganglia Motor Functions Cognitive Functions Injury Motor deficits Behavioral deficits Loss of initiative Spontaneous thought Emotional responses

Cerebral Cortex Divided into layers Neocortex – 6 layers Layers differ between different regions of the cerebral cortex Same 6 layers but they differ in thickness and appearance p. 413

Brodmann’s areas Cytoarchitectural areas Korbinian Brodmann – 1909 Figure 17-8 (page 413) Structure correlated with function

                                                Brodmann’s areas

Overall organization of cerebral cortex Primary Sensory Areas Sensory Association Areas Primary Motor Areas Motor Association Areas Heteromodal Association Areas

Primary Sensory Cortex Receives input from thalamic regions Only one type of sensation Somatosensory Auditory Visual Vestibular Representation of sensation is topographically organized

Primary Somatosensory Cortex Brodmann’s areas 3, 1, 2 (precentral gyrus) Function Location of stimuli Discriminate among shapes, sizes and textures Damage Loss of discrimination – location and strenght Crude awareness intact Localization of pain intact

Primary Auditory Cortex Brodmann’s area 41 (Superior Temporal Gyrus) Pathway Cochlea  Cochlear nucleus  inferior colliculus/medial geniculate body  CTX Function Conscious awareness of sound – bilateral Not extremely well lateralized Damage Loss of localization

Primary Vestibular Cortex Brodmann’s area 40 (Parietal-temporal-occipital association area) Function Information about head movement and position Information also travels through thalamus Damage Loss of conscious awareness of head position and movement

Primary Visual Cortex Pathway Brodmann’s area 17 – occipital lobe Retina  LGN  10 visual cortex Brodmann’s area 17 – occipital lobe Function is to distinguish Light/dark Various shapes Location of objects Movement of objects Damage – contralateral homonymous hemianopsia

Sensory Association Areas Contribute to the analysis on one type of sensation – unimodal Usually located adjacent to primary sensory cortex for that modality Input from both primary sensory cortical area and the thalamus Damage – Agnosia – inability to identify something using one sensation

Projections Primarily to primary motor cortex Also to Association areas Important in formulating motor plans for complex movements

Somatosensory Association Cortex Brodmann’s areas 5,7 Function Integrate tactile and proprioceptive information Stereognosis Memory of tactile and spatial environment Damage Astereognosis May avoid affected hand

Visual Association Cortex Brodmann’s areas 18-21 Function Analyzes colors and motion Directs visual fixation Damage Visual agnosia is contralateral visual field

Auditory Association Cortex Brodmann’s areas 22, 42 Function Compares sounds with memories of other sounds Categorizes sounds as music, language or noise Damage – auditory agnosia Left – unable to understand speech Right – loss in interpretation of noises

Primary Motor and Motor Planning Areas Primary motor cortex Supplementary motor cortex Premotor area Broca’s area Area corresponding to Broca’s area on the language non-dominant side of the brain

Primary motor cortex Brodmann’s area 4 Location – precentral gyrus, anterior part of paracentral lobule Function Source of many corticospinal neurons Contralateral voluntary movements for lower face and extremities Bilateral voluntary movements for upper face and back muscles

Damage to Primary Motor Cortex Contralateral paresis – mostly in lower face and distal extremities Loss – fractionation Speech problems – spastic dysarthria UMN disorder Harsh, awkward speech

Motor Planning Areas Located anterior to primary motor cortex Four regions Supplementary Motor Cortex Premotor Area Both are in Brodmann’s area 6 Broca’s Area Area on contralateral hemisphere corresponding to Broca’s

Supplementary Motor Cortex Medial and superior area 6 Functions Initiation of movement Orientation of head and eyes Planning bimanual and sequential movements

Premotor Area Lateral part of area 6 Functions Controls trunk and girdle muscles Medial activating systems

Broca’s Area Unilateral – Usually on L side Areas 44 and part of 45 Functions Motor speech Planning movements of mouth Grammar All the little word that help a sentence make sense

Area contralateral to Broca’s Obviously, usually on R side Functions Similar to Broca’s area but for non-verbal communication Plans nonverbal communication Adjusts tone of voice

Inputs to primary motor cortex Sensory input from thalamus and primary somatosensory cortex Motor input from motor planning regions Motor input from basal ganglia and cerebellum via the thalamus Primary Motor Cortex Cb Motor Thalamus BG

Inputs to motor planning regions Sensory information from sensory association areas From BG and Cb – relayed by the thalamus

Cortical Motor Output Fibers Location of neuronal cell bodies Corticospinal Corticobulbar Corticopontine Cortical projections to putamen Location of neuronal cell bodies Primary motor cortex, motor planning areas, and primary somatosensory cortex

Damage to Motor Planning Areas Apraxia Inability to perform voluntary movements Can perform involuntarily Damage to PMA or SMC Motor Preseveration Uncontrollable repetition of a movement Damage to SMC

Damage to area homologous to Broca’s area Damage to Broca’s area Broca’s aphasia Difficulty producing verbal communication Damage to area homologous to Broca’s area Difficulty producing nonverbal communication